Meeting Abstract

P3.72  Jan. 6  Would There Be Frontal and Temporal Lobes without an Insula? JOHNSON, J/I*; MORRIS, J/A; SWITZER, R/C; LUNDRIGAN, B/L; FOBBS, A/J; Michigan State University; Michigan State University; Neuroscience Assocates, Inc.; Michigan State University; National Museum of Health and Medicine, AFIP johnij@aol.com

We examined large number and diversity of mammalian brains and found a consistent a lateral portion of the cortex of the cerebral hemispheres just external to a claustrum. This �claustrocortex� is closely approximated to the lateral aspect of the putamen. In many species, the hemispheric surface folds into patterns of fissures, lobes, sulcuses and gyruses. The claustrum shows a modest degree of folding, paralleling that of the overlying cortex, but deep folding of claustrum and claustrocortex appears to be �forbidden� by some necessity to remain in close proximity to mass of putamen. Thus an island (insula) of cortex is formed, and other cortical regions around the claustrocortex are shaped into extensive lobes that fold over and bury the claustrocortex into its �island� configuration. This may be responsible to the common formation of a lateral sulcus (Sylvian fissure) with the insula, or Island of Reil buried in its depth. The surrounding outgrowths, in gyrencephalic brains are formed into temporal and frontal lobes. Just what is the short-connection, or developmental timing, factor that holds the insular cortex down has never been identified, but is worthy of detailed investigation. Supported by: Grants IBN 0131267, 0131826, and 0131028, from the National Science Foundation Division of Integrative Biology and Neuroscience.