Dorsal striatum coding for the timely execution of action sequences

The automatic initiation of actions can be highly functional. But
occasionally these actions cannot be withheld and are released at
inappropriate times, impulsively. Striatal activity has been shown to
participate in the timing of action sequence initiation and it has been
linked to impulsivity. Using a self-initiated task, we trained adult male
rats to withhold a rewarded action sequence until a waiting time interval
has elapsed. By analyzing neuronal activity we show that the striatal
response preceding the initiation of the learned sequence is strongly
modulated by the time subjects wait before eliciting the sequence.
Interestingly, the modulation is steeper in adolescent rats, which show a
strong prevalence of impulsive responses compared to adults. We
hypothesize this anticipatory striatal activity reflects the animals'
subjective reward expectation, based on the elapsed waiting time, while
the steeper waiting modulation in adolescence reflects age-related
differences in temporal discounting, internal urgency states, or
explore-exploit balance.