Prospective strategies underlie the control of interceptive actions

The purpose of this study was to test whether a constant bearing angle strategy could account for the displacement regulations produced by a moving observer when attempting to intercept a ball following a curvilinear path. The participants were asked to walk through a virtual environment and to change, if (deemed) necessary, their walking speed so as to intercept a moving ball that followed either a rectilinear or a curvilinear path. The results showed that ball path curvature did indeed influence the participants' displacement kinematics in a way that was predicted by adherence to a constant bearing angle strategy mode of control. Velocity modifications were found to be proportional to the magnitude of target curvature with opposing curvatures giving rise to mirror displacement velocity changes. The role of prospective strategies in the control of interceptive action is discussed.     

A specific role for efferent information in self-recognition

We investigated the specific contribution of efferent information in a self-recognition task. Subjects experienced a passive extension of the right index finger, either as an effect of moving their left hand via a lever ('self-generated action'), or imposed externally by the experimenter ('externally-generated action'). The visual feedback was manipulated so that subjects saw either their own right hand ('view own hand' condition) or someone else's right hand ('view other's hand' condition) during the passive extension of the index finger. Both hands were covered with identical gloves, so that discrimination on the basis of morphological differences was not possible. Participants judged whether the right hand they saw was theirs or not. Self-recognition was significantly more accurate when subjects were themselves the authors of the action, even though visual and proprioceptive information always specified the same posture, and despite the fact that subjects judged the effect and not the action per se. When the passive displacement of the participants right index finger was externally generated, and only afferent information was available, self-recognition performance dropped to near-chance levels. Differences in performance across conditions reflect the distinctive contribution of efferent information to self-recognition, and argue against a dominant role of proprioception in self-recognition.     

Perceptual distortion of intrapersonal and near-personal space sensed by proprioception

It is known that the illusory displacement of a vibrated limb can be transferred to a nonvibrated contacted limb. The purpose of this study was to quantify and compare the transferred illusory displacements occurring in the intrapersonal and near-personal space. In two tasks, 8 male and 8 female blindfolded subjects estimated (1) the height of the left elbow and (2) the height of an external object located at the same height as the left elbow, by the proprioception of the right arm which was Subject to illusory displacement. If the internal representation of the left elbow in one's body schema could provide precise information of its static position independently of the proprioception of the right arm, the perceived displacement of the right arm might be smaller when influenced by proprioceptive information from the static left arm, than when in contrast instead with an object which is not a body part. There was no difference in the estimation of illusory displacement between male and female subjects and between right and left arms. No significant difference was observed between transferred displacements of the left elbow and the object. This means that the perception of limb position sensed by the proprioception of another limb can be distorted as easily as the perception of location of an external object. This suggests that the internal representation of static limb position is not enough to provide the correct information of current limb position in the absence of vision.     

Limitations of distal effect anticipation when using tools

Modern technologies progressively create workplaces in which the execution of movements and the observation of their consequences are spatially separated. Challenging workplaces in which users act via technical equipment in a distant space include aviation, applied medical engineering and virtual reality. When using a tool, proprioceptive/tactile feedback from the moving hand (proximal action effect) and visual feedback from the moving effect point of the tool, such as the moving cursor on a display (the distal action effect) often do not correspond or are even in conflict. If proximal and distal feedback were equally important for controlling actions with tools, this discrepancy would be a constant source of interference. The human information processing system solves this problem by favoring the intended distal action effects while attenuating or ignoring proximal action effects. The study presents an overview of experiments aiming at the underlying motor and cognitive processes and the limitations of visual predominance in tool actions. The main findings are, that when transformations are in effect the awareness of one's own actions is quite low. This seems to be advantageous when using tools, as it allows for wide range of flexible sensorimotor adaptations and – may be more important – it evokes the feeling of being in control. Thus, the attenuation of perceiving one's own proximal action effects is an important precondition for using tools successfully. However, the ability to integrate discordant perception-action feedback has limits, especially, but not only, with complex transformations. When feature overlap between vision and proprioception is low, and when the existence of a transformation is obvious proximal action effects come to the fore and dominate action control in tool actions. In conclusion action–effect control plays an important role in understanding the constraints of the acquisition and application of tool transformations.     

A robust solution for dealing with environmental changes in intercepting moving balls

The authors tested whether a simple model based on the cancellation of the rate of change in bearing angle could account for the behavioral adaptations produced when individuals intercept moving balls while walking. In Experiment 1, the place of arrival of the ball and the angle of approach were varied. In accord with the model, velocity regulations were earlier and more pronounced the larger the angle of approach. In Experiment 2, ball speed unexpectedly changed during a trial, once again highlighting participants' functional velocity adaptations. A direct test of the model on the basis of each individual trial (N = 256) revealed that, on average, 70% of the total variance could be explained. Together, those results confirm the usefulness of such a robust strategy in the control of interceptive tasks.     

