Right hemisphere dominance in the metacontrol of cerebral arousal.

Abstract

In a series of four experiments, right-handed subjects identified nonsense syllables briefly presented unilaterally (left visual field (LVF) or right visual field (RVF)) or unilaterally on some trials and bilaterally (in the center of the field (CVF) or bilateral redundant (BVF)) on other trials. Both current and previous field of presentation affected performance. There was a RVF advantage on all tasks. In addition, on a task with only unilateral trials, performance was improved bilaterally following unilateral presentation in the LVF. In contrast, when unilateral and bilateral trials were intermixed, performance in the RVF was improved following LVF, CVF or BVF trials. There were no effects of present or prior field of presentation on a line orientation task. The effect of the previous field of stimulation is attributed to changes in the distribution of arousal to the cerebral hemispheres. The critical factor for its appearance seems to be direct stimulation of the right cerebral hemisphere, whether this occurs in isolation, or concurrently with left hemisphere stimulation. There is a great deal of evidence that the right hemisphere plays a dominant role in the bilateral control of cerebral arousal, and it is proposed that the right cerebral hemisphere is the site of a metacontrol system that governs differential arousal of the cerebral hemispheres in response to external stimulation. Interhemispheric collaboration was also investigated. The presentation of syllables to the lateral fields as well as centrally or bilaterally makes possible a comparison of performance on trials in which only one hemisphere has direct access to the stimulus to those in which the cerebral hemispheres have simultaneous access. There were demonstrable hemispheric differences in strategy, as revealed by error patterns in the unilateral fields. Stimuli presented in the center field or bilaterally redundant stimuli were processed in a manner intermediate between that used with LVF and RVF stimuli; it is concluded that both cerebral hemispheres encode the direct stimulus projection in a hemisphere-typical fashion, and then exchange information. Under the more naturalistic condition of bihemispheric availability of information, the cerebral hemispheres share the processing load.