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BioMed Research International
Volume 2013 (2013), Article ID 471792, 9 pages
http://dx.doi.org/10.1155/2013/471792
Research Article

The StartReact Effect on Self-Initiated Movements

1Physical Medicine and Rehabilitation Department, Faculty of Medicine, Universidad Complutense de Madrid, C/Ciudad Universitaria S/N, 28040 Madrid, Spain
2National School on Occupational Medicine, Instituto de Salud Carlos III, C/Sinesio Delgado 4, 28029 Madrid, Spain
3Division of Rehabilitation, Aged Care and Allied Health, Repatriation General Hospital, Flinders University, Daw Park, SA 5043, Australia
4EMG Unit, Neurology Department, Hospital Clínic, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Institut d’Investigacio Biomedica August Pi i Sunyer (IDIBAPS), Facultad de Medicina, Universitat de Barcelona, Calle Villarroel 170, 08036 Barcelona, Spain

Received 30 April 2013; Revised 17 July 2013; Accepted 1 August 2013

Academic Editor: Jean Blouin

Copyright © 2013 J. M. Castellote et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Preparation of the motor system for movement execution involves an increase in excitability of motor pathways. In a reaction time task paradigm, a startling auditory stimulus (SAS) delivered together with the imperative signal (IS) shortens reaction time significantly. In self-generated tasks we considered that an appropriately timed SAS would have similar effects. Eight subjects performed a ballistic wrist extension in two blocks: reaction, in which they responded to a visual IS, and action, in which they moved when they wished within a predetermined time window. In 20–25% of the trials, a SAS was applied. We recorded electromyographic activity of wrist extension and wrist movement kinematic variables. No effects of SAS were observed in action trials when movement was performed before or long after SAS application. However, a cluster of action trials was observed within 200 ms after SAS. These trials showed larger EMG bursts, shorter movement time, shorter time to peak velocity, and higher peak velocity than other action trials ( for all), with no difference from Reaction trials containing SAS. The results show that SAS influences the execution of self-generated human actions as it does with preprogrammed reaction time tasks during the assumed building up of preparatory activity before execution of the willed motor action.