Greg Hickok

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March 5, 2009
07:07 PM
1,451 views

Understanding language without ability to speak

by Greg Hickok in Talking Brains

In 1962 Eric Lenneberg published an interesting case report of an 8 year old boy who had a congenital disorder that prevented him from developing the ability to speak. He could perform many oro-facial behaviors like chewing, swallowing, blowing, licking and he spontaneously made noises "that sound somewhat like Swiss yodeling" but he could not speak. With intensive speech therapy he eventually achieved the ability to "repeat a few words after his speech therapist or his mother but the words are still barely intelligible" (p. 420). In contrast, his speech comprehension had been judged as fully normal by the author as well as by neurologists and speech pathologists over the course of 20 or so visits. Lenneberg goes on to report a more systematic examination of the boy's comprehension which revealed it to be well preserved.Lenneberg couched his case report, which he indicated is typical of a larger category of patients, in the context of theories of speech development which held that babbling and speech output was critical to the normal development language abilities including receptive (comprehension) skills. He argued that this type of case argues against the view that speech production is critical to the development of receptive speech. Today, Lenneberg might have highlighted the relevance of his case for mirror neuron/motor theories of speech perception. These theories claim that speech is perceived by mapping acoustic speech sounds onto motor representations coding the production of speech. For example, Rizzolatti and Arbib (1998) stated,mirror neurons represent the link between sender and receiver that Liberman postulated in his motor theory of speech perception as the necessary prerequisite for any type of communication (p. 189)Such a theory would seem to predict that if an individual failed to develop motor systems underlying speech production they should not be able to perceive and comprehend speech. Lenneberg's report demonstrates that this prediction is incorrect. Are there more recent cases of the development of normal language comprehension in the face of failures to develop speech production. Yes, here is a case I recently came across (Case 1 from Christen et al. 2000). A three month old girl had an acute febrile illness (possibly meningitis) with epileptic seizures. After recovery from the acute illness, her motor development was delayed, she exhibited constant drooling, took only pureed food, and never acquired expressive language. She attended a school for disabled children, but made normal progress in writing and reading. She was examined at 15 years old by the paper authors. The patient presented with pseudobulbar palsy (difficulty with orofacial movements such as chewing, swallowing, speech), her “mental state” was normal but she could communicate only by non-verbal means as she was unable to produce identifiable speech sounds. However her language comprehension was reported as normal. An MRI showed bilateral lesions of the anterior opercular region which the authors believed were acquired at age three months during the child's illness and which damaged speech output systems. Bilateral lesions in this region in adults produce a similar disruption of speech output, without affecting comprehension abilities, so called Foix-Chavany-Marie syndrome. Again, we have a clear demonstration of preserved receptive speech abilities despite a complete lack of development of motor speech capacity. This kind of result is not straightforwardly explained by theories which hold that speech production is critical for speech perception.ReferencesChristen HJ, Hanefeld F, Kruse E, Imhäuser S, Ernst JP, Finkenstaedt M. (2000). Foix-Chavany-Marie (anterior operculum) syndrome in childhood: a reappraisal ofWorster-Drought syndrome. Dev Med Child Neurol., 42, 122-32Lenneberg, E. (1962). Understanding language without ability to speak: a case report. Journal of Abnormal and Clinical Psychology, 65, 419-425.G Rizzolatti, M Arbib (1998). Language within our grasp Trends in Neurosciences, 21 (5), 188-194 DOI: 10.1016/S0166-2236(98)01260-0... Read more »

G Rizzolatti, & M Arbib. (1998) Language within our grasp. Trends in Neurosciences, 21(5), 188-194. DOI: 10.1016/S0166-2236(98)01260-0

March 12, 2009
03:40 PM
1,345 views

Bilateral lesions to Broca's area

by Greg Hickok in Talking Brains

A couple weeks ago a reader raised the question of whether unilateral lesions to Broca's area constitute a strong enough test of the motor theory of speech perception. I suggested they were because they sometimes severely disrupted speech production with minimal effects on the recognition (comprehension) of speech. The question continued to nag me though, so I started looking for cases in the literature of bilateral lesions to Broca's area. It turns out there are a handful. Here is the most interesting case report by Levine & Mohr in 1979. Case 3A 20-year-old woman suffered a large left perisylvian stroke including Broca's area and developed chronic severe Broca's aphasia. Nine years later she suffered another stroke, this one involving the right homologue to Broca's area. Here is Levine and Mohr's description of the patient's language abilities:The patient's speech production was absent, and she was unable even to vocalize. Her speech comprehension was very slightly impaired; she obeyed two-commission but not three-commission verbal commands, and performed approximately 1 standard deviation above the average aphasic patient in the auditory comprehension subsection of the BDAE. p. 932Clearly, the patient is able to comprehend words quite well; her only difficulty being the comprehension of rather complicated sentences, consistent with Broca's aphasia.So, large unilateral lesions that destroy speech production ability do not cause substantial speech recognition deficits (Cases 7, 11, 16, 17; Naeser et al. 1989); complete deactivation of the entire left hemisphere during Wada procedures does not cause substantial speech recognition deficits (Hickok et al. 2008); bilateral lesions to the frontal operculum that cause Foix–Chavany–Marie syndrome (anarthria/severe dysarthria and loss of voluntary muscular functions of the face and tongue including speech) do not cause substantial speech recognition deficits (Weller, 1993); failure to develop the ability to speak does not cause substantial speech recognition deficits (Lenneberg, 1962; Christen, et al. 2000);and, bilateral lesions to Broca's region does not cause substantial speech recognition deficits (Levine & Mohr, 1979).Now can we all agree that there is a small problem with the motor theory of speech perception?ReferencesChristen HJ, Hanefeld F, Kruse E, Imhäuser S, Ernst JP, Finkenstaedt M. (2000). Foix-Chavany-Marie (anterior operculum) syndrome in childhood: a reappraisal of Worster-Drought syndrome. Dev Med Child Neurol., 42, 122-32Hickok, G., Okada, K., Barr, W., Pa, J., Rogalsky, C., Donneley, K., Barde, L., & Grant, A. (2008). Bilateral capacity for speech sound processing in auditory comprehension: Evidence from Wada procedures Brain and Language, 107 (3), 179-184 DOI: 10.1016/j.bandl.2008.09.006Lenneberg, E. (1962). Understanding language without ability to speak: a case report. Journal of Abnormal and Clinical Psychology, 65, 419-425.Levine DN, Mohr JP. (1979) Language after bilateral cerebral infarctions: role of the minor hemisphere in speech. Neurology, 29(7):927-38.Naeser, M.A., Palumbo, C.L., Helm-Estabrooks, N., Stiassny-Eder, D., and Albert, M.L. (1989). Severe nonfluency in aphasia: Role of the medical subcallosal fasciculus and other white matter pathways in recovery of spontaneous speech. Brain 112, 1-38.Weller M. (1993) Anterior opercular cortex lesions cause dissociated lower cranial nerve palsies and anarthria but no aphasia: Foix-Chavany-Marie syndrome and "automatic voluntary dissociation" revisited. J Neurol, 240(4):199-208... Read more »

HICKOK, G., OKADA, K., BARR, W., PA, J., ROGALSKY, C., DONNELLY, K., BARDE, L., & GRANT, A. (2008) Bilateral capacity for speech sound processing in auditory comprehension: Evidence from Wada procedures. Brain and Language, 107(3), 179-184. DOI: 10.1016/j.bandl.2008.09.006

August 21, 2008
12:44 PM
1,337 views

Mirror neurons, hubs, and puppet masters

by Greg Hickok in Talking Brains

Hubs are IN in cognitive neuroscience. Griffiths and Warren have their computational hub in the planum temporale, and Patterson et al. have their semantic hub in the anterior temporal lobe. Long before the hub we had the convergence zone of Antonio Damasio and the transmodal node of Marcel Mesulam which he described as an "epicenter" (I like that term -- sounds very important). Despite the variation in terminology, the basic idea behind all these proposals is similar: there are regions in the brain that function to integrate information from different brain systems. This seems reasonable, and may even be right. So what do hubs have to do with mirror neurons and puppet masters? Everything, according to a recent paper in Nature by Damasio and Meyer. These authors argue that mirror neurons are not themselves the basis for action understanding, but rather function as a "convergence-divergence zone" (CDZ) -- a "hub" -- which activates a broad network of areas involved in action perception, including oft neglected sensory systems: "The [mirror] neurons ... are not so much like mirrors ..." Damsio and Meyer write, "They are more like puppet masters, pulling the strings of various memories" (p. 168).Damasio and Meyer's essay provides a welcome and rational view on the possible function of mirror neurons in action understanding. I wonder though, whether they are still giving mirror neurons too much credit. I fully agree with the claim that mirror neurons are part of a larger network involving in processing action-related information that is associatively linked via experience. But I question whether mirror neurons are the puppet masters. Maybe they are just a hand on the puppet.Antonio Damasio, Kaspar Meyer (2008). Behind the looking-glass Nature, 454 (7201), 167-168 DOI: 10.1038/454167a... Read more »

