An analysis of the effect of retinal ganglion cell impulses upon the firing probability of neurons in the dorsal lateral geniculate nucleus of the cat

Abstract

This study examines the probabilistic way in which LGN cells produce impulses. Simultaneous extracellular recordings were made from a single lateral geniculate nucleus (LGN) relay cell and the one retinal cell that triggered most of its impulses during vigorous responses. Impulses in the retinal train were classified as 'successful' in triggering an LGN impulse, or 'unsuccessful'. Similarly, the impulses in the LGN train were either 'Triggered' by a successful retinal impulse, or were 'Anonymous'. These impulses delimited various intervals whose distributions were compared to the relevant distribution of all intervals to determine whether short or long intervals tended to dominate in each case. Intervals between unsuccessful and successful impulses tended to be shorter than other retinal intervals, with their probability declining exponentially with duration. These data imply a decaying excitation produced by each impulse, but with a short refractory period following each Triggered impulse. Short intervals between Anonymous impulses were relatively common; Anonymous impulses thus lack the same refractoriness and tend to occur in bursts. The exponential excitation following an unsuccessful retinal impulse also facilitates Anonymous impulses, while Anonymous impulses (during visual stimulation) render the LGN slightly refractory for subsequent retinal impulses.