Proprioceptive Cues Research Articles

Do near-field cues enhance the plausibility of non-individual binaural rendering in a dynamic multimodal virtual acoustic scene?

It is commonly believed that near-field head-related transfer functions (HRTFs) provide perceptual benefits over far-field HRTFs that enhance the plausibility of binaural rendering of nearby sound sources. However, to the best of our knowledge, no study has systematically investigated whether using near-field HRTFs actually provides a perceptually more plausible virtual acoustic environment. To assess this question, we conducted two experiments in a six-degrees-of-freedom multimodal augmented reality experience where participants had to compare non-individual anechoic binaural renderings based on either synthesized near-field HRTFs or intensity-scaled far-field HRTFs and judge which of the two rendering methods led to a more plausible representation. Participants controlled the virtual sound source position by moving a small handheld loudspeaker along a prescribed trajectory laterally and frontally near the head, which provided visual and proprioceptive cues in addition to the auditory cues. The results of both experiments show no evidence that near-field cues enhance the plausibility of non-individual binaural rendering of nearby anechoic sound sources in a dynamic multimodal virtual acoustic scene as examined in this study. These findings suggest that, at least in terms of plausibility, the additional effort of including near-field cues in binaural rendering may not always be worthwhile for virtual or augmented reality applications.

Qualitative and quantitative assessment of magnetic vestibular stimulation in humans

The sensation of phantom motion or exhibition of bodily sway is often reported in the proximity of an MR scanner. It is proposed that the magnetic field stimulates the vestibular system. There are a number of possible mechanisms responsible, and the relative contributions of susceptibility on the otolithic receptors and the Lorentz force on the cupulae have not yet been explored. This exploratory study aims to investigate the impact of being in the proximity of a 7.0 T MR scanner. The modified clinical test of sensory interaction on balance (mCTSIB) was used to qualitatively ascertain whether or not healthy control subjects who passed the mCTSIB in normal conditions 1) experienced subjective sensations of dizziness, vertigo or of leaning or shifting in gravity when in the magnetic field and 2) exhibited visibly increased bodily sway whilst in the magnetic field compared to outside the magnetic field. Condition IV of the mCTSIB was video recorded outside and inside the magnetic field, providing a semi-quantitative measure of sway. For condition IV of the mCTSIB (visual and proprioceptive cues compromised), all seven locations/orientations around the scanner yielded significantly more sway than at baseline (p < 0.01 FDR). A Student’s t-test comparing the RMS velocity of a motion marker on the upper arm during mCTSIB condition IV showed a significant increase in the amount of motion exhibited in the field (T = 2.59; d.f. = 9; p = 0.029) compared to outside the field. This initial study using qualitative measures of sway demonstrates that there is evidence for MR-naïve individuals exhibiting greater sway while performing the mCTSIB in the magnetic field compared to outside the field. Directional polarity of sway was not significant. Future studies of vestibular stimulation by magnetic fields would benefit from the development of a sensitive, objective measure of balance function, which can be performed inside a magnetic field.

Caenorhabditis Elegans Learning and Decision-Making in a Structured Environment is a Multisensory Behavior

C. elegans' ability to exhibit associative, non-associative and imprinted memory in the context of chemical stimuli is well studied. Here, we show that C. elegans nematodes are capable of spatial associative learning, as they learn to associate food with a combination of proprioceptive cues, and information on the structure of their surroundings (maze), perceived through mechanosensation. By using the custom-made Worm-Maze platform, we demonstrate that C. elegans young adults can locate food in T-shaped mazes and, following that experience, learn to reach a specific maze arm. We show that C. elegans learning of space-related information is possible after a single training session, it resembles working memory, and it prevails over conflicting environmental cues. We provide evidence that C. elegans maze learning is a food-triggered multisensory behavior, which requires mechanosensory and proprioceptive input, and utilizes cues about the structural features of nematodes’ environment and their body actions. The CREB-like transcription factor, known for its role in learning, and dopamine signaling are also involved in maze performance. Interestingly, the observed aging-driven decline of C. elegans spatial learning ability can be reversed by starvation.