Antonio Damasio, & Kaspar Meyer. (2008) Behind the looking-glass. Nature, 454(7201), 167-168. DOI: 10.1038/454167a

September 9, 2008
12:45 PM
1,309 views

TMS to motor cortex affects lexical decision to body-part related words - What does this tell us?

by Greg Hickok in Talking Brains

One of the most impressive demonstrations of the functional relevance of motor cortex to action-word processing comes from a TMS study by Friedemann Pulvermuller and colleagues (2005, European Journal of Neuroscience, 21:793-97). These researchers stimulated motor cortex for hand or leg areas while subjects performed a lexical decision task. TMS to hand areas led to faster reaction times to hand-related words (e.g., pick) than leg-related words (e.g., kick), whereas the reverse held for TMS to leg areas. This seems to be a clear case of motor cortex involvement in motor-related language processing. Does this mean that the semantics of the word kick is encoded in the motor representation of kicking? Not at all. All it means is that there is an association between the semantics of the word kick and motor programs associated with kicking. It tells us nothing about the nature of the association. Suppose the lexical/conceptual representation of the word kick is stored in neural ensemble A which is distinct from, but connected to, the motor programs for the action kicking which is stored in neural ensemble M in motor cortex. Stimulation of M results in partial activation of A to which it is connected, thus priming the lexical/conceptual representation, which in turn results in faster RTs. The simplicity and intuitive appeal of embodied accounts of complex processes make it all too easy to accept empirical results as indisputable evidence in support of such accounts when in fact there is much to dispute.Friedemann Pulvermuller, Olaf Hauk, Vadim V. Nikulin, Risto J. Ilmoniemi (2005). Functional links between motor and language systems European Journal of Neuroscience, 21 (3), 793-797 DOI: 10.1111/j.1460-9568.2005.03900.x... Read more »

Friedemann Pulvermuller, Olaf Hauk, Vadim V. Nikulin, & Risto J. Ilmoniemi. (2005) Functional links between motor and language systems. European Journal of Neuroscience, 21(3), 793-797. DOI: 10.1111/j.1460-9568.2005.03900.x

November 3, 2008
04:56 PM
1,296 views

Ventral premotor cortex and action processing: Urgesi, et al.

by Greg Hickok in Talking Brains

Here is another pair of studies that a reviewer suggested I failed to discuss because they didn't support my pre-conceived hypothesis regarding mirror neurons. It's true that I didn't discuss them, but not because I cherry picked papers to discuss. I simply wasn't aware of these. After looking at them, I realized that they did not even test action understanding, so I could have justified leaving them out. Nonetheless, because they apparently are viewed a strong evidence for the link between the ventral premotor cortex and action processing, I included a discussion in my review. Here is a summary...Urgesi et al. (2007a/2007b) used rTMS to study the effects of functional deactivation of ventral premotor cortex (vPMc) on visual discrimination of action-related pictures In both of these studies, subjects were asked to make two-choice, match-to-sample judgments: a picture of a body configuration was presented (the sample) followed by a mask (500msec), and then a picture of two body configurations; the subject was asked to indicate which of the two matched the sample. First, as I mentioned above, it is important to notice that neither of these studies actually tested action understanding. That is, discrimination performance did not depend on understanding the meaning of the actions, and could be performed based on configural information alone.Urgesi, Candidi et al. (2007) compared the effects of stimulation of vPMc with stimulation of a ventral temporal-occipital location (the extrastriate body area, EBA) during action discrimination (which action matches the sample?) versus form discrimination (which actor matches the sample, independent of action?). For action judgments vPMc stimulation yielded longer reaction times than EBA stimulation, and the reverse held for form judgments, longer reaction times for EBA stimulation than vPMc stimulation. Stimulation had no effect on accuracy. In the other study (Urgesi, Calvo-Merino et al., 2007), subjects were asked to judge body configuration only, and an effect of accuracy was observed with vPMc stimulation associated with more errors on the configuration matching task than with EBA stimulation. Oddly, there were no reaction time effects.So the two studies showed that interference stimulation to vPMc negatively affected performance on a body configuration delayed matched-to-sample task. Again, because these studies did not assess action understanding, they cannot speak to the question of whether the mirror system supports action understanding. However, they do suggest that processing of body configurations at least in the delayed match-to-sample task involves vPMc to some extent. Given that the tasks involved working memory, it seems possible that this region may support some sort of working memory for body configurations. This is interesting, but in my view is more consistent the idea that the "mirror system" is a sensory-motor integration system, not a semantic system. For example, there are many claims regarding the sensory-motor nature of working memory systems (Buchsbaum & D'Esposito, 2008; Hickok, Buchsbaum, Humphries, & Muftuler, 2003; Pa, Wilson, Pickell, Bellugi, & Hickok, in press; Postle, 2006; Ruchkin et al., 2003; Wilson, 2001). Cosimo Urgesi, Matteo Candidi, Silvio Ionta, Salvatore M Aglioti (2006). Representation of body identity and body actions in extrastriate body area and ventral premotor cortex Nature Neuroscience, 10 (1), 30-31 DOI: 10.1038/nn1815C. Urgesi, B. Calvo-Merino, P. Haggard, S. M. Aglioti (2007). Transcranial Magnetic Stimulation Reveals Two Cortical Pathways for Visual Body Processing Journal of Neuroscience, 27 (30), 8023-8030 DOI: 10.1523/JNEUROSCI.0789-07.2007... Read more »

Cosimo Urgesi, Matteo Candidi, Silvio Ionta, & Salvatore M Aglioti. (2006) Representation of body identity and body actions in extrastriate body area and ventral premotor cortex. Nature Neuroscience, 10(1), 30-31. DOI: 10.1038/nn1815

C. Urgesi, B. Calvo-Merino, P. Haggard, & S. M. Aglioti. (2007) Transcranial Magnetic Stimulation Reveals Two Cortical Pathways for Visual Body Processing. Journal of Neuroscience, 27(30), 8023-8030. DOI: 10.1523/JNEUROSCI.0789-07.2007

October 16, 2008
02:29 PM
1,250 views

Speech recognition and the left hemisphere: Task matters!

