Brain structure gray matter

MRI studies of adolescent autistic children show increases in thickness of the cerebral cortex (gray matter) in specific areas of the brain coupled with decreases in thickness of fiber tracts (white matter) leading in and out of those and other areas.63 This provokes the idea that a combination of developmentally enlarged cortex and reduced white matter may be the structural basis of autism. But it s also possible that the anatomical differences may be a consequence of autistic behavior rather than a basis, since the development of the brain continues throughout childhood. 

FIGURE 30.1 Structure of the central nervous system (CNS). (a) The CNS includes the brain and the spinal cord, (b) The gray matter of the CNS contains the cell bodies of neurons as well as dendritic and axonal processes, (c) When an electrode is placed within the heterogeneous cellular environment of the CNS it is unclear which neuronal elements are effected by stimulation. 

The typical symptoms of untreated individuals with PKU are the manifestation of the neurotoxic effect of phenylalanine on the central nervous system. A morphological change in the brain in patients with PKU affects both white and gray matter. Microcephaly, where the brain mass can be 80 % of that of a healthy individual, is characteristic feature for many untreated PKU patients [37]. This symptom is caused by myelin structure anomalies that result in a loss of myelin volume, disturbances in cortical neuronal development, diffuse cortical atrophy, and general abnormalities in protein synthesis [37, 39, 40]. 

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