The body-ownership is unconsciously distorted in the brain: An event-related potential study of rubber hand illusion

Many studies have reported that bottom-up multisensory integration of visual, tactile, and proprioceptive information can distort our sense of body-ownership, producing rubber hand illusion (RHI). There is less evidence about when and how the body-ownership is distorted in the brain during RHI. To examine whether this illusion effect occurs preattentively at an early stage of processing, we monitored the visual mismatch negativity (vMMN) component (the index of automatic deviant detection) and N2 (the index for conflict monitoring). Participants first performed an RHI elicitation task in a synchronous or asynchronous setting and then finished a passive visual oddball task in which the deviant stimuli were unrelated to the explicit task. A significant interaction between Deviancy (deviant hand vs. standard hand) and Group (synchronous vs. asynchronous) was found. The asynchronous group showed clear mismatch effects in both vMMN and N2, while the synchronous group had such effect only in N2. The results indicate that after the elicitation of RHI bottom-up integration could be retrieved at the early stage of sensory processing before top-down processing, providing evidence for the priority of the bottom-up processes after the generation of RHI and revealing the mechanism of how the body-ownership is unconsciously distorted in the brain.

Disruption of Proprioceptive Information During Electrical Stimulation of the Cutaneous Afferents

Restoration of proprioception with neurotechnology is critical to improve effectiveness of robotic neuro-prostheses. Unfortunately, after initial enthusiasm clinical results showed that unlike touch, proprioception could not be reliably induced. Here we show that concurrent activation of multiple sensory modalities may trigger unwanted sensory regulation mechanisms that disrupt proprioception. We recorded intra-spinal neural activity induced by stimulation of proprioceptive afferents from the radial nerve in three monkeys. Then, we superimposed stimulation of the radial nerve cutaneous branch and quantified its impact on spinal neural activity via population analysis. Proprioceptive pulses produced robust neural trajectories in the neural manifold that were disrupted by concurrent stimulation of cutaneous afferents. This disruption correlated with a reduction of afferent volleys and multi-unit activity both in the spinal cord and somatosensory cortex. Our results suggest that limited specificity not only impacts localization of artificial percepts, but also their nature to an extent that was never considered.

The effects of uncertain context inference on motor adaptation

Humans have been shown to adapt their movements when a sudden change to the dynamics of the environment is introduced, a phenomenon called motor adaptation. If the change is reverted, the adaptation is also quickly reverted. Human are also able to adapt to multiple changes in dynamics presented separately, and to be able to switch between adapted movements on the fly. Such switching relies on contextual information which is often noisy or misleading, which affects the switch between adaptations. In this work, we introduce a computational model to explain the behavioral phenomena effected by uncertain contextual information. Specifically, we present a hierarchical model for motor adaptation based on exact Bayesian inference. This model explicitly takes into account contextual information and how the dynamics of context inference affect adaptation and action selection. We show how the proposed model provides a unifying explanation for four different experimentally-established phenomena: (i) effects of sensory cues and proprioceptive information on switching between tasks, (ii) the effects of previously-learned adaptations on switching between tasks, (iii) the effects of training history on behavior in new contexts, in addition to (iv) the well-studied savings, de-adaptation and spontaneous recovery.

Closed-loop control of a prosthetic finger via evoked proprioceptive information

Objective. Proprioceptive information plays an important role for recognizing and coordinating our limb’s static and dynamic states relative to our body or the environment. In this study, we determined how artificially evoked proprioceptive feedback affected the continuous control of a prosthetic finger. Approach. We elicited proprioceptive information regarding the joint static position and dynamic movement of a prosthetic finger via a vibrotactor array placed around the subject’s upper arm. Myoelectric signals of the finger flexor and extensor muscles were used to control the prosthesis, with or without the evoked proprioceptive feedback. Two control modes were evaluated: the myoelectric signal amplitudes were continuously mapped to either the position or the velocity of the prosthetic joint. Main Results. Our results showed that the evoked proprioceptive information improved the control accuracy of the joint angle, with comparable performance in the position- and velocity-control conditions. However, greater angle variability was prominent during position-control than velocity-control. Without the proprioceptive feedback, the position-control tended to show a smaller angle error than the velocity-control condition. Significance. Our findings suggest that closed-loop control of a prosthetic device can potentially be achieved using non-invasive evoked proprioceptive feedback delivered to intact participants. Moreover, the evoked sensory information was integrated during myoelectric control effectively for both control strategies. The outcomes can facilitate our understanding of the sensorimotor integration process during human-machine interactions, which can potentially promote fine control of prosthetic hands.

Disruption Of Proprioceptive Information During Electrical Stimulation Of The Cutaneous Afferents

Restoration of proprioception with neurotechnology is critical to improve effectiveness of robotic neuro-prostheses. Unfortunately, after initial enthusiasm clinical results showed that unlike touch, proprioception could not be reliably induced. Here we show that concurrent activation of multiple sensory modalities may trigger unwanted sensory regulation mechanisms that disrupt proprioception. We recorded intra-spinal neural activity induced by stimulation of proprioceptive afferents from the radial nerve in three monkeys. Then, we superimposed stimulation of the radial nerve cutaneous branch and quantified its impact on spinal neural activity via population analysis. Proprioceptive pulses produced robust neural trajectories in the neural manifold that were disrupted by concurrent stimulation of cutaneous afferents. This disruption correlated with a reduction of afferent volleys and multi-unit activity both in the spinal cord and somatosensory cortex. Our results suggest that limited specificity not only impacts localization of artificial percepts, but also their nature to an extent that was never considered.

