Strabismic suppression is mediated by inhibitory interactions in the primary visual cortex.
Most strabismic observers do not suffer from double vision because of suppression from conscious perception of 1 of the 2 eyes' conflicting views. Direct evidence for the site and neural substrate of strabismic suppression has not been available so far, although psychophysical data suggest a cortical origin. On the other hand, cross-orientation suppression among conflicting stimuli presented monocularly has recently been shown to have a strong thalamic component. Here we present evidence, using both visual stimulation and pharmacological techniques, that strabismic suppression occurs in the primary visual cortex and involves gamma-amino butyric acid (GABA)-mediated inhibition. We show that its dependency on the drift rate of the suppressing stimulus is consistent with a cortical origin; unlike monocular cross-orientation suppression, it cannot be evoked by very fast-moving stimuli. Furthermore, strabismic suppression is greatly reduced when GABAergic inhibition is locally blocked by the GABA(A) antagonist bicuculline.
Sengpiel
Frank
F
Cardiff School of Biosciences, Cardiff University, Museum Avenue, Cardiff, UK. SengpielF@cf.ac.uk
Jirmann
Kay-Uwe
KU
Vorobyov
Vasily
V
Eysel
Ulf T
UT
D000818:Animals; D002415:Cats; D004594:Electrophysiology; D009433:Neural Inhibition / Q000502:physiology*; D010775:Photic Stimulation; D013285:Strabismus; D015348:Vision, Binocular / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D005680:gamma-Aminobutyric Acid