45 posts · 18,119 views
This blog will highlight and comment on current research and hypotheses relating to how the brain wires itself up during development, how the end result can vary in different people and what happens when it goes wrong. It will include discussions of the genetic and neurodevelopmental bases of traits such as intelligence and personality characteristics, as well as of conditions such as schizophrenia, autism, dyslexia, epilepsy, synaesthesia and others.
Kevin Mitchell
45 posts
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- August 11, 2011
- 04:06 AM
- 300 views
Split brains, autism and schizophrenia
by Kevin Mitchell in Wiring the Brain
A new study suggests that a gene known to be causally linked to schizophrenia and other psychiatric disorders is involved in the formation of connections between the two hemispheres of the brain. DISC1 is probably the most famous gene in psychiatric genetics, and rightly so. It was discovered in a large Scottish pedigree, where 18 members were affected by psychiatric disease.
The diagnoses ranged from schizophrenia and bipolar disorder to depression and a range of “minor” psychiatric con........ Read more »
Osbun N, Li J, O'Driscoll MC, Strominger Z, Wakahiro M, Rider E, Bukshpun P, Boland E, Spurrell CH, Schackwitz W.... (2011) Genetic and functional analyses identify DISC1 as a novel callosal agenesis candidate gene. American journal of medical genetics. Part A, 155(8), 1865-76. PMID: 21739582
Halgren C, Kjaergaard S, Bak M, Hansen C, El-Schich Z, Anderson CM, Henriksen KF, Hjalgrim H, Kirchhoff M, Bijlsma EK.... (2011) Corpus Callosum Abnormalities, Mental Retardation, Speech Impairment, and Autism in Patients with Haploinsufficiency of ARID1B. Clinical genetics. PMID: 21801163
- August 3, 2011
- 05:14 AM
- 391 views
Welcome to your genome
by Kevin Mitchell in Wiring the Brain
There is a common view that the human genome has two different parts – a “constant” part and a “variable” part. According to this view, the bases of DNA in the constant part are the same across all individuals. They are said to be “fixed” in the population. They are what make us all human – they differentiate us from other species. The variable part, in contrast, is made of positions in the DNA sequence that are “polymorphic” – they come in two or more different versio........ Read more »
Gravel S, Henn BM, Gutenkunst RN, Indap AR, Marth GT, Clark AG, Yu F, Gibbs RA, The 1000 Genomes Project, & Bustamante CD. (2011) Demographic history and rare allele sharing among human populations. Proceedings of the National Academy of Sciences of the United States of America, 108(29), 11983-11988. PMID: 21730125
Walsh CA, & Engle EC. (2010) Allelic diversity in human developmental neurogenetics: insights into biology and disease. Neuron, 68(2), 245-53. PMID: 20955932
McClellan, J., & King, M. (2010) Genetic Heterogeneity in Human Disease. Cell, 141(2), 210-217. DOI: 10.1016/j.cell.2010.03.032
- July 25, 2011
- 03:06 PM
- 257 views
Hallucinating neural networks
by Kevin Mitchell in Wiring the Brain
Hearing voices is a hallmark of schizophrenia and other psychotic disorders, occurring in 60-80% of cases. These voices are typically identified as belonging to other people and may be voicing the person’s thoughts, commenting on their actions or ideas, arguing with each other or telling the person to do something. Importantly, these auditory hallucinations are as subjectively real as any external voices. They may in many cases be critical or abusive and are often highly distressing to the........ Read more »
Hoffman, R., & Mcglashan, T. (2001) Book Review: Neural Network Models of Schizophrenia. The Neuroscientist, 7(5), 441-454. DOI: 10.1177/107385840100700513
Hoffman, R., & McGlashan, T. (2006) Using a Speech Perception Neural Network Computer Simulation to Contrast Neuroanatomic versus Neuromodulatory Models of Auditory Hallucinations. Pharmacopsychiatry, 54-64. DOI: 10.1055/s-2006-931496