by Greg Hickok in Talking Brains

I fully agree with Dorte Hessler's assessment that left hemisphere damage can produce significant "problems to identify or discriminate speech sounds in the absence of hearing deficits." But here is the critical point that David and I have been harping on since 2000: the ability to explicitly identify or discriminate speech sounds (e.g., say whether /ba/ & /pa/ are the same or different) on the one hand, and the ability to implicitly discriminate speech sounds (e.e., recognize that bear refers to a forrest animal while pear is a kind of fruit) on the other hand, are two different things. While it is a priori reasonable to try to study speech sound perception by "isolating" that process in a syllable discrimination task (ba-pa, same or different?), it turns out that by doing so, we end up measuring something completely different from normal speech sound processing as it is used in everyday auditory comprehension. Given that our goal is to understand how speech is processed in ecologically valid situations -- no one claims to be studying the neural basis of the ability to make same-different judgments about nonsense syllables; they claim to be studying "speech perception" -- it follows that syllable discrimination tasks are invalid measures of speech sound processing. I believe the use of syllable discrimination tasks in speech research has impeded progress in understanding its neural basis. Let me explain.Some the same studies that Dorte correctly noted as providing evidence for deficits on syllable discrimination tasks following left hemisphere damage also show that the ability to perform syllable discrimination double-dissociates from the ability to comprehend words. Here is a graph from a study by Sheila Blumstein showing auditory comprehension scores plotted in the y-axis and three categories of performance on syllable discrimination & syllable identification tasks on the x-axis. The plus and minus signs indicate preserved or impaired performance respectively. The letters in the graph correspond to clinical aphasic categories (B=Broca's, W=Wernicke's). Notice the red arrows. They point to one patient who has the worst auditory comprehension score in the sample -- a Wernicke's aphasic, not surprisingly -- yet who is performing well on syllable discrimination/identification tasks, and to another patient who has the best auditory comprehension score in the sample -- a Broca's aphasic, not surprisingly -- yet who fails on both syllable discrimination and identification. A nice double-dissociation.But that's only two patients, and the measure of auditory comprehension is coarse in that it uses sentence level as well as word level performance. Fair enough. So here is data from Miceli et al. that compares auditory comprehension of words (4AFC with phonemic and semantic foils) and syllable discrimination. Notice that 19 patients are pathological on syllable discrimination yet normal on auditory comprehension and 9 patients show the reverse pattern. More double dissociations. Where are the lesions that are producing the deficits on syllable discrimination versus auditory comprehension? According to Basso et al, syllable discrimination deficits are most strongly associated with non-fluent aphasia, which is most strongly associated with frontal lesions. According to a more recent study by Caplan et al., the inferior parietal lobe is also a critical site. Notice that these regions have also been implicated in sensory-motor aspects of speech, including verbal working memory. This contrasts with work on the neural basis of auditory comprehension deficits (e.g., Bates et al.) which implicates the posterior temporal lobe (STG/MTG). Some case study contrasts from Caplan et al. underline the point. On the left is a patient who has a lesion in the inferior frontal lobe and who was classified as a Broca's aphasic. On the right, a patient with a temporal lobe lesion and a classification of Wernicke's aphasia. By definition, the Broca's patient will have better auditory comprehension than the Wernicke's patient. Yet look at the syllable discrimination scores of these patients. The Broca case is performing at 72% correct, whereas the Wernicke is at 90%. Again, the patient with better comprehension is performing poorly on syllable discrimination showing that syllable discrimination isn't measuring normal speech sound processing.To my reading the data are unequivocal. Syllable discrimination tasks tap a different set of processes to auditory comprehension tasks, even though both tasks ostensibly involve the processing of speech sounds. How can this be? Here's an explanation. Syllable discrimination involves activating a phonological representation of one syllable, maintaining that activation while the phonological representation of a second syllable is activated, then comparing the two, and then making a decision. Deficits on this task could arise from activating the phonological representations, maintaining both representations simultaneously in short term memory, comparing the two representations, or in making the decision. Only one of these processes is clearly shared by an auditory comprehension task, namely, activating the phonological representations. I suggest that the deficits in syllable discrimination following left hemisphere damage, particularly left frontal damage, result from one or more of the non-shared components of the task. The fact that the network implicated in syllable discrimination (fronto-parietal regions) is largely identical to that which is independently implicated in phonological working memory supports this claim. If, on the other hand, a patient had a significant disruption of the sensory system that activated phonological representations -- e.g., patients with bilateral lesions and word deafness -- then such a disruption should be evident on both discrimination and comprehension tasks. It is hard for us to give up syllable discrimination as our bread and butter task in speech research. It seem so rigorous and controlled. But the empirical facts show that it doesn't work. In the neuroscience branch of speech research, the task produces invalid and misleading results (if our goal is to understand speech perception under ecologically valid listening conditions). It's time to move on.ReferencesBasso, A., Casati, G. & Vignolo, L. A. (1977). Phonemic identification defects in aphasia. Cortex, 13, 84-95Elizabeth Bates, Stephen M. Wilson, Ayse Pinar Saygin, Frederic Dick, Martin I. Sereno, Robert T. Knight, Nina F. Dronkers (2003). Voxel-based lesion–symptom mapping Nature Neuroscience DOI: 10.1038/nn1050S Blumstein, W Cooper, E Zurif, A Caramazza (1977). The perception and production of Voice-Onset Time in aphasia Neuropsychologia, 15 (3), 371-372 DOI: 10.1016/0028-3932(77)90089-6Caplan, D., Gow, D. & Makris, N. (1995). Analysis of lesions by MRI in stroke patients with acoustic-phonetic processing deficits. Neurology, 45: 293 - 298.G Hickok, D Poeppel (2000). Towards a functional neuroanatomy of speech perception Trends in Cognitive Sciences, 4 (4), 131-138 DOI: 10.1016/S1364-6613(00)01463-7Gregory Hickok, David Poeppel (2007). The cortical organization of speech processing Nature Reviews Neuroscience, 8 (5), 393-402 DOI: 10.1038/nrn2113G MICELI, G GAINOTTI, C CALTAGIRONE, C MASULLO (1980). Some aspects of phonological impairment in aphasia*1 Brain and Language, 11 (1), 159-169 DOI: 10.1016/0093-934X(80)90117-0... Read more »

Elizabeth Bates, Stephen M. Wilson, Ayse Pinar Saygin, Frederic Dick, Martin I. Sereno, Robert T. Knight, & Nina F. Dronkers. (2003) Voxel-based lesion–symptom mapping. Nature Neuroscience. DOI: 10.1038/nn1050

S Blumstein, W Cooper, E Zurif, & A Caramazza. (1977) The perception and production of Voice-Onset Time in aphasia. Neuropsychologia, 15(3), 371-372. DOI: 10.1016/0028-3932(77)90089-6

G Hickok, & D Poeppel. (2000) Towards a functional neuroanatomy of speech perception. Trends in Cognitive Sciences, 4(4), 131-138. DOI: 10.1016/S1364-6613(00)01463-7

Gregory Hickok, & David Poeppel. (2007) The cortical organization of speech processing. Nature Reviews Neuroscience, 8(5), 393-402. DOI: 10.1038/nrn2113

G MICELI, G GAINOTTI, C CALTAGIRONE, & C MASULLO. (1980) Some aspects of phonological impairment in aphasia*1. Brain and Language, 11(1), 159-169. DOI: 10.1016/0093-934X(80)90117-0

February 19, 2009
02:28 PM
1,240 views

Reflections on mirror neurons and speech perception

by Greg Hickok in Talking Brains

In the very first empirical report of mirror neurons di Pellegrino, Fadiga, Gallese, & Rizzolatti (1992) noted the surface similarity between mirror neurons and the motor theory of speech perception. [the invariance of the acoustic patterns of speech] led several authors to propose that the objects of speech perception were to be found not in the sound, but in the phonetic gesture of the speaker, represented in the brain as invariant motor commands (see Liberman and Mattingly 1985). Although our observations by no means prove motor theories of perception, nevertheless they indicate that in the premotor cortical areas there are neurons which are endowed with properties that such theories require. -di Pellegrino et al., 1992By 1992 the motor theory of speech perception was effectively dead in the world of speech science due to extensive empirical work that undermined many of its claims. However, the discovery of mirror neurons, their interpretation as supporting action understanding, and their suggested link to speech resuscitated the motor theory of speech perception -- at least among non-speech scientists.So does the discovery of mirror neurons in fact provide any new support for the motor theory of speech perception? This is the question we (Andre Lotto, Greg Hickok, & Lori Holt) tackled in a Trends in Cognitive Science paper that has just recently become available as an e-pub. Short answer: no. See the abstract below for a slightly longer summary, and the paper for the details. Abstract. The discovery of mirror neurons, a class of neurons that respond when a monkey performs an action and also when the monkey observes others producing the same action, has promoted a renaissance for the Motor Theory (MT) of speech perception. This is because mirror neurons seem to accomplish the same kind of one to one mapping between perception and action that MT theorizes to be the basis of human speech communication. However, this seeming correspondence is superficial, and there are theoretical and empirical reasons to temper enthusiasm about the explanatory role mirror neurons might have for speech perception. In fact, rather than providing support for MT, mirror neurons are actually inconsistent with the central tenets of MT.ReferencesG. Pellegrino, L. Fadiga, L. Fogassi, V. Gallese, G. Rizzolatti (1992). Understanding motor events: a neurophysiological study Experimental Brain Research, 91 (1) DOI: 10.1007/BF00230027Andrew J. Lotto, Gregory S. Hickok, Lori L. Holt (2009). Reflections on mirror neurons and speech perception Trends in Cognitive Sciences DOI: 10.1016/j.tics.2008.11.008... Read more »

G. Pellegrino, L. Fadiga, L. Fogassi, V. Gallese, & G. Rizzolatti. (1992) Understanding motor events: a neurophysiological study. Experimental Brain Research, 91(1). DOI: 10.1007/BF00230027

Andrew J. Lotto, Gregory S. Hickok, & Lori L. Holt. (2009) Reflections on mirror neurons and speech perception. Trends in Cognitive Sciences. DOI: 10.1016/j.tics.2008.11.008

December 10, 2008
04:10 PM
1,199 views

Stuttering, the planum temporale, and delayed auditory feedback

by Greg Hickok in Talking Brains

This is a follow up to my previous post on the (reduced) effect of delayed auditory feedback (DAF) in conduction aphasia. Here we consider the possible relation between anatomical abnormalities in the planum temporale and DAF in stutterers. Paradoxically, DAF can improve fluency in people who stutter (it decreases fluency in control subjects). Some stutterers also have an anatomically atypical planum temporale. A study published in Neurology by Foundas et al. (2004) sought to determine whether there was a relation between the paradoxical DAF effect and planum temporale anatomy. There was: stutterers with atypical planum temporale asymmetries (RL) showed the paradoxical DAF effect, whereas stutterers with typical planum asymmetries did not show the paradoxical DAF effect. This line of investigation provides a further bit of evidence linking an auditory-motor integration system to the planum temporale. Our functionally defined area Spt (e.g., Hickok et al., 2003), which we believe supports auditory-motor integration, is located in the posterior portion of the left planum temporale. I suspect that it is this region that is somehow implicated in stuttering. Why the symptoms of conduction aphasia and developmental stuttering are different is an important question (assuming that some aspect of the same system is involved)...Other disorders have been linked to planum temporale (dys)function including dyslexia, schizophrenia, and autism. I seriously doubt that dysfunction of the auditory-motor integration system involving the planum is going to explain the speech/auditory symptoms of all these disorders as there are probably lots of ways to disrupt speech/auditory functions. Following the example in the Foundas et al. study, I wonder if planum temporale atypicalities plus DAF effects might be used in combination to better characterize what might be going on in these disorders. ReferencesA. L. Foundas, MD, A. M. Bollich, PhD, J. Feldman, MD, D. M. Corey, PhD, M. Hurley, PhD, L. C. Lemen, PhD and K. M. Heilman, MD (2004). Aberrant auditory processing and atypical planum temporale in developmental stuttering Neurology, 63, 1640-1646Gregory Hickok, Bradley Buchsbaum, Colin Humphries, Tugan Muftuler (2003). Auditory–Motor Interaction Revealed by fMRI: Speech, Music, and Working Memory in Area Spt Journal of Cognitive Neuroscience, 15 (5), 673-682 DOI: 10.1162/089892903322307393M LINCOLN, A PACKMAN, M ONSLOW (2006). Altered auditory feedback and the treatment of stuttering: A review Journal of Fluency Disorders, 31 (2), 71-89 DOI: 10.1016/j.jfludis.2006.04.001... Read more »

