Supplementary Figure 4: Optogenetic substitution of whisker stimulation.

(a) Mice were trained to lick in response to C2 whisker stimulation and, after achieving stable, good behavioral performance, the lick response to optogenetic stimulation of S1 whisker barrel cortex was tested at different light durations (n = 6 mice; 5 ms data same as shown in Fig. 1e). (b) To control for non-specific effects of the blue light stimulus, the optical fiber was moved to a part of the cortex not expressing ChR2. Light flashes delivered to cortical regions not expressing ChR2 did not evoke licking (n = 6 mice). (c) ChR2-YFP was expressed in the S1 forepaw representation and mice were trained to detect C2 whisker stimuli. Coronal section through the center of the injection site in S1 forepaw cortex (left, 0.02 mm anterior Bregma) and another section from the same mouse showing no expression in whisker barrel cortex (right, 1.7 mm posterior to Bregma). On the transfer test day, mice failed to respond with licking to optogenetic stimulation of the S1 forepaw area (n = 3 mice). (d) Mice were trained to lick in response to optogenetic stimulation of S1 whisker barrel cortex. On the transfer test day, the ability of a C2 whisker stimulus, of differing pulse durations, to drive licking responses was checked (n = 3 mice; 1 ms data same as shown in Fig. 1f). (d) In subsequent ‘no whisker stimulus’ blocks of control trials, the iron filings were removed from the whisker. Magnetic pulses during these ‘No stim’ control trials did not evoke licking above the false alarm rate (n = 3 mice). Data shown as mean ± sem.