Augmented visual feedback increases finger tremor during postural pointing

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Title Augmented visual feedback increases finger tremor during postural pointing
Author Keogh, J.; Morrison, Steven; Barrett, Rod
Journal Name Experimental Brain Research
Editor R F Schmidt, V J Wilson
Year Published 2004
Place of publication Germany
Publisher Springer-Verlag
Abstract Physiological tremor in the upper limb of eight adults was examined during the performance of a unilateral pointing task under conditions where the visual feedback, limb used and target size were altered. All subjects were required to aim a hand-held laser pointer at a circular target 5.5 m away with the goal of keeping the laser emission within the centre of the target. Visual feedback was defined as either normal vision (NV) of their limb tremor, where the laser was switched off, or augmented vision (AV) where the laser was switched on. Postural tremor from the segments of the upper limb, forearm muscle EMG activity, and target accuracy measures were recorded and analysed in the time and frequency domains. Accuracy-tremor relations were assessed using cross correlation and linear regression. Results revealed a high degree of similarity in the general pattern of the tremor output seen for each limb segment across conditions with only scalar (amplitude) changes being seen as a function of the different constraints imposed. For any single condition the tremor amplitude increased from proximal to distal segments. The frequency profile for the tremor in any segment displayed two prominent frequency peaks (at 2–4 Hz and 8–12 Hz). A third, higher frequency peak (18–22 Hz) was observed in the index fingers only. Across all conditions significant coupling relations were observed only between the hand-finger and forearm-upper arm segment pairs. Altering the visual feedback was shown to have the greatest effect on limb tremor with increased tremor and EMG activity and decreased coupling being seen under AV conditions. In trying to reduce tremor output when the augmented feedback was provided novice subjects instead increased muscle activity which resulted in increased tremor. Overall these results indicate that the physiological tremor output observed in neurologically normal subjects is not simply the product of intrinsic oscillations but is influenced by the nature of the task being performed.
Peer Reviewed Yes
Published Yes
Alternative URI
Volume 159
Page from 467
Page to 477
ISSN 0014-4819
Date Accessioned 2004-12-06
Language en_AU
Research Centre Menzies Health Institute Qld; Centre for Musculoskeletal Research
Faculty Griffith Health Faculty
Subject PRE2009-Motor Control
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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