Subjective visual vertical and visual dependency in patients with multiple sclerosis

BackgroundSpatial orientation is an inherent ability governed by the complex integration of visual, vestibular and proprioceptive inputs. The degree to which an individual relies upon visual cues, as opposed to the vestibular or proprioceptive cues, is termed visual dependence. Although abnormal visual dependence has been documented in other neurological disorders, it is not known whether MS leads to visual dependence, and if so whether this is related to disease progression, clinical disability, or neuro-inflammatory burden in the central nervous system. ObjectiveTo evaluate SVV and visual dependence using a novel mobile virtual reality-based system for subjective visual vertical assessment (VIRVEST) and evaluate its relationship with the Expanded Disability Scale Score (EDSS), MS course and clinical findings. MethodsThe study included 59 patients with MS and 59 controls. Four tests were integrated in VIRVEST system and performed by each patient: a static SVV, dynamic SVV with clockwise and counter-clockwise background stimulus rotation, and SVV in a virtual reality background – a boat floating in the wavy water - to be adjusted vertically. Visual dependence was evaluated as a function of dynamic SVV. ResultsPatients with MS manifest larger biases in both static and dynamic SVV than healthy controls (p<0.001), in addition to higher visual dependence scores (p<0.05). MS patients with an EDSS score >4.5 had larger values of dynamic SVV and when compared to MS patients with lower EDSS scores (p<0.01), and visual dependence was related to disease severity. Patients with progressive MS disease course demonstrated statistically significantly larger dynamic SVV and visual dependence scores when compared to MS patients with relapsing-remitting disease (p<0.01). The mean System Usability Scores for the VIRVEST system corresponded to a patient perceived adjective rating of ``excellent''. ConclusionWe have evaluated the application of a novel virtual reality-based SVV test in patients with MS. We identified greater dynamic SVV errors suggestive of visual dependence in patients with MS versus controls and show that dynamic SVV abnormalities are related to disability measures. We suggest that this paradigm is effective at identifying visual dependence in neurological patients, and may have application in clinical settings, given high system usability scores.

Path integration in large-scale space and with novel geometries: Comparing vector addition and encoding-error models.

Path integration is thought to rely on vestibular and proprioceptive cues yet most studies in humans involve primarily visual input, providing limited insight into their respective contributions. We developed a paradigm involving walking in an omnidirectional treadmill in which participants were guided on two sides of a triangle and then found their back way to origin. In Experiment 1, we tested a range of different triangle types while keeping the distance of the unguided side constant to determine the influence of spatial geometry. Participants overshot the angle they needed to turn and undershot the distance they needed to walk, with no consistent effect of triangle type. In Experiment 2, we manipulated distance while keeping angle constant to determine how path integration operated over both shorter and longer distances. Participants underestimated the distance they needed to walk to the origin, with error increasing as a function of the walked distance. To attempt to account for our findings, we developed configural-based computational models involving vector addition, the second of which included terms for the influence of past trials on the current one. We compared against a previously developed configural model of human path integration, the Encoding-Error model. We found that the vector addition models captured the tendency of participants to under-encode guided sides of the triangles and an influence of past trials on current trials. Together, our findings expand our understanding of body-based contributions to human path integration, further suggesting the value of vector addition models in understanding these important components of human navigation.

Commutative Properties of Head Direction Cells during Locomotion in 3D: Are All Routes Equal?

Navigation often requires movement in three-dimensional (3D) space. Recent studies have postulated two different models for how head direction (HD) cells encode 3D space: the rotational plane hypothesis and the dual-axis model. To distinguish these models, we recorded HD cells in female rats while they traveled different routes along both horizontal and vertical surfaces from an elevated platform to the top of a cuboidal apparatus. We compared HD cell preferred firing directions (PFDs) in different planes and addressed the issue of whether HD cell firing is commutative-does the order of the animal's route affect the final outcome of the cell's PFD? Rats locomoted a direct or indirect route from the floor to the cube top via one, two, or three vertical walls. Whereas the rotational plane hypothesis accounted for PFD shifts when the animal traversed horizontal corners, the cell's PFD was better explained by the dual-axis model when the animal traversed vertical corners. Responses also followed the dual-axis model (1) under dark conditions, (2) for passive movement of the rat, (3) following apparatus rotation, (4) for movement around inside vertical corners, and (5) across a 45° outside vertical corner. The order in which the animal traversed the different planes did not affect the outcome of the cell's PFD, indicating that responses were commutative. HD cell peak firing rates were generally equivalent along each surface. These findings indicate that the animal's orientation with respect to gravity plays an important role in determining a cell's PFD, and that vestibular and proprioceptive cues drive these computations.SIGNIFICANCE STATEMENT Navigating in a three-dimensional (3D) world is a complex task that requires one to maintain a proper sense of orientation relative to both local and global cues. Rodent head direction (HD) cells have been suggested to subserve this sense of orientation, but most HD cell studies have focused on navigation in 2D environments. We investigated the responses of HD cells as rats moved between multiple vertically and horizontally oriented planar surfaces, demonstrating that HD cells align their directional representations to both local (current plane of locomotion) and global (gravity) cues across several experimental conditions, including darkness and passive movement. These findings offer critical insights into the processing of 3D space in the mammalian brain.

Pathophysiological dissociation of the interaction between time pressure and trait anxiety during spatial orientation judgments.

