Visuomotor behaviours during functional task performance with a myoelectric prosthesis

Sobuh, MMD

Abstract

Myoelectric hand prostheses are controlled via electromyographic (EMG) signals measured at the residual forearm musculature. Active functional use requires control of force and motion of the prosthetic hand in the absence of proprioceptive and tactile feedback from the hand. Many amputees often choose not to use their prosthesis in this way in everyday life. Current clinical tools provide little insight into why this is, and the few studies of motor control strategies and motor learning provide only a very partial explanation. Further studies are therefore required to inform the development of new prostheses and improved training protocols. Moreover, despite the general agreement that amputees compensate for missing proprioception through vision, at the start of the PhD there were no studies of gaze behaviour in upper limb amputees. The aims of the thesis were to:
1. To identify visuomotor behaviours that change over learning to use a myoelectric prosthesis and;

2. To identify the visuomotor behaviours of established users of myoelectric prostheses and their relationships with results from validated clinical evaluation tools.

To allow investigation of visuomotor behaviours, an everyday task was chosen, namely reaching for and acquiring a carton, then pouring water from it into a glass. A novel coding scheme for objective analysis of gaze data during task performance was developed and validated. Additionally, methods for describing upper limb kinematics were implemented. Using these tools a study of learning to use a myoelectric prosthesis simulator in anatomically intact subjects revealed a number of variables whose values change dramatically with the introduction of the prosthesis and remain different from baseline, even after practice. For example, subjects remained slower at reaching and more variable in their movement and gaze behaviour. Additionally, subjects had to pay considerable attention to the immediate task requirements. The latter findings may be interpreted as showing that prosthesis use may be attentionally demanding. A second study was then carried out involving established trans-radial myoelectric prosthesis users. Similar behaviours to those reported in the first study (following only a very brief period of practice) were observed, giving insight into why current prostheses remain difficult to use in everyday life; amputees had to pay a high degree of visual attention to the immediate requirements of the task, thus limiting their ability to plan subsequent actions of the task. Additionally, subjects who performed well on the task, were also found to perform well on the clinical evaluation tools.

Citation

Sobuh, M. Visuomotor behaviours during functional task performance with a myoelectric prosthesis. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Aug 19, 2013
• Publicly Available Date: Aug 19, 2013
• Additional Information: Funders : University of Jordan