- July 8, 2011
- 08:56 AM
- 402 views
Environmental influences on autism - splashy headlines from dodgy data
by Kevin Mitchell in Wiring the Brain
A couple of recent papers have been making headlines in relation to autism, one claiming that it is caused less by genetics than previously believed and more by the environment and the other specifically claiming that antidepressant use by expectant mothers increases the risk of autism in the child. But are these conclusions really supported by the data? Are they strongly enough supported to warrant being splashed across newspapers worldwide, where most readers will remember only the headlin........ Read more »
Hallmayer J, Cleveland S, Torres A, Phillips J, Cohen B, Torigoe T, Miller J, Fedele A, Collins J, Smith K.... (2011) Genetic Heritability and Shared Environmental Factors Among Twin Pairs With Autism. Archives of general psychiatry. PMID: 21727249
Lichtenstein P, Carlström E, Råstam M, Gillberg C, & Anckarsäter H. (2010) The genetics of autism spectrum disorders and related neuropsychiatric disorders in childhood. The American journal of psychiatry, 167(11), 1357-63. PMID: 20686188
Rosenberg, R., Law, J., Yenokyan, G., McGready, J., Kaufmann, W., & Law, P. (2009) Characteristics and Concordance of Autism Spectrum Disorders Among 277 Twin Pairs. Archives of Pediatrics and Adolescent Medicine, 163(10), 907-914. DOI: 10.1001/archpediatrics.2009.98
Croen LA, Grether JK, Yoshida CK, Odouli R, & Hendrick V. (2011) Antidepressant Use During Pregnancy and Childhood Autism Spectrum Disorders. Archives of general psychiatry. PMID: 21727247
- June 28, 2011
- 04:15 AM
- 366 views
Complex interactions among epilepsy genes
by Kevin Mitchell in Wiring the Brain
A debate has been raging over the last few years over the nature of the genetic architecture of so-called “complex” disorders. These are disorders - such as schizophrenia, epilepsy, type II diabetes and many others - which are clearly heritable across the population, but which do not show simple patterns of inheritance. A new study looking at the profile of mutations in hundreds of genes in patients with epilepsy dramatically illustrates this complexity. The possible implications are far........ Read more »
Klassen T, Davis C, Goldman A, Burgess D, Chen T, Wheeler D, McPherson J, Bourquin T, Lewis L, Villasana D.... (2011) Exome sequencing of ion channel genes reveals complex profiles confounding personal risk assessment in epilepsy. Cell, 145(7), 1036-48. PMID: 21703448
Kasperaviciute, D., Catarino, C., Heinzen, E., Depondt, C., Cavalleri, G., Caboclo, L., Tate, S., Jamnadas-Khoda, J., Chinthapalli, K., Clayton, L.... (2010) Common genetic variation and susceptibility to partial epilepsies: a genome-wide association study. Brain, 133(7), 2136-2147. DOI: 10.1093/brain/awq130
Mitchell KJ. (2011) The genetics of neurodevelopmental disease. Current opinion in neurobiology, 21(1), 197-203. PMID: 20832285
- June 21, 2011
- 08:10 AM
- 392 views
Synaesthesia and savantism
by Kevin Mitchell in Wiring the Brain
“We only use 10% of our brain”. I don’t know where that idea originated but it certainly took off as a popular meme – taxi drivers seem particularly taken with it. It’s rubbish of course – you use more than that just to see. But it captures an idea that we humans have untapped intellectual potential – that in each of us individually, or at least in humans in general lies the potential for genius. Part of what has fed into that idea is the existence of so-called “savants” ........ Read more »
Murray, A. (2010) Can the existence of highly accessible concrete representations explain savant skills? Some insights from synaesthesia. Medical Hypotheses, 74(6), 1006-1012. DOI: 10.1016/j.mehy.2010.01.014
Bor, D., Billington, J., & Baron-Cohen, S. (2008) Savant Memory for Digits in a Case of Synaesthesia and Asperger Syndrome is Related to Hyperactivity in the Lateral Prefrontal Cortex. Neurocase, 13(5), 311-319. DOI: 10.1080/13554790701844945
