Cellular electrophysiology of human epilepsy

The electrophysiological characteristics of neurons in human epileptic tissue are reviewed, with emphasis on experiments employing in vitro slice analysis of human neocortex and hippocampus. There is little evidence for an alteration in intrinsic properties of cortical or hippocampal neurons in human epileptic tissue. However, data support some decrease in functional inhibition and/or increase in synaptic excitation. In slices from epileptic brain, bursting discharge can be evoked under conditions that do not elicit such discharge patterns in normal animal tissue. Most bursts are generated from prolonged and/or enhanced EPSPs; spontaneous bursting activity, and all-or-none discharge (i.e., paroxysmal depolarizations) are rarely seen in vitro. Underlying structural alterations have been correlated with increased excitability, but cause/effect relationships have not been established. These data suggest that a variety of mechanisms may contribute to epileptogenicity in human cortical tissues.