Spatial localization under conflict conditions: is there a single explanation?

Visual--auditory (VA) and visual--proprioceptive (VP) localization conflict paradigms were varied to explore the comparability of the conflict situations. In experiment 1 various attempts were made to decrease the dominance of visual information over proprioceptive and auditory target information. Pairing auditory with proprioceptive information against conflicting visual information did not lessen the visual dominance, nor did dimming the visual field. A 'cognitive' manipulation, in which the subject was led to doubt the reliability of the visual information, reduced visual dominance over audition but not visual dominance over proprioception. This difference between the two conflict situations was further explored and corroborated in experiment 2. In experiment 3 no attempt was made to lead the subject to believe that paired discrepant targets were related, and the visual dominance of audition was strong while the visual dominance of proprioception did not occur. The apparent differences between the VA and VP conflict situations are discussed with regard to the feability of generating a unitary explanation of localization conflict results. Several further factors are discussed that must be explored before undertaking such a unitary formulation.     

Repetitive pointing to remembered proprioceptive targets improves 3D hand positioning accuracy

Repetitive pointing movements to remembered proprioceptive targets were investigated to determine whether dynamic proprioception could be used to modify the initial sensorimotor conditions associated with an active definition of the target position. Twelve blindfolded subjects used proprioception to reproduce a self-selected target position as accurately as possible. Ten repetitions for each limb were completed using overhead and scapular plane pointing tasks. A 3D optical tracking system determined hand trajectory start and endpoint positions for each repetition. These positions quantified three-dimensional pointing errors relative to the target position and the initial and preceding movement repetitions, as well as changes in movement direction and extent. Target position and cumulative start position errors were significantly greater than the corresponding preceding movement (inter-repetition) errors, and increased as the trial progressed. In contrast, hand trajectory start and endpoint inter-repetition errors decreased significantly with repeated task performance, as did movement extent, although it was consistently underestimated for each repetition. Pointing direction remained constant, except for the angle of elevation for scapular plane pointing, which consistently decreased throughout the trial. The results suggest that the initial conditions prescribed by actively defining a proprioceptive target were subsequently modified by dynamic proprioception, such that movement reproduction capability improved with repeated task performance.     

The role of proprioception in the perception and control of human movement: Toward a theoretical reassessment

The theoretical role of proprioception in the perception and control of human movement is elusive because of the obvious inability to manipulate experimentally the various receptive systems. Individuals who have had the metacarpophalangeal joint and joint capsule removed and replaced with silastic inserts afford a unique opportunity to evaluate a principal source of proprioception, namely, slowly adapting joint afferents. In a set of experiments, we show that such individuals show no deficits in finger localization following joint replacement. We take this and other complementary findings as a preliminary basis for proposing a dynamic rather than kinematic account of movement production. In addition, we provide a reconceptualization of the function of proprioceptive information in the CNS. Our arguments focus on proprioceptive inputs as tuning or modulating interneuronal pools rather than providing dimension-pecific information to the brain, as is commonly assumed.     

Visuokinesthetic realignment in a video-controlled reaching task

The authors investigated the accuracy of horizontal pointing movements toward a visual target viewed on a vertical video monitor; the view included a directional distortion between perceptual and action spaces. Although accurate coding of the movement vector in a relative (visual) system of coordinates has been found to occur when there is a prismatic perturbation, provided that the hand and the target are continuously visible, such accurate performance has never been reported for video-controlled situations with larger deviations. To evaluate whether visual relative coding is task specific or depends on the magnitude of the induced misalignment, the authors manipulated the intensity of directional perturbation (10 degrees or 40 degrees) in a video-controlled task. Whatever the directional bias, participants (N = 40) were initially inaccurate but adapted quickly within a few trial rehearsals, with a concomitant recalibration of segmental proprioception. In contrast with prism studies, relative coding of the hand-to-target vector seemed not to be operative in video-controlled situations, suggesting that target location is specified in an egocentric system of reference that includes hand-related proprioceptive signals, despite the presence of a (consciously) detected misalignment between visual and kinesthetic systems.     

Inertial constraints on limb proprioception are independent of visual calibration

When the coincidence of a limb's spatial axes and inertial eigenvectors is broken, haptic proprioception of the limb's position conforms to the eigenvectors. Additionally, when prisms break the coincidence between an arm's visual and actual positions, haptic proprioception is shifted toward the visual-spatial direction. In 3 experiments, variation of the arm's mass distribution was combined with prism adaptation to investigate the hypothesis that the proprioceptive effects of inertial and visual manipulations are additive. This hypothesis was supported across manipulations of plane of motion, body posture, proprioceptive target, and proprioceptive experience during prism adaptation. Haptic proprioception seems to depend on local, physical reference frames that are relative to the physical reference frames for the body's environmental position and orientation.     

