FIGURE 2.

Applications of optogenetics in the analysis of circuit functions. (A) Mice were presented with oriented drifting gratings while in vivo cell-attached recordings of putative pyramidal neurons in the visual cortex were performed. Either Pvalb or Sst interneurons were photoactivated using ChR2. Pvalb interneuron photoactivation (left) resulted in divisive inhibition of pyramidal neurons where suppression was stronger at orientations where pyramidal neuron responses were also stronger. Sst interneuron photoactivation (right) resulted in subtractive inhibition where suppression was uniform along all orientations. Adapted from Wilson et al. (2012). (B) Mice were trained to lick for a water reward in response to whisker stimulation of varying intensities. Perceptual detection as a function of stimulus intensity formed a sigmoid curve. When L5 pyramidal neuron apical dendrites were photoinhibited (iChloC) or when Sst interneurons were photoactivated (ChR2), the curve shifted to lower detection probabilities. When L5 pyramidal neuron apical dendrites were photoactivated (ChR2), the curve shifted to higher detection probabilities. Adapted from Takahashi et al. (2016). (C) Mice were trained to press a lever following an auditory cue to obtain a water reward. Two-photon imaging was performed in M1 throughout learning to track dendritic spine dynamics in pyramidal neurons. Control animals developed a stereotyped lever-press movement with learning but this was impaired if Sst interneurons were photoactivated (ChR2) or photoinhibited (eNpHR) (bottom left). Furthermore Sst interneuron photoinhibition resulted in increased stabilization of dendritic spines while photoactivation resulted in increased elimination. (bottom right). Adapted from Chen et al. (2015).