Motor cortex involvement during choice reaction time: a transcranial magnetic stimulation study in man

Area of Science:

• Neuroscience
• Cognitive Science
• Human Motor Control

Background:

• Transcranial magnetic stimulation (TMS) is a tool for studying information processing.
• Previous studies using simple reaction time (RT) have yielded results difficult to interpret.
• Choice reaction time tasks may offer a more robust framework for TMS research.

Purpose of the Study:

• To investigate the effects of TMS on choice reaction time.
• To differentiate the effects of TMS on motor cortex from sensory artifacts.
• To explore the temporal dynamics of TMS effects on motor responses.

Main Methods:

• TMS was applied over the motor cortex during choice reaction time tasks.
• Control experiments included ipsilateral motor cortex stimulation and off-scalp stimulation.
• Effects were compared to electrical median nerve stimulation (H-reflex).

Main Results:

• TMS noise and skin sensation caused intersensory facilitation, shortening RT.
• Motor cortex stimulation delayed RT, counteracting the facilitatory effect.
• The delay increased as TMS timing approached the overt response.

Conclusions:

• TMS applied to the motor cortex can modulate choice reaction time.
• Careful control for sensory artifacts is crucial in TMS studies.
• TMS timing relative to the motor response influences its effect on RT.