A striatal role in sensory-driven learning behaviors

The striatum, the input nucleus of the basal ganglia, has primarily been implicated in the generation, initiation and selection of motor commands. In contrast to its anterior sub-area, the posterior part (pStr) or the “tail” of the striatum, is heavily innervated by auditory, visual and somatosensory regions suggesting its unique role in sensory-driven behaviors. Recent studies have shown a role for auditory pStr afferents in learned defensive behaviors. Despite these evidences, much remains unknown about striatal responses to various sensory modalities, their cellular specificity and how multi-sensory afferents shape learning through the modulation of downstream striatal outputs. To study this, we first anatomically investigated the localization and overlap of sensory projections to the pStr, and then used an auditory-discrimination task as a proxy to examine the role of the pStr in sensory-driven behaviors using two-photon calcium imaging. We confirmed primary sensory cortical/thalamic innervations to the pStr, with partial overlaps across sensory modalities, but interestingly, observed secondary but not primary motor afferents. Furthermore, differential sensory inputs to dorsal vs ventral pStr implicated a possible preservation of topographic sensory representation from the cortex to the striatum. Preliminary imaging data shows a small sub-population of sound-responsive pStr neurons, and a larger fraction responding to tone and movement. In our appetitive learning task, contrary to previous studies in fear conditioning, the tone-responsive fraction lessens, average amplitudes diminish and the peak is followed by a sustained quiescence. Ongoing experiments will address these differences, and examine pStr neural mechanisms underlying multisensory processing and sensorimotor transformations.