Simner, J., Mayo, N., & Spiller, M. (2009) A foundation for savantism? Visuo-spatial synaesthetes present with cognitive benefits. Cortex, 45(10), 1246-1260. DOI: 10.1016/j.cortex.2009.07.007
Yaro, C., & Ward, J. (2007) Searching for Shereshevskii: What is superior about the memory of synaesthetes?. The Quarterly Journal of Experimental Psychology, 60(5), 681-695. DOI: 10.1080/17470210600785208
- May 25, 2011
- 09:43 AM
- 209 views
Somatic mutations make twins’ brains less identical
by Kevin Mitchell in Wiring the Brain
There is a paradox at the heart of behavioural and psychiatric genetics. On the one hand, it is very clear that practically any psychological trait one cares to study is partly heritable - i.e., the differences in the trait between people are partly caused by differences in their genes. Similarly, psychiatric disorders are also highly heritable and, by now, mutations in hundreds of different genes have been identified that cause them. However, these studies also highlight the limits of geneti........ Read more »
Maiti S, Kumar KH, Castellani CA, O'Reilly R, & Singh SM. (2011) Ontogenetic de novo copy number variations (CNVs) as a source of genetic individuality: studies on two families with MZD twins for schizophrenia. PloS one, 6(3). PMID: 21399695
Piotrowski, A., Bruder, C., Andersson, R., de Ståhl, T., Menzel, U., Sandgren, J., Poplawski, A., von Tell, D., Crasto, C., Bogdan, A.... (2008) Somatic mosaicism for copy number variation in differentiated human tissues. Human Mutation, 29(9), 1118-1124. DOI: 10.1002/humu.20815
Fraga, M. (2005) From The Cover: Epigenetic differences arise during the lifetime of monozygotic twins. Proceedings of the National Academy of Sciences, 102(30), 10604-10609. DOI: 10.1073/pnas.0500398102
- May 14, 2011
- 07:42 AM
- 174 views
The miswired brain; making connections from neurodevelopment to psychopathology
by Kevin Mitchell in Wiring the Brain
Recent evidence indicates that psychiatric disorders can arise from differences, literally, in how the brain is wired during development. Psychiatric genetic approaches are finding new mutations associated with mental illness at an amazing rate, thanks to new genomic array and sequencing technologies. These mutations include so-called copy number variants (deletions or duplications of sections of a chromosome) or point mutations (a change in the code at one position of the DNA sequence). At t........ Read more »
Mitchell KJ. (2011) The miswired brain: making connections from neurodevelopment to psychopathology. BMC biology, 9(1), 23. PMID: 21489316
- January 12, 2011
- 04:14 AM
- 300 views
Hotheads by nature
by Kevin Mitchell in Wiring the Brain
If some guy spilt your beer by accident, would you punch him in the face? If he was unapologetic, you might at least consider it – you might in fact feel a pretty strong urge to do it. What stops you? Or, if you’re the type who acts on those urges, what doesn’t stop you? New research has found a mutation in one gene that may contribute to these differences in temperament. Self-control is the ability to inhibit an immediate course of action in the pursuit of a longer-term goal or to c........ Read more »
Verweij KJ, Zietsch BP, Medland SE, Gordon SD, Benyamin B, Nyholt DR, McEvoy BP, Sullivan PF, Heath AC, Madden PA.... (2010) A genome-wide association study of Cloninger's temperament scales: implications for the evolutionary genetics of personality. Biological psychology, 85(2), 306-17. PMID: 20691247
Bevilacqua L, Doly S, Kaprio J, Yuan Q, Tikkanen R, Paunio T, Zhou Z, Wedenoja J, Maroteaux L, Diaz S.... (2010) A population-specific HTR2B stop codon predisposes to severe impulsivity. Nature, 468(7327), 1061-6. PMID: 21179162
- December 21, 2010
- 04:13 AM
- 391 views
Self-organising principles in the nervous system
by Kevin Mitchell in Wiring the Brain
