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This Article Full Text Full Text (PDF) All Versions of this Article: 94/3/1861    most recent 00320.2005v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Obhi, S. S. Articles by Goodale, M. A. Search for Related Content PubMed PubMed Citation Articles by Obhi, S. S. Articles by Goodale, M. A.

Bimanual Interference in Rapid Discrete Movements Is Task Specific and Occurs at Multiple Levels of Processing

Department of Psychology, University of Western Ontario, London, Ontario, Canada

Submitted 28 March 2005; accepted in final form 17 May 2005

It has been suggested that interference in symbolically cued bimanual reaction time tasks is caused primarily by the perceptual processing of stimuli and not by motor preparation of the required movements. Here subjects made movements of the right and left index fingers that varied in their spatial and motor congruence. Spatial congruence was manipulated by presenting symbolic cues (i.e., pairs of letters) on a computer screen cueing the required movement directions. Motor congruence was manipulated by altering hand orientation. Results showed that interference occurs at both the stage of stimulus processing and the stage of motor preparation. These effects were reflected in the latencies of the different bimanual movements with both motor incongruence and spatial incongruence causing significant increases in reaction time. However, spatially incongruent movements that were made in response to incongruent visual cues demonstrated changes in reaction time that were more than double those of movements that required simultaneous activation of nonhomologous muscles. Therefore in symbolically cued bimanual reaction-time tasks, although both motor and spatial constraints operate, there is a clear dominance of spatial incongruence on performance. While motor congruence effects are likely due to cross-facilitation in corticospinal pathways, spatial incongruence effects are probably due to interference between the mechanisms that identify incongruent stimuli and translate these cues into the appropriate movements.