title: Temporal interactions in the cat visual system. II. Suppressive and facilitatory effects in the lateral geniculate nucleus.
abstract: Extracellular responses were recorded from single neurons in the lateral geniculate nucleus (LGN) of the cat during presentation of pairs of brief visual stimuli identical to those that produce orientation-selective paired-pulsed suppression in the visual cortex. LGN neurons also show paired-pulse suppression, but the suppression is not orientation selective, and it occurs only for short interstimulus intervals (ISIs; usually less than 200 msec). At longer ISIs, most LGN neurons show a period of facilitation. Thus, the paired-pulse suppression in the LGN cannot account for that seen in the visual cortex. Paired-pulse suppression in the LGN was found to be enhanced by stimulation of the receptive field surround. LGN neurons also showed a second type of suppression, termed "offset suppression," which consisted of a more long-lasting suppression of spontaneous activity following the offset of an excitatory visual stimulus. The suppression of spontaneous activity was accompanied by a reduction of the antidromic excitability, assessed by stimulating LGN axons within the cortex or optic radiation. Unlike paired-pulsed suppression, offset suppression was not enhanced by increased stimulation of the receptive field surround. Paired-pulse suppression and offset suppression are most likely due to different mechanisms because they have different time courses and depend differently on the spatial properties of the stimuli. Functionally, paired-pulse suppression may be related to the reduced visual sensitivity that accompanies eye movements, while offset suppression may serve to enhance temporal contrast.
authors.affiliation: Robert Bosch Vision Research Center, Salk Institute for Biological Studies, San Diego, California 92138.
authors.forename: S B
authors.initials: SB
authors.lastname: Nelson
mesh_terms: D000818:Animals; D002415:Cats; D004558:Electric Stimulation; D005829:Geniculate Bodies / Q000166:cytology / Q000502:physiology*; D009433:Neural Inhibition; D009474:Neurons / Q000502:physiology; D010775:Photic Stimulation; D013997:Time Factors; D014785:Vision, Ocular / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology