Abstract
Little is known about the long term neuromorphological consequences of corpus callosotomy in human cerebral cortex. To this end, the present study examined the dendritic systems of supragranular pyramidal neurons in three cortical areas (Brodmann’s areas 4, 10, 44) across both hemispheres. Tissue was obtained post-mortem from a 47 year old male who had had a corpus callosotomy at age 13 years. After processing sections with a Golgi-Kopsch technique, 15 neurons were quantified per brain region (N=90) on a Neurolucida computer/microscope system (Microbrightfield, Inc.). Cells were evaluated for total dendritic length, mean segment length, dendritic segment count, dendritic spine number and dendritic spine density. Results indicated significant quantitative regional differences, but no consistent pattern in terms of regional variability. Hemispheric differences were not significant. Qualitative evaluation of the tissue revealed an unusual sub-population of deep layer III pyramidal neurons, each with an extensive, asymmetric, tap-root basilar dendrite (reminiscent of those seen with some Betz cells). These were located predominately in Broca’s area, but were also found in other regions. Subsequent quantitative analysis of five of these cells revealed that they were equivalent in dendritic length to other pyramidal neurons. However, they tended to exhibit fewer, but longer branch segments. This unusual sub-population of pyramidal neurons may represent long-term dendritic alterations in response to callosotomy.