Degraded expression of learned feedforward control in movements released by startle

Abstract

Recent work has shown that preplanned motor programs can be rapidly released via fast conducting pathways using a startling acoustic stimulus (SAS). Our question is whether the startle-elicited response might also release a recently learned internal model, which draws on experience to predict and compensate for expected perturbations in a feedforward manner. Our initial investigation using adaptation to robotically produced forces showed some evidence of this, but the results were potentially confounded by co-contraction caused by startle. In this study, we eliminate this confound by asking subjects to make reaching movements in the presence of a visual distortion. Results show that a startle stimulus (1) decreased performance of the recently learned task, and (2) reduced after-effect magnitude. Since the recall of learned control was reduced, but not eliminated during startle trials, we suggest that multiple neural centers (cortical and subcortical) are involved in such learning and adaptation. These findings have implications for motor training in areas such as piloting, teleoperation, sports, and rehabilitation.

A rapid visuomotor response on the human upper limb is selectively influenced by implicit motor learning

“…Our results, which demonstrate a selective influence of implicit motor learning on this descending pathway, may also explain the adaptation of these responses during various motor learning paradigms. For example, both startReact and corrective reach movements are modulated during motor learning induced by a force field (Franklin et al 2012;Wright et al 2015) or, as studied here, a visuomotor rotation (Hayashi et al 2016;Telgen et al 2014). However, the contribution of implicit vs. explicit components of motor learning was not considered in these paradigms.…”

StartReact increases the probability of muscle activity and distance in severe/moderate stroke survivors during two-dimensional reaching task

“…Most previous SR work has evaluated only single joint movement (Cressman et al 2006;Maslovat et al 2009Maslovat et al , 2011Carlsen et al 2011Carlsen et al , 2012Alibiglou and MacKinnon 2012;Ravichandran et al 2013;Castellote and Valls-Solé 2015;Sutter et al 2016;Marinovic et al 2017;Leow et al 2018) including the previous work in individuals with stroke Perreault 2012, 2014;Marinovic et al 2016). In unimpaired individuals, SR readily evokes multi-jointed reaching movements (Wright et al 2015;Ossanna et al 2019) and combined tasks such as simultaneous pinch and elbow flexion (Castellote and Kofler 2018) in an unrestricted workspace but individuals with stroke have abnormal muscle activity patterns and spasticity which casts doubt on if SR would be accessible during unrestricted reaching movements post-stroke and more relevantly generate quantitative changes that improve reaching performance in this population. Moreover, SR extension movements are interrupted by functionally inappropriate flexor activity disrupting movement to the intended target (Honeycutt and Perreault 2014;Tazoe and Perez 2017;Choudhury et al 2019).…”

Startle evokes nearly identical movements in multi-jointed, two-dimensional reaching tasks

“…The objective of this study was to evaluate the ability of startReact to evoke unrestricted, multi-joint movements during two-dimensional reaching tasks that are equivalent to voluntary movements in all metrics except onset latency. Based on previous work showing that startReact was present during multi-joint reaching in a single direction (Wright et al 2015), we hypothesized that startReact would evoke similar multi-joint reaching movements when compared to voluntary movements. We expand upon Wright, et al, by more extensively quantifying multi-joint reaching characteristics including movement accuracy and muscle activation patterns within a larger workspace.…”