The truth-telling motor cortex: response competition in M1 discloses deceptive behaviour

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Motor Control

Background:

• Neural circuits involved in response conflict are active during deception.
• Detecting deception is a significant challenge in various fields, including law and security.

Purpose of the Study:

• To investigate if competing motor responses in the primary motor cortex can be used to detect lies.
• To explore the neurobiological underpinnings of deception and response conflict.

Main Methods:

• Utilized transcranial magnetic stimulation (TMS) to measure motor-evoked potentials (MEPs).
• Participants responded truthfully or deceitfully regarding facial familiarity using either their little finger or thumb.
• MEPs from muscles associated with both digits were recorded to track motor plan development.

Main Results:

• When preparing to deceive, the MEP of the non-responding digit (truthful plan) exceeded the MEP of the responding digit (lie).
• A mirror-reversed pattern was observed when participants told the truth.
• This response conflict effect interacted with stimulation timing during a speeded reaction period.
• Digit-specific cortical representations were activated even with verbal-only responses during deception.

Conclusions:

• Findings support neurobiological models integrating cognitive decision-making and motor programming.
• Suggests a novel index for discriminating between honest and intentionally false facial recognition based on motor-evoked potentials.