Cerebral Cortex Advance Access originally published online on January 4, 2006
Cerebral Cortex 2006 16(12):1750-1758; doi:10.1093/cercor/bhj110
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Strabismic Suppression Is Mediated by Inhibitory Interactions in the Primary Visual Cortex
1 Cardiff School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3US, UK, 2 Department of Neurophysiology, Ruhr-University Bochum, D-44780 Bochum, Germany
Address correspondence to Frank Sengpiel, Cardiff School of Biosciences, Museum Avenue, Cardiff CF10 3US, UK. Email: SengpielF{at}cf.ac.uk.
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
-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 fastmoving stimuli. Furthermore, strabismic suppression is greatly reduced when GABAergic inhibition is locally blocked by the GABAA antagonist bicuculline.
Key Words: GABA inhibition orientation strabismus striate cortex