The circuitry of the brain is too complex to be completely specified by genetic information – at least not down to the level of each connection. There are hundreds of billions of neurons in your brain, each making an average of 1,000 connections to other cells. There are simply not enough genes in the genome to specify all of these connections. What the genetic program can achieve is a very good wiring diagram of initial projections between neurons in different brain areas (or layers or bet........ Read more »
Kaschube M, Schnabel M, Löwel S, Coppola DM, White LE, & Wolf F. (2010) Universality in the evolution of orientation columns in the visual cortex. Science (New York, N.Y.), 330(6007), 1113-6. PMID: 21051599
- November 29, 2010
- 05:51 AM
- 368 views
New insights into Rett syndrome
by Kevin Mitchell in Wiring the Brain
A pair of papers from the lab of Fred Gage has provided new insights into the molecular and cellular processes affected in Rett syndrome. This syndrome is associated with arrested development and autistic features. It affects mainly girls, who typically show normal development until around age two, followed by a sudden and dramatic deterioration of function, regression of language skills and the emergence of autistic symptoms. It is caused mainly by mutations in the gene encoding MeCP2, which........ Read more »
Marchetto MC, Carromeu C, Acab A, Yu D, Yeo GW, Mu Y, Chen G, Gage FH, & Muotri AR. (2010) A model for neural development and treatment of rett syndrome using human induced pluripotent stem cells. Cell, 143(4), 527-39. PMID: 21074045
Muotri AR, Marchetto MC, Coufal NG, Oefner R, Yeo G, Nakashima K, & Gage FH. (2010) L1 retrotransposition in neurons is modulated by MeCP2. Nature, 468(7322), 443-6. PMID: 21085180
- November 22, 2010
- 03:17 PM
- 381 views
A synaesthetic mouse?
by Kevin Mitchell in Wiring the Brain
An amazing study just published in Cell starts out with fruit flies insensitive to pain and ends up with what looks very like a synaesthetic mouse. Penninger and colleagues were interested in the mechanisms of pain sensation and have been using the fruit fly as a model to investigate the underlying biological processes. Like any good geneticist faced with profound ignorance of how a process works, they began by screening for mutant flies that are insensitive to pain. Making use of a very powe........ Read more »
Neely GG, Hess A, Costigan M, Keene AC, Goulas S, Langeslag M, Griffin RS, Belfer I, Dai F, Smith SB.... (2010) A Genome-wide Drosophila Screen for Heat Nociception Identifies α2δ3 as an Evolutionarily Conserved Pain Gene. Cell, 143(4), 628-38. PMID: 21074052
Beauchamp MS, & Ro T. (2008) Neural substrates of sound-touch synesthesia after a thalamic lesion. The Journal of neuroscience : the official journal of the Society for Neuroscience, 28(50), 13696-702. PMID: 19074042
- October 24, 2010
- 12:51 PM
- 357 views
Searching for a needle in a needle-stack
by Kevin Mitchell in Wiring the Brain
Whole-genome sequencing is a game-changer for human genetics. It is now possible to deduce every base of an individual’s genome (all 6 billion of them – two copies of 3 billion each) for a couple of thousand euros, and dropping. (Yes, euros). Even Ozzy Osbourne just got his genome sequenced! For researchers searching for the causes of genetic disease (or resistance to vast quantities of drugs and alcohol), this means they no longer have to infer where a mutation is by tracking a sampling........ Read more »
Mitchell KJ. (2010) The genetics of neurodevelopmental disease. Current opinion in neurobiology. PMID: 20832285
- October 18, 2010
- 09:21 AM
- 402 views
Colour my world
by Kevin Mitchell in Wiring the Brain
Colour does not exist. Not out in the world at any rate. All that exists in the world is a smooth continuum of light of different wavelengths. Colour is a construction of our brains. A lot is known about how the brain does this, beginning with complicated circuits in the retina itself. Thanks to a new paper from Greg Field and colleagues we now have an even more detailed picture of how retinal circuits are wired to enable light to be categorized into different colours. This study illustrat........ Read more »
