Autistic brain neuropathological studies

The following section explores the five areas most consistently found to be abnormal in postmortem studies of autistic brains - amygdala, septal nucleus, hippocampus, anterior cingulate cortex, and cerebellum - and discusses their hypothetical relationship to emotional and interpersonal psychopathology in autism. Note that other brain areas, which are inconsistently abnormal in neuropathological studies, may express inconsistent associated symptoms, variations in psychopathological subtypes, or inconsequential anomalies and are not discussed in this section. 

Neuropathological studies in autistic brains have also demonstrated smaller neuronal size and increased cell packing density in the hippocampus, another limbic system structure. The morphology of hippocampal neurons in two cases of infantile autism was studied and investigators found smaller cells with reduced perikaryon area and dendritic branching in comparison with neurons of age-matched control children [63], This result is consonant with MRI results evidencing a smaller area dentata of the hippocampus in autistic children from 2 to 4 years [64]. However, the density and distribution of some 5-HT receptors in the hippocampus were not statistically different between autistic children and controls [65]. 

This chapter correlates emotions and attachment behavior in autism with the disturbed neuroanatomy found in the brains of these individuals. Neuropathological postmortem studies have consistently found abnormalities in the limbic system and the cerebellum of autistic individuals. Abnormal limbic structures include the amygdala, hippocampus, septal nucleus, and anterior cingulate cortex. In the cerebellum, abnormalities have been found in the cerebellar hemispheres and in the fastigial, emboliform, and globose nuclei. 

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