Several studies today are looking at different changes in the brain structures in healthy vs. non-healthy development, and other brain diseases. In a study just published in the Journal of Neuroscience, David van Essen and colleagues studied the brains of people suffering from Williams syndrome, a rare genetic developmental order that is characterised by "a distinctive, "elfin" facial appearance, an unusually cheerful demeanor, ease with strangers, mental retardation coupled with an unusual facility with language, a love for music, cardiovascular problems such as supravalvular aortic stenosis, and transient hypercalcemia."
In this study, van Essen found that the brains of these people were different in 33 areas, and that there was a surprising bilateral symmetry to the differences from the control group. 16 changes in the left hemisphere was mirrored by 16 changes in the right hemisphere. In addition, hemispheric asymmetry of the temporal lobe was generally smaller in this group compared to controls.
Since Williams syndrome is caused by a deletion of material in region q11.2 of chromosome 7, we can speculate that these functions normally subserve both the development and function of these brain regions, in addition to an effect of strength of hemispheric specialization and lateralization. One interesting point is that the genes affected here produce diverse changes in the brain, not strictly following traditional cognitive-functional borders. Williams syndrome is not a brain-only disease, also affecting other somatic functions such as the cardiac system. One can only speculate at this point how many regions of chromosome 7 affects the brain, how many the cardiac system, and to what extent there is an overlap between gene-brain-body mapping.
Here is the abstract:
Van Essen D, Dierker D, Snyder A, Raichle ME, Reiss A, Korenberg J. Symmetry of cortical folding abnormalities in Williams syndrome revealed by surface-based analyses. The Journal of Neuroscience, May 17, 2006.
We analyzed folding abnormalities in the cerebral cortex of subjects with Williams syndrome (WS), a genetically based developmental disorder, using surface-based analyses applied to structural magnetic resonance imaging data. Surfaces generated from each individual hemisphere were registered to a common atlas target (the PALS-B12 atlas). Maps of sulcal depth (distance from the cerebral hull) were combined across individuals to generate maps of average sulcal depth for WS and control subjects, along with depth-difference maps and t-statistic maps that accounted for within-group variability. Significant structural abnormalities were identified in 33 locations, arranged as 16 bilaterally symmetric pairs plus a lateral temporal region in the right hemisphere. Discrete WS folding abnormalities extended across a broad swath from dorsoposterior to ventroanterior regions of each hemisphere, in cortical areas associated with multiple sensory modalities as well as regions implicated in cognitive and emotional behavior. Hemispheric asymmetry in the temporal cortex is reduced in WS compared with control subjects. These findings provide insights regarding possible developmental mechanisms that give rise to folding abnormalities and to the spectrum of behavioral characteristics associated with WS.
While discussing Williams syndrome, it is important to mention the work of Andreas Meyer-Lindenberg, who is doing an impressive amount of work on this rare disease, and reporting dazzling findings on the relationship between genes, brain and (social) behaviour.