Modulation of somatosensory evoked potentials during coordination between posture and movement

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• Voluntary movements are preceded by complex neural processes.
• Somatosensory evoked potentials (SEPs) reflect sensory pathway processing.
• Amplitude modulation of SEPs, termed 'gating', is observed during motor tasks.

Purpose of the Study:

• To investigate SEP modifications during a motor task involving anticipatory postural adjustment and focal arm movement.
• To determine the temporal relationship between SEP gating and specific phases of motor preparation and execution.

Main Methods:

• Participants performed a fast, forward arm elevation task while standing.
• Electrical stimulation of the posterior tibial nerve was applied at two time points: before leg muscle EMG and during leg muscle EMG but before arm muscle EMG.
• SEPs were recorded and compared between the motor task and quiet stance conditions.

Main Results:

• A significant decrease in the early P42-N50 SEP component was observed before focal arm movement, irrespective of anticipatory leg muscle activity.
• The N50-P60 SEP component increased in amplitude, particularly when stimulation occurred earlier in the motor preparation phase.
• SEP amplitude reduction (gating) was evident prior to anticipatory postural adjustments and persisted through the focal movement.

Conclusions:

• SEP gating occurs before anticipatory postural adjustments, indicating early sensory processing modulation during motor preparation.
• The findings suggest that sensory processing is modified well in advance of overt movement execution.
• This study elucidates the temporal dynamics of sensory-motor integration during voluntary action.