Figure 4.

Effects of GABA_A receptor blockade on baseline receptive field properties. (a) Receptive field raster plots from untrained cells illustrating the effect of SR-95531 application on response properties. Across different receptive field locations a control cell tended to show greater variability in the times of visually evoked spikes, whereas spikes in a SR-95531 cell tended to occur at similar times following the stimulus and during a relatively short time window. (b) Consistent with the examples in a, there were significant differences in the timing of stimulus-evoked action potentials between control and SR-95531 conditions. Comparing spike-time histograms for all responses of all cells in the two groups showed that the onset of responses in SR-95531 cells tended to be later and all spiking occurred over a narrower time window than in control cells. (c) Examination of the cumulative distribution functions for these spike-time distributions showed a highly significant difference in spike timing between the two groups (P < 0.001, Kolmogorov-Smirnov test).