To localize one's hand, i.e., to find out its position with respect the body, humans may use proprioceptive information or visual both. It is still not known how CNS combines simultaneous and information. In this study, we investigate in what a horizontal plane hand localized on basis of compare positions which it proprioception only vision only. Seated at table, subjects matched target table top their unseen left under table. The experiment consisted three series. each these series, were...

The origin of variability in goal-directed movements is not well understood. Variability can originate from several neural processes such as target localization, movement planning, and execution. Here we examine resulting noise In experiments, subjects moved their unseen hand to visual targets, under conditions which were designed minimize the expected localization planning processes. We tested short 32 directions a center-out reaching task. endpoints initial direction varied systematically...

One generally has the impression that one feels one's hand at same location as sees it. However, because our brain deals with possibly conflicting visual and proprioceptive information about position by combining it into an optimal estimate of hand's location, mutual calibration is not necessary to achieve such a coherent percept. Does sensory integration nevertheless entail calibration? We asked subjects move their between targets. Blocks trials without any feedback were alternated blocks...

Our movements are variable, but the origin of this variability is poorly understood. We examined sources in human saccadic eye movements. In two experiments, we measured spatiotemporal saccade trajectories as a function movement direction and amplitude. One our new observations that smaller for purely horizontal vertical saccades than oblique directions. also found amplitude, duration, peak velocity all correlated with one another. To determine observed variability, estimated noise motor...

We often encounter pairs of variables in the world whose mutual relationship can be described by a function. After training, human responses closely correspond to these functional relationships. Here we study how humans predict unobserved segments function that they have been trained on and compare predictions differ those made various function-learning models literature. Participants' performance was best predicted polynomial functions generated observations. Further, participants were able...

The movements that we make are variable. It is well established at least a part of this variability caused by noise in central motor planning. Here, studied how the random effects planning translate into changes Are independently added to constant mean end point, or do they accumulate over movements? To distinguish between these possibilities, examined repeated, discrete various tasks which output could be decomposed task-relevant and task-irrelevant component. We found all component had...

The durations and trajectories of our saccadic eye movements are remarkably stereotyped. We have no voluntary control over these properties but they determined by the movement amplitude and, to a smaller extent, also direction initial orientation. Here we show that stereotyped optimal for minimizing variability in saccade endpoints is caused motor noise. duration can be understood from nature noise, which combination signal-dependent noise favoring long durations, constant prefers short...

Motor learning is driven by movement errors. The speed of can be quantified the rate, which proportion an error that corrected for in planning next movement. Previous studies have shown rate depends on reliability signal and uncertainty motor system’s own state. These dependences are agreement with predictions Kalman filter, a state estimator used to determine optimal each such expected minimized. Here we test whether not only average behaviour optimal, as previous showed, but if chosen...

In sports such as golf and darts it is important that one can produce ballistic movements of an object towards a goal location with little variability possible. A factor influences this the extent to which motor planning updated from movement based on observed errors. Previous work has shown for reaching movements, our system uses learning rate (the proportion error corrected in next movement) optimal minimizing endpoint variability. Here we examined whether hard-wired therefore...

Even when provided with feedback after every movement, adaptation levels off before biases are completely removed. Incomplete has recently been attributed to forgetting: the is already partially forgotten by time next movement made. Here we test whether this idea correct. If so, final level of determined a balance between learning and forgetting. Because learn from perceived errors, scaling these errors magnification factor same effect as subjects increasing amount which they each error. In...

To localize a seen object, the CNS has to integrate object's retinal location with direction of gaze. Here we investigate this process by examining localization static objects during smooth pursuit eye movements. The normally experienced stability visual world suggests that essentially compensates for movement when judging target locations. However, certain systematic errors are made, and use these study sensorimotor integration. During an movement, image moves across retina. Objects produce...

Does the nervous system continuously realign senses so that objects are seen and felt in same place? Conflicting answers to this question have been given. Research imposing a sensory mismatch has provided evidence realigns reduce mismatch. Other studies shown when subjects point with unseen hand visual targets, their end points show visual-proprioceptive biases do not disappear after episodes of feedback. These indicative intersensory mismatches does align for. Here, we directly compare how...

It is well established that if multiple cues provide information about the same quantity, from these combined by weighting each cue inverse of its variance. This implies weights are determined variances only. However, this view challenged studies showed feedback actual value can induce changes in when consistent with one but not other. We developed a paradigm allowed us to measure time course reweighting. Subjects placed an object flush onto slanted surface. Monocular and binocular provided...

Faster movements are typically more variable-a speed-accuracy trade-off known as Fitts' law. Are that initiated faster also variable? Neurophysiological work has associated larger neural variability during motor preparation with longer reaction time (RT) and movement variability, implying decreases increasing RT. Here, we recorded over 30,000 reaching in 11 human participants who moved to visually cued targets. Half of the visual cues were accompanied by a beep evoke wide RT range each...

It only makes sense to talk about the position of a moving object if one specifies time at which its is interest. The authors here show that when flash or tone moment interest, subjects estimate be closer where it passes fixation point and further in direction motion than really is. propose these biases arise from combination large temporal uncertainty, asymmetry related sampling object's position, bias toward believing looking what sees.

In everyday life, we frequently have to decide which hand use for a certain action. It has been suggested that this decision the brain calculates expected costs based on action values, such as biomechanical costs, success rate, handedness, and skillfulness. Although these conclusions were experiments in stationary subjects, often act while body is motion. We investigated how choice affected by passive motion, directly affects of arm movement due its inertia. With linear motion platform, 12...

It has been suggested that sensorimotor adaptation involves at least two processes (i.e., fast and slow) differ in retention error sensitivity. Previous work shown repeated exposure to an abrupt force field perturbation results greater sensitivity for both the slow processes. Although this implies faster relearning is associated with increased sensitivity, it remains unclear what aspects of prior experience modulate In present study, we manipulated initial training using different schedules,...

In the course of its interaction with world, human nervous system must constantly estimate various variables in surrounding environment. Past research indicates that environmental may be represented as probabilistic distributions a priori information (priors). Priors for do not change much over time have been widely studied. Little is known, however, about how priors develop environments nonstationary statistics. We examine whether humans their reliance on prior based recent changes...