Effect of Transcranial Magnetic Stimulation on Bimanual Movements

Abstract

Transcranial magnetic stimulation (TMS) of the motor cortex can interrupt voluntary contralateral rhythmic limb movements. Using the method of "resetting index" (RI), our study investigated the TMS effect on different types of bimanual movements. Six normal subjects participated. For unimanual movement, each subject tapped either the right or left index finger at a comfortable rate. For bimanual movement, index fingers of both hands tapped in the same (in-phase) direction or in the opposite (antiphase) direction. TMS was applied to each hemisphere separately at various intensities from 0.5 to 1.5 times motor threshold (MT). TMS interruption of rhythm was quantified by RI. For the unimanual movements, TMS disrupted both contralateral and ipsilateral rhythmic hand movements, although the effect was much less in the ipsilateral hand. For the bimanual in-phase task, TMS could simultaneously reset the rhythmic movements of both hands, but the effect on the contralateral hand was less and the effect on the ipsilateral hand was more compared with the unimanual tasks. Similar effects were seen from right and left hemisphere stimulation. TMS had little effect on the bimanual antiphase task. The equal effect of right and left hemisphere stimulation indicates that neither motor cortex is dominant for simple bimanual in-phase movement. The smaller influence of contralateral stimulation and the greater effect of ipsilateral stimulation during bimanual in-phase movement compared with unimanual movement suggest hemispheric coupling. The antiphase movements were resistant to TMS disruption, and this suggests that control of rhythm differs in the 2 tasks. TMS produced a transient asynchrony of movements on the 2 sides, indicating that both motor cortices might be downstream of the clocking command or that the clocking is a consequence of the 2 hemispheres communicating equally with each other.

Deficits in Coordinative Bimanual Timing Precision in Children With Specific Language Impairment

“…This makes sense given that interlimb coordination develops over a protracted period (Corbetta & Thelen, 1996). Unimanual and bimanual actions are also organized differently in the brain, with unimanual actions organized contralaterally and bimanual actions showing a strong left hemisphere dominance (Jäncke et al, 1998;Serrien et al, 2003;Viviani, Perani, Grassi, Bettinardi, & Fazio, 1998; but see Chen et al, 2005;Foltys et al, 2001). …”

Spatiotemporal re-organization of large-scale neural assemblies underlies bimanual coordination

“…An alternative way to identify the cortical networks responsible for bimanual coordination is by using techniques such as transcranial electric or magnetic stimulation to perturb relevant brain areas , and subsequently following the effects of these perturbations on switching behavior (Meyer-Lindenberg et al, 2002;Stinear and Byblow, 2002;Steyvers et al, 2003;Chen et al, 2005). Cortical structures where stimulation was most likely to elicit switching from antiphase to inphase were right premotor (PM) areas, and to a lesser degree, the supplementary motor area (SMA), left PM, and right and left motor and somatosensory cortices (Meyer-Lindenberg et al, 2002).…”

Multiple interactions between hemispheres of the brain modulating coupling of bilateral movements

“…These results indicate that the right and left motor systems were strongly coupled. According to previous studies, ipsilateral innervations of the left primary motor cortex are more prominent than that of the right primary motor cortex [8] [9]. In addition, the left primary motor cortex inhibits the right primary motor cortex more effectively than vice versa [10] and also during symmetric bilateral movements, there is asymmetric activation between the right and left primary motor cortexes [11].…”