The sensorimotor theory is an influential, non-mainstream account of perception and perceptual consciousness intended to improve in various ways on orthodox theories. It is often taken to be a variety of enactivism, and in common with enactivist cognitive science more generally, it de-emphasises the theoretical role played by internal representation and other purely neural processes, giving theoretical pride of place instead to interactive engagements between the brain, non-neural body and outside environment. In addition to offering a distinctive account of the processing that underlies perceptual consciousness, the sensorimotor theory aims to offer a new and improved account the logical and phenomenological character of perceptual experience, and the relation between physical and phenomenal states. Since its inception in a 2001 paper by O'Regan and Noë, the theory has prompted a good deal of increasingly prominent theoretical and practical work in cognitive science, as well as a large body of secondary literature in philosophy of cognitive science and philosophy of perception. In spite of its influential character, many of the theory's most basic tenets are incompletely or ambiguously defined, and it has attracted a number of prominent objections. This thesis aims to clarify the conceptual foundations of the sensorimotor theory, including the key theoretical concepts of sensorimotor contingency, sensorimotor mastery, and presence-as-access, and defends a particular understanding of the respective theoretical roles of internal representation and behavioural capacities. In so doing, the thesis aims to highlight the sensorimotor theory's virtues and defend it from some leading criticisms, with particular attention to a response by Clark which claims that perception and perceptual experience plausibly depend on the activation of representations which are not intimately involved in bodily engagements between the agent and environment. A final part of the thesis offers a sensorimotor account of the experience of temporally extended events, and shows how with reference to this we can better understand object experience.

The past twenty years have seen a successful formalization of the idea that perception is a form of probabilistic inference. Bayesian Decision Theory (BDT) provides a neat mathematical framework for describing how an ideal observer and actor should interpret incoming sensory stimuli and act in the face of uncertainty. The predictions of BDT, however, crucially depend on the observer’s internal models, represented in the Bayesian framework by priors, likelihoods, and the loss function. Arguably, only in the simplest scenarios (e.g., with a few Gaussian variables) we can expect a real observer’s internal representations to perfectly match the true statistics of the task at hand, and to conform to exact Bayesian computations, but how humans systematically deviate from BDT in more complex cases is yet to be understood. In this thesis we theoretically and experimentally investigate how people represent and perform probabilistic inference with complex (beyond Gaussian) one-dimensional distributions of stimuli in the context of sensorimotor decision making. The goal is to reconstruct the observers’ internal representations and details of their decision-making process from the behavioural data – by employing Bayesian inference to uncover properties of a system, the ideal observer, that is believed to perform Bayesian inference itself. This “inverse problem” is not unique: in principle, distinct Bayesian observer models can produce very similar behaviours. We circumvented this issue by means of experimental constraints and independent validation of the results. To understand how people represent complex distributions of stimuli in the specific domain of time perception, we conducted a series of psychophysical experiments where participants were asked to reproduce the time interval between a mouse click and a flash, drawn from a session-dependent distribution of intervals. We found that participants could learn smooth approximations of the non-Gaussian experimental distributions, but seemed to have trouble with learning some complex statistical features such as bimodality. To investigate whether this difficulty arose from learning complex distributions or computing with them, we conducted a target estimation experiment in which “priors” where explicitly displayed on screen and therefore did not need to be learnt. Lack of difference in performance between the Gaussian and bimodal conditions in this task suggests that acquiring a bimodal prior, rather than computing with it, is the major difficulty. Model comparison on a large number of Bayesian observer models, representing different assumptions about the noise sources and details of the decision process, revealed a further source of variability in decision making that was modelled as a “stochastic posterior”. Finally, prompted by a secondary finding of the previous experiment, we tested the effect of decision uncertainty on the capacity of the participants to correct for added perturbations in the visual feedback in a centre of mass estimation task. Participants almost completely compensated for the injected error in low uncertainty trials, but only partially so in the high uncertainty ones, even when allowed sufficient time to adjust their response. Surprisingly, though, their overall performance was not significantly affected. This finding is consistent with the behaviour of a Bayesian observer with an additional term in the loss function that represents “effort” – a component of optimal control usually thought to be negligible in sensorimotor estimation tasks. Together, these studies provide new insight into the capacity and limitations people have in learning and performing probabilistic inference with distributions beyond Gaussian. This work also introduces several tools and techniques that can help in the systematic exploration of suboptimal behaviour. Developing a language to describe suboptimality, mismatching representations and approximate inference, as opposed to optimality and exact inference, is a fundamental step to link behavioural studies to actual neural computations.

Thesis (Ph. D.)--University of California, San Diego, 2008. / Title from first page of PDF file (viewed September 24, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 133-135).

Neuropsychological tests have been used in differentially diagnosing schizophrenic and brain damaged populations. Research indicated some subgroups of schizophrenia exhibit certain symptoms of brain damage; and that schizophrenia involves difficulty in sensory integration. The Haptic Visual Discrimination Test (HVDT) designed to test tactilevisual integration, Bender Gestalt, and Information and Digit Symbol subtests of the WAIS were used to test performance abilities of forty schizophrenic subjects, forty subjects medically diagnosed as brain damaged (10 right hemisphere, 10 left hemisphere, and 20 diffuse), and normals as defined by the standardized age norm scores.

