The Role of Visuomotor Behaviours in Understanding the Functionality of Upper Limb Prostheses
Creators: Cheng, Kodi
Publisher: name: University of Alberta Library
Year: 2024

<p>Introduction: Upper limb prostheses aim to restore the complex capacities of the human hand. Coordinated hand and arm function relies on an intact visuomotor system during object interaction. However, unlike individuals with intact arm function, prosthesis users face additional challenges due to an absence of the natural channels for motor control and feedback sensations from the amputated limb. These challenges necessitate constant visual monitoring of the prosthesis and lend to disruptions to normal patterns of eye-hand coordination. Novel prosthetic interventions are thus developed to facilitate increased functionality, while also minimizing the attentional demand associated with operating these devices. To evaluate this visual demand, eye tracking is a technology that has enabled researchers to delve into our understanding of the visuomotor behaviours of upper limb prosthesis users and provides the potential of quantifying the usability of prosthetic devices.</p>

<p>Objectives: The first objective of this thesis was to employ a scoping review in order to understand how eye tracking metrics have been used in the literature to date to describe the visual behaviours of upper limb prosthesis users. The review aimed to characterize the visuomotor behaviours of upper limb prosthesis, summarize the eye tracking metrics and variables used to describe these behaviours, and identify gaps in the literature and potential areas for future research. Building on the research gaps presented in the scoping review, the second objective of this thesis was to explore the relationship between gaze behaviour and prosthesis skill level using measures of hand movement. The goal was to understand whether improved motor planning, as reflected by eye gaze behaviour, was associated with more efficient hand movement patterns when performing object manipulation tasks with a prosthesis. Finally, the third objective of this thesis was to investigate the effects of an advanced myoelectric control strategy on the visuomotor behaviours of upper limb prosthesis users. That is, to determine whether a more reliable control strategy could reduce the visual demand associated with prosthetic control.</p>

<p>Methods: To tackle the first objective, a scoping review was performed, in which five online databases were searched for academic literature that involved the use of eye tracking and the assessment of visuomotor behaviours for upper limb prosthetic use. Data on the level of amputation, type of prosthetic device, type of eye tracker, primary eye metrics, secondary outcome metrics, experimental task, aims, and key findings were extracted to understand the ways in which eye tracking has been used to evaluate upper limb prosthesis use. For the second objective, participants without limb difference used a simulated myoelectric prosthetic device to perform an object manipulation task, while eye tracking and motion capture data were collected. Correlational analyses were carried out to investigate the relationship between measures of gaze behaviour (percent fixation and eye latencies) and measures of hand kinematic function (hand distance travelled, hand trajectory variability, number of movement units, and phase durations). Lastly, to accomplish the third objective, two myoelectric control strategies were compared, a baseline control strategy and an advanced control strategy that was designed to be more reliable in multiple limb positions. Participants without limb difference controlled a simulated myoelectric prosthesis on two separate days, with either the baseline or advanced control strategy. Eye tracking and motion capture data were collected, and the resulting visuomotor metrics were compared between control strategies. </p>

<p>Results: The research findings in this thesis indicated that prosthesis users have a characteristic visuomotor behaviour that differs from individuals with intact arm function, such that prosthesis users fixate more towards their hand and less towards target objects or locations. Additionally, measures of gaze behaviours were shown to be related to measures of hand kinematic function, which suggests that a reduced reliance on visual attention and improved motor planning is associated with improved grasp control. Furthermore, modulating prosthetic control demonstrated to be successful in improving the visuomotor behaviours of myoelectric prosthesis users.  </p>

<p>Recommendations: Eye tracking technology has contributed significantly to our understanding of the visuomotor behaviours of upper limb prosthesis users. This thesis demonstrated, for the first time, the sensitivity of eye metrics in response to prosthetic control interventions. Future work should thus consider the inclusion of eye tracking as an outcome measure when evaluating novel prosthetic control strategies to ensure that research work is guided towards developing prostheses that are both functional and useable.  </p>