Incidence of laterality effects in mandibular and manual performance of dichoptic visual pursuit tracking

In dichotic pursuit auditory tracking tasks (PAT) subjects match a continuously varying pure tone presented to one ear with a second tone presented to the other ear and controlled by unidimensional movements of part of their motor system. In previous studies in which tonal frequency was varied, performance was significantly better when the tone controlled by a speech articulator (tongue, jaw) was presented to the right ear, rather than the left, but not if the tone was hand controlled. This study examined a visual analog of the PAT in which subjects matched the vertical position of a continually moving horizontal line (target) presented on one side of their point of fixation, with a second line (cursor) presented on the other side of their fixation point. Two predictions were confirmed for 12 right handed subjects: that there would be no significant laterality effect for articulatory (jaw) tracking because previous auditory tracking findings were speech related; and, that there would be a significant laterality effect (cursor right field-left hemisphere) for right hand tracking because of the development of a specialized sensorimotor integration mechanism for eye-right hand coordination in the left hemisphere. Alternative explanations for the right hand tracking results, and for the nonsignificant trend towards a laterality effect (cursor left field-right hemisphere) for left hand tracking, were discussed.