تعامل دو طرفه زمینه ای، تخصص نیمکره غربی و پتانسیل برانگیخته زمان انتقال بین نیمکره

The interrelationship between bilateral visual field processing, hemispheric specialization and interhemispheric transmission time (IHTT) was examined in two experiments in order to test two theories regarding callosal function and lateralized visual processing. Contrary to both theoretical speculations [Braun, Neuropsychology Review, Vol. 3, pp.321–365, 1992] and a recent report [Nowicka et al. Neuropsychologia, Vol. 34, pp. 147–151, 1996], the directional asymmetry in evoked potential measures of IHTT did not vary with task differences in indices of hemispheric specialization. IHTT was faster from right to left hemispheres regardless of visual field advantage for the task. Similarly, patterns of correlation between IHTT and bilateral field advantage did not change between verbal and spatial matching tasks, despite differences in visual field advantage. Since the latter data did not consistently support the Brown and Jeeves [Neuropsychologia, Vol. 31. pp. 1267–1281, 1993] hypothesis, an alternative hypothesis involving hemispheric asymmetries in attention rather than processing specialization was proposed.

Recent research concerning the corpus callosum has focused attention on asymmetry in transmission speed and the functional significance of this asymmetry for interhemispheric interactions and hemispheric specialization. Faster transmission has been noted from the right hemisphere to the left hemisphere (compared to left-to-right transmission) in both crossed–uncrossed differences (CUD) in RTs [17], [5], [6], [7]and visual evoked potentials [9]. One area of debate concerns reports that the asymmetry in speed of callosal transmission may be dynamically related to task specific differences in hemispheric dominance [5], [6], [7], [22]. Another area of debate concerns how IHTT affects performance on bilateral information matching tasks. Brown and Jeeves [8]proposed that the performance advantage for bilateral (vs unilateral) visual matching is related to faster IHTT from the hemisphere that is specialized for the task to the nonspecialized hemisphere, resulting in enhancement of processing in the less able hemisphere. This paper presents data which address both of these areas of debate.