Interactions between imagined movement and the initiation of voluntary movement: a TMS study.
OBJECTIVE
The purpose was to examine motor imagery-induced enhancement in corticospinal excitability during a reaction time (RT) task.


METHODS
Nine young and healthy subjects performed an isometric finger flexion tasks in response to a visual imperative cue. In the pre-cue period, they were instructed to: (1) rest; (2) imagine flexing their fingers isometrically (ImFlex); or (3) imagine extending their fingers isometrically (ImExt). Surface EMGs from the finger flexors and extensors were monitored to ensure EMG silence before movement onset. Transcranial magnetic stimulation (TMS) was used to evaluate changes in motor-evoked potentials (MEP) in the finger flexor and extensor muscles during the response phase. TMS was delivered either with the imperative cue, or 120 ms before and after the imperative cue.


RESULTS
RT was slower when they were imagining finger extension prior to the visual imperative cue. MEPs were significantly increased for the finger flexors during imagined finger flexion and for the finger extensors during imagined finger extension at both TMS delivery time points, reflecting movement specific enhancement in corticospinal excitability during motor imagery. When TMS was delivered 120 ms after the cue, finger flexor MEPs were further facilitated under the Rest and ImFlex conditions, but not under the ImExt condition, suggesting additive interactions between imagery-induced enhancement and early rise in corticospinal excitability during the initiation of a reaction time response.


CONCLUSIONS
Our results provide neurophysiological evidence mediating dynamic interactions between imagined movement and the initiation of voluntary movement.


CONCLUSIONS
Motor imagery can be integrated into a rehabilitation protocol to facilitate motor recovery.
Li
Sheng
S
Motor Control Laboratory, School of Physical Therapy and Rehabilitation Science, University of Montana, Missoula, MT 59812, USA. sheng.li@umontana.edu
Stevens
Jennifer A
JA
Rymer
W Zev
WZ
D000328:Adult; D003463:Cues; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D005385:Fingers / Q000294:innervation / Q000502:physiology; D006801:Humans; D007092:Imagination / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D011712:Pyramidal Tracts / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D012046:Rehabilitation / Q000639:trends; D050781:Transcranial Magnetic Stimulation; D014796:Visual Perception / Q000502:physiology*