A. L. Foundas, MD, A. M. Bollich, PhD, J. Feldman, MD, D. M. Corey, PhD, M. Hurley, PhD, L. C. Lemen, PhD and K. M. Heilman, MD. (2004) Aberrant auditory processing and atypical planum temporale in developmental stuttering. Neurology, 1640-1646. DOI: http://www.neurology.org/cgi/content/abstract/63/9/1640?maxtoshow

Gregory Hickok, Bradley Buchsbaum, Colin Humphries, & Tugan Muftuler. (2003) Auditory–Motor Interaction Revealed by fMRI: Speech, Music, and Working Memory in Area Spt. Journal of Cognitive Neuroscience, 15(5), 673-682. DOI: 10.1162/089892903322307393

M LINCOLN, A PACKMAN, & M ONSLOW. (2006) Altered auditory feedback and the treatment of stuttering: A review. Journal of Fluency Disorders, 31(2), 71-89. DOI: 10.1016/j.jfludis.2006.04.001

September 25, 2008
02:08 PM
1,193 views

Broca's area, sentence comprehension, and working memory

by Greg Hickok in Talking Brains

Broca's area shows a "sentence complexity" effect. It responds more during the comprehension of object relative (OR) constructions than easier to process subject relative (SR) constructions:OR: The man that the boy pushes is wearing a red shirtSR: The man that pushes the boy is wearing a red shirtWhat is driving the complexity effect? Presumably it is some form of working memory. In the case of OR sentences, you have to hold two items in memory -- the man, the boy -- before you get to the verb that tells you the role these items will play in the sentence. In SR sentences, you only have one item in memory -- the man -- before you encounter the verb which establishes the role of the noun phrase. But what is the nature of this working memory process? It is a syntactic-specific form of working memory? Or is it an ordinary, domain-general form of working memory, like Baddeley's phonological loop?David Caplan and colleagues (2000) addressed this issue a while ago in an imaging study that tested for the existence of a sentence complexity effect in Broca's area under conditions of articulatory suppression (subject was continuously articulating a phrase). This manipulation effectively eliminates articulatory rehearsal, a major component of phonological working memory. If the sentence complexity effect in Broca's area was due to phonological working memory -- the articulatory rehearsal component in particular -- then no complexity effect should be evident during articulatory suppression. Caplan et al. reported a complexity effect in Broca's area even during articulatory suppression, however, and so they concluded that the effect was due to "processing syntactic forms themselves" rather than to articulatory rehearsal/phonological working memory. I like Caplan et al. study, but it doesn't convince me fully that at least part of the complexity effect isn't due to phonological working memory. For one thing, they used written stimuli, and I'm never convinced that reading generalizes to auditory comprehension -- my primary interest. For another thing, the activation focus in Broca's area was very anterior, likely in the pars triangularis/BA45, not in the pars opercularis/BA44 which is more likely a site involved in articulatory rehearsal. Maybe a good chunk of the suppression effect in "Broca's area" -- usually defined as the combination of the two areas noted above -- IS driven by plain old articulatory rehearsal. Former TB West grad student, Corianne Rogalsky, decided to find out. We first conducted a simple behavioral experiment where undergrads were asked to comprehend sentences either during articulatory suppression, or while performing a control secondary task, finger tapping. During both secondary tasks, subjects were basically at ceiling for active sentences, passive-voice sentences, and SR sentences, but performance dropped off for OR sentences, as expected. Importantly, performance was significantly worse on OR sentences during articulatory suppression compared to finger tapping, indicating that articulatory suppression was interfering with "complex" sentence comprehension above and beyond the general effects of performing two tasks at once. So, articulatory rehearsal seems to be involved in comprehending OR sentences. What is the role of Broca's area in these effects? We used fMRI to find out. Subjects listened to SR or OR sentences and made semantic plausibility judgments about them during articulatory suppression, finger tapping, or without any secondary task. We also mapped the activation patterns associated with the secondary tasks alone. Without any concurrent task, we found a robust sentence complexity effect in Broca's area, that included both the pars triangularis and pars opercularis:During articulatory suppression, much of the complexity effect disappeared, leaving only a focus in the pars triangularis similar to Caplan et al.'s finding:Somewhat unexpectedly, finger tapping also led to an elimination of much of the complexity effect activation in Broca's area, although with a very different distribution. Now the complexity effect is evident in the pars opercularis:This pars opercularis focus, but not the triangularis focus, was also strongly activated by the articulatory suppression task alone, indicating that this more posterior portion of Broca's region is the IFG correlate of articulatory rehearsal, as previous work has indicated. So what does all this mean? First, we can conclude that plain old, domain-general articulatory rehearsal contributes to sentence comprehension under high load conditions (i.e., OR sentences), and at least part of the sentence complexity effect in Broca's area is attributable solely to articulatory rehearsal, namely the pars opercularis part. Second, we replicated Caplan's result showing that a portion of Broca's area, the pars triangularis, persists in showing a sentence complexity effect even during articulatory suppression. However, this effect was eliminated during concurrent finger tapping, possibly arguing against a syntactic specific interpretation of the sentence complexity effect in the pars-T. Oddly though, finger tapping alone didn't activate the pars-T, it just reduced the amplitude of the response to the OR sentences (without an obvious drop in behavioral performance). So the story on the pars opercularis seems clear: it supports articulatory rehearsal, which in turn supports the processing of high load sentences. But the story on Mr. T is mysterious. We're open to suggestions.ReferencesDavid Caplan, Nathaniel Alpert, Gloria Waters, Anthony Olivieri (2000). Activation of Broca's area by syntactic processing under conditions of concurrent articulation Human Brain Mapping, 9 (2), 65-71 DOI: 10.1002/(SICI)1097-0193(200002)9:23.0.CO;2-4Rogalsky C, Matchin W and Hickok G (2008) Broca's area, sentence comprehension, and working memory: an fMRI study. Front. Hum. Neurosci. doi:10.3389/neuro.09.014.2008... Read more »

David Caplan, Nathaniel Alpert, Gloria Waters, & Anthony Olivieri. (2000) Activation of Broca's area by syntactic processing under conditions of concurrent articulation. Human Brain Mapping, 9(2), 65-71. DOI: 10.1002/(SICI)1097-0193(200002)9:23.0.CO;2-4

February 20, 2009
11:33 AM
1,178 views

Lip reading involves two cortical mechansims

by Greg Hickok in Talking Brains

It is well known that visual speech (lip reading) affects auditory perception of speech. But how? There seem to be two ideas. One idea, dominant among sensory neuroscientists, is that visual speech accesses auditory speech systems via cross sensory integration. The STS is a favorite location in this respect. The other, dominant among speech scientists, particularly those with a motor theory bent, is that visual speech accesses motor representations of the perceived gestures which then influences perception. A hot-off-the-press (well actually still in press) paper in Neuroscience Letters by Kai Okada and yours truly proposes that both ideas are correct. Specifically, that there are two routes by which visual speech can influence auditory speech, a "direct" and dominant cross sensory route involving the STS, and an "indirect" and less dominant sensory-motor route involving sensory-motor circuits. The goal of our paper was to outline existing evidence in favor of a two mechanism model, and to test one prediction of the model, namely that perceiving visual speech should activate speech related sensory-motor networks, including our favorite area, Spt. Short version of our findings: as predicted, viewing speech gestures (baseline = non-speech gestures) activates speech-related sensory-motor areas including Spt as defined by a typical sensory-motor task (listen and reproduce speech). We interpret this as evidence for a sensory-motor route through which visual speech can influence heard speech, possibly via some sort of motor-to-sensory prediction mechanism. Viewing speech also activated a much broader set of regions along the STS, which may reflect the more direct cross sensory route. Have a look and let me know what you think!K OKADA, G HICKOK (2009). Two cortical mechanisms support the integration of visual and auditory speech: A hypothesis and preliminary data Neuroscience Letters DOI: 10.1016/j.neulet.2009.01.060... Read more »

K OKADA, & G HICKOK. (2009) Two cortical mechanisms support the integration of visual and auditory speech: A hypothesis and preliminary data. Neuroscience Letters. DOI: 10.1016/j.neulet.2009.01.060

September 11, 2008
04:28 PM
1,169 views

Do right motor cortex lesions cause verb processing impairments?

