A basolateral amygdala to dorsolateral striatum projection modulates stimulus-evoked motor behavior.

The dorsal striatum is divided into dorsomedial (DMS) and dorsolateral (DLS) subregions, which support distinct aspects of motor learning. The basolateral amygdala (BLA) encodes emotionally salient information and can influence striatal function, but its connection to the sensorimotor DLS remains poorly understood. Using mice, we identify a direct, functional BLA-DLS projection that arises from a neuronal population distinct from BLA neurons projecting to the DMS. Although sparser than BLA-DMS inputs, BLA-DLS synapses preferentially targeted the distal dendrites of striatal projection neurons, positioning them to modulate heterosynaptic integration. Repeated optogenetic activation of BLA-DLS inputs potentiated stimulus-evoked grooming and induced heterosynaptic plasticity. This projection was also pathologically strengthened in compulsively grooming Sapap3 null mice. Together, these findings reveal a direct mechanism through which limbic input from the amygdala shapes sensorimotor striatal circuits and motor output.