A columnar-supporting mode of astroglial architecture in the cerebral cortex of adult primates?

Abstract

Neuronal modular (columnar) organisation of the cerebral cortex may represent an evolutionary acquisition that could optimize communication and information processing with the least volume compromise in terms of wiring. Yet, for such columns to be functionally operative adequate isolation from neighbouring units would be required, otherwise their spatial definition could be compromised. Evidence for "cable-like" processes stemming from astroglial cells has been recently presented although their existence has been forgotten for more than a century. These processes tend to form a sort of "palisade" or "brush" whose spatial distribution appears to correlate with the distribution of apical dendrites within the supragranular cortical layers. Patterned neuronal organization in the striate cortex is associated with a patterned distribution of GFAP-IR processes, both at the cellular and cell-aggregate levels. It can be tentatively proposed that evolutionary pressures resulted, in primates, in the progressive appearance of an increased length of astroglial processes in the supragranular region which may be associated with optimization of cerebral cortex modular (columnar) organization. It is interesting that this cortical region has undergone the larger growth among mammalian species during evolution, and would bear a crucial role in corticocortical interactions.