by Greg Hickok in Talking Brains

I'm still looking for compelling evidence that damage to the motor system affects verb processing. TMS data was not convincing, nor was ALS data (see previous posts). Now I'm looking at a lesion study by Neininger & Pulvermuller (2003, Word-category specific deficits after lesions in the right hemisphere. Neuropsychologia, 41:53-70), and I have to admit this is a reasonably impressive result -- but not exactly air tight. Twelve patients with right frontal lobe damage and left hemiparesis were studied, as well as six patients with damage to right inferior temporal-occipital regions. None of the patients were aphasic, consistent with the fact that the lesions were in the right hemisphere. A group of control patients were also tested. Nouns with strong visual associations and verbs with strong action associations were presented visually and subjects were asked to make a lexical decision on each item. A third category of words was included that they called "bimodal nouns" -- nouns with both strong visual and motor associations. The basic result was that frontal patients made significantly more lexical decision errors on verbs than on both categories of nouns, whereas the temporal-occipital patients made more errors on visual nouns than on verbs, and on visual nouns than bimodal nouns. Controls showed no differences. In reaction time data, there was an overall difference between bimodal nouns and action verbs, but no other effects. In sum, they got a nice double-dissociation in accuracy data, with frontal lesions impairing action verb judgments and temporal-occipital lesions impairing visual noun judgments. No such effect was seen in the RT data, however.We could quibble about why the effect wasn't seen in RT data when such an effect would be expected (in fact both the frontal and the temp-occ groups were actually numerically slower on the verb than noun stimuli), or with the fact that three of the right frontal patients were ambidextrous, or with the fact that two of the temp-occ patients had sensory-motor defects. But let's take the result as valid with this set of patients.There are a couple of problems. One is the varied location of the lesions, particularly in the frontal group. Eight of the 12 "frontal" patients had involvement of the temporal lobe, and seven had parietal lobe involvement. All had damage to the basal ganglia. No individual accuracy data was reported. To what extent can we attribute the pattern of errors to "motor cortex" let alone the frontal lobe? We can't. We can conclude that large middle cerebral artery infarcts in the right hemisphere can cause patients to make lexical decision errors on action verbs relative to nouns. This is interesting, but not exactly solid evidence for the view that motor systems support action word processing. Another problem, which underscores problem number one, is that TMS data from Pulvermuller's group appears to refute the involvement of right motor cortex in action word processing. In the study highlighted in the previous blog entry, TMS to right motor cortex did not lead to any effect on lexical decision responses, unlike the reported effect in the left hemisphere. Apparently, something else is going on in the case of large MCA lesions.B Neininger (2003). Word-category specific deficits after lesions in the right hemisphere Neuropsychologia, 41 (1), 53-70 DOI: 10.1016/S0028-3932(02)00126-4... Read more »

B Neininger. (2003) Word-category specific deficits after lesions in the right hemisphere. Neuropsychologia, 41(1), 53-70. DOI: 10.1016/S0028-3932(02)00126-4

April 21, 2009
02:06 PM
1,168 views

Einstein's brain: anomalous auditory/language dorsal stream

by Greg Hickok in Talking Brains

A forthcoming paper in Frontiers in Evolutionary Neuroscience by Dean Falk shows that Albert Einstein's brain had some rare anatomical anomalies involving language-related sensory-motor areas, regions I consider to be part of the auditory "dorsal stream" -- or more accurately, the vocal-tract sensory-motor integration circuit (Hickok & Poeppel, 2007; Pa & Hickok, 2008). Falk suggests that these anomalies may be related to Einstein's reported delay in language development as well as to his self-reported tendency to use visual imagery over audio-verbal imagery. Falk analyzed gross anatomical features of Einstein's brain from photographs. He reported atypicalities in the pre- and post-central gyrus region, but most striking to my eye is the tangled mess of Einstein's posterior Sylvian region. His post central sulcus (Pti) extends into the Sylvian fissure at which point the Sylvian seems to just end. It would seem that this arrangement destroys the typical configuration of the planum temporale, parietal operculum, and the entire supramarginal gyrus. In fact, Falk suggest that Einstein's BA40 (the supramarginal gyrus) is split into two parts as indicated on the rendering from Falk's paper where A is the typical arrangement and B is Einstein's.It is not clear at all where sensory-motor area Spt (Hickok et al. 2009) might be in this pattern. We have suggested that area Spt, as part of a sensory-motor integration circuit, is critical for speech development (Hickok & Poeppel, 2007), but there is little direct evidence on this point. I'm not sure I would count Einstein's anomalies in this region and associated language delay as evidence, but it is an interesting observation. ReferencesFalk D (2009) New Information about Albert Einstein's Brain. Front. Evol. Neurosci. doi:10.3889/neuro.18.003.2009Hickok, G., Okada, K., & Serences, J. (2008). Area Spt in the Human Planum Temporale Supports Sensory-Motor Integration for Speech Processing Journal of Neurophysiology, 101 (5), 2725-2732 DOI: 10.1152/jn.91099.2008Hickok, G., & Poeppel, D. (2007). The cortical organization of speech processing Nature Reviews Neuroscience, 8 (5), 393-402 DOI: 10.1038/nrn2113PA, J., & HICKOK, G. (2008). A parietal–temporal sensory–motor integration area for the human vocal tract: Evidence from an fMRI study of skilled musicians Neuropsychologia, 46 (1), 362-368 DOI: 10.1016/j.neuropsychologia.2007.06.024... Read more »

Hickok, G., Okada, K., & Serences, J. (2008) Area Spt in the Human Planum Temporale Supports Sensory-Motor Integration for Speech Processing. Journal of Neurophysiology, 101(5), 2725-2732. DOI: 10.1152/jn.91099.2008

Hickok, G., & Poeppel, D. (2007) The cortical organization of speech processing. Nature Reviews Neuroscience, 8(5), 393-402. DOI: 10.1038/nrn2113

PA, J., & HICKOK, G. (2008) A parietal–temporal sensory–motor integration area for the human vocal tract: Evidence from an fMRI study of skilled musicians. Neuropsychologia, 46(1), 362-368. DOI: 10.1016/j.neuropsychologia.2007.06.024

March 3, 2009
06:41 PM
1,148 views

Neural mechanisms underlying auditory feedback control of speech

by Greg Hickok in Talking Brains

Auditory feedback is an important aspect of speech production. Delayed auditory feedback results in non-fluencies, and altered speech feedback, e.g., shifting fundamental frequency, results in compensatory speech adjustments opposite the direction of the alteration. What is the neural mechanism underlying this system? That was the question addressed in a recent report by Tourville, Reilly, & Guenther (2008).The design of their fMRI experiment was straightforward. Subjects produced words under two conditions, (i) normal auditory feedback and (ii) auditory feedback in which the first formant frequency of their speech was shifted either up or down in real time. As expected subjects compensated for this shift rapidly, within about 100 msec. To identify the brain regions involved in this processes Tourville et al. compared the shifted speech condition with the non-shifted speech condition. Here's what they found:It is no surprise that auditory cortex is involved in registering the shift; it is perhaps interesting that a good chunk of right STG is highlighted in this pitch shift manipulation. The involvement of right pre-motor cortex is a bit of a mystery... But what I'm most excited about is the location of the major blob of activation in the left hemisphere. This seems to be centered right over area Spt, which of course is the region I believe supports sensory-motor integration for speech and related functions (i.e., it translates between sensory and motor speech representations). The observation that this area is involved in auditory feedback control fits perfectly with this view. After all, sensory-motor integration is critically involved in auditory feedback control of speech. My previous posts on the link between delayed auditory feedback and this left planum temporale region converge nicely with this new study. I highly recommend having a close look at this paper. There's a lot more in it than I have the energy to outline here, including a nice computational model (Guenther's DIVA model), structural equation modeling, and very useful literature review. ReferencesJ TOURVILLE, K REILLY, F GUENTHER (2008). Neural mechanisms underlying auditory feedback control of speech NeuroImage, 39 (3), 1429-1443 DOI: 10.1016/j.neuroimage.2007.09.054... Read more »

J TOURVILLE, K REILLY, & F GUENTHER. (2008) Neural mechanisms underlying auditory feedback control of speech. NeuroImage, 39(3), 1429-1443. DOI: 10.1016/j.neuroimage.2007.09.054

