GABA-induced remote inactivation reveals cross-orientation inhibition in the cat striate cortex.
We investigated the contributions of lateral intracortical connections to the orientation tuning of area 17 cells using micro-iontophoresis of the inhibitory transmitter gamma-aminobutyric acid (GABA) to inactivate small cortical sites in the vicinity of a recorded cell. GABA was ejected from an array of micropipettes each with an average horizontal distance of 500 microns from the recording site. Of 54 cells tested, 33 showed a reduction and 3 a loss of orientation selectivity due to an increase in responses to non-optimal orientations during GABA inactivation. The response to the optimal orientation remained constant in more than half of the cells and increased or decreased in others. Given that a complete cycle of orientations occupies a tangential distance of 1000 microns, the observed broadening of orientation tuning is presumably due to GABA-mediated inactivation of inhibitory interneurones with different preferred orientations from those of their target cell.
Eysel
U T
UT
Abteilung Neurophysiologie, Medizinische Fakultät, Ruhr-Universität Bochum, Federal Republic of Germany.
Crook
J M
JM
Machemer
H F
HF
D000818:Animals; D002415:Cats; D005556:Form Perception / Q000502:physiology*; D009433:Neural Inhibition / Q000187:drug effects*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D014793:Visual Cortex / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology*
D005680:gamma-Aminobutyric Acid