The case for proprioception

In formulating a theory of perception that does justice to the embodied and enactive nature of perceptual experience, proprioception can play a valuable role. Since proprioception is necessarily embodied, and since proprioceptive experience is particularly integrated with one’s bodily actions, it seems clear that proprioception, in addition to, e.g., vision or audition, can provide us with valuable insights into the role of an agent’s corporal skills and capacities in constituting or structuring perceptual experience. However, if we are going to have the opportunity to argue from analogy with proprioception to vision, audition, touch, taste, or smell, then it is necessary to eschew any doubts about the legitimacy of proprioception’s inclusion into the category of perceptual modalities. To this end, in this article, I (1) respond to two arguments that Shaun Gallagher (2003) presents in “Bodily self-awareness and objectperception” against proprioception’s ability to meet the criteria of object perception, (2) present a diagnosis of Gallagher’s position by locating a misunderstanding in the distinction between proprioceptive information and proprioceptive awareness, and (3) show that treating proprioception as a perceptual modality allows us to account for the interaction of proprioception with the other sensory modalities, to apply the lessons we learn from proprioception to the other sensory modalities, and to account for proprioceptive learning. Finally, (4) I examine Sydney Shoemaker’s (1994) identification constraint and suggest that a full-fledged notion of object-hood is unnecessary to ground a theory of perception.     

Visuokinesthetic Realignment in a Video-Controlled Reaching Task

The authors investigated the accuracy of horizontal pointing movements toward a visual target viewed on a vertical video monitor; the view included a directional distortion between perceptual and action spaces. Although accurate coding of the movement vector in a relative (visual) system of coordinates has been found to occur when there is a prismatic perturbation, provided that the hand and the target are continuously visible, such accurate performance has never been reported for video-controlled situations with larger deviations. To evaluate whether visual relative coding is task specific or depends on the magnitude of the induced misalignment, the authors manipulated the intensity of directional perturbation (10° or 40°) in a video-controlled task. Whatever the directional bias, participants (N = 40) were initially inaccurate but adapted quickly within a few trial rehearsals, with a concomitant recalibration of segmental proprioception. In contrast with prism studies, relative coding of the hand-to-target vector seemed not to be operative in video-controlled situations, suggesting that target location is specified in an egocentric system of reference that includes hand-related proprioceptive signals, despite the presence of a (consciously) detected misalignment between visual and kinesthetic systems.     

The use of proprioception and tactile information in haptic search

To investigate how tactile and proprioceptive information are used in haptic object discrimination we conducted a haptic search task in which participants had to search for either a cylinder, a bar or a rotated cube within a grid of aligned cubes. Tactile information from one finger is enough to detect a cylinder amongst the cubes. For detecting a bar or a rotated cube amongst cubes touch alone is not enough. For the rotated cube this is evident because its shape is identical to that of the non-targets, so proprioception must provide information about the orientation of the fingers and hand when touching it. For the bar one either needs proprioceptive information about the distance and direction of a single finger’s movements along the surfaces, or proprioceptive information from several fingers when they touch it simultaneously. When using only one finger, search times for the bar were much longer than those for the other two targets. When the whole hand or both hands were used the search times were similar for all shapes. Most errors were made when searching for the rotated cube, probably due to systematic posture-related biases in judging orientation on the basis of proprioception. The results suggest that tactile and proprioceptive information are readily combined for shape discrimination.     

Face proprioception does not modulate access to visual awareness of emotional faces in a continuous flash suppression paradigm

An important question in neuroscience is which multisensory information, presented outside of awareness, can influence the nature and speed of conscious access to our percepts. Recently, proprioceptive feedback of the hand was reported to lead to faster awareness of congruent hand images in a breaking continuous flash suppression (b-CFS) paradigm. Moreover, a vast literature suggests that spontaneous facial mimicry can improve emotion recognition, even without awareness of the stimulus face. However, integration of visual and proprioceptive information about the face to date has not been tested with CFS. The modulation of visual awareness of emotional faces by facial proprioception was investigated across three separate experiments. Face proprioception was induced with voluntary facial expressions or with spontaneous facial mimicry. Frequentist statistical analyses were complemented with Bayesian statistics. No evidence of multisensory integration was found, suggesting that proprioception does not modulate access to visual awareness of emotional faces in a CFS paradigm.     

