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Transcranial Magnetic Stimulation for Investigating Causal Brain-behavioral Relationships and their Time Course
Published on: July 18, 2014
Conditioning transcranial magnetic stimulation of ventral premotor cortex shortens simple reaction time
Andrea Zangrandi1, Alessandro Mioli1, Marco D'Alonzo1
1Research Unit of Neurophysiology and Neuroengineering of Human-Technology Interaction, Università Campus Bio-Medico, Rome, Italy.
Abstract:
The ventral premotor cortex (PMv) is a key area of the sensorimotor control loop, it subtends complex motor sequences, especially when the hand is involved. However, its specific contribution to simple motor response to sensory cue is still not completely clear. To investigate the role of PMv, we used transcranial magnetic stimulation (TMS) to interfere with its function during a simple reaction time (SRT) task. We ran two experiments where participants were required to respond as fast as possible to a median nerve stimulation (go-signal), while sub-M1-threshold single pulse TMS was delivered either on left (contralateral) PMv or right (ipsilateral to sensory stimulus and motor response) PMv, 5-65 ms after the go-signal. TMS delivered on either PMv up to 25 ms after the go-signal shortened reaction time. This is the time window compatible with the arrive of sensory afferences, as if conditioning before sensory afferences arrive lower the threshold needed to release the pre-planned motor program to the primary motor cortex. This is in line with a putative PMv function of buffer of pre-planned motor program not strictly lateralized in one hemisphere.
Insights
The ventral premotor cortex (PMv) helps prepare motor responses. Interfering with PMv shortly after a sensory cue speeds up reaction times, suggesting it buffers pre-planned movements.
Area of Science:
- Neuroscience
- Motor Control
- Human Motor Performance
Background:
- The ventral premotor cortex (PMv) is crucial for sensorimotor control and complex motor sequences, particularly hand movements.
- Its precise role in simple motor responses to sensory cues remains unclear.
Purpose of the Study:
- To investigate the contribution of the ventral premotor cortex (PMv) to simple motor responses using transcranial magnetic stimulation (TMS).
- To determine the temporal dynamics of PMv involvement in reaction time tasks.
Main Methods:
- Two experiments utilized a simple reaction time (SRT) task with median nerve stimulation as the go-signal.
- Single-pulse TMS was applied to either the left (contralateral) or right (ipsilateral) PMv, 5-65 ms after the go-signal.
- Stimulation intensity was sub-M1-threshold.
Main Results:
- TMS applied to either PMv within 25 ms after the go-signal significantly shortened reaction times.
- This facilitation occurred within the expected arrival window of sensory afferences.
- The findings suggest a role for PMv in modulating motor preparation.
Conclusions:
- The ventral premotor cortex (PMv) appears to facilitate motor responses by lowering the threshold for releasing pre-planned motor programs.
- This function may not be strictly lateralized, with potential involvement of both hemispheres.
- PMv may act as a buffer for pre-planned motor programs before execution.
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