Alterations in human motor cortex during dual motor task by transcranial magnetic stimulation study

Area of Science:

• Neuroscience
• Motor Control
• Human Physiology

Background:

• The primary motor cortex (M1) plays a crucial role in motor control.
• Understanding how M1 adapts during complex dual motor tasks is essential for motor learning and rehabilitation.

Purpose of the Study:

• To investigate the impact of dual motor tasks on M1 excitability.
• To determine the influence of specific task properties, such as gait speed and prehension force, on M1 modulation.

Main Methods:

• Utilized transcranial magnetic stimulation (TMS) to measure motor-evoked potentials (MEPs) in forearm and hand muscles.
• Subjects performed concurrent tasks: treadmill walking at varying speeds and finger prehension with different force outputs.
• Experiment 2 involved synchronized and desynchronized walking and finger-tapping tasks at different frequencies.

Main Results:

• MEPs were significantly reduced at 50% of maximum walking speed compared to 30% and 80% speeds during a 5% maximal voluntary contraction (MVC) prehension task.
• A 2-Hz dual motor task resulted in greater MEP reduction than a 0.7-Hz task, indicating altered M1 excitability with different temporal demands.

Conclusions:

• M1 excitability is dynamically modulated during dual motor tasks.
• Gait speed, the precision of the concurrent task (force output), and the temporal relationship between movements significantly influence M1 adaptation.