Observation-Related Activity in Human Motor Cortex Increases with Effector Anthropomorphicity

Area of Science:

• Neuroscience
• Motor Control
• Human-Computer Interaction

Background:

• Motor cortex neurons are active during both action execution and observation of others' movements.
• Previous research has not explored motor cortical responses to observing assistive or prosthetic devices controlled via intracortical brain-computer interfaces (iBCIs).

Purpose of the Study:

• To investigate how motor cortical neurons respond to observing movements performed by virtual agents of varying human-likeness.
• To determine if the anthropomorphism of an observed effector influences neural activity in the motor cortex.

Main Methods:

• Recorded single-unit activity in the precentral gyrus of iBCI users.
• Presented participants with grasp-like movements from virtual effectors including human, robotic, and hand-like dot stimuli.
• Correlated neural activity with effector anthropomorphicity and participant feedback.

Main Results:

• Found a relationship between neural modulation and effector anthropomorphicity at both ensemble and individual neuron levels.
• Motor cortex activity incrementally increased with the observed agent's human-likeness.
• Neural activity during attempted hand movements was consistent regardless of the observed effector, suggesting effector anthropomorphicity may not hinder iBCI control.

Conclusions:

• Human motor cortex activity is gradually modulated by the perceived human-likeness of an observed agent.
• This modulation advances the understanding of "mirror" activity in the brain.
• Findings may inform the design of brain-controlled prostheses for individuals with paralysis.