Interhemispheric motor inhibition: its role in controlling electromyographic mirror activity

Abstract

Electromyographic mirror activity (MA) refers to involuntary activation of the non-active limb during intended strictly unilateral movements of the other limb. MA occurs in the majority of healthy adults but little is known about its neurophysiological foundation. Here we examined in healthy adults the hypothesis that transcallosal interhemispheric inhibition (IHI) between the primary motor cortices determines the extent to which MA occurs. IHI was tested by an established paired transcranial magnetic stimulation protocol [A. Ferbert et al. (1992) J. Physiol. (Lond.), 453, 525-546]. In a first experiment we found that the magnitudes of IHI and MA were inversely correlated. In a second experiment we sought to establish a more causative relation by exploring the changes induced by low-frequency repetitive transcranial magnetic stimulation of primary motor cortex on IHI and MA. These changes were also significantly inversely correlated, i.e. a repetitive transcranial magnetic stimulation-induced increase in IHI was associated with a decrease in MA, and a decrease in IHI was associated with an increase in MA. These results provide strong and consistent evidence that transcallosal inhibitory interhemispheric interaction provides a significant route by which unwanted MA during intended unimanual motor tasks can be controlled.

Congenital mirror movements: a clue to understanding bimanual motor control

“…It also has a high spatial and temporal specificity for corresponding left and right intrinsic hand muscles [54] and negatively correlates with the electromyographic mirror activity [29]. Likewise, the interhemispheric inhibition negatively correlates with the electromyographic mirror activity, as well as the interhemispheric inhibition changes induced by repetitive transcranial magnetic stimulation [37]. In addition, the positive correlation between transcallosal motor fiber density and the degree of interhemispheric inhibition in healthy volunteers [85] suggests that structural abnormalities of transcallosal fibers may account for the defective interhemispheric inhibition in congenital MM.…”

Spatiotemporal Dynamics of Bimanual Integration in Human Somatosensory Cortex and Their Relevance to Bimanual Object Manipulation

“…To enable differentiated and independent patterns of activity between the hands during simultaneous bimanual tactile exploration of objects, callosal inhibition may alternately suppress interfering signals of the homologous cortical area, because it was demonstrated in primary motor cortex MI (Hübers et al, 2008). Callosal inhibition might also be mandatory to suppress preferred coupling modes (Swinnen, 2002), to encode the difference between special features of two objects by different levels of inhibition, or to accomplish the interhemispheric comparison of action phase controlling contact events (Johansson and Flanagan, 2009).…”

Callosal anatomical and effective connectivity between primary motor cortices predicts visually cued bimanual temporal coordination performance

“…Even though a large body of evidence exists, that the motor corpus callosum plays a pivotal role in this context (Jeeves et al 1988;Serrien et al 2001;Tuller and Kelso 1989), disclosure of its specific nature and function has only started recently. This became possible with the advent of imaging and electrophysiological techniques which can precisely and directly relate structural connectivity or effective connectivity to behavior (Johansen-Berg et al 2007;Hübers et al 2008). Likewise, effective connectivity as referred to the influence that one neural system exerts over another (Friston et al 1993), either at a synaptic or population level, can be assessed by modern imaging and electrophysiological techniques and specifically linked with aspects of motor behavior (Hübers et al 2008).…”

“…This became possible with the advent of imaging and electrophysiological techniques which can precisely and directly relate structural connectivity or effective connectivity to behavior (Johansen-Berg et al 2007;Hübers et al 2008). Likewise, effective connectivity as referred to the influence that one neural system exerts over another (Friston et al 1993), either at a synaptic or population level, can be assessed by modern imaging and electrophysiological techniques and specifically linked with aspects of motor behavior (Hübers et al 2008). Variation of white matter microstructural features in the body of the CC predicted variation in the performance of a bimanual coordination task (Johansen-Berg et al 2007).…”