title: Does the StartReact Effect Apply to First-Trial Reactive Movements?
abstract: BACKGROUND
  StartReact is the acceleration of reaction time by a startling acoustic stimulus (SAS). The SAS is thought to release a pre-prepared motor program. Here, we investigated whether the StartReact effect is applicable to the very first trial in a series of repeated unpractised single-joint movements.
  
  
  METHODS
  Twenty healthy young subjects were instructed to perform a rapid ankle dorsiflexion movement in response to an imperative stimulus. Participants were divided in two groups of ten. Both groups performed 17 trials. In one group a SAS (116 dB) was given in the first trial, whereas the other group received a non-startling sound (70 dB) as the first imperative stimulus. In the remaining 16 trials, the SAS was given as the imperative stimulus in 25% of the trials in both groups. The same measurement was repeated one week later, but with the first-trial stimuli counterbalanced between groups.
  
  
  RESULTS
  When a SAS was given in the very first trial, participants had significantly shorter onset latencies compared to first-trial responses to a non-startling stimulus. Succeeding trials were significantly faster compared to the first trial, both for trials with and without a SAS. However, the difference between the first and succeeding trials was significantly larger for responses to a non-startling stimulus compared to responses triggered by a SAS. SAS-induced acceleration in the first trial of the second session was similar to that in succeeding trials of session 1.
  
  
  CONCLUSIONS
  The present results confirm that the StartReact phenomenon also applies to movements that have not yet been practiced in the experimental context. The excessive SAS-induced acceleration in the very first trial may be due to the absence of integration of novel context-specific information with the existing motor memory for movement execution. Our findings demonstrate that StartReact enables a rapid release of motor programs in the very first trial also without previous practice, which might provide a behavioural advantage in situations that require a rapid response to a potentially threatening environmental stimulus.
authors.affiliation: Radboud University Medical Centre, Donders Centre for Neuroscience, Department of Rehabilitation, Nijmegen, The Netherlands.
authors.forename: Katrin
authors.initials: K
authors.lastname: Sutter
authors.affiliation: Radboud University Medical Centre, Donders Centre for Neuroscience, Department of Rehabilitation, Nijmegen, The Netherlands.
authors.forename: Jorik
authors.initials: J
authors.lastname: Nonnekes
authors.affiliation: Radboud University Medical Centre, Donders Centre for Neuroscience, Department of Rehabilitation, Nijmegen, The Netherlands.|Department GF Ingrassia, Section of Neurosciences, University of Catania, Catania, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Dibilio
authors.affiliation: Radboud University Medical Centre, Donders Centre for Neuroscience, Department of Rehabilitation, Nijmegen, The Netherlands.|Sint Maartenskliniek Research, Nijmegen, The Netherlands.
authors.forename: Alexander C
authors.initials: AC
authors.lastname: Geurts
authors.affiliation: Radboud University Medical Centre, Donders Centre for Neuroscience, Department of Rehabilitation, Nijmegen, The Netherlands.|Sint Maartenskliniek Research, Nijmegen, The Netherlands.
authors.forename: Vivian
authors.initials: V
authors.lastname: Weerdesteyn
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D000842:Ankle / Q000502:physiology; D004576:Electromyography; D005260:Female; D005528:Foot / Q000502:physiology; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D009068:Movement / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D013216:Reflex, Startle / Q000502:physiology*; D055815:Young Adult