Citation

Forgaard CJ, Maslovat D, Carlsen AN, Chua R, Franks IM. J. Neurophysiol. 2013; 110(9): 2129-2139.

Affiliation

University of British Columbia.

Copyright

(Copyright © 2013, American Physiological Society)

DOI

10.1152/jn.00888.2012

PMID

23926044

Abstract

Muscles involved in rapid, targeted movements about a single-joint often display a triphasic (agonist - antagonist - agonist) electromyographic (EMG) pattern. Early work using movement perturbations suggested that for short movements, the entire EMG pattern was prepared and initiated in advance (Wadman et al. 1979), whereas more recent TMS evidence indicates that the ANT may be programmed separately (MacKinnon and Rothwell 2000) with execution of the bursts occurring serially (Irlbacher et al. 2006). The purpose of the current study was to investigate the generation of triphasic EMG bursts for movements of different amplitudes. In Experiment 1, participants performed rapid elbow extension movements to 20° and 60° targets and on some trials, a startling acoustic stimulus (SAS), which is thought to trigger prepared motor commands at short latency, was delivered at the onset of AG1. For short movements, this perturbation elicited ANT and AG2 early, suggesting the agonist and antagonist bursts may have been programmed independently. In contrast, the same manipulation did not disrupt EMG timing parameters for the long movements, raising the possibility that ANT and AG2 were not fully programmed in advance of movement onset. In Experiment 2, a SAS was delivered later in the movement which produced early onset of both ANT and AG2. We propose that the triphasic pattern is executed serially but believe the trigger signal for initiating the ANT burst occurs not in relation to the AG1 burst, but rather in close temporal proximity to the expected onset of ANT.

Language: en