Visual attention, EEG alpha power and T7-Fz connectivity are implicated in prosthetic hand control and can be optimized through gaze training

Abstract

Background: Prosthetic hands impose a high cognitive burden on the user that often results in fatigue, frustration and prosthesis rejection. However, efforts to directly measure this burden are sparse and little is known about the mechanisms behind it. There is also a lack of evidence-based training interventions designed to improve prosthesis hand control and reduce the mental effort required to use them. In two experiments, we provide the first direct evaluation of this cognitive burden using measurements of EEG and eye-tracking (Experiment 1), and then explore how a novel visuomotor intervention (gaze training; GT) might alleviate it (Experiment 2). Methods: In Experiment 1, able-bodied participants (n = 20) lifted and moved a jar, first using their anatomical hand and then using a myoelectric prosthetic hand simulator. In experiment 2, a GT group (n = 12) and a movement training (MT) group (n = 12) trained with the prosthetic hand simulator over three one hour sessions in a picking up coins task, before returning for retention, delayed retention and transfer tests. The GT group received instruction regarding how to use their eyes effectively, while the MT group received movement-related instruction typical in rehabilitation. Results: Experiment 1 revealed that when using the prosthetic hand, participants performed worse, exhibited spatial and temporal disruptions to visual attention, and exhibited a global decrease in EEG alpha power (8-12 Hz), suggesting increased cognitive effort. Experiment 2 showed that GT was the more effective method for expediting prosthesis learning, optimising visual attention, and lowering conscious controlas indexed by reduced T7-Fz connectivity. Whilst the MT group improved performance, they did not reduce hand-focused visual attention and showed increased conscious movement control. The superior benefits of GT transferred to a more complex tea-making task. Conclusions: These experiments quantify the visual and cortical mechanisms relating to the cognitive burden experienced during prosthetic hand control. They also evidence the efficacy of a GT intervention that alleviated this burden and promoted better learning and transfer, compared to typical rehabilitation instructions. These findings have theoretical and practical implications for prosthesis rehabilitation, the development of emerging prosthesis technologies and for the general understanding of human-tool interactions.

On the Visuomotor Behavior of Amputees and Able-Bodied People During Grasping

“…This increased visual attention is most likely to compensate for the lack of tactile and proprioceptive feedback from their prostheses. A similar finding was also reported when able-bodied subjects were engaged in similar tasks using a prosthetic simulator (Blank et al, 2010; Sobuh et al, 2014; Parr et al, 2018, 2019). Almost all of these studies investigated this disruption in eye-hand coordination precisely for this reason, namely to measure the subject's proficiency in controlling the prosthesis.…”

“…Although Figure 4B suggests that this window will at least be as long for amputated users, one may argue that this result is not representative for movements performed with a prosthesis. However, previous studies showed without exception that prosthetic users still fixate the target object for the majority of the reaching phase (Bouwsema et al, 2012; Sobuh et al, 2014; Chadwell et al, 2016; Hebert et al, 2019; Parr et al, 2019), albeit alternating it more often with fixations on the hand (i.e., the “switching” strategy). Moreover, this reaching phase may actually take more than twice as long as compared to the same movement performed with the anatomical limb (Sobuh et al, 2014; Hebert et al, 2019).…”

Combined action observation and motor imagery facilitates visuomotor adaptation in children with developmental coordination disorder

“…A target-locking score was then calculated by subtracting the percentage of cursor fixation time from the percentage of target fixation time to create a ratio measure of the allocation of visual attention. This method has previously been used to determine the gaze control of participants performing visuomotor adaptation tasks (Marshall et al, 2019), surgical tasks (Wilson, McGrath, Vine, Brewer, Defriend & Masters , 2010), and tasks involving the control of a prosthetic hand (Parr, Vine, Harrison & Wood, 2018;Parr, Vine, Wilson, Harrison & Wood, 2019). Using this method, a more positive score reflects more time fixating on targets whereas a negative score reflects more time spent fixating the cursor.…”

Combining Action Observation and Motor Imagery Improves Eye–Hand Coordination during Novel Visuomotor Task Performance

“…A score of '0' reflects equal time spent fixating the cursor and targets and represents a 'switching strategy'. This has been shown to be a reliable measure of eye-hand coordination in studies (1) examining expertise in prosthetic hand control (Parr et al, 2018) and surgery (Wilson et al, 2010); (2) in studies that have examined the development of eye-hand coordination (Parr, Vine, Wilson, Harrison & Wood, 2019;Wilson et al, 2011); and (3) in studies examining the effect of pressurized performance environments on eye-hand coordination (Vine, Freeman, Moore, Chandra-Ramanan, & Wilson, 2013).…”