SUMMARY
Dopamine (DA) is a critical modulator of brain circuits that control voluntary movements, but our understanding of its influence on the activity of target neurons in vivo remains limited. Here, we use two-photon Ca2+ imaging to simultaneously monitor the activity of direct and indirect-pathway spiny projection neurons (SPNs) in the striatum of behaving mice during acute and prolonged manipulations of DA signaling. We find that, contrary to prevailing models, DA does not modulate activity rates in either pathway strongly or differentially. Instead, DA exerts a prominent influence on the overall number of direct and indirect pathway SPNs recruited during behavior. Chronic loss of midbrain DA neurons in a model of Parkinson’s disease selectively impacts direct pathway ensembles and profoundly alters how they respond to DA elevation. Our results indicate that DA regulates striatal output by dynamically reconfiguring its sparse ensemble code and provide novel insights into the pathophysiology of Parkinson’s disease.
