Evidence for left hemisphere superiority in processing movement-related tonal signals

A pursuit auditory tracking (PAT) paradigm was used to investigate asymmetric hemispheric processing and control for a sensorimotor task analogous to speech. In PAT subjects match a continuously varying target tone (ranging from 100 Hz to 2 kHz) presented to one ear with a qualitatively similar second tone (the cursor) presented to the other ear and controlled by mandibular elevation and depression movements. Twenty right-handed subjects were given the standard dichotic mode of counterbalanced target/cursor signal presentations. Another group of 16 right-handed subjects underwent, after extensive task familiarization, tracking with only the target signal presented in counterbalanced order to one ear at a time with white noise presented to the other ear. The results of the standard tracking group replicated past studies showing a statistically significant tracking advantage in favor of cursor/right ear presentations. The No-Cursor group showed a significant target/right ear advantage. These results are discussed with reference to two theoretical hypotheses to explain the tracking laterality effect--a division-of-labor hypothesis and a sensorimotor integration hypothesis.