Abstract
Visual detection is a process that not only requires sensory processing, but also includes decision mechanisms that map sensory events onto motor actions and perceptual states. With that view in mind, we hypothesized that manipulating the activity in neural circuits involved in the decision process might change both detection criteria and sensitivity. To test this idea, we used optogenetics to artificially activate specific neuronal populations in the striatum, a brain region best known for its role in reinforcement learning and action selection, in mice performing a visual detection task. The visual stimuli consisted of two vertically oriented Gabor gratings superimposed on a pink noise background. Head-fixed mice walked on a Styrofoam wheel, and the drifting rate of visual gratings depended on walking speed. During individual trials, after mice traveled a randomized distance, one of the two gratings changed its orientation. The task of the mice was to lick the spout if an orientation change happened, and to otherwise withhold from licking. We used transgenic mice and viral systems to target the direct and indirect pathway medium spiny neurons (MSNs) in the striatum. During optogenetic stimulation experiments, a brief light pulse was delivered to the striatum through an implanted optic fiber at the onset of the orientation change in a randomized subset of trials. Our preliminary data show that: 1) activating indirect MSNs caused a large reduction (~0.5) in sensitivity for visual stimuli presented contralateral to the stimulation side, and reductions (~0.4) in response criterion for both ipsilateral and contralateral stimuli; 2) activating direct MSNs caused a larger reduction (~0.7) of response criterion for the contralateral side, and a similar but small reduction (~0.3) of sensitivity for both sides. These results suggest that striatal direct and indirect pathways play differential roles in the decision mechanisms underlying visual detection.
Meeting abstract presented at VSS 2016