Postsynaptic Inhibition in the Lateral Geniculate Nucleus and Its Relation to ‘Recovery Cycle’ of Geniculate Population Response

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Abstract
The prolonged suppression of the responsiveness of the geniculate neuron population following the optic nerve stimulation was studied in cats anesthetized with chloralose-urethane mixture. Unit activity of the geniculate relay cells was recorded extracellularly and paired stimuli were applied to one optic nerve at 20-60 msec. intervals. The latency for action spike generation by the second stimulus was lengthened in a graded manner upon increase in strength of the first stimulus. Some geniculate cells responded with a train of several action spikes in response to a single stimulus to 1 optic nerve. The action spikes decreased in number in a graded manner with increase in stimulus strength. Suppression can be generated in a graded manner in a single geniculate neuron. Gradation was also observed in a hyper polarization associated with an action spike on intracellular recording from the geniculate relay cell.