Field GD, Gauthier JL, Sher A, Greschner M, Machado TA, Jepson LH, Shlens J, Gunning DE, Mathieson K, Dabrowski W.... (2010) Functional connectivity in the retina at the resolution of photoreceptors. Nature, 467(7316), 673-7. PMID: 20930838
Jacobs, G., Williams, G., Cahill, H., & Nathans, J. (2007) Emergence of Novel Color Vision in Mice Engineered to Express a Human Cone Photopigment. Science, 315(5819), 1723-1725. DOI: 10.1126/science.1138838
Jameson KA, Highnote SM, & Wasserman LM. (2001) Richer color experience in observers with multiple photopigment opsin genes. Psychonomic bulletin , 8(2), 244-61. PMID: 11495112
- October 4, 2010
- 03:49 PM
- 372 views
Mice with fully functioning human brains
by Kevin Mitchell in Wiring the Brain
I wouldn’t usually discuss politics in a blog like this, but a recent story caught my eye, as it provides an example of the depressing and sometimes bizarre level of scientific illiteracy among elected officials or some people who hope to be elected. The example is from the United States, which is an easy target in this regard, but we have had a similar episode in Ireland recently so I don’t think we (or indeed any other non-Americans) can feel particularly smug about it. This one is espec........ Read more »
Snyder BR, Chiu AM, Prockop DJ, & Chan AW. (2010) Human multipotent stromal cells (MSCs) increase neurogenesis and decrease atrophy of the striatum in a transgenic mouse model for Huntington's disease. PloS one, 5(2). PMID: 20179764
Salazar DL, Uchida N, Hamers FP, Cummings BJ, & Anderson AJ. (2010) Human neural stem cells differentiate and promote locomotor recovery in an early chronic spinal cord injury NOD-scid mouse model. PloS one, 5(8). PMID: 20806064
Lee HJ, Lim IJ, Lee MC, & Kim SU. (2010) Human neural stem cells genetically modified to overexpress brain-derived neurotrophic factor promote functional recovery and neuroprotection in a mouse stroke model. Journal of neuroscience research. PMID: 20818776
- September 17, 2010
- 08:59 AM
- 351 views
Ancient origins of the cerebral cortex
by Kevin Mitchell in Wiring the Brain
Just how special is the human brain? Compared to other mammals, the thing that stands out most is the size of the cerebral cortex – the thick sheet of cells on the outside of the brain, which is so expanded in humans that it has to be folded in on itself in order to fit inside the skull. The cortex is the seat of higher brain functions, the bit of the brain we see with, hear with, think with. In particular, one of its main functions is association – bringing sensory information together ........ Read more »
Tomer R, Denes AS, Tessmar-Raible K, & Arendt D. (2010) Profiling by image registration reveals common origin of annelid mushroom bodies and vertebrate pallium. Cell, 142(5), 800-9. PMID: 20813265
- September 8, 2010
- 06:48 AM
- 413 views
Wild-type humans
by Kevin Mitchell in Wiring the Brain
Wild-type is the term geneticists use to refer to non-mutants. It literally means organisms that are the same, genetically, as those in the wild, compared to ones that have been grown under coddled conditions in the lab for generations, going soft in the absence of natural selection, or that are specifically mutant at some gene or other. There are no wild-type humans. Well, maybe there are a few, somewhere, but even they are not really non-mutants. We all carry millions of mutations in our g........ Read more »
Ng, S., Turner, E., Robertson, P., Flygare, S., Bigham, A., Lee, C., Shaffer, T., Wong, M., Bhattacharjee, A., Eichler, E.... (2009) Targeted capture and massively parallel sequencing of 12 human exomes. Nature, 461(7261), 272-276. DOI: 10.1038/nature08250
Roach, J., Glusman, G., Smit, A., Huff, C., Hubley, R., Shannon, P., Rowen, L., Pant, K., Goodman, N., Bamshad, M.... (2010) Analysis of Genetic Inheritance in a Family Quartet by Whole-Genome Sequencing. Science, 328(5978), 636-639. DOI: 10.1126/science.1186802
