Structure Learning in Bayesian Sensorimotor Integration

Previous studies have shown that sensorimotor processing can often be described by Bayesian learning, in particular the integration of prior and feedback information depending on its degree of reliability. Here we test the hypothesis that the integration process itself can be tuned to the statistical structure of the environment. We exposed human participants to a reaching task in a three-dimensional virtual reality environment where we could displace the visual feedback of their hand position in a two dimensional plane. When introducing statistical structure between the two dimensions of the displacement, we found that over the course of several days participants adapted their feedback integration process in order to exploit this structure for performance improvement. In control experiments we found that this adaptation process critically depended on performance feedback and could not be induced by verbal instructions. Our results suggest that structural learning is an important meta-learning component of Bayesian sensorimotor integration.     

Sensorimotor Integration in Dyslexic Children under Different Sensory Stimulations

Dyslexic children, besides difficulties in mastering literacy, also show poor postural control that might be related to how sensory cues coming from different sensory channels are integrated into proper motor activity. Therefore, the aim of this study was to examine the relationship between sensory information and body sway, with visual and somatosensory information manipulated independent and concurrently, in dyslexic children. Thirty dyslexic and 30 non-dyslexic children were asked to stand as still as possible inside of a moving room either with eyes closed or open and either lightly touching a moveable surface or not for 60 seconds under five experimental conditions: (1) no vision and no touch; (2) moving room; (3) moving bar; (4) moving room and stationary touch; and (5) stationary room and moving bar. Body sway magnitude and the relationship between room/bar movement and body sway were examined. Results showed that dyslexic children swayed more than non-dyslexic children in all sensory condition. Moreover, in those trials with conflicting vision and touch manipulation, dyslexic children swayed less coherent with the stimulus manipulation compared to non-dyslexic children. Finally, dyslexic children showed higher body sway variability and applied higher force while touching the bar compared to non-dyslexic children. Based upon these results, we can suggest that dyslexic children are able to use visual and somatosensory information to control their posture and use the same underlying neural control processes as non-dyslexic children. However, dyslexic children show poorer performance and more variability while relating visual and somatosensory information and motor action even during a task that does not require an active cognitive and motor involvement. Further, in sensory conflict conditions, dyslexic children showed less coherent and more variable body sway. These results suggest that dyslexic children have difficulties in multisensory integration because they may suffer from integrating sensory cues coming from multiple sources.     

A Fully Automated Rodent Conditioning Protocol for Sensorimotor Integration and Cognitive Control Experiments

Rodents have been traditionally used as a standard animal model in laboratory experiments involving a myriad of sensory, cognitive, and motor tasks. Higher cognitive functions that require precise control over sensorimotor responses such as decision-making and attentional modulation, however, are typically assessed in nonhuman primates. Despite the richness of primate behavior that allows multiple variants of these functions to be studied, the rodent model remains an attractive, cost-effective alternative to primate models. Furthermore, the ability to fully automate operant conditioning in rodents adds unique advantages over the labor intensive training of nonhuman primates while studying a broad range of these complex functions.Here, we introduce a protocol for operantly conditioning rats on performing working memory tasks. During critical epochs of the task, the protocol ensures that the animal''s overt movement is minimized by requiring the animal to ''fixate'' until a Go cue is delivered, akin to nonhuman primate experimental design. A simple two alternative forced choice task is implemented to demonstrate the performance. We discuss the application of this paradigm to other tasks.     

Sensorimotor Transformations in the Zebrafish Auditory System

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Structure Learning in a Sensorimotor Association Task

Learning is often understood as an organism''s gradual acquisition of the association between a given sensory stimulus and the correct motor response. Mathematically, this corresponds to regressing a mapping between the set of observations and the set of actions. Recently, however, it has been shown both in cognitive and motor neuroscience that humans are not only able to learn particular stimulus-response mappings, but are also able to extract abstract structural invariants that facilitate generalization to novel tasks. Here we show how such structure learning can enhance facilitation in a sensorimotor association task performed by human subjects. Using regression and reinforcement learning models we show that the observed facilitation cannot be explained by these basic models of learning stimulus-response associations. We show, however, that the observed data can be explained by a hierarchical Bayesian model that performs structure learning. In line with previous results from cognitive tasks, this suggests that hierarchical Bayesian inference might provide a common framework to explain both the learning of specific stimulus-response associations and the learning of abstract structures that are shared by different task environments.     

