Two different experiments utilizing the motor imagery of nger movement were conducted. We attempted to reveal the difference in corticospinal excitability between tonic contraction (TC) and rhythmic movement (RM) by transcranial magnetic stimulation (TMS). The magnetic coil was placed over the subject s primary motor cortex to elicit motor-evoked potentials (MEPs) by TMS. We have previously shown that the MEP amplitude is modulated by the frequency of active and passive nger movements. We hypothesized that visual feedback affects the corticospinal excitability. In the present study, the subject observed both TCs and RMs, and the MEP amplitudes elicited by TMS during both tasks were analyzed to assess changes in corticospinal excitability in uenced by the motor imagery. A mirror box was used to show the subject the nger movement executed by a third person as if it were his own nger movement. For the TC task, the third person performed a pinching task consisting of TC of the index nger and thumb. The subject received visual feedback of the TC in the mirror. For the RM task, the subject observed the mirror while the third person performed RM of the index nger until TMS was applied. The frequencies of nger movement were 0.5, 1, 2, 3, and 4 Hz. The resulting MEP amplitudes for the RM task at movement frequencies of 2, 3, and 4 Hz were signi cantly lower than that for the TC task. These results indicate that corticospinal excitability is increased by visual feedback of TC but is modulated by that of RM.
The central pattern generator (CPG) in the spinal cord oscillates a motor command to produce rhythmic movement, whereas several studies have described the movement frequency coding in the primary motor cortex and other motor area. However it is still unclear that the modulation of excitability in the cortico-spinal tract during rhythmic movement. We assessed cortico-spinal excitability during rhythmic movement using transcranial magnetic simulation (TMS), and analyzed the changing CPG frequency characteristic. When the subject performed rhythmic finger flexion-extension movements, TMS was applied on the primary motor cortex. Then the amplitude of the motor evoked potential (MEP) was measured on the target muscle. The frequency of the movement was varied between 0.5 and 4 Hz. We confirmed attenuated MEP was observed at 3 Hz for the finger rhythmic movements. We concluded that the motor command producing the rhythmic movement from motor cortex was decreased during specific rhythmic movement.
Bilateral information in primary motor cortices of human cerebral hemispheres is needed to produce simultaneous bilateral limb movement. The corpus callosum connecting homologous areas of cortex between the hemispheres is an important area to exert bilateral finger movements. It is unclear that the movement state of both fingers influences corticospinal excitability involving in contralateral movement. We measured corticospinal excitability during passive movement of both fingers using transcranial magnetic stimulation (TMS) on the primary motor cortex. The subjects performed passive movement of fingers using servomotors.TMS was applied at the two movement states of maximum flexion and extension position on metacarpophalangeal joint (MP joint) of dominant index finger, respectively. There were three kinds of movement task of symmetry, asymmetry and one-finger movements in this experiment. In one-finger movement task, the highest motor evoked potential (MEP) in electromyogram was measured with TMS timing of maximum extension of MP joint angle. Moreover, MEP with maximum extension of MP joint was lowest in symmetry movement task, but the MEP was conversely lowest with maximum flexion in asymmetry movement task.These results suggested that MEP depended on MP joint angle and the corticospinal excitability was inhibited when contralateral MP joint angle was with maximum extension.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.