Parvalbumin interneurons gate and shape striatal sequences

Loss of parvalbumin-expressing striatal interneurons (PV+) is associated with impulsive and uncontrolled behaviors. The underlying disruption in striatal information processing is unclear. We compared spiking of five identified neuron types in sensorimotor striatum, as unrestrained rats waited for a cue then performed brief, well-practiced actions. During waiting PV+ selectively increased firing, and suppressing PV+ at this time increased premature movements. This indicates a role in action restraint. However, suppressing PV+ after the cue had the opposite effect: slowed initiation and execution of actions. We found that each action was accompanied by a distinct, rapid striatal firing sequence, including both direct and indirect pathway spiny projection neurons (SPNs) and overlaid by sequential PV+ firing. Nearby pairs of PV+ and SPNs showed millisecond-level synchrony, and PV+ firing inhibited SPNs [~]2ms later. PV+ interneurons thus provide both broad restraint and precise sculpting of striatal output to achieve fluid, appropriately timed behavior.