| Summary: | The main goal of this experiment was to detect on-line programming as it
occurred during the execution of forearm extension movements by including a
probe reaction time paradigm within an extension-flexion movement task. The
experiment included a primary and a secondary task condition and subjects
performed these tasks in both single and dual-task situations. For the primary
task in the single task condition, subjects performed forearm extension (E), and
two types of extension-flexion movements for which the time between
successive extension and flexion movements was varied (i.e., this time period
was 50-100 msec (EFS) or 250-300 msec (EFL)). For the secondary task in the
single task condition, subjects wore headphones through which an auditory
stimulus (i.e., probe) was delivered at seven positions, either before or after the
primary task stimulus. The onset of this probe was determined by either an
absolute time interval, or by on-line analysis of EMG and acceleration profile
data. Subjects closed their jaw as quickly as possible following the probe. In
the dual task condition, the forearm movement and the jaw clench response
were performed simultaneously.
The reaction times were comparable for E, EFS and EFL movements in
the dual task condition, suggesting that subjects programmed the flexion
movement during the execution of the extension movement. By combining
probe reaction time measures with those from the initial latency period, a more
accurate description could be given of where in time these on-line control
processes took place. Specifically, the probe reaction times were lengthened
when the probe occurred at the end of the extension movement for EFL
movements. It appeared that subjects delayed the execution of the jaw clench
response until the programming of the flexion movement had been completed
and hence the jaw clench and flexion response were initiated concurrently at
this probe position (evidenced by EMG activity of the Masseter and Biceps
muscles). Subjects appeared to use this same strategy for probes occurring
during the pause time for EFL movements and at the point at which peak
velocity was obtained for EFS movements. === Education, Faculty of === Kinesiology, School of === Graduate
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