Evoked and Induced Gamma-Frequency Oscillations in Autism

Recent studies by our group have characterized the neuropathology of autism as that of a minicolumnopathy. Postmortem studies using computerized image analysis of pyramidal cell arrays have found that the brains of autistic individuals have smaller minicolumns with most of the decrease stemming from a reduction in its peripheral neuropil space, with little, if any reduction, in their core space. This finding has been reproduced using different techniques (e.g., GLI) and independent populations (Casanova et al. 2002a, b, c, 2006a, b). It is now known that minicolumnar width reduction in autism spans supragranular, granular, and infragranular layers (Casanova et al. 2010). The most parsimonious explanation for the findings is the possible abnormality of an anatomical element in common to all layers. The peripheral neuropil space of minicolumns provides, among other things, for inhibitory elements distributed throughout all of its laminae. This is the so-called shower curtain of inhibition of the minicolumn described by Szentagothai and Arbib (1975). Our findings therefore suggest a deficit within the inhibitory elements that surround the cell minicolumn (Casanova et al. 2006a).