October 2, 2008
05:57 PM
1,141 views

More evidence for a sensory-motor interface in the posterior planum temporale region (area Spt)

by Greg Hickok in Talking Brains

We have argued previously that the posterior-medial planum temporale is not part of auditory cortex, but instead is multisensory and subserves sensory-motor integration, much like sensory-motor integration areas in the parietal lobe (Pa & Hickok, 2008). (See also a previous post on the topic.) A new paper by Novraj Dhanjal, Richard Wise, and colleagues in J. Neurosci. provides additional evidence for this view. In an fMRI experiment, they had subjects produce speech (either count or produce propositional utterances) or, in other conditions, make silent repetitive jaw or tongue movements. One would expect a sensory-motor integration area to show somatosensory responses during articulation as this is useful information in movement control (it helps to know where your articulators are), and indeed, sensory-motor integration areas in the parietal lobe of human and non-human primates, areas such as saccade-related LIP and the parietal reach region (PRR), show somato responses. So does area Spt show somatosensory responses? Yes, according to this new study. The medial planum temporale activated for both the speech articulation and mouth movement conditions, whereas other speech-related areas such as the lateral STG/STS only activated for the speech conditions. So now we have direct evidence that this portion of the planum temporale is multisensory, as our hypothesis predicts. This is also consistent with evidence from animal studies which have found that the posterior supratemporal plane in monkeys shows multisensory properties (Hackett, et al., 2007). ReferencesN. S. Dhanjal, L. Handunnetthi, M. C. Patel, R. J. S. Wise (2008). Perceptual Systems Controlling Speech Production Journal of Neuroscience, 28 (40), 9969-9975 DOI: 10.1523/JNEUROSCI.2607-08.2008Troy A. Hackett, Lisa A. De La Mothe, Istvan Ulbert, George Karmos, John Smiley, Charles E. Schroeder (2007). Multisensory convergence in auditory cortex, II. Thalamocortical connections of the caudal superior temporal plane The Journal of Comparative Neurology, 502 (6), 924-952 DOI: 10.1002/cne.21326J PA, G HICKOK (2008). A parietal–temporal sensory–motor integration area for the human vocal tract: Evidence from an fMRI study of skilled musicians Neuropsychologia, 46 (1), 362-368 DOI: 10.1016/j.neuropsychologia.2007.06.024... Read more »

N. S. Dhanjal, L. Handunnetthi, M. C. Patel, & R. J. S. Wise. (2008) Perceptual Systems Controlling Speech Production. Journal of Neuroscience, 28(40), 9969-9975. DOI: 10.1523/JNEUROSCI.2607-08.2008

Troy A. Hackett, Lisa A. De La Mothe, Istvan Ulbert, George Karmos, John Smiley, & Charles E. Schroeder. (2007) Multisensory convergence in auditory cortex, II. Thalamocortical connections of the caudal superior temporal plane. The Journal of Comparative Neurology, 502(6), 924-952. DOI: 10.1002/cne.21326

J PA, & G HICKOK. (2008) A parietal–temporal sensory–motor integration area for the human vocal tract: Evidence from an fMRI study of skilled musicians. Neuropsychologia, 46(1), 362-368. DOI: 10.1016/j.neuropsychologia.2007.06.024

April 16, 2009
09:12 PM
1,125 views

Broca's area: It's a dessert topping! No it's a floor wax! No it's a cognitive control mechanism!

by Greg Hickok in Talking Brains

Debates over the function of Broca's area remind me of the old Saturday Night Live skit where a husband (Dan Aykroyd) and wife (Gilda Radner) are arguing about whether a product, "New Shimmer" is a dessert topping or a floor wax: Wife: New Shimmer is a floor wax! Husband: No, new Shimmer is a dessert topping! Wife: It's a floor wax! Husband: It's a dessert topping! Wife: It's a floor wax, I'm telling you! The spokesman (Chevy Chase) quickly enters at this point and says: Hey, hey, hey, calm down, you two. New Shimmer is both a floor wax and a dessert topping! With respect to Broca's area we're in the middle of an even more complicated argument. Grodzinsky: It's syntactic movement!Friederici: It's a hierarchical structure processor!Rogalsky/Hickok: It's articulatory rehearsal (at least in the back part)!Rizzolatti/Fadiga: It's action understanding!To this argument we can add another view; one that doesn't get talked about as much. Novick, Trueswell, Thompson-Schill: It's a cognitive control mechanism!This is an interesting claim and I wonder to what extent "cognitive control" may be our Chevy Chase, telling us that Broca's area can do more than one thing.Of course, I think at least some of these territorial claims to Broca's area will be resolved simply by mapping these various functions (within subjects) to the different subregions that comprise the foot of the third frontal convolution. But we won't worry about those details at this point. For now let's just see what Novick et al. suggest.First, Novick et al. are addressing the claim that Broca's area is specifically involved in syntactic computation or in the temporary storage of syntactic information. They are not trying to address the many other claims. This is fine, but eventually we'll have to deal with the full range of data.Now, what do they mean by cognitive control. Well, basically it is a mechanism for conflict resolution. Ok, what's that? The define conflict as:...cases in which an individual receives incompatible information either about how best to characterize a stimulus or how best to respond to that stimulus. p. 265They mention the Stroop task as a classic example. So cognitive control in this context would be the process of shifting attention toward task-relevant stimulus characteristics in order to override automatically generated but currently irrelevant representations (paraphrased from page 265). What's the link to Broca's area? Well, incongruent trials on Stroop tasks activate Broca's area as does the processing or gardenpath sentences which requires resolution of syntactic ambiguity (conflict). Lesion and individual difference data are also presented along these lines. A subsequent empirical study by this group found that Stroop tasks and syntactic ambiguity resolution co-localize in Broca's area (January, Trueswell, & Thompson-Schill, in press, Journal of Cognitive Neuroscience). I don't think necessarily that this hypothesis is going to solve the problem of what Broca's area is doing -- it's not going to be that simple. For example, it doesn't explain why portions of Broca's area activates during simple articulatory rehearsal. But there is enough evidence that this sort of claim needs to be included in the discussion. Importantly, mechanisms such as this need to be considered when discussing the role of "motor areas" -- Broca's being a centerpiece in the mirror neuron "motor system" -- in speech perception. I suggested in my critique of D'Ausilio et al.'s paper that motor speech systems may influence perception in the following way:motor and perceptual information may converge on higher-order executive processes where this information is used to color decision-making processesThis may be particularly relevant in situations where the speech stimuli are ambiguous, as in the noise degraded stimuli of D'Ausilio et al.They responded to this suggestion by saying that this...interpretation reminds [us of] 18-19th century models of the human mind, in the sense that requires an additional functional moduleI'm no expert but my guess is that folks who study decision making for a living might argue (convincingly) that such as system is needed on independent grounds. In any case, the point is that "Broca's area" may be involved in certain functions that could be considered "executive" and one shouldn't be to hasty to ascribe a motor explanation to everything that happens in Broca's area.NOVICK, J., TRUESWELL, J., & THOMPSON-SCHILL, S. (2005). Cognitive control and parsing: Reexamining the role of Broca's area in sentence comprehension Cognitive, Affective, & Behavioral Neuroscience, 5 (3), 263-281 DOI: 10.3758/CABN.5.3.263... Read more »

NOVICK, J., TRUESWELL, J., & THOMPSON-SCHILL, S. (2005) Cognitive control and parsing: Reexamining the role of Broca's area in sentence comprehension. Cognitive, Affective, , 5(3), 263-281. DOI: 10.3758/CABN.5.3.263

October 14, 2008
07:08 PM
1,101 views

Does Parkinson's disease impair action verb processing?

by Greg Hickok in Talking Brains

I've been slogging through the evidence typically cited as support for an embodied cognition view of language processing. Much of this research focuses on processing actions verbs, which according to the "EC" view, critically involve motor representations as part of their semantics. In previous posts I've discussed studies that use TMS, ALS, and stroke data to make the case for an embodied view of action word processing. None of it, I argued, was particularly compelling. Here we have a close look at a recent paper involving Parkinson's disease (PD) patients (Boulenger et al., 2008). These authors used a lexical-decision, masked, identity-priming paradigm: primes were identical to targets (= identity-priming) and were presented rapidly, followed by a mask which precludes conscious awareness of the prime (= masked); priming effects were assessed relative to a control condition where the "prime" was a string of consonants. Priming was compared for visually presented nouns and verbs in PD patients both on and off medication. This is an interesting design because it allowed the team to assess processing when the basal ganglia circuit was relatively functional compared to when it was not. Control subjects were also tested. So what did they find? On medication, PD patients showed priming for both nouns and verbs (middle panel in figure below), whereas off medication, PD patients only showed priming for nouns. Since nouns primed even off medication, this argues against generalized attentional, perceptual, etc. explanations of the failure of verbs to prime off medication.(White circles are nouns, black circles are verbs.)This is a pretty cool result and is interpreted as "compelling evidence that processing lexico-semantic information about action words depends on the integrity of the motor system" (p. 743). I beg to differ.First, PD is NOT limited to the motor system. In fact, Boulenger et al. point out that "deficits in cognitive functions and subtle semantic language deficits have also been reported" (p. 744). It is impossible to know whether the failure to show priming effects is strictly a matter of motor dysfunction, or whether it stems from disruption of other functions supported by basal ganglia circuits. This is a point similar to one I raised in connection with ALS: just because a prominent symptom of a disease is motor, doesn't mean that the motor deficit is causing all the symptoms.Second, depending on what you focus on in the reaction time data, the pattern of results could either support a verb processing deficit or a noun processing deficit. Have a look at the top "Patients OFF" panel in the graph above. While it is clear that nouns are priming and verbs are not, it is also the case that RTs to nouns are quite a bit slower than RTs to verbs in the control, unprimed condition (left side of graph). This is puzzling given that ON medication, the PD patients showed no RT difference to the same nouns vs. the same verbs. So one way to look at the result is that being off medication causes a selective deficit in noun processing relative to verb processing! How do we reconcile these two interpretations? I don't know. It depends on which measure (raw recognition time vs. priming) is a better measure of "lexico-semantic" processing. Sometimes it helps to re-state the findings without all the interpretive baggage. Assuming that basal ganglia dysfunction is exaggerated when the PD patients are off Levodopa medication, the present study leads to the following conclusions: 1. Basal ganglia dysfunction reduces the masked-primer induced pre-activation of essential parts of the cerebral networks for verb (but not noun) processing. (This is a paraphrase of the underlying mechanism of masked priming as provided by the authors on page 744.)2. Basal ganglia dysfunction slows the ability to recognize nouns relative to verbs in a lexical decision task. Maybe priming-related pre-activation is a critical function of lexico-semantic networks, but it seems to me that slowed recognition is a bad thing as well, maybe even worse. Still, I don't know whether PD causes noun or verb problems (or both).More generally, I'm beginning to wonder what lexical decision effects in these sorts of studies are actually telling us. On the one hand, it is possible to argue that lexical decision provides a highly sensitive measure of aspects of language processing, some of which are automatic and unconscious. In this sense, it seems like a good task. On the other hand, we don't normally walk around making lexical decisions on visually presented words. Does this task involve meta-linguistic processes that aren't normally involved in noun and verb processing? Is it a modality-specific (i.e., reading-related) effect? Note that modality-specific verb deficits have been reported (Hillis, et al. 2002).So while the findings are certainly interesting, and add to the large literature demonstrating dissociations between noun and verb processing, the Boulenger et al. paper is not "compelling evidence" for motor involvement in action verb processing. We don't know that it is the motor system that is causing the problem, the results suggest the possibility of a selective noun deficit, and it is not clear what the task is measuring. ReferencesBoulenger, V., Mechtouff, L., Thobois, S., Broussolle, E., Jeannerrod, M., Nazir, T.A. (2008). Word processing in Parkinson's disease is impaired for action verbs but not for concrete nouns Neuropsychologia, 46 (2), 743-756 DOI: 10.1016/j.neuropsychologia.2007.10.007Argye E. Hillis, Elizabeth Tuffiash, Alfonso Caramazza (2002). Modality-Specific Deterioration in Naming Verbs in Nonfluent Primary Progressive Aphasia Journal of Cognitive Neuroscience, 14 (7), 1099-1108 DOI: 10.1162/089892902320474544... Read more »

