Different strategies do not moderate primary motor cortex involvement in mental rotation: a TMS study

Area of Science:

• Neuroscience
• Cognitive Psychology
• Motor Control

Background:

• The dorsal visual stream is crucial for mental rotation.
• The role of the primary motor cortex (M1) in mental rotation remains unclear.
• The strategy hypothesis suggests M1 involvement depends on internal versus external strategies.

Purpose of the Study:

• To investigate the relationship between mental rotation strategy and M1 activity.
• To test the strategy hypothesis regarding M1 involvement.

Main Methods:

• Twenty-two subjects performed a mental rotation task with stimuli designed to elicit internal or external strategies.
• Single-pulse Transcranial Magnetic Stimulation (TMS) measured Motor Evoked Potentials (MEPs) in the right hand muscle to quantify M1 activity.

Main Results:

• No interaction was found between stimulus category and corticospinal excitability, contrary to the strategy hypothesis.
• Corticospinal excitability was generally increased during mental rotation compared to rest.
• Subjects reported using the external strategy more frequently across all stimulus categories.

Conclusions:

• M1 involvement in mental rotation is not solely linked to the internal strategy.
• M1 activity appears directly related to the mental rotation process itself.
• Alternatively, M1 activation may result from 'spill-over' effects from adjacent brain regions.