Vestibular stimulation affects dichotic lexical decision performance

We report an experimental attempt to shift, by vestibular stimulation, heal thy subjects' right ear advantage (REA) in a dichotic listening (DL) task w ith words and nonwords as stimuli. Forty right-handed men performed the tas k under two different conditions, once while sitting in a stationary turnin g chair (baseline) and once during sinusoidal rotation. In this latter cond ition, every other stimulation was received during maximal left-to-right (i .e., clockwise), every other during maximal right-to-left (i.e., counterclo ckwise) acceleration. There was a reliable REA for lexical decision accurac y in the baseline and right-to-left trials but not during left-to-right rot ation. While right ear performance was unaffected by rotation, there were m ore correct lexical decisions to left ear targets exclusively during left-t o-right turns (one-tailed P = 0.05). Since there were no parallel shifts in auditory thresholds under the different conditions, this effect is not due to any hypothetical auditory-vestibular interactions on a primary sensory level. The improvement in left ear DL performance, although small in our st udy, is comparable to the symptom-alleviating effect of caloric vestibular stimulation in patients with left-sided hemispatial neglect and interpreted as a consequence of a rotation-induced attentional shift towards the left hemispace. (C) 1999 Elsevier Science Ltd. All rights reserved.