The Journal of Cognitive Neuroscience, Vol 10, 153-166, Copyright © 1998 by The MIT Press
Modular Subdivisions of Dolphin Insular Cortex: Does Evolutionary History Repeat Itself?
Paul Manger, Monika Sum, Michael Szymanski, Sam Ridgway and Leah Krubitzer
The structural organization of the insular cortex in the bottlenose dolphin
was investigated by examining Nissl- and myelin-stained tissue that was
sectioned coronally and tangentially. An uneven distribution of cell
clusters that coincided with myelin-light zones was observed in layer II.
When the present observations were compared to descriptions of modules in
other animals, we found that the range of module size is restricted, while
the size of the brain, particularly the neo-cortex, varies dramatically.
Indeed, despite the tremendous expansion of the cetacean neocortex, the
size of the modules in the insular cortex is similar to that described for
small-brained mammals like the mouse, suggesting that module size is
evolutionarily stable across species. Selection for optimal-size processing
units, in terms of the lengths of connections within and between them, is a
likely source of this stability.