Following unilateral stroke there is significant loss of function in the body side contralateral to the damage and a robust degenerative-regenerative cascade of events in both hemispheres. It is natural to compensate for loss of function by relying more on the less-affected body side to accomplish everyday living tasks (e.g. brushing teeth, drinking coffee). This is accompanied by a “learned disuse” of the impaired side thought to occur due to repeated experience with its ineptness. However, as investigated in these studies, it may also be due to brain changes instigated by experience with the intact body side. The central hypothesis of these dissertation studies is that experience with the intact forelimb, after unilateral sensorimotor cortex (SMC) damage, disrupts functional recovery with the impaired forelimb and interferes with peri-lesion neural plasticity. Following unilateral ischemic lesions, rats were trained on a skilled reaching task with their intact (less-affected) forelimb or received control procedures. The impaired forelimb was then trained and tested on the same skilled reaching task. Intact forelimb experience worsened performance with the impaired forelimb even when initiated at a more delayed time point following lesions. Intact forelimb training also reduced peri-lesion expression of FosB/ΔFosB, a marker of neuronal activation, and caudal forelimb motor map areas compared to animals without intact forelimb training. It was further established that it is focused training of the intact forelimb and not experience with this limb per se, as animals trained with both forelimbs in an alternating fashion did not exhibit this effect. Transections of the corpus callosum blocked the maladaptive effect of intact forelimb experience on impaired forelimb recovery, suggesting a disruptive influence of the intact hemisphere onto the lesion hemisphere that is mediated by experience. Together these dissertation studies provide insight into how experience with the less-affected, intact body side, can influence peri-lesion neural plasticity and recovery of function with the impaired forelimb. The findings from these studies suggest that compensatory use of the less-affected (intact) body side following unilateral brain damage is not advantageous if the ultimate goal is to improve function in the impaired body side. / text

This thesis investigated whether different textured surfaces have a role to play in changing balance performance in healthy young and older adults. A review of the literature showed that balance may be improved by standing on surfaces, or wearing foot insoles, with texture compared to those that are smooth, possibly by providing enhanced plantar tactile stimulation. It also showed that textured footwear interventions can influence lower limb muscle activity during functional activities. However, some major gaps in current literature were identified. There was limited evidence relating to the effect of texture in older adults: a population known to show poor balance and at high risk of falling. The importance of the geometric textured pattern in changing balance had not been investigated. It was also unclear whether textured interventions altered lower limb muscle activity, as a component of sensorimotor function of balance control. The purpose of this thesis was to address these important areas of research and contribute novel evidence to the field. In two separate studies, 24 young and 50 older healthy adults conducted tests of bilateral quiet standing with eyes open and closed on two different textured surfaces and a smooth surface as control. Centre of pressure based sway variables were extracted from a force platform and lower limb muscle activity was collected using surface electromyography, over 30 seconds. Textured surfaces did not significantly alter sway variables or lower limb muscle activity in healthy young adults. Closer observation of the data tentatively suggested texture may have the capacity to alter anterior-posterior sway and centre of pressure velocity in young adults. These findings supported the aims of this thesis to explore the possibility of a textured effect in people with poor balance ability: older adults. Textured surfaces significantly changed mediolateral sway range and centre of pressure velocity in healthy older adults, in the absence of visual information. No significant changes were observed for lower limb muscle activity, between the textured conditions. Exploratory sub-group analysis for gender generated speculative data suggesting the effect of texture on balance and muscle activity may be more marked in older females. Evidence from both studies suggests that relative to control, the two textured conditions have opposite effects on postural sway. There may be an optimal textured pattern which could be therapeutically beneficial for enhancing balance performance in healthy and pathological groups. Further investigation is required.

A blockade of GABAergic inhibition increases the receptive field(RF) size of most somatosensory cortex (SI) and some ventrobasal thalamus (VB) neurons. The results suggest RF size of cuneate neurons may be modulated through GABAa and GABAb receptors, independent of firing frequency.

