Somatosensory temporal discrimination learning generalizes to motor interval production

The present study investigated whether a common timing mechanism underlies the ability to analyze incoming sensory information and control outgoing motor commands. Participants were presented with two pairs of air puffs on the ventral surface of the right forearm. One pair (the standard interval) was separated by 500 ms on every trial for half of the participants (“500 group”) and 800 ms on every trial for the other half (“800 group”). The duration of the comparison interval was always longer but varied adaptively to determine discrimination thresholds. Participants indicated which of the two intervals was longer. Both groups performed two motor interval production tasks (pressing a button twice in succession with the right thumb) before and again after somatosensory training. The target inter-press interval was 500 ms in one task and 800 ms in the other. A critical feature of the design was that only one of the motor tasks for each of the groups shared temporal properties with the somatosensory discrimination task. The results showed that somatosensory discrimination learning generalizes to motor interval production when the two tasks share temporal properties. Specifically, the 500 group showed a greater reduction in motor timing variability on the 500 ms task than the 800 ms task, whereas the 800 group showed a greater reduction in motor timing variability on the 800 ms task than the 500 ms task. The possible neural basis of temporal learning generalization is discussed.