Proprioception and Motor Control in Parkinson's Disease

ABSTRACT

Parkinson's disease (PD) is a neurodegenerative disorder that leads to a progressive decline in motor function. Growing evidence indicates that PD patients also experience an array of sensory problems that negatively impact motor function. This is especially true for proprioceptive deficits, which profoundly degrade motor performance. This review specifically address the relation between proprioception and motor impairments in PD. It is structured around 4 themes: (a) It examines whether the sensitivity of kinaesthetic perception, which is based on proprioceptive inputs, is actually altered in PD. (b) It discusses whether failed processes of proprioceptive-motor integration are central to the motor problems in PD. (c) It presents recent findings focusing on the link between the proprioception and the balance problems in PD. And (d) it discusses the current state of knowledge of how levodopa medication and deep brain stimulation affect proprioceptive and motor function in PD. The authors conclude that a failure to evaluate and to map proprioceptive information onto voluntary and reflexive motor commands is an integral part of the observed motor symptoms in PD.     

Visuomotor Adaptation and Proprioceptive Recalibration

ABSTRACT

Motor learning, in particular motor adaptation, is driven by information from multiple senses. For example, when arm control is faulty, vision, touch, and proprioception can all report on the arm's movements and help guide the adjustments necessary for correcting motor error. In recent years we have learned a lot about how the brain integrates information from multiple senses for the purpose of perception. However, less is known about how multisensory data guide motor learning. Most models of, and studies on, motor learning focus almost exclusively on the ensuing changes in motor performance without exploring the implications on sensory plasticity. Nor do they consider how discrepancies in sensory information (e.g., vision and proprioception) related to hand position may affect motor learning. Here, we discuss research from our lab and others that shows how motor learning paradigms affect proprioceptive estimates of hand position, and how even the mere discrepancy between visual and proprioceptive feedback can affect learning and plasticity. Our results suggest that sensorimotor learning mechanisms do not exclusively rely on motor plasticity and motor memory, and that sensory plasticity, in particular proprioceptive recalibration, plays a unique and important role in motor learning.     

Allocation of attention and the locus of adaptation to displaced vision.

Experimental subjects were exposed to prism-induced visual displacement of a target whose location was correctly given by proprioceptive-kinesthetic information. Control subjects were exposed alternately to visual displacement or proprioceptive-kinesthetic location information. During the adaptation period, experimental subjects in the visual attention condition performed a localization task that directed them to attend selectively to the visual modality; experimental subjects in the proprioceptive attention condition attended selectively to the proprioceptive modaltiy; control subjects performed the task on the basis of the available modality. Measures of adaptation and aftereffect were secured separately in each of the two modalities. These confirmed the predictions that the shifts in the experimental conditions would be confirmed to localization tests dependent on the unattended modality and that control subjects would not exhibit adaptation. We proposed that allocation of attention determines situational dominance and that dominance determines the locus of adaptation. The findings were compared to those reported by Canon (1970) and were applied to a reassessment of the "visual capture" phenomenon.     

Sensory conflict in judgments of spatial direction

Artificial discrepancy was created between information about azimuth coming from different sense modalities. The resolution of this discrepancy was examined for the cases of vision and proprioception, proprioception and audition, and vision and audition. Vision biases proprioceptive and auditory judgments. Proprioception biases auditory judgments and has a small effect on visual judgments. The results suggest that the combinations of sense modalities do not behave as an integrated system and the data are interpreted as indicating that different processes are involved in the resolution of discrepant directional information from different pairs of modalities.     

Control strategies when intercepting slowly moving targets

In 3 experiments, the authors investigated and described how individuals control manual interceptive movements to slowly moving targets. Participants (N = 8 in each experiment) used a computer mouse and a graphics tablet assembly to manually intercept targets moving across a computer screen toward a marked target zone. They moved the cursor so that it would arrive in the target zone simultaneously with the target. In Experiment 1, there was a range of target velocities, including some very slow targets. In Experiment 2, there were 2 movement distance conditions. Participants moved the cursor either the same distance as the target or twice as far. For both experiments, hand speed was found to be related to target speed, even for the very slowly moving targets and when the target-to-cursor distance ratios were altered, suggesting that participants may have used a strategy similar to tracking. To test that notion, in Experiment 3, the authors added a tracking task in which the participants tracked the target cursor into the target zone. Longer time was spent planning the interception movements; however, there was a longer time in deceleration for the tracking movements, suggesting that more visually guided trajectory updates were made in that condition. Thus, although participants scaled their interception movements to the cursor speed, they were using a different strategy than they used in tracking. It is proposed that during target interception, anticipatory mechanisms are used rather than the visual feedback mechanism used when tracking and when pointing to stationary targets.     

Intermodality relations in localization in blind and sighted people

Developmental data were gathered on the relative importance of vision, audition, and proprioception in determining spatial direction in a conflict situation. Age trends did not support the hypothesis that information from different modalities becomes better differentiated with age. In a follow-up study, blind children of different ages were tested under auditory-proprioceptive conflict conditions. No age changes were found. The possibility of a visual involvement in auditory and proprioceptive localization is discussed.