Research presented in this dissertation has the central aim of applying a novel method of source localization called beamforming to neuromagnetic recordings for characterizing dynamic spatiotemporal activity of sensorimotor brain processes in subjects during rhythmic auditory stimulation, self-paced movement, and two sensorimotor coordination (synchronization and syncopation) tasks known to differentiate on the basis of behavioral stability. Each experimental condition was performed at different rates resulting in 26 experimental runs per subject. Event-related neural responses were recorded with a whole-head MEG system and characterized in terms of their phase-locked (evoked) and non-phase-locked (induced) activity within the brain using both whole-brain analysis and region of interest (ROI) analysis. The analysis of the auditory conditions revealed that neural activity within extraauditory areas throughout the brain, including sensorimotor cortex, is modulated by rhythmic auditory stimulation. Additionally, the temporal profile of this activity was markedly different between sensorimotor and auditory cortex, possibly revealing different physiological processes, entrained within a common network for representing isochronic auditory events. During self-paced movements cycle-by-cycle dynamics of induced neural activity was measured and consistent neuro-modulation in the form of event-related desynchronization (ERD) and synchronization (ERS) was observed at all rates investigated (0.25 - 1.75Hz). ERD and ERS modulations exhibited dynamic scaling properties on a cycle-by-cycle basis that depended on the period of movement. Activity in the beta- and mu-bands also exhibited patterns of phase locking between sensorimotor locations. Phase locking patterns exhibited abrupt decreases with increases in movement rate. / During sensorimotor coordination tasks, the effect of temporal positioning of the auditory stimulus was apparent within sensorimotor cortical sites. This finding offers direct source level support for previous sensor level analysis revealing a differentiation of functional specificity for mu- and beta-band activity (Chen, Ding, Kelso, 2003; Jantzen, Fuchs, Mayville et al., 2001; Mayville, Fuchs, Ding et al., 2001), and may be reflective of specific coupling mechanisms between auditory and sensorimotor networks. The beamformer analysis applied within this dissertation successfully characterized large-scale neural networks during a variety of rhythmic perceptual, motor, and sensorimotor tasks resulting in the general message that information processes across disparate parts of the brain from different sensory, motor, and cognitive modalities appear to have the ability for widespread integration. / by Paul Ferrari. / Thesis (Ph.D.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

Yue Xiaomin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 47-55). / Abstracts in English and Chinese. / Chapter CHAPTER I --- INTRODUCTION / Chapter 1 --- Neuronal Synchronization --- p.1 / Chapter 2. --- Synchronization and attention --- p.4 / Chapter CHAPTER II --- METHODOLOGY OF EEG SIGNAL ANALYSIS / Chapter 1 --- A time series and a stochastic process --- p.8 / Chapter 2 --- Methods to capture neuronal synchronization --- p.10 / Chapter 3 --- Disadvantage of traditional method to calculate coherent --- p.11 / Chapter 4 --- Multivariate AutoRegressive model (MVAR) --- p.12 / Chapter 5 --- Estimation algorithm of MVAR model --- p.15 / Chapter 6 --- Validation of the algorithm by simulation --- p.17 / Chapter CHAPTER III --- EXPERIMENTS AND RESULTS / Chapter 1 --- Experiment --- p.1 / Chapter 1.1 --- Participants and experimental procedures --- p.21 / Chapter 1.2 --- EEG recording and processing --- p.22 / Chapter 1.3 --- Results and discussion --- p.23 / Chapter 2 --- Experiment / Chapter 2.1 --- Participants and experimental procedures --- p.32 / Chapter 2.2 --- EEG recording and processing --- p.32 / Chapter 2.3 --- Results and discussion --- p.33 / Chapter CHAPTER IV --- DISCUSSION AND CONCLUSION / Chapter 1 --- Functional connection between different cortical areas --- p.42 / Chapter 2 --- Relationship of coherence to motor behavior --- p.45 / Chapter 3 --- Automatic synchronization --- p.46 / Reference --- p.48

Background: Current smoking-cessation medicines can assist smokers to quit, but have limited efficacy. Supplementing them with a replacement for the sensory and behavioural aspects of smoking, which are hypothesised to act as secondary reinforcers, could in theory help to alleviate urges to smoke and withdrawal, and may assist smoking cessation. Methods: Three studies were conducted to examine sensorimotor replacement (SMR) effects. The first two employed a cross-over design to assess the effects of two SMR products, nicotine-free electronic cigarettes (ECs) and de-nicotinised cigarettes (DNCs), on short-term withdrawal, urges to smoke, and user acceptability. Study 1 (N= 35), compared EC to a stress ball (SB) to control for behavioural distraction and Study 2 (N=41) tested whether SMR effects were ‘dose dependent’ by comparing DNCs with ECs. The final study was part of a randomised controlled trial (N= 200) of DNCs in combination with standard treatment. It examined whether SMR effects on abstinence are moderated by scores on a ‘behavioural’ dependence measure (GN-SBQ). Results: The EC was preferred over the SB, and alleviated urge to smoke more than SB, but the effect was modest and short-lived. The DNC and EC had similar effects acutely, but DNC suppressed urges to smoke and withdrawal to a somewhat greater extent over a day of abstinence. DNCs combined with standard smoking-cessation treatment improved short-term abstinence regardless of GN-SBQ scores. Conclusion: SMR effects on urge and withdrawal alleviation were modest and a ‘dose response’ effect was not clearly established. An attempt to identify smokers for whom SMR may be of particular benefit was not successful. SMR however, was perceived as helpful and appealing, and results from the trial suggest that adding SMR may enhance existing treatments. It was proposed that rather than directly alleviating urges/withdrawal, SMR may operate as a coping tool in ‘high-risk’ situations, by providing an alternative to smoking.