Laminar analysis of spindles and of spikes of the spike and wave discharge of feline generalized penicillin epilepsy.
Intracortical laminar profiles of spindles and spikes of spike and wave complexes in feline generalized penicillin epilepsy were studied using two methods: (i) sequential microelectrode recordings at various cortical depths, and simultaneous recordings at multiple cortical depths using a fine multi-contact electrode. Raw EEG data and EEG epochs averaged with respect to peaks of surface EEG waves were analyzed. Spindles and the spikes of the spike and wave complexes showed similar laminar profiles. This supports the hypothesis that the two are basically the same cortical electrophysiological phenomenon, the spike being a spindle wave enhanced and slightly altered because of the penicillin-induced increased cortical excitability. The latter causes the weight of the thalamic input to shift from superficial to more deep lying synapses. Both surface negative and surface positive phases of spindles and of spikes of spike and wave complexes show similar laminar profiles, those of the former suggesting activation of excitatory synapses in the superficial cortical layers, those of the latter suggesting activation of more deeply located excitatory synapses. The profiles generally conform to the dipole hypothesis of cortical electrogenesis and suggest that spindles and spikes of spike and wave complexes are generated by the same pyramidal neurons, probably through activation of the same sets of synapses. Some inconstant and relatively minor deviations of the laminar profiles from the pattern predicted by the dipole theory of cortical electrogenesis were encountered and are tentatively explained in the light of some of the complexities of the microanatomical organization of mammalian neocortex.
D000200:Action Potentials; D000818:Animals; D002415:Cats; D002540:Cerebral Cortex / Q000502:physiology; D004569:Electroencephalography; D009434:Neural Pathways / Q000502:physiology; D010400:Penicillin G; D012640:Seizures / Q000139:chemically induced / Q000503:physiopathology*; D013569:Synapses / Q000502:physiology; D013787:Thalamic Nuclei / Q000502:physiology
D010400:Penicillin G