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This Article Full Text Full Text (PDF) All Versions of this Article: 584/1/97    most recent jphysiol.2007.136291v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Nijhuis, L. B. O. Articles by Overeem, S. Search for Related Content PubMed PubMed Citation Articles by Nijhuis, L. B. O. Articles by Overeem, S. Related Collections Neuroscience

¹ Department of Neurology and Clinical Neurophysiology
³ Department of Biophysics
⁴ Department of Epidemiology and Biostatistics, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
² Department of Neurology and Clinical Neurophysiology, Leiden University Medical Centre, Leiden, The Netherlands

Auditory startle reflexes can accelerate simple voluntary reaction times (StartReact effect). To investigate the role of startle reflexes on more complex motor behaviour we formulated two questions: (1) can auditory startle reflexes shorten choice reaction times?; (2) is the StartReact effect differentially modulated when startling auditory stimuli are delivered ipsilaterally or contralaterally to an imperative ‘go’ signal? We instructed 16 healthy subjects to rotate their head as rapidly as possible to the left or to right in response to a guiding visual imperative stimulus (IS), in both a simple and choice reaction protocol. Startling acoustic stimuli (113 dB) were delivered simultaneously with the IS (from either the same or opposite side) to induce the StartReact effect. We recorded kinematics of head rotations and electromyographic responses. The StartReact effect was present during choice reaction tasks (56 ms onset reduction; P < 0.001). The presentation side of the startling stimulus (left/right) did not influence the effect in choice reaction tasks. We observed a directional effect in simple reaction tasks, but this probably occurred due to a flooring effect of reaction times. Onsets of EMG responses in neck muscles were not influenced by the direction of the acoustic startling stimulus. Startling acoustic stimuli decrease reaction times not only in simple but also in choice reaction time tasks, suggesting that startle reflexes can accelerate adequate human motor responses. The absence of a clear directional sensitivity of reaction times to startling acoustic stimuli suggests that the acceleration is not highly specific, but seems to provide a global preparatory effect upon which further tailored action can be undertaken more quickly.

(Received 16 May 2007; accepted after revision 17 July 2007; first published online 19 July 2007)
Corresponding author B. R. Bloem: Radboud University Nijmegen Medical Centre, Department of Neurology 935, PO Box 9101, 6500 HB Nijmegen, The Netherlands. Email: b.bloem{at}neuro.umcn.nl

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