Cerebral Hemispheric Asymmetry in Humans

Abstract

Morphological asymmetry of the frontal operculum and temporal planum becomes measurable at the 29th week of gestation. There is evidence of subsequent differential development of the planum in favor of the left, with the left planum larger than the right. While both the frontal operculum and left planum were always present, the right planum ranged in size from absent (10%)to larger than the left (about 10%). Females predominated (P less than .05) in the latter group. The findings suggest that (1) a higher percentage of persons may have right-sided cerebral representation for speech than has been assumed previously; (2) a predetermined morphological asymmetry contributes to establishing the ultimate pattern of cerebral speech representation following an early insult to a predisposed hemisphere; and (3) it is necessary to scrutinize clinical material for the differential organization of hemispheric development between sexes.

Functional Neuroimaging of Speech Perception in Infants

“…This is consistent with the left lateralization observed in ERPs (7,8) and in dichotic listening during syllable discrimination tasks in infants (20). An anatomical asymmetry is detectable in the planum temporale as early as 31 weeks of gestation (21). Our fMRI results indicate that this anatomical difference supports an early functional asymmetry in the processing capacities of the two hemispheres.…”

Improved method for noninvasive measurement of regional cerebral blood flow by 133Xenon inhalation. Part I: description of method and normal values obtained in healthy volunteers.

“…Recent morphological studies of the human brain indicate that the area of the left temporal cortex is larger than that of the right hemisphere. 40 Psychophysiological activation in the present study, including counting, talking to the subject, and having him listen to dance music with familiar ballads, resulted in significant increases in rCBF of the left hemisphere.…”

Electrophysiological signatures: Magnetoencephalographic studies of the neural correlates of language impairment in autism spectrum disorders

“…Although the human brain is generally symmetric, the existence of specific structural and functional asymmetries is one of the foundations of modern neuroscience. From a structural perspective, a majority of the population shows greater width and length in right versus left frontal regions (Weinberger et al, 1982;Durara et al, 1991), but the left occipital region is wider and larger than the right occipital region (Wada et al, 1975;Lemay and Kido, 1978;Durara et al, 1991). Particular attention has been drawn to cerebral asymmetries in the region of the planum temporale (PT), especially because of this region's importance in language function.…”