Computations underlying sensorimotor learning

The study of sensorimotor learning has a long history. With the advent of innovative techniques for studying learning at the behavioral and computational levels new insights have been gained in recent years into how the sensorimotor system acquires, retains, represents, retrieves and forgets sensorimotor tasks. In this review we highlight recent advances in the field of sensorimotor learning from a computational perspective. We focus on studies in which computational models are used to elucidate basic mechanisms underlying adaptation and skill acquisition in human behavior.This work was supported by the Wellcome Trust, the Human Frontiers Science Program, the Royal Society (Noreen Murray Professorship in Neurobiology to D.M.W.) and the Canadian Institutes of Health Research.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.conb.2015.12.00

Computations underlying sensorimotor learning.

The study of sensorimotor learning has a long history. With the advent of innovative techniques for studying learning at the behavioral and computational levels new insights have been gained in recent years into how the sensorimotor system acquires, retains, represents, retrieves and forgets sensorimotor tasks. In this review we highlight recent advances in the field of sensorimotor learning from a computational perspective. We focus on studies in which computational models are used to elucidate basic mechanisms underlying adaptation and skill acquisition in human behavior.This work was supported by the Wellcome Trust, the Human Frontiers Science Program, the Royal Society (Noreen Murray Professorship in Neurobiology to D.M.W.) and the Canadian Institutes of Health Research.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.conb.2015.12.00

The quick and the dead: when reaction beats intention

Everyday behaviour involves a trade-off between planned actions and reaction to environmental events.Evidence from neurophysiology, neurology and functional brain imaging suggests different neural bases for the control of different movement types. Here we develop a behavioural paradigm to test movement dynamics for intentional versus reaction movements and provide evidence for a ‘reactive advantage’ in movement execution, whereby the same action is executed faster in reaction to an opponent. We placed pairs of participants in competition with each other to make a series of button presses. Within subject analysis of movement times revealed a 10 per cent benefit for reactive actions. This was maintained when opponents performed dissimilar actions, and when participants competed against a computer, suggesting that the effect is not related to facilitation produced by action observation. Rather, faster ballistic movements may be a general property of reactive motor control, potentially providing a useful means of promoting survival

The quick and the dead: when reaction beats intention

Everyday behaviour involves a trade-off between planned actions and reaction to environmental events.Evidence from neurophysiology, neurology and functional brain imaging suggests different neural bases for the control of different movement types. Here we develop a behavioural paradigm to test movement dynamics for intentional versus reaction movements and provide evidence for a ‘reactive advantage’ in movement execution, whereby the same action is executed faster in reaction to an opponent. We placed pairs of participants in competition with each other to make a series of button presses. Within subject analysis of movement times revealed a 10 per cent benefit for reactive actions. This was maintained when opponents performed dissimilar actions, and when participants competed against a computer, suggesting that the effect is not related to facilitation produced by action observation. Rather, faster ballistic movements may be a general property of reactive motor control, potentially providing a useful means of promoting survival

Decision making in slow and rapid reaching : Sacrificing success to minimize effort

Acknowledgement This work was supported by the James S. McDonnell Foundation (Scholar Award to ARH). Supplementary Material Data available at: https://zenodo.org/record/3604284Peer reviewedPostprin

The Speed, Precision and Accuracy of Human Multisensory Perception following Changes to the Visual Sense

Human adults can combine information from multiple senses to improve their perceptual judgments. Visual and multisensory experience plays an important role in the development of multisensory integration, however it is unclear to what extent changes in vision impact multisensory processing later in life. In particular, it is not known whether adults account for changes to the relative reliability of their senses, following sensory loss, treatment or training. Using psychophysical methods, this thesis studied the multisensory processing of individuals experiencing changes to the visual sense. Chapters 2 and 3 assessed whether patients implanted with a retinal prosthesis (having been blinded by a retinal degenerative disease) could use this new visual signal with non-visual information to improve their speed or precision on multisensory tasks. Due to large differences between the reliabilities of the visual and non-visual cues, patients were not always able to benefit from the new visual signal. Chapter 4 assessed whether patients with degenerative visual loss adjust the weight given to visual and non-visual cues during audio-visual localization as their relative reliabilities change. Although some patients adjusted their reliance on vision across the visual field in line with predictions based on cue relative reliability, others - patients with visual loss limited to their central visual field only - did not. Chapter 5 assessed whether training with either more reliable or less reliable visual feedback could enable normally sighted adults to overcome an auditory localization bias. Findings suggest that visual information, irrespective of reliability, can be used to overcome at least some non-visual biases. In summary, this thesis documents multisensory changes following changes to the visual sense. The results improve our understanding of adult multisensory plasticity and have implications for successful treatments and rehabilitation following sensory loss