A Bayesian Perspective on Sensory and Cognitive Integration in Pain Perception and Placebo Analgesia

The placebo effect is a component of any response to a treatment (effective or inert), but we still ignore why it exists. We propose that placebo analgesia is a facet of pain perception, others being the modulating effects of emotions, cognition and past experience, and we suggest that a computational understanding of pain may provide a unifying explanation of these phenomena. Here we show how Bayesian decision theory can account for such features and we describe a model of pain that we tested against experimental data. Our model not only agrees with placebo analgesia, but also predicts that learning can affect pain perception in other unexpected ways, which experimental evidence supports. Finally, the model can also reflect the strategies used by pain perception, showing that modulation by disparate factors is intrinsic to the pain process.     

Sensorimotor and cognitive laterality profiles

Different types of functional asymmetries, which form individual laterality profiles, were compared with the use of a battery of sensorimotor and cognitive laterality tests (TOPOS), the Benziger thinking style assessment (BTSA) test, the Cattell 17PF test, and psychosemantic multidimensional scaling. The proportion of men was shown to be higher among individuals with the left-side, symmetrical, and intersecting motor laterality profiles. Men with a dominant left leg or without asymmetry in the profile were more frequent than women, whereas women prevailed among persons with a dominant left eye. Different laterality profiles were obtained for different factors of the Cattell test. Comparison of the sensorimotor laterality and the BTSA data showed that more than half of persons with the left-hemispheric sensorimotor profile prefer right-hemispheric cognitive strategies. The results suggest that lateralities of different types may be nonuniform.Translated from Fiziologiya Cheloveka, Vol. 31, No. 2, 2005, pp. 24–33.Original Russian Text Copyright © 2005 by Chernigovskaya, Gavrilova, Voinov, Strelnikov.     

Lateral Preferences as Possible Phenotypic Predictors of the Reserves of the Cardiovascular System and the Features of Sensorimotor Integration in Climbers

The lateral preferences of the hands, the reserves of the cardiovascular system and the features of sensorimotor integration in mountain climbers as possible predictors of adaptation to extreme factors of the external environment have been investigated. The subjects were 15 climbers of high class (men aged 25.5–62.8 years). We used the following methods: reflexometric technique ReBFB (complex sensorimotor reaction in the model of go/no-go, computer simulation according to Chernikov); the assessment of lateral preferences using the standard samples; the orthostatic test (with the recording of the heart rate and evaluation of adaptive reserves based on the indices of mathematical analysis of the cardiac rhythm in the transition period according to a technique by Riftin). Sensorimotor integration was performed under normal conditions and under normobaric hypoxia. All indicators were correlated with the age and proficiency of the climbers. We observed no statistically significant correlations between age and the reserves of the cardiovascular system in the group of climbers. Reflexometry in normoxic conditions showed an improvement in the orientation of subjects in the sensory flow as compared with the initial level. The sensorimotor integration (as a response of sensorimotor responses) was more stable during hypoxia as compared with the same indices in normoxia. Noticeable correlation was observed between the results of the humeral test and the reserves of the cardiovascular system defined by orthostatic hypotension: the reserves were higher in the subjects with a higher level of left-hand preference. The regulation of the autonomic nervous system is correlated with left-handedness, which results in more effective adaptation to the high altitude in left-handers. The parameter of handedness can be used as a phenotypic predictor of the level of the cardiovascular system reserves in climbers. It is suggested that the factor of hypoxia with small exposure has a stimulating effect on sensorimotor integration in climbers.     

