Abstract
In the primary visual cortex (V1), a neuronal response to stimulation of the classical receptive field (CRF) is suppressively modulated by the stimulus presented at the receptive field surround (SRF). Using stationary flashes of sinusoidal grating as stimuli, we examined the dependency of effect of SRF stimulation on the orientation-contrast (OC) between CRF and SRF stimuli (Exp.1) and that on the presentation duration (50 ms vs. 500 ms) (Exp.2) in V1 neurons of anesthetized cats. In Exp.1, CRF was stimulated with a flash (500 ms) of the grating patch with optimal parameters and SRF was stimulated with a flash (50 ms) of the grating annulus that was either iso- or cross-oriented to the CRF stimulus orientation. The late (> 80 ms) component of response was suppressed specifically by iso-oriented SRF stimulus, while the early (40–80 ms) component of response was suppressed by SRF stimulus regardless of OC. In Exp.2, the suppressive effect of short (50 ms) SRF stimulation lasted up to the offset of CRF stimulus (500 ms), and its time course of the suppression was compatible with that of long (500 ms) SRF stimulation. In conclusion, the short (50 ms) presentation of SRF stimulus is sufficient to evoke both orientation-nonspecific fast component and orientation-specific slow component of suppressive effect. [J Physiol Sci. 2006;56 Suppl:S178]
