Uncertainty in when a perturbation will arrive influences the preparation and release of triggered responses

Rosalind L. Heckman*, Eric J. Perreault

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


The timing and magnitude of muscle responses to perturbations are critical for acting in uncertain environments. A planned movement can strongly influence average muscle responses to perturbations, but certainty in when a perturbation will arrive changes this effect. The objective of this study was to investigate how uncertainty in perturbation timing influences the preparation and release of involuntary, perturbation-triggered responses. We hypothesized that uncertainty would influence the average magnitude of triggered responses and how they develop in time. We investigated three levels of uncertainty in when a proprioceptive cue to move would arrive by changing the duration and variability of the time between a preparation and movement cue. Participants performed ballistic elbow extension movements in response to the movement cue. Unexpected, large perturbations that flexed the elbow were delivered at various times between the preparation and movement cues to evaluate how cue uncertainty influenced the development of triggered responses. We found that this uncertainty strongly influences how a motor response is prepared, and the efficacy of triggering that response by a postural perturbation. When timing was certain, the motor plan was prepared within 150 ms of the expected disturbance, and consistently released earlier by a perturbation than could be done voluntarily. Less predictable stimuli led to much earlier planning and a lower probability of releasing the plan early. These results clarify how uncertainty in when to move influences the planning and early release of perturbation-triggered responses, demonstrating an effect similar to previous reports on the planning of volitional movements.

Original languageEnglish (US)
Pages (from-to)2353-2365
Number of pages13
JournalExperimental Brain Research
Issue number9
StatePublished - Sep 1 2019


  • Motor planning
  • Startle
  • Stretch reflex
  • Temporal uncertainty
  • Triggered reactions

ASJC Scopus subject areas

  • Neuroscience(all)


Dive into the research topics of 'Uncertainty in when a perturbation will arrive influences the preparation and release of triggered responses'. Together they form a unique fingerprint.

Cite this