Figure 6: ISs interfere with normal visual processing.

(a) Schematic of the experimental setup and exemplificative traces at two different contrasts. (b) The upper panel shows the probability distribution of IS onset in respect of the stimulus (red trace: lower panel experiment; gray area: mean +/− SD for n = 8 animals). The lower panel shows the raster plot obtained by sorting VEP traces according to the delay between stimulus and IS. The dotted black line represents the appearance of IS; time 0 indicates the stimulus presentation. (c) Black trace reports a single response to a stimulus presentation in the control recording (before of BMI superfusion), the blue and red traces report the responses when IS immediately preceded (−0.35 to 0.05 s, blue) or followed (0.05 to 0.35 s, red) stimulus presentation; in green there are the mean traces obtained when the stimulus and the closest IS were farther away than 0.35 s. These windows are indicated by the colored bars adjacent to the raster plot in b. (d) VEP amplitudes depend on the lag between stimulus and contralateral ISs (N = 6 mice; average in thick line, each mouse in thin lines). The colored shaded zones span the time windows used for the averaging in c. The percentages report the fraction of stimuli falling in the three conditions averaged on all mice. (e) Periods of VEP alteration have been superimposed on the peri-IS spike histogram of Fig. 5d with the same color code in d, to show the relationship between the effect of ISs on neuronal firing and VEP alteration. (f) Contrast sensitivity for the three groups of responses compared to control (n = 8 mice). Curves from the VEPs falling after the ISs (IS pre VEP) and for the VEPs interrupted by the ISs (IS during VEP) showed a significant difference, while curve from the VEPs far from the ISs was no significantly different from control (t-test, p-value > 0.05). (g) Mean VEP waveforms recorded in the same mouse at different contrasts for the different conditions reported in f.