tbrannon at CSEE.Lehigh.Edu (tbrannon) writes:
>Can someone provide a brief overview of what neural columns are?
The newer parts of cerebral cortex seem to have two levels of "modular"
organization, about 300 minicolumns (about 30-50 microns in diameter, possibly
corresponding to those lined-up cells you see in Nissl stains, radiating
up from the white matter) nestled inside a macrocolumn (maybe 0.5 mm in size).
Physiologically, they are defined by clustering of response types: a
typical minicolumn is the orientation column of visual cortex, all of
whose neurons seemingly interested in lines/edges at about the same
(within 10 degrees) orientation. A typical macrocolumn is the ocular
dominance column, best defined in layer IVc whose cells are only
responsive to one eye; move laterally and you find another 0.5mm wide
group that are interested in the other eye.
Some other collections have been called "columns" such as Hubel & Wiesel's
hypercolumns (essentially two ocular dominance columns, left and right,
taken together, each of which has a full range of orientation columns
embedded in it). Somatosensory cortex is where macrocolumns were
discovered in the first place by Mountcastle in 1957, where modalities
(skin vs joint sensation, for instance) cluster. They have been seen in
several of the secondary visual areas, specializing in various kinds of
feature detection. There is no general theory for what association cortex
might be doing with this kind of organization, though I find myself working
on one (and NO, there is nothing on this in my books such as CEREBRAL
SYMPHONY or ASCENT OF MIND; it's all happened recently, e.g., Soc. Neurosci.
Abstr. 18:214.18, 1992).
William H. Calvin WCalvin at U.Washington.edu
University of Washington NJ-15
Psychiatry & Behavioral Sciences
Seattle, Washington 98195 FAX:1-206-720-1989