- August 27, 2010
- 06:48 AM
- 426 views
Coloured hearing in Williams syndrome
by Kevin Mitchell in Wiring the Brain
The idea that our genes can affect many of the traits that define us as individuals, including our personality, intelligence, talents and interests is one that some people find hard to accept. That this is the case is very clearly and dramatically demonstrated, however, by a number of genetic conditions, which have characteristic profiles of psychological traits. Genetic effects include influences on perception, sometimes quite profound, and other times remarkably selective. A recent study su........ Read more »
Thornton-Wells, T., Cannistraci, C., Anderson, A., Kim, C., Eapen, M., Gore, J., Blake, R., & Dykens, E. (2010) Auditory Attraction: Activation of Visual Cortex by Music and Sound in Williams Syndrome. American Journal on Intellectual and Developmental Disabilities, 115(2), 172. DOI: 10.1352/1944-7588-115.172
Marenco, S., Siuta, M., Kippenhan, J., Grodofsky, S., Chang, W., Kohn, P., Mervis, C., Morris, C., Weinberger, D., Meyer-Lindenberg, A.... (2007) Genetic contributions to white matter architecture revealed by diffusion tensor imaging in Williams syndrome. Proceedings of the National Academy of Sciences, 104(38), 15117-15122. DOI: 10.1073/pnas.0704311104
- August 20, 2010
- 07:45 AM
- 510 views
When to blame your parents, and for what
by Kevin Mitchell in Wiring the Brain
Studies linking some aspect of parental behaviour with some trait in their offspring are depressingly common in the sociological literature. Though these studies typically only report a correlation between parental behaviour and whatever the trait is in the offspring, the implication, and often the explicit conclusion, is that one causes the other. These kinds of stories get huge play in the popular press (and in the blogosphere), where the conclusion of a causative relationship is rarely chal........ Read more »
Evans, M., Kelley, J., Sikora, J., & Treiman, D. (2010) Family scholarly culture and educational success: Books and schooling in 27 nations. Research in Social Stratification and Mobility, 28(2), 171-197. DOI: 10.1016/j.rssm.2010.01.002
Rice, F., Harold, G., Boivin, J., Hay, D., van den Bree, M., & Thapar, A. (2009) Disentangling prenatal and inherited influences in humans with an experimental design. Proceedings of the National Academy of Sciences, 106(7), 2464-2467. DOI: 10.1073/pnas.0808798106
- August 13, 2010
- 05:03 AM
- 401 views
Defining developmental disorders through genetics
by Kevin Mitchell in Wiring the Brain
To many people, the term “autism” suggests a specific disorder – one with characteristic and recognizable symptoms, presumably reflecting the same underlying cause. In fact, no such disorder exists. Autism refers to a variable spectrum of symptoms – including deficits in social interaction, impaired communication (especially a delay in developing language), narrow, restricted interests and stereotyped behaviours. Any one child who is diagnosed with autism may show only some of th........ Read more »
Shen, Y., Dies, K., Holm, I., Bridgemohan, C., Sobeih, M., Caronna, E., Miller, K., Frazier, J., Silverstein, I., Picker, J.... (2010) Clinical Genetic Testing for Patients With Autism Spectrum Disorders. PEDIATRICS, 125(4). DOI: 10.1542/peds.2009-1684
Piton, A., Gauthier, J., Hamdan, F., Lafrenière, R., Yang, Y., Henrion, E., Laurent, S., Noreau, A., Thibodeau, P., Karemera, L.... (2010) Systematic resequencing of X-chromosome synaptic genes in autism spectrum disorder and schizophrenia. Molecular Psychiatry. DOI: 10.1038/mp.2010.54
Bruining H, de Sonneville L, Swaab H, de Jonge M, Kas M, van Engeland H, & Vorstman J. (2010) Dissecting the clinical heterogeneity of autism spectrum disorders through defined genotypes. PloS one, 5(5). PMID: 20526357
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