Interference and Shaping in Sensorimotor Adaptations with Rewards

When a perturbation is applied in a sensorimotor transformation task, subjects can adapt and maintain performance by either relying on sensory feedback, or, in the absence of such feedback, on information provided by rewards. For example, in a classical rotation task where movement endpoints must be rotated to reach a fixed target, human subjects can successfully adapt their reaching movements solely on the basis of binary rewards, although this proves much more difficult than with visual feedback. Here, we investigate such a reward-driven sensorimotor adaptation process in a minimal computational model of the task. The key assumption of the model is that synaptic plasticity is gated by the reward. We study how the learning dynamics depend on the target size, the movement variability, the rotation angle and the number of targets. We show that when the movement is perturbed for multiple targets, the adaptation process for the different targets can interfere destructively or constructively depending on the similarities between the sensory stimuli (the targets) and the overlap in their neuronal representations. Destructive interferences can result in a drastic slowdown of the adaptation. As a result of interference, the time to adapt varies non-linearly with the number of targets. Our analysis shows that these interferences are weaker if the reward varies smoothly with the subject''s performance instead of being binary. We demonstrate how shaping the reward or shaping the task can accelerate the adaptation dramatically by reducing the destructive interferences. We argue that experimentally investigating the dynamics of reward-driven sensorimotor adaptation for more than one sensory stimulus can shed light on the underlying learning rules.     

Sensorimotor integration: locating locomotion in neural circuits

Neural components of the circuits that transform sensory cues into changes in motor activities are largely unknown. Several recent studies have now functionally mapped the sensorimotor circuits responsible for locomotion behaviors under defined environmental conditions in the nematode Caenorhabditis elegans.     

Lateralizing Sensorimotor Deficits in a Case of Pseudopheochromocytoma

Pseudopheochromocytoma is a poorly understood, rare cause of severe paroxysmal hypertension that mimics the symptomatology of pheochromocytoma in the absence of biochemical evidence of this tumor. Symptoms such as headache, nausea, sweating, and palpitations during hypertensive episodes have been described. In this paper, we describe previously unreported findings of lateralizing sensorimotor deficits in a patient with pseudopheochromocytoma. These changes presented during a hypertensive episode and were concerning for stroke but were not accompanied by acute radiologic abnormalities. The deficits improved over 1.5 weeks as blood pressure stabilized with beta-blockade. We also review relevant literature on the clinical features, pathophysiology, and management of pseudopheochromocytoma.     

Sensorimotor Reactivity of Children Living in a Radionuclide-Contaminated Zone

Schoolchildren aged 8 to 13 years were examined in Gomel. The children's sensorimotor reaction to light and acoustic stimuli is characterized with regard for their age and sex on the basis of the latency of sensorimotor reactions (LSMR), which shortened significantly with age in children of either sex. This developed unevenly in the children examined, as may be seen from the quite broad ranges of the LSMR fluctuation in each age group. The boys had a stronger sensorimotor reaction to both light and acoustic stimuli than the girls. At the same time, both the boys and the girls reacted to the acoustic stimulus more actively than to the light stimulus.     

Sensorimotor control of navigation in arthropod and artificial systems

Arthropods exhibit highly efficient solutions to sensorimotor navigation problems. They thus provide a source of inspiration and ideas to robotics researchers. At the same time, attempting to re-engineer these mechanisms in robot hardware and software provides useful insights into how the natural systems might work. This paper reviews three examples of arthropod sensorimotor control systems that have been implemented and tested on robots. First we discuss visual control mechanisms of flies, such as the optomotor reflex and collision avoidance, that have been replicated in analog VLSI (very large scale integration) hardware and used to produce corrective behavior in robot vehicles. Then, we present a robot model of auditory localization in the cricket; and discuss integration of this behavior with the optomotor behavior previously described. Finally we present a model of olfactory search in the moth, which makes use of several sensory cues, and has also been tested using robot hardware. We discuss some of the similarities and differences of the solutions obtained.     

Sensorimotor learning configures the human mirror system

Cells in the "mirror system" fire not only when an individual performs an action but also when one observes the same action performed by another agent [1-4]. The mirror system, found in premotor and parietal cortices of human and monkey brains, is thought to provide the foundation for social understanding and to enable the development of theory of mind and language [5-9]. However, it is unclear how mirror neurons acquire their mirror properties -- how they derive the information necessary to match observed with executed actions [10]. We address this by showing that it is possible to manipulate the selectivity of the human mirror system, and thereby make it operate as a countermirror system, by giving participants training to perform one action while observing another. Before this training, participants showed event-related muscle-specific responses to transcranial magnetic stimulation over motor cortex during observation of little- and index-finger movements [11-13]. After training, this normal mirror effect was reversed. These results indicate that the mirror properties of the mirror system are neither wholly innate [14] nor fixed once acquired; instead they develop through sensorimotor learning [15, 16]. Our findings indicate that the human mirror system is, to some extent, both a product and a process of social interaction.