THE POFFENBERGER AND DIMOND PARADIGMS - INTERRELATED APPROACHES TO THE STUDY OF INTERHEMISPHERIC DYNAMICS

Brown and Jeeves (1993) found that an evoked potential estimate of int erhemispheric transfer time, from the left to the right hemisphere, co rrelated negatively with a bilateral field advantage (BFA) in a respon se-choice letter matching task, We implemented a go no-go dot size mat ching task to determine whether the crossed-uncrossed difference (CUD) in reaction time, commission errors and omission errors (estimates of the ''cost'' of interhemispheric transfer), would correlate with BFAs in data from the same experiment and whether the type of decision ('' same'' versus ''different'') would modulate the CUDs and/or BFAs. Sixt een normal right handed subjects were tested. The CUDs were negatively correlated with the BFAs. Canonical correlation analysis of this set of relations was lightly significant (r = .95). Estimates of left-to-r ight relay were far more strongly related to BFA (p = .0001) than were estimates of right-to-left relay (p = .03). ''Same'' decisions yielde d a unilateral field advantage and ''different'' decisions a bilateral field advantage in omission error data, this crossed interaction reac hing significance. More efficient interhemispheric relay favored BFAs, i.e., strongly suggesting in such cases an advantage of interhemisphe ric over intrahemispheric integration, This effect appeared to be mark edly asymmetric. Furthermore, resource sharing within and between the hemispheres was a function of the ''same'' versus ''different'' dimens ions of the decision to be made, especially in omission errors. The op posite dissociation occurred less markedly in the reaction times, this double dissociation reaching significance, revealing presence of a su btle speed-accuracy trade-off in interhemispheric dynamics. (C) 1997 A cademic Press.