Integrator dynamics in the cortico-basal ganglia loop for flexible motor timing

"Flexible control of motor timing is crucial for behaviour1,2,3,4. Before volitional movement begins, the frontal cortex and striatum exhibit ramping spiking activity, with variable ramp slopes anticipating movement onsets5,6,7,8,9,10,11,12. This activity in the cortico-basal ganglia loop may function as an adjustable timer,' triggering actions at the desired timing. However, because the frontal cortex and striatum share similar ramping dynamics and are both necessary for timing behaviours, distinguishing their individual roles in this timer function remains challenging."

"Following transient silencing of the frontal cortex, cortical and striatal activity swiftly returned to pre-silencing levels and resumed ramping, leading to a shift in lick timing close to the silencing duration. Conversely, briefly inhibiting the striatum caused a gradual decrease in ramping activity in both regions, with ramping resuming from post-inhibition levels, shifting lick timing beyond the inhibition duration. Thus, inhibiting the frontal cortex and striatum effectively paused and rewound the timer, respectively."

Transient silencing experiments and multi-regional electrophysiology in mice performing a flexible lick-timing task reveal distinct causal roles for frontal cortex and striatum in motor timing. Transient frontal cortex inhibition produced rapid recovery of cortical and striatal ramping activity, resuming from pre-inhibition levels and shifting lick timing by roughly the inhibition duration, consistent with a paused timer. Brief striatal inhibition produced a gradual decrease in ramping across both regions and resumption from a reduced activity level, shifting lick timing beyond the inhibition duration, consistent with a rewound timer. The findings support a model where the striatum temporally integrates frontal cortical input to generate ramping activity that regulates motor timing.

Read at www.nature.com