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Cortical involvement in the StartReact effect
A J T Stevenson1, C Chiu2, D Maslovat3
1School of Kinesiology, University of British Columbia, Vancouver, BC, Canada; Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
Neuroscience
|April 1, 2014
Summary
The StartReact effect, a rapid movement release triggered by a startling acoustic stimulus (SAS), involves the primary motor cortex (M1). This study found M1 involvement in both limb and speech movements, challenging purely subcortical explanations.
Area of Science:
- Neuroscience
- Motor Control
- Human Physiology
Background:
- The StartReact effect describes rapid movement release triggered by a startling acoustic stimulus (SAS), with observed premotor reaction times (PMTs) under 70 ms.
- Two hypotheses exist: subcortical triggering or a faster subcortico-cortical pathway.
- The role of the primary motor cortex (M1) in this effect remains debated.
Purpose of the Study:
- To investigate the involvement of the primary motor cortex (M1) in the StartReact effect.
- To differentiate between subcortical and cortical triggering mechanisms for SAS-induced movements.
- To examine StartReact in both limb and speech motor tasks.
Main Methods:
- Experiment 1: Used transcranial magnetic stimulation (TMS) to induce a cortical silent period in M1 during reaction time (RT) for wrist extension movements.
- Participants responded to a control stimulus or SAS.
- Experiment 2: Assessed the StartReact effect in speech (consonant-vowel syllable) production.
Main Results:
- Startling acoustic stimulus (SAS) trials showed faster PMTs than control trials.
- TMS significantly delayed movement onset, indicating M1's role.
- A robust StartReact effect was observed in speech tasks, similar to limb movements.
Conclusions:
- The findings provide evidence for the involvement of the primary motor cortex (M1) in the StartReact effect.
- This suggests that the SAS can trigger movements via cortical pathways.
- The StartReact effect is not limited to limb movements and extends to speech production.
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