Abstract
Synchronized discharges, which are frequently recorded from visual neurons, are accompanied by γ-range (20–80 Hz) oscillations in a manner that depends on certain key features of the light stimulus. Although these neural activities are assumed to play an important role in perceptual integration, their functional significance has yet to be elucidated. Applying the multi-electrode recording technique to retinas isolated from frogs, we recorded spike discharges from multiple off-sustained ganglion cells (dimming detectors). An expanding dark spot, which was projected to the isolated retina, generated oscillatory synchronized discharges among dimming detectors. Oscillatory synchronization was abolished by bicuculline, a GABAA (γ-aminobutyric acid) receptor antagonist, whereas it was potentiated by (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA), a GABAC receptor antagonist. However, both antagonists increased spike discharges in dimming detectors. Escape behaviour elicited by the expanding dark spot was suppressed by intraocular bicuculline injection whereas it was enhanced by intraocular TPMPA injection. Behavioural changes could not be predicted by changes in other response properties of ganglion cells. Furthermore, optokinetic responses to moving stripes were not affected by intraocular injection of either antagonist. We conclude that retinal oscillatory synchronized discharges encode escape-related information in frogs. Our results provide a direct support for the functional relevance of oscillatory synchronization in the visual system. [Jpn J Physiol 55 Suppl:S49 (2005)]
