Influence of isoluminant monochromatic and polychromatic background on single neuron activity in cat visual cortex...

The role of colour vision in night-active cats has not been elucidated completely hitherto. In order to assess the colour sensitivity in cat cortical neurons we used large isoluminant computer-generated monochromatic and polychromatic background stimuli which were superimposed on moving and stationary (on/off) light bars. Background stimuli were moved at different speeds, either inphase or antiphase. The modulatory effect of the visual noise on the neuronal bar was the primary objective of the study. The maximum PSTH peaks of some 40% of the neurons tested was influenced by both moving and stationary bars. About two thirds of maximum peak-sensitive cells also showed altered direction selectivity. Latencies, on the other hand, turned out to be rather stable. The retino-cortical conduction time was not influenced either. In conclusion, a large portion of cat cortical visual neurons is remarkably sensitive to the spectral composition of the visual noise process surrounding the stimulating light bar.