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This Article Full Text Full Text (PDF) All Versions of this Article: 586/18/4453    most recent jphysiol.2008.156042v1 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 Google Scholar Articles by Queralt, A. Articles by Duysens, J. PubMed PubMed Citation Articles by Queralt, A. Articles by Duysens, J. Related Collections Neuroscience

¹ Instituto de Salud Carlos III, Madrid, Spain
² Departamento de Educación Física y Deportiva, Universidad de Valencia, Valencia, Spain
³ Department of Rehabilitation, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
⁴ Sint Maartenskliniek Research, Development & Education, Nijmegen, the Netherlands
⁵ Unitat d'EMG, Servei de Neurologia, Hospital Clínic, Universitat de Barcelona, IDIBAPS (Institut d'Investigació Biomèdica August Pi i Sunyer), Barcelona, Spain
⁶ Motor Control Laboratory, Department of Biomedical Kinesiology, KU Leuven, Belgium

Movement execution is speeded up when a startle auditory stimulus is applied with an imperative signal in a simple reaction time task experiment, a phenomenon described as StartReact. The effect has been recently observed in a step adjustment task requiring fast selection of specific movements in a choice reaction time task. Therefore, we hypothesized that inducing a StartReact effect may be beneficial in obstacle avoidance under time pressure, when subjects have to perform fast gait adjustments. Twelve healthy young adults walked on a treadmill and obstacles were released in specific moments of the step cycle. On average the EMG onset latency in the biceps femoris shortened by 20% while amplitude increased by 50%, in trials in which an auditory startle accompanied obstacle avoidance. The presentation of a startle increased the probability of using a long step strategy, enlarged stride length modifications and resulted in higher success rates, to avoid the obstacle. We also examined the effects of the startle in a condition in which the obstacle was not present in comparison to a condition in which the obstacle was visibly present but it did not fall. In the latter condition, the obstacle avoidance reaction occurred with a similar latency but smaller amplitude as in trials in which the obstacle was actually released. Our results suggest that the motor programmes used for obstacle avoidance are probably stored at subcortical structures. The release of these motor programmes by a startling auditory stimulus may combine intersensory facilitation and the StartReact effect.

(Received 29 April 2008; accepted after revision 18 July 2008; first published online 24 July 2008)
Corresponding author V. Weerdesteyn: Department of Rehabilitation, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500 HB Nijmegen, the Netherlands.  Email: v.weerdesteyn{at}reval.umcn.nl