Boulenger, V., Mechtouff, L., Thobois, S., Broussolle, E., Jeannerrod, M., & Nazir, T.A. (2008) Word processing in Parkinson's disease is impaired for action verbs but not for concrete nouns. Neuropsychologia, 46(2), 743-756. DOI: 10.1016/j.neuropsychologia.2007.10.007

Argye E. Hillis, Elizabeth Tuffiash, & Alfonso Caramazza. (2002) Modality-Specific Deterioration in Naming Verbs in Nonfluent Primary Progressive Aphasia. Journal of Cognitive Neuroscience, 14(7), 1099-1108. DOI: 10.1162/089892902320474544

January 8, 2009
12:50 PM
1,101 views

Functional organization of the planum temporale

by Greg Hickok in Talking Brains

This is the title of a talk I'm giving at the Auditory Cognitive Neuroscience Society meeting tomorrow in Tucson. What I'm going to argue is that there is no such thing. Let me explain...The planum temporale is a gross anatomical feature. Although it is often referred to and studied as a functional region -- e.g., The Planum Temporale as a Computational Hub (Griffiths and Warren, 2002) among many other papers -- there is no evidence to support this view. Cytoarchitectonic data indicate at least four distinct fields within the PT that themselves do not respect the anatomical boundaries of the region; i.e., the cytoarchitectonic areas extend beyond the PT to include the lateral STG, parietal operculum, and supramarginal gyrus. Further, although the PT is often referred to as "auditory cortex" only the anterior portion of it appears to be auditory cortex proper.In other words, the PT is not a functionally unitary region, and we should stop trying to characterize it as such. Griffiths and Warren (2002) noticed correctly that a range of different types of stimuli can activate the PT. To account for this observation they proposed that the PT functions as a computational hub, which they envision as a kind of pattern matcher/router: various kinds of input come in and get sorted and routed to the appropriate processing systems. I've looked closely at two functions that have consistently implicated the PT region, spatial hearing and sensory-motor integration. It turns out that if you look at the activation maps associated with these two functions on a within subject basis, they lite up distinct areas of the PT region. Spatial hearing-related activations (listening to sounds coming from a variety of spatial locations from a single location) activate a more anterior location that is likely within the auditory cortex portion of the PT and the sensory motor activations (regions that activate both during the perception and covert production of speech) are more posterior, likely within the non-auditory regions of the PT. This kind of result provides further evidence for a functionally heterogenous PT, and argues against hypotheses like the Griffith and Warren's computational hub. T Griffiths, J Warren (2002). The planum temporale as a computational hub Trends in Neurosciences, 25 (7), 348-353 DOI: 10.1016/S0166-2236(02)02191-4... Read more »

T Griffiths, & J Warren. (2002) The planum temporale as a computational hub. Trends in Neurosciences, 25(7), 348-353. DOI: 10.1016/S0166-2236(02)02191-4

September 11, 2008
05:00 PM
1,069 views

Lipstick on a pig: a neural perspective

by Greg Hickok in Talking Brains

Abstract. Purpose: To investigate the effects of political party affiliation on the interpretation of metaphoric expressions. Approach: Millions of subjects were exposed to a single metaphor, "You can put lipstick on a pig -- It's still a pig" and were asked to indicate the intended referent of the word, "pig." Data collection and analysis: Response data were collected via tedious monitoring of television news channels, particularly CNN, where interpretations of "pig" were offered (repeatedly) by a handful of "representative" subjects. Each responder was classified as belonging either to the Democratic or Republican party, and interpretations were tabulated. Results: Democrats uniformly interpreted "pig" to refer to John McCain's proposed policies, whereas Republicans uniformly interpreted "pig" to refer to Sarah Palin. Conclusion: metaphor interpretation is strongly influenced by political affiliation.There's only one problem with this study. In a less biased sample of subjects, including myself, a couple of acquaintances, and the audience at Obama's speech which roared with laughter at the comment and (reportly) began chanting "no more pit bull," even some democrats interpreted pig as referencing Sarah Palin. At the very least (admit it), you interpreted the comment as a reference to her pit bull, hockey mom, & lipstick joke. Here's why: Brains are pretty good at associative learning. Cream and _____, peanut butter and ____, and now, lipstick and _____ ... pit bulls? Sarah Palin? "Lipstick on a pig" was close enough to trigger the association with Sarah Palin and her lipstick joke. We can't help but think of it. It turns out as well, that there is some commonality in the brain basis for metaphor interpretation and associative learning. Metaphor interpretation compared to the interpretation of literal sentences consistently activates the left inferior frontal gyrus (BA 45/47 for you brain nerds) (Eviatar & Just, 2006; Rapp et al., 2004; Shibata, et al., 2007; Stringaris, et al. 2007). The same area also seems to be activated when subjects listen to phrases that violate semantic associations, such as She spread her bread with socks relative to phrases that are consistent with previous associations, She spread her bread with butter (Willems et al., 2008). This area is often interpreted as supporting the integration of semantic information. Other studies have shown that this inferior frontal gyrus region is involved in semantic memory for previously presented words: it responds differently to a word if that word was presented to the subject previously, even when days intervene between presentation (Meister et al., 2007). Given this patterns of results, it seems likely that this chunk of frontal cortex is involved in our association of Obama's pig and Palin's pit bull. Does this mean Obama was calling Palin a pig? Not necessarily. A metaphor isn't restricted to one meaning. It could have been a comment on McCain's more-of-the-same policies, and a jab at the lipstick joke. Whatever the intention, the comment certainly opened the door to Republican critics. Obama should have consulted with a language scientist... ReferencesZ EVIATAR, M JUST (2006). Brain correlates of discourse processing: An fMRI investigation of irony and conventional metaphor comprehension Neuropsychologia, 44 (12), 2348-2359 DOI: 10.1016/j.neuropsychologia.2006.05.007Ingo G. Meister, Dorothee Buelte, Roland Sparing, Babak Boroojerdi (2007). A repetition suppression effect lasting several days within the semantic network Experimental Brain Research, 183 (3), 371-376 DOI: 10.1007/s00221-007-1051-8A RAPP, Leube DT, Erb M, Grodd W, Kircher TT. (2004). Neural correlates of metaphor processing Cognitive Brain Research, 20 (3), 395-402 DOI: 10.1016/j.cogbrainres.2004.03.017M SHIBATA, J ABE, A TERAO, T MIYAMOTO (2007). Neural mechanisms involved in the comprehension of metaphoric and literal sentences: An fMRI study Brain Research, 1166, 92-102 DOI: 10.1016/j.brainres.2007.06.040.A STRINGARIS, N MEDFORD, V GIAMPIETRO, M BRAMMER, A DAVID (2007). Deriving meaning: Distinct neural mechanisms for metaphoric, literal, and non-meaningful sentences Brain and Language, 100 (2), 150-162 DOI: 10.1016/j.bandl.2005.08.001Willems RM, Ozyürek A, Hagoort P. (2008). Seeing and hearing meaning: ERP and fMRI evidence of word versus picture integration into a sentence context. J Cogn Neurosci. 20(7):1235-49.... Read more »

