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NEW JERSEY INSTITUTE OF TECHNOLOGY |
Abstract. Very fast field oscillations (>70 Hz) occur in a number of contexts: superimposed upon physiological and epileptiform sharp waves, prior to focal seizure discharges, and in short bursts during persistent gamma (30-70 Hz) oscillations. Experimental data indicate that gap junctions are necessary for such very fast oscillations, and the requisite gap junctions most likely couple the proximal axons of principal neurons. Electrical coupling between principal neurons also facilitates the synchronization of neurons produced by recurrent synaptic excitation, when synaptic inhibition is weakened. A prediction of these ideas is that physically isolated axonal networks can generate very fast oscillations, and in vitro experiments are consistent. In neocortex in vitro, runs of synchronized bursts occur at frequencies of 10 Hz and above, the electrographic correlate of EEG polyspikes and tonic seizures; such runs are facilitated by an additional factor besides gap junctions: strong recurrent synaptic connections between layer 4 spiny stellate neurons.