Hemispheric Asymmetry of Frequency-Dependent Suppression in the Ipsilateral Primary Motor Cortex During Finger Movement: A Functional Magnetic Resonance Imaging Study

Abstract

Electrophysiological studies have suggested that the activity of the primary motor cortex (M1) during ipsilateral hand movement reflects both the ipsilateral innervation and the transcallosal inhibitory control from its counterpart in the opposite hemisphere, and that their asymmetry might cause hand dominancy. To examine the asymmetry of the involvement of the ipsilateral motor cortex during a unimanual motor task under frequency stress, we conducted block-design functional magnetic resonance imaging with 22 normal right-handed subjects. The task involved visually cued unimanual opponent finger movement at various rates. The contralateral M1 showed symmetric frequency-dependent activation. The ipsilateral M1 showed task-related deactivation at low frequencies without laterality. As the frequency of the left-hand movement increased, the left M1 showed a gradual decrease in the deactivation. This data suggests a frequency-dependent increased involvement of the left M1 in ipsilateral hand control. By contrast, the right M1 showed more prominent deactivation as the frequency of the right-hand movement increased. This suggests that there is an increased transcallosal inhibition from the left M1 to the right M1, which overwhelms the right M1 activation during ipsilateral hand movement. These results demonstrate the dominance of the left M1 in both ipsilateral innervation and transcallosal inhibition in right-handed individuals.

Using a Hybrid Brain Computer Interface and Virtual Reality System to Monitor and Promote Cortical Reorganization through Motor Activity and Motor Imagery Training

“…However, in order to support this hypothesis, additional experiments using haptic feedback and sound are required. The larger modulation of the activity of the right brain hemisphere for all frequency bands and conditions is consistent with results that support the existence of a transcallosal inhibition from the left to the right hemisphere capable of overwhelming the activity of the right hemisphere [52]. In this experiment, aspects such as the effect of the experimental condition on the level of engagement in the task [53] or the modulation of the sense of presence [54] or ownership [55] can be crucial for explaining the different brain activity patterns.…”

Network Dynamics Mediating Ipsilateral Motor Cortex Activity during Unimanual Actions

“…Further support for this inhibitory control hypothesis comes from several previous fMRI (e.g., Hayashi et al, 2008) and TMS (e.g., Duque et al, 2007) studies of the cortical dynamics during movement. This work has shown a suppression of activity/excitability in M1 during the preparation and execution of an ipsilateral movement.…”

“…This work has shown a suppression of activity/excitability in M1 during the preparation and execution of an ipsilateral movement. However, when the movements are complex, there is an increase in bilateral activation (e.g., Verstynen et al, 2005), and correspondingly, the suppression of M1 is attenuated (Hayashi et al, 2008), at least in the left hemisphere. Inhibitory mechanisms (Duque et al, 2010;Gilio, Rizzo, Siebner, & Rothwell, 2003;Ferbert et al, 1992) may be required to ensure that bilateral representations of action plans do not result in involuntary actions of the nonmoving hand.…”

Laterality of Asymmetry in Movements of the Corners of the Mouth during Voluntary Smile

“…31 The ipsilateral motor cortex receives an inhibitory signal from the other side of the motor cortex and asymmetric recruitment of neuronal activity at the cortical level through the uncrossed corticospinal tract has also been reported. 32 The asymmetric response of the motor cortex during ipsilateral movement probably represents the asymmetry of the summation of the ipsilateral innervation and transcallosal inhibitory control. 32,33 It can, therefore, be speculated that the asymmetries of neuronal activity in the motor cortices might be a possible explanation of the asymmetry and laterality in the facial motor output to the lower one third of the face determined in the present study.…”