Bypassing use-dependent plasticity in the primary motor cortex to preserve adaptive behavior

Area of Science:

• Neuroscience
• Motor Control
• Cognitive Neuroscience

Background:

• Behavioral adaptation in voluntary movement relies on cognitive control.
• The conflict-adaptation effect demonstrates improved performance after incongruent trials.
• The role of the primary motor cortex (M1) in these adjustments is not well understood.

Purpose of the Study:

• To investigate changes in corticospinal excitability during conflict adaptation.
• To determine M1's involvement in between-trial adjustments.
• To link corticospinal excitability to behavioral adaptation mechanisms.

Main Methods:

• Used single-pulse transcranial magnetic stimulation (TMS) to measure motor-evoked potentials (MEPs).
• Applied TMS between trials in an interference flanker task.
• Measured MEPs during agonist and antagonist voluntary movements.

Main Results:

• MEP amplitude in agonist movements favored repetition but showed no change based on trial congruency.
• For antagonist movements, MEPs following incongruent trials positively correlated with behavioral adaptation (RT shortening).
• A post-conflict increase in corticospinal excitability was observed for antagonist muscles.

Conclusions:

• M1 contributes to conflict adaptation through modulation of corticospinal excitability.
• Increased excitability in antagonist muscles may compensate for movement history biases.
• This mechanism prepares the motor system for rapid adaptation in unpredictable contexts.