Abstracts

Subcortical white matter (SCWM) cells are a common feature of primate cortex. Their function is unknown, but during early development their processes are widespread. Greater numbers of SCWM cells have been reported in several neurological disorders.
To assess SCWM cells in epilepsy, we are characterizing their distribution and morphology in human temporal lobes resected for treatment of mesial temporal lobe epilepsy (MTLE). Following fixation, tissue was stained with NeuN to identify SCWM neurons or with MAP-2 to assess the distribution of processes originating from SCWM cells. Cell density was established by counting NeuN stained cells in 425 X 340 micron windows.
The number of stained cells in the SCWM of MTLE tissue exceeded that found in comparison tissue from patients with temporal lobe lesions (8.32 +/- 0.92 vs. 1.45 +/- 0.26, respectively). In the SCWM of MTLE tissue, the distribution of NeuN stained cells was not uniform; among the overall increased numbers of cells, clusters with particularly high cell densities were evident. The morphology of the SCWM cells was variable; multipolar, bipolar and undifferentiated cells without processes were heterogeneously distributed throughout the depth of the SCWM. MAP-2 staining revealed that many of the SCWM cells had processes that extended into the higher layers of cortex. Often these varicose processes were parallel within the SCWM. Elsewhere however, the MAP-2 stained processes were highly disorganized and did not exhibit a clear orientation.
As our analyses continue, we will be studying the connectivity of the SCWM cells and their potential for influencing cortical activity.
[Supported by: NIH P01-NS39092 and R01-NS38287]