Motor-Evoked Potentials for Early Individual Elements of an Action Sequence During Planning Reflect Parallel...

Area of Science:

• Neuroscience
• Cognitive Psychology
• Computational Modeling

Background:

• The neural basis of action planning remains unclear, with competing computational models.
• Simple chaining models predict only the first action element is active during planning.
• Parallel activation models propose serial inhibition and a competitive gradient for action ordering.

Purpose of the Study:

• To investigate the neural activation patterns during action sequence planning.
• To differentiate between competing computational models of action planning.
• To examine the temporal dynamics of response selection in action sequences.

Main Methods:

• Used transcranial magnetic stimulation (TMS) to probe neural activity.
• Measured motor-evoked potentials (MEPs) at the right index finger.
• Participants planned a five-letter word sequence with a unique right-hand response at varying serial positions.

Main Results:

• No significant difference in MEP amplitude at 200 ms across serial positions.
• A graded pattern of MEP amplitude at 400 ms, with earlier positions showing higher activation.
• Earlier planned right-index finger responses exhibited greater neural activation compared to later ones.

Conclusions:

• Findings support competitive queuing models of action planning.
• Neural activation reflects a competitive process for ordering action elements.
• Action planning involves dynamic neural competition that becomes apparent later in the planning phase.