Interhemispheric integration of simple visuomotor responses in patients with partial callosal defects.

Full Abstract

Because of the organization of visual and motor pathways, simple manual responses to a light stimulus in the right or left visual hemifields are performed faster with uncrossed hand-field combinations than with crossed hand-field combinations. Uncrossed responses can be integrated within a single hemisphere, whereas crossed responses require a time-consuming interhemispheric transfer via the corpus callosum which is reflected in the difference between crossed and uncrossed reaction times. We investigated crossed-uncrossed differences (CUDs) in speed of simple visuomotor responses to lateralized flashes in seven subjects with an anterior section of the corpus callosum sparing the splenium and in one subject with an agenetic absence of the splenium due to a cerebrovascular malformation. There was no evidence of an abnormal prolongation of the CUDs in any of these subjects, in sharp contrast with the very long CUDs exhibited by an epileptic subject with a complete callosal section and two subjects with total callosal agenesis tested in the same experimental situation [1]. The normality of the CUDs in the subjects with partial callosal defects was not due to a postoperatory reorganization of interhemispheric communication, since there was no indication of an increased CUD in a patient tested as early as 5 days after the anterior callosotomy. These results are compatible with the assumption that both anterior and posterior callosal routes may subserve the integration of speeded manual responses to a visual stimulus directed to the hemisphere ipsilateral to the responding hand.

Author information

Author/s: Tassinari, G (G); Aglioti, S (S); Pallini, R (R); Berlucchi, G (G); Rossi, G F (GF);

Affiliation: Istituto di Fisiologia Umana, Università di Verona, Italy.

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: Behavioural brain research (Behav Brain Res), published in NETHERLANDS. (Language: eng)

Reference: 1994-Oct; vol 64 (issue 1-2) : pp 141-9

Dates: Created 1995/03/08; Completed 1995/03/08; Revised 2006/11/15;

PMID: 7840880, status: MEDLINE (last retrieval date: 2/18/2009, IMS Date: )

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