Z EVIATAR, & M JUST. (2006) Brain correlates of discourse processing: An fMRI investigation of irony and conventional metaphor comprehension. Neuropsychologia, 44(12), 2348-2359. DOI: 10.1016/j.neuropsychologia.2006.05.007

Ingo G. Meister, Dorothee Buelte, Roland Sparing, & Babak Boroojerdi. (2007) A repetition suppression effect lasting several days within the semantic network. Experimental Brain Research, 183(3), 371-376. DOI: 10.1007/s00221-007-1051-8

A RAPP, Leube DT, Erb M, Grodd W, & Kircher TT. (2004) Neural correlates of metaphor processing. Cognitive Brain Research, 20(3), 395-402. DOI: 10.1016/j.cogbrainres.2004.03.017

M SHIBATA, J ABE, A TERAO, & T MIYAMOTO. (2007) Neural mechanisms involved in the comprehension of metaphoric and literal sentences: An fMRI study. Brain Research, 92-102. DOI: 10.1016/j.brainres.2007.06.040

A STRINGARIS, N MEDFORD, V GIAMPIETRO, M BRAMMER, & A DAVID. (2007) Deriving meaning: Distinct neural mechanisms for metaphoric, literal, and non-meaningful sentences. Brain and Language, 100(2), 150-162. DOI: 10.1016/j.bandl.2005.08.001

December 10, 2008
03:08 PM
1,065 views

Conduction aphasia and delayed auditory feedback

by Greg Hickok in Talking Brains

Here's an interesting nugget of information: conduction aphasics appear to be less susceptible to the disruptive effect of delayed auditory feedback. Why is this interesting? Because it is more evidence for a link between systems supporting auditory-motor interaction and the deficit in conduction aphasia. Here are the details...Delayed auditory feedback (DAF) disrupts speech production. You can prove this to yourself either by trying to talk on a microphone in a large stadium (where your echo is delayed) or, if you don't regularly speak in large stadiums, you can simply talk to yourself on two cell phones: call one phone with the other, hold them both to your ears and start talking; there is a slight delay in transmission leading to delayed auditory feedback, and so speaking becomes difficult. DAF is strong evidence that auditory speech information interacts with speech production systems.While the classic view is that conduction aphasia is a disconnection syndrome resulting from damage to the arcuate fasciculus, this view is no longer tenable. I have been promoting the view that the syndrome results from damage to our favorite brain region, Spt, which we believe is a critical node in a network that supports auditory-motor interaction (e.g., see Hickok et al., 2000). This, we claim, explains why conduction aphasics make phonemic errors in production (because speech planning is guided to some degree by auditory speech systems) and why they have trouble with verbatim repetition under conditions of high phonological load such as with multisyllablic words, unfamiliar phrases, or non-words (because these kinds of stimuli maximally rely on sensory speech guidance). One prediction of this view is that conduction aphasics should exhibit other "symptoms" of a disrupted auditory-motor integration system.So I was digging through some old papers on conduction aphasia and came across two, both published by Francois Boller in 1978, that suggested that conduction aphasics are less susceptible to DAF than controls and patients with other aphasia types. One was a group study that found that conduction aphasics were the least affected by DAF of the groups studied (Boller, Vrtunski, Kim, & Mack, 1978), and the other was a case study showing no effect of DAF (and even some improvement!) on the repetition of speech in a conduction aphasic (Boller & Marcie, 1978). This decreased DAF effect in conduction aphasia makes sense if the system that supports auditory-motor interaction is disrupted in that syndrome. ReferencesF Boller, P Marcie (1978). Possible role of abnormal auditory feedback in conduction aphasia Neuropsychologia, 16 (4), 521-524 DOI: 10.1016/0028-3932(78)90078-7Boller, F., Vrtunski, B., Kim, Y., & Mack, J.L. (1978). Delayed auditory feedback and aphasia. Cortex, 14, 212-226.G Hickok, et al. (2000). A functional magnetic resonance imaging study of the role of left posterior superior temporal gyrus in speech production: implications for the explanation of conduction aphasia Neuroscience Letters, 287 (2), 156-160 DOI: 10.1016/S0304-3940(00)01143-5... Read more »

F Boller, & P Marcie. (1978) Possible role of abnormal auditory feedback in conduction aphasia. Neuropsychologia, 16(4), 521-524. DOI: 10.1016/0028-3932(78)90078-7

G Hickok, et al. (2000) A functional magnetic resonance imaging study of the role of left posterior superior temporal gyrus in speech production: implications for the explanation of conduction aphasia. Neuroscience Letters, 287(2), 156-160. DOI: 10.1016/S0304-3940(00)01143-5

December 8, 2008
05:44 PM
1,062 views

The Cortical Dynamics of Intelligible Speech

by Greg Hickok in Talking Brains

This is the title of a new paper in J. Neuroscience by Alexander Leff and company (Jennifer Crinion, Karl Friston, and Cathy Price among others) at the Wellcome Trust Centre, University College London. The report is beautifully straightforward and fills an important gap in our understanding of the pathways that support the processing of meaningful speech. They set out to test two competing hypotheses regarding information flow in the temporal and frontal lobes during the processing of intelligible speech. One hypothesis, put forward by Sophie Scott and Richard Wise, suggests that the pathway for intelligible speech projects anteriorly into the temporal lobe from primary auditory cortex. The other hypothesis, recently promoted by us (Hickok & Poeppel, 2000, 2004, 2007), but by no means unique to us (it is a rather conventional view), holds that the posterior STS is an important projection target for acoustic speech information on its way to being comprehended. Leff, et al. used fMRI to identify a network of brain regions active during the perception of intelligible speech, which was defined as regions that responded more to word pairs than to time reversed versions of word pairs. Here is a summary map of the regions activated by this contrast:They didn't see much bilateral activation (must be something in the London water because we have just finished a similar experiment and see TONS of activation on both sides -- more on this in the future), but that's not the point of the paper. Notice that there are foci of activation in the posterior as well as anterior STS, and an inferior frontal area as well that falls within BA47, outside of Broca's region. They then used dynamic causal modeling and Baysian parameter estimation to determine the model of information flow among these three nodes that best fit their data. Of 216 models tested -- all possible combinations of input (squares with arrows) and interactions between ROIs (dotted lines), diagram on left -- the winning model (right diagram) had sensory input entering the network only via pSTS and projecting in separate pathways to aSTS on the one hand and IFG on the other. In other words, information flow is not exclusively anterior from primary auditory cortex, nor is it flowing in parallel from A1 to aSTS and pSTS, but rather projects first posteriorly and then anteriorly within the temporal lobe; i.e., the ventral stream runs through the pSTS. In proposing an exclusively anterior-going pathway from primary auditory cortex, Scott and Wise were particularly persuaded by three observations. (i) monkey data suggested anterior projections from the auditory core, (ii) their own imaging data suggested an anterior focus of activity for intelligible versus unintelligible speech, and (iii) semantic dementia involves word level semantic deficits and has anterior temporal degeneration as a hallmark feature. Their proposal was quite reasonable in light of these facts, but it just didn't seem to pan out: (i) monkey data is useful as a guide, but may not generalize to humans especially when language systems are involved, (ii) subsequent experiments looking at intelligible speech, such as the present one, clearly identified posterior activation foci, and (iii) it seems that the deficit in semantic dementia is to some extent supramodal, i.e., may be well beyond the linguistic computations that appear to be supported by the pSTS, and lesion (stroke) evidence implicates posterior temporal regions in word-level semantic deficits. To be fair, we didn't completely predict the findings of the Leff, et al. study either. Specifically, we posited no direct projection from pSTS to aSTS, and discussed the function of the anterior temporal region in the context of grammatical type processes only. Neither did we discuss a direct influence of pSTS on the IFG (BA47) within the ventral stream. (Notice that this link does not, presumably, reflect the dorsal stream, which involves more posterior portions of the IFG and should not be a dominant node in network supporting language comprehension.)Know that we know a bit more about the nature of information flow in this network, it's time to try to figure out exactly what these different regions might be doing. Our suggestion regarding the posterior STS is that it supports phonological processing of some sort. This still makes sense I think. But what is the anterior STS doing? ReferencesA. P. Leff, T. M. Schofield, K. E. Stephan, J. T. Crinion, K. J. Friston, C. J. Price (2008). The Cortical Dynamics of Intelligible Speech Journal of Neuroscience, 28 (49), 13209-13215 DOI: 10.1523/JNEUROSCI.2903-08.2008Sophie K. Scott, C. Catrin Blank, Stuart Rosen and Richard J. S. Wise (2000) Identification of a pathway for intelligible speech in the left temporal lobe. Brain, Vol. 123, No. 12, 2400-2406... Read more »

A. P. Leff, T. M. Schofield, K. E. Stephan, J. T. Crinion, K. J. Friston, & C. J. Price. (2008) The Cortical Dynamics of Intelligible Speech. Journal of Neuroscience, 28(49), 13209-13215. DOI: 10.1523/JNEUROSCI.2903-08.2008

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