Performance monitoring during action observation and auditory lexical decisions

How does the brain monitor performances? Does expertise modulate this process? How does an observer’s error related activity differ from a performers own error related activity? How does ambiguity change the markers of error monitoring? In this thesis, I present two EEG studies and a commentary that sought to answer these questions. Both empirical studies concern performance monitoring in two different contexts and from two different personal perspectives, i.e. investigating the effects of expertise on electroencephalographic (EEG) neuromarkers of performance monitoring and in terms of monitoring own and others’ errors during actions and language processing. My first study focused on characterizing the electrophysiological responses in experts and control individuals while they are observing domain-specific actions in wheelchair basketball with correct and wrong outcomes (Chapter II). The aim of the commentary in the following chapter was to highlight the role of Virtual Reality approaches to error prediction during one’s own actions (Chapter III). The fourth chapter hypothesised that the error monitoring markers are present during both one’s own performance errors in a lexical decision task, and the observation of others’ performance errors (Chapter IV), however, the results suggested a further modulation of uncertainty created by our task design. The final chapter presents a general discussion that provides an overview of the results of my PhD work (Chapter V). The present chapter consists of a literature review in the leading frameworks of performance monitoring, action observation, visuo-motor expertise and language processing

Planning multiple movements within a fixed time limit: The cost of constrained time allocation in a visuo-motor task

S.-W. Wu, M. F. Dal Martello, and L. T. Maloney (2009) evaluated subjects' performance in a visuo-motor task where subjects were asked to hit two targets in sequence within a fixed time limit. Hitting targets earned rewards and Wu et al. varied rewards associated with targets. They found that subjects failed to maximize expected gain; they failed to invest more time in the movement to the more valuable target. What could explain this lack of response to reward? We first considered the possibility that subjects require training in allocating time between two movements. In Experiment 1, we found that, after extensive training, subjects still failed: They did not vary time allocation with changes in payoff. However, their actual gains equaled or exceeded the expected gain of an ideal time allocator, indicating that constraining time itself has a cost for motor accuracy. In a second experiment, we found that movements made under externally imposed time limits were less accurate than movements made with the same timing freely selected by the mover. Constrained time allocation cost about 17% in expected gain. These results suggest that there is no single speed–accuracy tradeoff for movement in our task and that subjects pursued different motor strategies with distinct speed–accuracy tradeoffs in different conditions

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Sub-Optimal Allocation of Time in Sequential Movements

The allocation of limited resources such as time or energy is a core problem that organisms face when planning complex actions. Most previous research concerning planning of movement has focused on the planning of single, isolated movements. Here we investigated the allocation of time in a pointing task where human subjects attempted to touch two targets in a specified order to earn monetary rewards. Subjects were required to complete both movements within a limited time but could freely allocate the available time between the movements. The time constraint presents an allocation problem to the subjects: the more time spent on one movement, the less time is available for the other. In different conditions we assigned different rewards to the two tokens. How the subject allocated time between movements affected their expected gain on each trial. We also varied the angle between the first and second movements and the length of the second movement. Based on our results, we developed and tested a model of speed-accuracy tradeoff for sequential movements. Using this model we could predict the time allocation that would maximize the expected gain of each subject in each experimental condition. We compared human performance with predicted optimal performance. We found that all subjects allocated time sub-optimally, spending more time than they should on the first movement even when the reward of the second target was five times larger than the first. We conclude that the movement planning system fails to maximize expected reward in planning sequences of as few as two movements and discuss possible interpretations drawn from economic theory