SYNCHRONIZING ACTIONS WITH EVENTS - THE ROLE OF SENSORY INFORMATION

Tasks requiring the subject to tap in synchrony to a regular sequence of stimulus events (e.g., clicks) usually elicit a response pattern in which the tap precedes the click by about 30-50 msec. This ''negative asynchrony'' was examined, first, by instructing subjects to use diff erent effectors for tapping (hand vs. foot; Experiments 1 and 2), and second, by administering extrinsic auditory feedback in addition to th e intrinsic tactile/kinesthetic feedback (Experiment 2). Experiment 3 controlled whether the results observed in Experiment 2 were due to pu rely sensory factors within the auditory modality. Results suggest tha t taps are synchronized with clicks at the central level by superimpos ing two sensory codes in time: the tactile/kinesthetic code that repre sents the tap (the afferent movement code) and the auditory code that represents the click (the afferent code that results from the guiding signal). Because the processing times involved in code generation are different for these two central codes, the tap has to lead over the cl ick.