Evidence for two concurrent inhibitory mechanisms during response preparation

Area of Science:

• Neuroscience
• Motor Control
• Cognitive Psychology

Background:

• Inhibitory mechanisms are crucial for goal-directed behaviors.
• Understanding how inhibition shapes motor representations during response preparation is key.

Purpose of the Study:

• To investigate the neural mechanisms of response inhibition during motor preparation.
• To differentiate the roles of cortical and spinal circuits in response selection and suppression.

Main Methods:

• Choice reaction time tasks were employed.
• Motor evoked potentials (MEPs) via transcranial magnetic stimulation (TMS) and H-reflexes were recorded from left hand muscles.
• Participants prepared for cued responses involving either the left or right hand.

Main Results:

• Left MEPs and H-reflexes were suppressed when the left hand was cued, indicating spinal inhibition of selected responses.
• Left MEPs were suppressed, but H-reflexes were not, when the right hand was cued (and left hand was a possible response), suggesting cortical inhibition of non-selected responses.
• These findings reveal distinct inhibitory processes operating at different neural levels.

Conclusions:

• Two inhibitory mechanisms operate during response preparation: one at the spinal level for selected responses and one at the cortical level for non-selected responses.
• These mechanisms work concurrently to control movement initiation and selection during goal-directed behavior.