The nature of hemispheric specialization in man

Abstract

The traditional verbal/nonverbal dichotomy is inadequate for completely describing cerebral lateralization. Musical functions are not necessarily mediated by the right hemisphere; evidence for a specialist left-hemisphere mechanism dedicated to the encoded speech signal is weakening, and the right hemisphere possesses considerable comprehensional powers. Right-hemisphere processing is often said to be characterized by holistic or gestalt apprehension, and face recognition may be mediated by this hemisphere partly because of these powers, partly because of the right hemisphere's involvement in emotional affect, and possibly through the hypothesized existence of a specialist face processor or processors in the right. The latter hypothesis may, however, suffer the same fate as the one relating to a specialist encodedness processor for speech in the left. Verbal processing is largely the province of the left because of this hemisphere's possession of sequential, analytic, time-dependent mechanisms. Other distinctions (e.g., focal/diffuse and serial/parallel) are special cases of an analytic/holistic dichotomy. More fundamentally, however, the left hemisphere is characterized by its mediation of discriminations involving duration, temporal order, sequencing, and rhythm, at thesensory(tactual, visual, and, above all, auditory) level, and especially at themotorlevel (for fingers, limbs, and, above all, the speech apparatus). Spatial aspects characterize the right, the mapping of exteroceptive body space, and the positions of fingers, limbs, and perhaps articulators, with respect to actual and target positions. Thus there is a continuum of function between the hemispheres, rather than a rigid dichotomy, the differences being quantitative rather than qualitative, of degree rather than of kind.

Form-specific visual priming for new associations in the right cerebral hemisphere

“…Our hypothesis that holistic processing characterizes an SVF subsystem that operates more effectively in the RH than in the LH is roughly consistent with previous theories that emphasize general aspects oflateralized analytical versus holistic processing (e.g., Bever, 1980;Bradshaw & Nettleton, 1981;Corballis, 1989;Diamond & Carey, 1986;Levine & Calvanio, 1989). In addition, our hypothesis is consistent with several past findings and may help to illuminate interesting interpretations of them.…”

Right ear advantage for vocal communication in frogs results from both structural asymmetry and attention modulation

“…Morphological leftright asymmetries in the brain are well known in anamniotes [1]. For example, the habenular nuclei are markedly asymmetrical in size in lampreys, hagfish, sharks, some teleost fish and amphibians [64,65]. The left habenula appear to have a more lobate structure than its right counterpart.…”

Handedness, hemispheric asymmetries, and joke comprehension

“…Behavioral tests of hemispheric specialization, such as dichotic listening and tapping interference paradigms, indicate that lateralization of language functions is less extreme among left-handers than their right-handed counterparts (see Ref. [5] for a review). On the dichotic listening task, for instance, the right ear advantage for accuracy has been found to correlate with handedness [10].…”