title: Dynamic differentiation of GABAA-sensitive influences on orientation selectivity of complex cells in the cat striate cortex.
abstract: The influence of GABAA receptors on orientation selectivity of cat complex cells was tested by iontophoresis of the GABAA receptor blockers bicuculline and N-methyl-bicuculline while stimulating with drifting sinusoidal gratings. Reduction of orientation tuning was markedly less than reported in previous studies that used drifting bars as visual stimuli. Only 3/31 cells lost orientation selectivity, with an average increase in bandwidth of 33%, as opposed to half the cells losing selectivity and a bandwidth increase for the remainder of 47% as reported previously. Infusion of GABAA blockers revealed a prominent stimulus onset transient response, lasting about 120 ms, that showed a broadening of orientation selectivity comparable to that found using drifting bars under similar circumstances. We believe that drifting gratings emphasize a steady-state response component that retains, in the presence of GABAA blockers, significant orientation selectivity. Because the onset transient is initially unselective for orientation, we suggest that the steady-state, orientation-selective response component develops from an alternate inhibitory mechanism, possibly mediated by GABAB receptors.
authors.affiliation: Department of Biomedical and Electrical Engineering, Vanderbilt University, Nashville, TN 37235, USA.
authors.forename: B
authors.initials: B
authors.lastname: Pfleger
authors.forename: A B
authors.initials: AB
authors.lastname: Bonds
mesh_terms: D000818:Animals; D001640:Bicuculline / Q000031:analogs & derivatives / Q000494:pharmacology; D002415:Cats; D018756:GABA Antagonists / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists; D007478:Iontophoresis; D009949:Orientation / Q000187:drug effects / Q000502:physiology*; D010775:Photic Stimulation; D011963:Receptors, GABA-A / Q000187:drug effects*; D014793:Visual Cortex / Q000166:cytology / Q000187:drug effects / Q000502:physiology*
chemical_list: D018756:GABA Antagonists; D058787:GABA-A Receptor Antagonists; D011963:Receptors, GABA-A; C006749:bicuculline methochloride; D001640:Bicuculline