Visuo-proprioceptive integration and recalibration with multiple visual stimuli

To organize the plethora of sensory signals from our environment into a coherent percept, our brain relies on the processes of multisensory integration and sensory recalibration. We here asked how visuo-proprioceptive integration and recalibration are shaped by the presence of more than one visual stimulus, hence paving the way to study multisensory perception under more naturalistic settings with multiple signals per sensory modality. We used a cursor-control task in which proprioceptive information on the endpoint of a reaching movement was complemented by two visual stimuli providing additional information on the movement endpoint. The visual stimuli were briefly shown, one synchronously with the hand reaching the movement endpoint, the other delayed. In Experiment 1, the judgments of hand movement endpoint revealed integration and recalibration biases oriented towards the position of the synchronous stimulus and away from the delayed one. In Experiment 2 we contrasted two alternative accounts: that only the temporally more proximal visual stimulus enters integration similar to a winner-takes-all process, or that the influences of both stimuli superpose. The proprioceptive biases revealed that integration—and likely also recalibration—are shaped by the superposed contributions of multiple stimuli rather than by only the most powerful individual one.

Corollary discharge enables proprioception from lateral line sensory feedback

Animals modulate sensory processing in concert with motor actions. Parallel copies of motor signals, called corollary discharge (CD), prepare the nervous system to process the mixture of externally and self-generated (reafferent) feedback that arises during locomotion. Commonly, CD in the peripheral nervous system cancels reafference to protect sensors and the central nervous system from being fatigued and overwhelmed by self-generated feedback. However, cancellation also limits the feedback that contributes to an animal’s awareness of its body position and motion within the environment, the sense of proprioception. We propose that, rather than cancellation, CD to the fish lateral line organ restructures reafference to maximize proprioceptive information content. Fishes’ undulatory body motions induce reafferent feedback that can encode the body’s instantaneous configuration with respect to fluid flows. We combined experimental and computational analyses of swimming biomechanics and hair cell physiology to develop a neuromechanical model of how fish can track peak body curvature, a key signature of axial undulatory locomotion. Without CD, this computation would be challenged by sensory adaptation, typified by decaying sensitivity and phase distortions with respect to an input stimulus. We find that CD interacts synergistically with sensor polarization to sharpen sensitivity along sensors’ preferred axes. The sharpening of sensitivity regulates spiking to a narrow interval coinciding with peak reafferent stimulation, which prevents adaptation and homogenizes the otherwise variable sensor output. Our integrative model reveals a vital role of CD for ensuring precise proprioceptive feedback during undulatory locomotion, which we term external proprioception.

Assessment of Ankle Joint Proprioception in Cricket Players

Background and Aims: Superior balance ability is necessary to achieve the highest competitive level and avoid lower limb injuries. Balance control improvement is one of the most important goals in sports and exercise. Better the balance, better is the performance. Proprioception plays an important role in balance control and ankle proprioception is arguably the most important. Cricket is an evolving sport and it the ankle-foot complex in the only part that comes in contact with the ground which further leads to ankle injuries. Ankle proprioception is altered by sport related injuries or fatigue all of which subsequently leads to altered balance mobility. Ankle injuries often leads to disruption of muscles and tendons with associated damage to inherent mechanoreceptors which detrimentally alters the quality of proprioceptive information required for balance control. This study consists of an assessment of ankle joint proprioception in cricket players using an active to active reproduction test. Methodology: An observational study was conducted among 40 cricket players. Ankle proprioception was assessed using an active to active reproduction test. The mean difference between both the positions were then calculated. Results: The result of this study showed a clinically significant difference in both ankle plantarflexion and ankle dorsiflexion. The results also showed that right sided movements were affected in subjects who are right sided dominant and the same was there for left sided dominant subjects. The mean errors in Right PF and Left PF was 4.15º and 1.75º respectively which signifies that Right PF is affected in cricket players. The mean errors in Right DF and Left DF was 2.825º and 2.025º respectively which signifies that Right DF is more affected than that of Left DF. Conclusion: The ankle proprioception was affected in majority of the individuals. A clinically significant increase is noted in Right PF, Right DF and Left DF. Right plantarflexion was affected more than that of left plantarflexion and right dorsiflexion was affected more than that of left dorsiflexion. Hence, right sided dominant people showed affection in right sided movements and those who were left sided dominant showed affection in left sided movements. These results thus signify that the players are at mild risk of having ankle injuries because ankle proprioception is associated with ankle injuries which then indirectly affects the performance of the player. Key words: Ankle proprioception, Cricket Players, Balance, Active to Active reproduction test.

The Relative Contributions of Visual and Proprioceptive Inputs on Hand Localization in Early Childhood

Forming an accurate representation of the body relies on the integration of information from multiple sensory inputs. Both vision and proprioception are important for body localization. Whilst adults have been shown to integrate these sources in an optimal fashion, few studies have investigated how children integrate visual and proprioceptive information when localizing the body. The current study used a mediated reality device called MIRAGE to explore how the brain weighs visual and proprioceptive information in a hand localization task across early childhood. Sixty-four children aged 4–11 years estimated the position of their index finger after viewing congruent or incongruent visuo-proprioceptive information regarding hand position. A developmental trajectory analysis was carried out to explore the effect of age on condition. An age effect was only found in the incongruent condition which resulted in greater mislocalization of the hand toward the visual representation as age increased. Estimates by younger children were closer to the true location of the hand compared to those by older children indicating less weighting of visual information. Regression analyses showed localizations errors in the incongruent seen condition could not be explained by proprioceptive accuracy or by general attention or social differences. This suggests that the way in which visual and proprioceptive information are integrated optimizes throughout development, with the bias toward visual information increasing with age.