Parvalbumin interneurons gate and shape striatal sequences

Impulsive and uncontrolled behaviors are associated with loss of parvalbumin-expressing striatal interneurons (PV+). To understand this microcircuit mechanism we compared spiking of five classes of identified neurons in sensorimotor striatum, as rats waited for a cue, then performed brief actions. During waiting PV+ increased firing, and suppression of PV+ increased premature movements, supporting a role in action restraint. Once underway, each action was accompanied by a rapid striatal firing sequence, including PV+ and direct and indirect pathway spiny projection neurons (SPNs). Nearby PV+ and SPNs showed millisecond-level synchrony, and PV+ firing inhibited SPNs ~2ms later. Suppressing PV+ immediately changed which SPNs participated in sequences, and slowed movements. PV+ thus provide both broad restraint and precise sculpting of striatal output to achieve fluid, appropriately timed behavior.