Selective Changes in the Microorganization of the Human Epileptogenic Neocortex Revealed by Parvalbumin Immunoreactivity

The microanatomy of the human lateral temporal cortex removedfrom patients with intractable temporal lobe epilepsy was studiedusing correlative light and electron microscopic immunocytochemicalmethods for the localization of the calcium-binding proteinparvalbumin (PV). PV immunostaining was mainly used to labela subpopulation of powerful cortical inhibitory interneuronsthat have been shown to be lost at epileptic foci in certainanimal models of epilepsy. In the human neocortex with normalappearance, we identified the same local neuronal circuitryas in the normal monkey cortex, but in some regions of the samecortex, a fine disorganization of neuronal circuits (loss ofinhibitory neurons and presumptive thalamocortical terminals)was found. This abnormal circuitry may interfere with normalcerebral activity in epileptic patients. These results alsoindicate that PV immunoreactivity can be a useful tool to studynormal and abnormal synaptic circuits in the human cerebralcortex.