Biology subjects

Hewitson, C. L.

Publications and source records attributed to Hewitson, C. L..

5 recordsLinked to original sources

bioRxiv2023

Context versus aiming in motor learning when both feedforward and feedback control processes are engaged

Theories of human motor learning commonly assume that movement plans are adjusted in response to the precision of sensory feedback received regarding their success. However, support for this assumption has mainly come from experiments that limit feedback correction during an ongoing movement. In contrast, we have recently shown that when this restriction is relaxed, and both within-movement and between-movement corrections can occur, movement plans undergo large and abrupt changes that are strongly correlated with the degree of sensory uncertainty present on the previous trial and are insensitive to the magnitude and direction of recently experienced movement errors. A class of models in which sensory uncertainty influences an aiming process with no retention from one trial to the next best accounted for these data. Here, we examine an alternative possibility that sensory uncertainty acts as a contextual cue to shunt motor learning and control to one of many context-specific internal models. Although both aiming and context models provide good fits for our data, the aiming model performed best. Author summaryA large body of literature shows that sensory uncertainty inversely scales the degree of error-driven corrections made to motor plans from one trial to the next. However, by limiting sensory feedback to the endpoint of movements, these studies prevent corrections from taking place during the movement. We have recently shown that when such corrections are permitted, sensory uncertainty punctuates between-trial movement corrections with abrupt changes that closely track the degree of sensory uncertainty but are insensitive to the magnitude and direction of recently experienced movement error. Here, we ask whether this pattern of behaviour is more consistent with sensory uncertainty driving changes in an aiming process or context-specific motor learning.

neuroscience↗

bioRxiv2023

Sensory uncertainty influences motor learning differently in blocked versus interleaved trial contexts when both feedforward and feedback processes are engaged

Theories of human motor learning commonly assume that the degree to which movement plans are adjusted in response to movement errors scales with the precision of sensory feedback received regarding their success. However, support for such error-scaling models has mainly come from experiments that limit the amount of correction that can occur within an ongoing movement. In contrast, we have recently shown that when this restriction is relaxed, and both within-movement and between-movement corrections co-occur, movement plans undergo large and abrupt changes that are strongly correlated with the degree of sensory uncertainty present on the previous trial and are insensitive to the magnitude and direction of the experienced movement error. Here, we show that the presence of these abrupt and error-insensitive changes can only be reliably detected when different levels of sensory precision are interleaved pseudo randomly on a trial-by-trial basis. These results augment our earlier findings and suggest that the co-occurrence of within-movement and between-movement corrections is not the only important aspect of our earlier study that challenged the error-scaling models of motor learning under uncertainty. Author summaryA large body of literature shows that sensory uncertainty inversely scales the degree of error-driven corrections made to motor plans from one trial to the next. However, by limiting sensory feedback to the endpoint of movements, these studies prevent corrections from taking place during the movement. We have recently shown that when such corrections are promoted, sensory uncertainty punctuates between-trial movement corrections with abrupt changes that closely track the degree of sensory uncertainty but are insensitive to the magnitude and direction of movement error. Here, we show that this result requires different levels of sensory uncertainty to be mixed on a trial-by-trial basis. This carries important implications for how previous studies of motor learning under uncertainty are interpreted, and what future studies will likely constitute progress for the field.

neuroscience↗

bioRxiv2023

Metacognitive Judgments during Visuomotor Learning Reflect the Integration of Error History

People form metacognitive representations of their own abilities across a range of tasks. How these representations are influenced by errors during learning is poorly understood. Here we ask how metacognitive confidence judgments of performance during motor learning are shaped by the learners recent history of errors. Across four motor learning experiments, our computational modeling approach demonstrated that peoples confidence judgments are best explained by a recency-weighted averaging of visually observed errors. Moreover, in the formation of these confidence estimates, people appear to re-weight observed motor errors according to a subjective cost function. Confidence judgments were adaptive, incorporating recent motor errors in a manner that was sensitive to the volatility of the learning environment, integrating a shallower history when the environment was more volatile. Finally, confidence tracked motor errors in the context of both implicit and explicit motor learning, but only showed evidence of influencing behavior in the latter. Our study thus provides a novel descriptive model that successfully approximates the dynamics of metacognitive judgments during motor learning. NEW & NOTEWORTHYThis study examined how, during visuomotor-learning, peoples confidence in their performance is shaped by their recent history of errors. Using computational modeling, we found that confidence incorporated recent error-history, tracked subjective error-costs, was sensitive to environmental volatility, and in some contexts may influence learning. Together, these results provide a novel model of metacognitive judgments during motor-learning that could be applied to future computational and neural studies at the interface of higher-order cognition and motor control.

neuroscience↗

bioRxiv2022

Sensory uncertainty punctuates motor learning independently of movement error when both feedforward and feedback control processes are engaged

Integrating sensory information during movement and adapting motor plans over successive movements are both essential for accurate, flexible motor behavior. When an ongoing movement is off target, feedback control mechanisms update the descending motor commands to counter the sensed error. Over longer timescales, errors induce adaptation in feedforward planning so that future movements become more accurate and require less online adjustment from feedback control processes. Both the degree to which sensory feedback is integrated into an ongoing movement and the degree to which movement errors drive adaptive changes in feedforward motor plans have been shown to scale inversely with sensory uncertainty. However, since they have only been studied in isolation of each other, little is know about how they respond to sensory uncertainty in real-world movement contexts where they co-occur. Here, we show that sensory uncertainty impacts feedforward adaptation of reaching movements differently when feedback integration is present versus when it is absent. In particular, participants gradually adjust their movements from trial-to-trial in a manner that is well characterised by a slow and consistent envelope of error reduction. Riding on top of this slow envelope, participants display large and abrupt changes in their initial movement vectors that clearly correlate with the degree of sensory uncertainty present on the previous trial. However, these abrupt changes are insensitive to the magnitude and direction of the sensed movement error. These results prompt important questions for current models of sensorimotor learning under uncertainty and open up exciting new avenues for future exploration. Author SummaryA large body of literature shows that sensory uncertainty inversely scales the degree of error-driven corrections made to motor plans from one trial to the next. However, by limiting sensory feedback to the endpoint of movements, these studies prevent corrections from taking place during the movement. Here, we show that when such corrections are promoted, sensory uncertainty punctuates between-trial movement corrections with abrupt changes that closely track the degree of sensory uncertainty but are insensitive to the magnitude and direction of movement error. This result marks a significant departure from existing findings and opens up new paths for future exploration.

animal behavior and cognition↗

bioRxiv2019

Enhanced visuomotor learning and generalization in expert surgeons

Although human motor learning has been intensively studied for many decades, it remains unknown whether group differences are present in expert cohorts that must routinely cope with and learn new visuomotor mappings such as minimally invasive surgeons. Here we show that expert surgeons exhibit greater adaptation and generalization compared to naive controls in a standard visuomotor adaptation task. These findings run counter to a widespread background assumption in the field of motor learning that visuomotor adaptation performance should be largely uniform across the adult human population. Our findings also indicate that differences in basic visuomotor learning capacities, either innate or acquired, might be an important source of difficulty in learning and performing minimally invasive surgery. This information holds potential to guide surgical candidate selection or optimize training programs to address individual needs.

neuroscience↗