The MRI scans indicated that two areas of gray matter that control reading comprehension and speaking (known respectively as Wernicke's area and Broca's area) were highly similar in size in identical twins, which share an identical set of genes.
The Broca's and Wernicke's areas were also similar in non-identical twins, who on average share about half of their genes. But these differences were greater than in the comparison of identical twins, and fewer than in two unrelated individuals.
The study shows that the more closely related two people are, the more likely they are to share similar brain structure in regions heavily controlled by genetics. They are also more likely to share vulnerabilities to specific diseases affecting these areas.
While these ideas are not new, Thompson's work is the first detailed study showing how strongly brain structure is determined by genes and inheritance.
The results are described in the November issue of the journal Nature Neuroscience.
Thompson's study is part of a much broader effort to understand which regions of the brain are associated with brain diseases such as Alzheimer's, schizophrenia, and Parkinson's.
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