METABOLIC AND FUNCTIONAL MAPPING OF THE NEURAL-NETWORK SUBSERVING INFERIOR COLLICULAR SEIZURE GENERALIZATION

The sensory-motor portion of the inferior collicular cortex is capable of seizure genesis that is characterized initially by coincident wild running behaviors and localized electrographic afterdischarge. With r epeated stimulations, this seizure activity spreads into the forebrain , producing generalized tonic-clonic or myoclonic seizure activity. In order to characterize the neural network subserving this caudal-rostr al seizure generalization, three mapping techniques were used: a-deoxy glucose (2-DG) utilization, c-fos expression and local anesthetic micr oinjection. Kindled seizure generalization from the inferior collicula r cortex produced a global increase in 2-DG accumulation, while relati ve 2-DG increases were found in the inferior collicular cortex, dorsal lateral lemniscus, dorsal central gray, peripeduncular nucleus, media l geniculate nucleus, substantia nigra, entopeduncular nucleus, ventro posterior and centromedian thalamus and tenia tectum, as well as the p erirhinal, somatosensory and frontal cortices. Kindled seizure general ization also increased c-fos-like immunoreactivity (FLI) in the inferi or collicular cortex, cuneiform nucleus, dorsal lateral nucleus of the lateral lemniscus, peripeduncular nucleus, caudal central gray, denta te gyrus of the hippocampus, rhinal fissure area of the perirhinal cor tex and the frontal cortex. Microinjections of procaine into the amygd ala, perirhinal cortex, entopeduncular nucleus, substantia nigra, peri peduncular nucleus, dorsal central gray, and pontine reticular nucleus all prevented generalized seizure behaviors, but had no effect on the wild running seizures. Conversely, procaine microinjection into the a rea of the cuneiform nucleus/pedunculopontine tegmental nucleus preven ted the wild running seizure but did not block the generalized seizure activity. Neither wild running, nor generalized seizures were altered following procaine microinjections into the anterior thalamus, sub-th alamus, lateral hypothalamus, hippocampus or deep superior colliculus. Thus, specific forebrain sites form a widespread neural network that mediates the generalization of seizure activity from the inferior coll icular cortex into the forebrain.