Stimulation over primary motor cortex during action observation impairs effector recognition

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Motor Control

Background:

• Motor cortical processing during action observation influences object recognition.
• The role of motor cortex in recognizing the 'effector' (e.g., hand) performing an action is less understood.

Purpose of the Study:

• To investigate if transcranial magnetic stimulation (TMS) over the primary motor cortex (M1) during action observation impairs recognition of the effector making the action.
• To determine if motor processing during action observation is essential for forming representations of the effector.

Main Methods:

• Two experiments used single-pulse TMS over the hand area of M1 during observation of hand actions.
• Participants later identified static images or videos of hands, assessing recognition accuracy.
• Control conditions included sham TMS or stimulation over the vertex.

Main Results:

• TMS over M1 during action observation significantly impaired recognition of static hand images.
• Recognition of hands shown statically and control dot patterns were unaffected.
• Effector recognition was impaired when TMS was applied mid- or late- in the action observation period.

Conclusions:

• Motor cortical activity during action observation is critical for subsequent effector recognition.
• Interfering with M1 activity during action observation impacts memory representations of the effector.
• This provides evidence for the motor system's role in forming effector representations beyond the observation period.