Related Experiment Videos
Stimulation-induced within-representation and across-representation plasticity in human motor cortex
Ulf Ziemann1, George F Wittenberg, Leonardo G Cohen
1Human Cortical Physiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-1428, USA. u.ziemann@em.uni-frankfurt.de
Summary
Repetitive transcranial magnetic stimulation (rTMS) during ischemic nerve block (INB) can modify motor cortex output. Stimulating nearby areas can increase or decrease upper arm representation, suggesting bidirectional plasticity for functional modulation.
Area of Science:
- Neuroscience
- Motor Control
- Cortical Plasticity
Background:
- The human motor cortex has dynamic, distributed motor representations shaped by activity.
- Within-representation plasticity increases motor output with repeated stimulation.
- Ischemic nerve block (INB) reduces motor cortex inhibition, facilitating plasticity.
Purpose of the Study:
- To investigate how stimulating adjacent motor cortex representations affects upper arm motor output.
- To explore the impact of repetitive transcranial magnetic stimulation (rTMS) on motor cortical plasticity during INB.
Main Methods:
- Six healthy subjects received INB alone or with 0.1 Hz rTMS targeting face, hand, arm, leg, or arm/hand overlap areas.
- Motor output from the upper arm representation was measured using motor evoked potentials in the biceps.
- Effects were assessed after INB alone, INB + leg rTMS, INB + arm/hand rTMS, and INB + face/hand rTMS.
Main Results:
- INB alone and leg rTMS produced short-lasting (<20 min) increases in arm motor output.
- Arm and arm/hand rTMS induced prolonged (>60 min) within-representation increases.
- Face and hand rTMS abolished the increase and caused long-lasting decreases in arm motor output.
Conclusions:
- Experimentally disinhibited motor cortex exhibits bidirectional plasticity: within-representation increases and across-representation decreases.
- This plasticity could enable purposeful modulation of human cortical functions.