Biomedical subjects

I Collin

Publications and source records attributed to I Collin.

3 recordsLinked to original sources

PubMed1997

The "Poffenberger" and "Dimond" paradigms: interrelated approaches to the study of interhemispheric dynamics?

Brown and Jeeves (1993) found that an evoked potential estimate of interhemispheric transfer time, from the left to the right hemisphere, correlated negatively with a bilateral field advantage (BFA) in a response-choice letter matching task. We implemented a go no-go dot size matching 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. Sixteen normal right-handed subjects were tested. The CUDs were negatively correlated with the BFAs. Canonical correlation analysis of this set of relations was highly significant (r = .95). Estimates of left-to-right relay were far more strongly related to BFA (p = .0001) than were estimates of right-to-left relay (p = .03). "Same" decisions yielded a unilateral field advantage and "different" decisions a bilateral field advantage in omission error data, this crossed interaction reaching significance. More efficient interhemispheric relay favored BFAs, i.e., strongly suggesting in such cases an advantage of interhemispheric over intrahemispheric integration. This effect appeared to be markedly asymmetric. Furthermore, resource sharing within and between the hemispheres was a function of the "same" versus "different" dimensions of the decision to be made, especially in omission errors. The opposite dissociation occurred less markedly in the reaction times, this double dissociation reaching significance, revealing presence of a subtle speed-accuracy trade-off in interhemispheric dynamics.

Adult↗

PubMed1996

Intermanual transfer of somaesthetic information: a two-point discrimination experiment.

Twenty-four men and 24 women, all university students, judged whether two-point aesthesiometric applications, either both to the same palm (intramanual condition) or one to each palm (intermanual condition) were of the "same" or "different" spans. The main question was to determine the extent to which there is a loss of accuracy during intermanual comparisons, and by inference, interhemispheric relay. A second question, the extent to which this loss is a function of the difficulty of the task, was to be answered by the inclusion of span-differences above, at, and below threshold. Difficult trials were associated with a highly significant intramanual advantage of 4.74%, and easy trials with a non-significant intramanual advantage of 1.16%. For both intra- and intermanual conditions, subjects made more errors as a function of decreasing "span-difference". The two hands performed equally well, and the order of stimulation between the two hands made no difference in the results. The intramanual advantage could not be construed as an effect of response set (i.e., an artefact of subject's inherent bias for "same" or "different" judgements), nor as a scaling effect (e.g., of span scales relating to receptive field properties, relating in turn to interhemispheric relay). There was no evidence of a sex difference in basic ability, nor in the cost of hemispheric relay. It was concluded that there is a loss of precision in interhemispheric relay of somaesthetic discrimination, but this can only be detected close to threshold.

Adult↗

PubMed1995

Does so-called interhemispheric transfer time depend on attention?

To our knowledge none of many past attempts to experimentally modulate the crossed-uncrossed differential (CUD) or so-called "interhemispheric transfer time" derived from appropriate visual reaction time experiments has ever succeeded. The present 4 experiments were designed to establish that (a) under normal attentional constraints, significant CUDs would be obtained, but that (b) lateral mobilization of attention by probabilistic (valid and invalid) cuing as to target location would significantly and systematically alter the CUDs. In a baseline experiment, a significant CUD was obtained. In Experiments 2-4, CUDs were rendered nonsignificant by probabilistic cuing. Specific experimental conditions generally did not significantly influence the CUD in a systematic direction. In only one of many analyses of those results did an experimental effect on the CUD reach significance: In Experiment 3 intrasubject mean reaction times yielded a significant complex dissociation of CUDs as a function of type of cuing (valid or invalid) and stimulus onset asynchrony. It was concluded that the CUD can be significantly modulated by target location cuing, but only under very specific conditions. The direction of the trends in all the experiments, and in the significant finding, suggests that the CUD component that is most markedly influenced by such cues is a postcallosal, motor component.

Adult↗