title: Cortical involvement in the StartReact effect.
abstract: The rapid release of prepared movements by a loud acoustic stimulus capable of eliciting a startle response has been termed the StartReact effect (Valls-Solé et al., 1999), and premotor reaction times (PMTs) of <70 ms are often observed. Two explanations have been given for these short latency responses. The subcortical storage and triggering hypothesis suggests movements that can be prepared in advance of a "go" signal are stored and triggered from subcortical areas by a startling acoustic stimulus (SAS) without cortical involvement. Alternatively, it has been hypothesized that the SAS can trigger movements from cortical areas through a faster pathway ascending from subcortical structures. Two experiments were designed to examine the possible role of the primary motor cortex in the StartReact effect. In Experiment 1, we used suprathreshold transcranial magnetic stimulation (TMS) during the reaction time (RT) interval to induce a cortical silent period in the contralateral primary motor cortex (M1). Thirteen participants performed 20° wrist extension movements as fast as possible in response to either a control stimulus (82 dB) or SAS (124 dB). PMTs for startle trials were faster than for control trials, while TMS significantly delayed movement onset compared to No TMS or Sham TMS conditions. In Experiment 2, we examined the StartReact effect in a highly cortically represented action involving speech of a consonant-vowel (CV) syllable. Similar to previous work examining limb movements, a robust StartReact effect was found. Collectively, these experiments provide evidence for cortical (M1) involvement in the StartReact effect.
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, BC, Canada; Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: A J T
authors.initials: AJ
authors.lastname: Stevenson
authors.affiliation: Department of Linguistics, University of British Columbia, Vancouver, BC, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Chiu
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, BC, Canada. Electronic address: dmaslovat@langara.bc.ca.
authors.forename: D
authors.initials: D
authors.lastname: Maslovat
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, BC, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Chua
authors.affiliation: Department of Linguistics, University of British Columbia, Vancouver, BC, Canada; Haskins Laboratories, New Haven, CT, USA.
authors.forename: B
authors.initials: B
authors.lastname: Gick
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, BC, Canada; Brain Research Centre, University of British Columbia, Vancouver, BC, Canada.
authors.forename: J-S
authors.initials: JS
authors.lastname: Blouin
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, BC, Canada.
authors.forename: I M
authors.initials: IM
authors.lastname: Franks
mesh_terms: D000161:Acoustic Stimulation; D004576:Electromyography; D005260:Female; D006801:Humans; D008046:Lip / Q000502:physiology*; D008297:Male; D008959:Models, Neurological; D009044:Motor Cortex / Q000502:physiology*; D009483:Neuropsychological Tests; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013216:Reflex, Startle / Q000502:physiology*; D013060:Speech / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D014953:Wrist / Q000502:physiology*; D055815:Young Adult
keywords: StartReact; motor cortex; motor preparation; speech; startle; transcranial magnetic stimulation