Reduced minicolumns in the frontal cortex of patients with autism.

Cell minicolumns were shown to be narrower in frontal regions in brains of autistic patients compared with controls. This was not found in primary visual cortex. Within the frontal cortex, dorsal and orbital regions displayed the greatest differences while the mesial region showed the least change. We also found that minicolumns in the brain of a 3-year-old autistic child were indistinguishable from those of the autistic adult in two of three frontal regions, in contrast to the control brains. This may have been due to the small size of the columns in the adult autistic brain rather than to an accelerated development. The presence of narrower minicolumns supports the theory that there is an abnormal increase in the number of ontogenetic column units produced in some regions of the autistic brain during corticoneurogenesis.

Lateralization of minicolumns in human planum temporale is absent in nonhuman primate cortex.

Gross analyses of large brain areas, as in MRI studies of macroanatomical structures, average subtle alterations in small regions, inadvertently missing significant anomalies. We developed a computerized imaging program to microscopically examine minicolumns and used it to study Nissl-stained slides of normal human, chimpanzee, and rhesus monkey brains in a region of the planum temporale. With this method, we measured the width of cell columns, the peripheral neuropil space, the spacing density of neurons within columns, and the Gray Level index per minicolumn. Only human brain tissue revealed robust asymmetry in two aspects of minicolumn morphology: wider columns and more neuropil space on the left side. This asymmetry was absent in chimpanzee and rhesus monkey brains.

Morphological differences between minicolumns in human and nonhuman primate cortex.

Our study performed a quantitative investigation of minicolumns in the planum temporale (PT) of human, chimpanzee, and rhesus monkey brains. This analysis distinguished minicolumns in the human cortex from those of the other nonhuman primates. Human cell columns are larger, contain more neuropil space, and pack more cells into the core area of the column than those of the other primates tested. Because the minicolumn is a basic anatomical and functional unit of the cortex, this strong evidence showed reorganization in this area of the human brain. The relationship between the minicolumn and cortical volume is also discussed.

Quantitative analysis of cell columns in the cerebral cortex.

We present a quantified imaging method that describes the cell column in mammalian cortex. The minicolumn is an ideal template with which to examine cortical organization because it is a basic unit of function, complete in itself, which interacts with adjacent and distance columns to form more complex levels of organization. The subtle details of columnar anatomy should reflect physiological changes that have occurred in evolution as well as those that might be caused by pathologies in the brain. In this semiautomatic method, images of Nissl-stained tissue are digitized or scanned into a computer imaging system. The software detects the presence of cell columns and describes details of their morphology and of the surrounding space. Columns are detected automatically on the basis of cell-poor and cell-rich areas using a Gaussian distribution. A line is fit to the cell centers by least squares analysis. The line becomes the center of the column from which the precise location of every cell can be measured. On this basis several algorithms describe the distribution of cells from the center line and in relation to the available surrounding space. Other algorithms use cluster analyses to determine the spatial orientation of every column.

Cortical gyrification in the rhesus monkey: a test of the mechanical folding hypothesis.

A quantitative measure of the degree of cortical folding was used to test the mechanical hypothesis of cortical folding and to analyze structural properties of the rhesus monkey cortex. The rhesus monkey cortex has both its maximal degree of cortical folding and the largest ratios of supragranular laminae to the lower granular and infragranular layers in the caudal cortex, over the posterior parietal-anterior occipital regions. Low values for cortical folding and for the ratios of inner and outer cortical layers characterize frontal regions. Topographically intermediate regions are intermediate in both sets of values. Ratios of the amounts of white and gray matter have a topographic pattern that differs from those of cortical folding, suggesting that the sizes of subcortical axonal bundles are not directly associated with the degree of cortical folding. Whereas differences in mean degrees of cortical folding are correlated with brain weights among species of primates, the amount of folding is not associated with brain weight within the species.