Modulation of intracortical circuits in primary motor cortex during automatic action tendencies

Area of Science:

• Neuroscience
• Motor Control
• Cognitive Psychology

Background:

• Humans exhibit automatic action tendencies, reacting faster to approach positive stimuli and avoid negative ones.
• The primary motor cortex is implicated in automatic actions, evidenced by motor evoked potentials.
• The specific role of intracortical circuits in automatic action tendencies remains unclear.

Purpose of the Study:

• To investigate the involvement of intracortical circuits, specifically short-interval intracortical inhibition and facilitation, in automatic action tendencies.
• To elucidate the neural mechanisms underlying the rapid behavioral responses to emotional stimuli.

Main Methods:

• Utilized paired-pulse transcranial magnetic stimulation protocols to measure intracortical inhibition and facilitation.
• Employed the manikin task to simulate approaching and avoiding emotional stimuli.
• Measured reaction times to assess behavioral speed and efficiency.

Main Results:

• Intracortical facilitation was significantly stronger during automatic behavior compared to regulated behavior.
• A negative correlation was observed between reaction times and intracortical facilitation during automatic behavior.
• No significant differences in short-interval intracortical inhibition were found between automatic and regulated behaviors.

Conclusions:

• The intracortical facilitation circuit within the primary motor cortex plays a critical role in mediating automatic action tendencies.
• This facilitation, driven by excitatory glutamatergic neurons, supports rapid behavioral responses to emotional cues.
• Findings reinforce the connection between emotional perception and the motor action system.