Role of Ipsilateral Motor Cortex in Bimanual Motor Control

Jeff Summers1, Florian Kagerer1, Shirley Wilson2, &
Andras Semjen3

1. School of Psychology, University of Tasmania, Tasmania
2. University of Southern Queensland, Toowoomba, Australia
3. Cognitive Neuroscience Laboratory, Marseille, France


There is growing evidence that the ipsilateral motor cortex may be involved in the generation of mirror movements and the functional recovery from stroke. In this paper it will be proposed that disinhibition of ipsilateral motor pathways may also contribute to the marked manual asymmetries that have been observed in a bimanual circling task under frequency scaling. Two lines of research examining this issue will be presented. The first is a computer simulation of the circling task based on the assumption that the motor systems controlling each hand are prone to neural cross-talk. Assuming predominating coupling influences from the dominant to the nondominant limb, the simulations successfully reproduced the main characteristics of performance on the bimanual circling task. The second are ongoing experiments using transcranial magnetic stimulation (TMS) to identify and characterise ipsilateral corticospinal pathways in healthy adults. The findings so far indicate that ipsilateral pathways can be activated by TMS and that they are of longer latency than contralateral responses and that thresholds are some 30% higher than for contralateral responses.