The interlaminar glia: from serendipity to hypothesis

An account of work performed at the UNA laboratories since 1992 on the detection and description of interlaminar glial processes, is presented. The incidental observation (serendipity) of longer than expected glial processes in the superficial layers of the cerebral cortex in hemiparkinsonian Cebus apella monkeys, was expanded afterwards to cover the largest possible sampling of representatives of mammalian orders and species, as well as in experimental and pathological conditions, in human and non-human primates. The term interlaminar was coined to differentiate these processes from the classical astroglial stellate, intralaminar ones. Such account grew to the point of inspiring, on speculative grounds, possible roles in the organization of the cerebral cortex. Interlaminar glial processes represent an essentially primate characteristic, affected by neuropathological conditions such as DS and AD and experimental procedures affecting normal sensory input, suggesting thalamic involvement in their normal expression. Their ontogenetic development, phylogenetic evolution and aging changes are described.