Proactive Inhibition Activation Depends on Motor Preparation: A Single Pulse TMS Study

Area of Science:

• Cognitive Neuroscience
• Human Motor Control

Background:

• Environmental cues enhance reaction times (RTs) by facilitating motor preparation.
• Short cue-target intervals (<300 ms) can paradoxically increase RTs (warning cost).
• Proactive inhibition is hypothesized as a motor gating mechanism causing this cost.

Purpose of the Study:

• To investigate the role of proactive inhibition in the paradoxical warning cost.
• To determine if proactive inhibition is a default state of executive control.
• To examine the relationship between motor preparation and cueing effects.

Main Methods:

• Psychophysically manipulated stimulus duration in a simple RT task to ensure motor preparation.
• Measured transcranial magnetic stimulation (TMS)-elicited motor evoked potentials (MEPs) to assess corticospinal excitability.
• Compared RTs and MEPs under cued and uncued trials with short cue-target intervals.

Main Results:

• The paradoxical warning cost disappeared when motor preparation was equated across cued and uncued trials.
• RTs were consistently faster on cued trials compared to uncued trials.
• MEPs did not show suppression at target onset, refuting the proactive inhibition hypothesis.

Conclusions:

• Proactive inhibition is not actively engaged by default in simple RT tasks.
• The activation of proactive inhibition depends on the degree of motor preparation.
• Paradoxical warning costs are likely related to insufficient motor preparation rather than inhibition.