Brief optogenetic stimulation of either PV or SST neurons similarly impairs contrast change detection. A, Trial schematic. The visual stimulus contrast is fixed at 75%, except during a 100 ms reduction. ChR2-expressing interneurons were illuminated with blue light for 100 ms concurrent with reductions in contrast on a randomly selected half of the trials. B, Representative single-session performance for a PV mouse. Dots represent false-alarm corrected performance for trials with (teal) and without (black) activation of PV interneurons. Curves indicate best fitting Weibull functions that were used to determine detection thresholds (dotted vertical lines) and 95% CIs (solid horizontal lines). C, Same as in B, but for an SST mouse. Blue represents trials with SST stimulation. D, Summary of PV and SST stimulation effects. Circles represent the contrast change detection threshold from individual sessions with (y axis) and without (x axis) PV (teal, 2 mice, 20 sessions) or SST (blue, 2 mice, 18 sessions) stimulation. Filled circles represent sessions with a significant shift in threshold (37 of 38; bootstrapped). E, Representative behavioral performance from a single contrast decrement session where one 100 ms contrast decrement was paired with PV stimulation (LED power was 0.5 mW in this example session). Filled dots represent performance for trials with (blue) and without (black) activation of PV interneurons for different contrast decrements. Solid line indicates psychometric function fit to performance on visual only trials. Blue dashed line connecting dots indicates magnitude of perceptual impairment (Δ Percent Correct) on the selected contrast decrement with (blue) and without (black) optogenetic activation of PV neurons. F, The perceptual impairment induced by PV activation scales with optogenetic stimulation intensity. Individual points depict performance impairment from individual sessions (there are two sessions at 0.1 mW). Gray line indicates a maximum likelihood linear regression anchored at the origin (r2 = 0.67).