REGIONAL DIFFERENTIATION OF CELL DENSITIES IN THE LEFT AND RIGHT HIPPOCAMPI OF EPILEPTIC PATIENTS

Neuronal cell densities in surgically removed left or right hippocampa l tissue of epileptic patients suffering from temporal lobe epilepsy w ere determined in CA1, CA4, and the dentate gyrus (DG). Mean densities showed no statistically significant left-right asymmetry in CA1 and t he DG, consistent with findings by others. Mean densities did show pre viously unreported asymmetry in CA4; densities were significantly lowe r in the right CA4 than in the left. Another new finding is an asymmet ry in regional intercorrelations: positive and significant correlation s among the three subfields were obtained only in the left hippocampus . In addition, we confirmed previous findings of positive correlation between neuronal densities in CA1 and age of onset of habitual epileps y, on either side. Taken together, the results suggest subtle left-rig ht asymmetries in the vulnerability of the hippocampi to epilepsy-asso ciated damage and/or higher neuronal connectivity or interdependence o n the left than on the right.