Figure 2.

The elevation of basal synaptic transmission does not reflect a passive response to high illuminance conditions. A, Maximal FP augmentation (140–150%) occurs in the absence of light exposure. Animals were introduced to a toy (during the periods marked by gray rectangles on the graph). The first exposure began at time 0 for 15 min. B, A low-contrast object elicited a similar amount of exploration, measured by the locomotor activity (centimeters per minute) and compared with the baseline period (black bar) under dark conditions. Analysis from the first 5 min immediately after the introduction of the object showed a slightly increased activity for the high-contrast object (white bars) compared with the low-contrast one (gray bars). Nonetheless, overall locomotor activity for all three periods for both objects do not differ significantly. C, Analogs represent FPs evoked at the points marked in the figures. Calibration: 5 ms, 1 mV. D, Relative gamma power in the same groups of rats reflects the level of visual exploration induced by the objects presentation. The low-contrast object (gray bar) drives oscillatory activity to a significantly higher extent than the control level (black bar), and to a significantly lower extent than the high contrast-induced gamma augmentation (white bar). *p < 0.05; ***p < 0.001. Error bars indicate SEM.