Spatial orientation is achieved by integrating visual, vestibular and proprioceptive cues. Individuals that rely strongly upon visual cues to facilitate spatial orientation are termed visually dependent. Heightened visual reliance commonly occurs in patients following vestibular dysfunction and can influence clinical outcome. Additionally, psychological factors, including anxiety, are associated with poorer clinical outcome following vestibular dysfunction. Given that visual dependency measures are affected by psychological and contextual influences, such as time pressure, we investigated the interaction between time pressure and anxiety upon visual dependency in healthy controls and vestibular migraine patients. Visual dependency was assessed using a "Rod and Disk" task at baseline and under time pressure (3s to complete the task). Non-situational (trait) and situational (state) anxiety levels were quantified using the Spielberg State-Trait Anxiety Inventory. We calculated the change in visual dependency (VD) [∆VD=VDtime pressure -VDbaseline ] and correlated it with participants' trait anxiety scores. We observed a significant negative correlation between trait anxiety and the change in VD (R2 =.393, p<.001) in healthy controls and a positive correlation in dizzy patients (R2 =.317, p<.001). That is, healthy individuals that were more anxious became less visually dependent under time pressure (i.e., more accurate), whereas less anxious individuals became more visually dependent. The reverse was observed in vestibular migraine patients. Our results illustrate that anxiety can differentially modulate task performance during spatial orientation judgements under time pressure in healthy individuals and dizzy patients. These findings have potential implications for individualised patient rehabilitation therapies.

On the Role of Lateral Force in Texture-Induced Motion Bias During Reaching Tasks.

In the previous work, we reported that tactile information (tactile slip) during finger sliding and reaching actions over a textured surface contributes to the control of the hand movement. More specifically, we observed a significant bias in the motion trajectories, which was explained by the tactile estimate accounted by the tactile flow model-i.e. a perceived motion direction always perpendicular to the ridge orientation, and its integration with the muscular-skeletal proprioceptive cues. However, to which extent this observed behavior also depends on the reaction force exerted by the surface ridges on the finger pad during the dynamic interaction still represents a largely unexplored research question. If not properly addressed, this point could rise the alternative explanation that the systematic bias is determined by the insufficient compensation of the reaction force by participants. In this article, we investigate the role of the lateral component of the reaction force on the surface plane (lateral force) in texture-related motion bias. We asked participants to slide their finger straight on a lubricated ridged plate towards a target goal displayed in a virtual reality environment. They exerted two different levels of normal force, which produced two different levels of lateral force during the finger interaction with the ridges. The effect of ridge orientation was found to be larger for the high compared to the low force level. However, also in the latter case, we still observed the same biased trajectories reported in our previous work, despite the negligible value of the lateral force. This supports our hypothesis that the motor bias arises from the integration of the tactile motion estimate, biased by the texture, and the other proprioceptive cues.

Attentional Modulation of Vision Versus Proprioception During Action.

To control our actions efficiently, our brain represents our body based on a combination of visual and proprioceptive cues, weighted according to how (un)reliable—how precise—each respective modality is in a given context. However, perceptual experiments in other modalities suggest that the weights assigned to sensory cues are also modulated “top-down” by attention. Here, we asked whether during action, attention can likewise modulate the weights (i.e., precision) assigned to visual versus proprioceptive information about body position. Participants controlled a virtual hand (VH) via a data glove, matching either the VH or their (unseen) real hand (RH) movements to a target, and thus adopting a ``visual'' or ``proprioceptive'' attentional set, under varying levels of visuo-proprioceptive congruence and visibility. Functional magnetic resonance imaging (fMRI) revealed increased activation of the multisensory superior parietal lobe (SPL) during the VH task and increased activation of the secondary somatosensory cortex (S2) during the RH task. Dynamic causal modeling (DCM) showed that these activity changes were the result of selective, diametrical gain modulations in the primary visual cortex (V1) and the S2. These results suggest that endogenous attention can balance the gain of visual versus proprioceptive brain areas, thus contextualizing their influence on multisensory areas representing the body for action.

Uncertainty in when a perturbation will arrive influences the preparation and release of triggered responses.

The timing and magnitude of muscle responses to perturbations are critical for acting in uncertain environments. A planned movement can strongly influence average muscle responses to perturbations, but certainty in when a perturbation will arrive changes this effect.The objective of this study was to investigate how uncertainty in perturbation timinginfluences the preparation and release of involuntary, perturbation-triggered responses.We hypothesized that uncertainty would influence the average magnitude of triggered responses and how they develop in time.We investigated three levels of uncertainty in when a proprioceptive cue to move would arrive by changing the duration and variability of the time between a preparation and movement cue. Participants performed ballistic elbow extension movements in response to the movement cue. Unexpected, large perturbations that flexed the elbow were delivered at various times between the preparation and movement cues to evaluate how cue uncertainty influenced the development of triggered responses.We found that this uncertainty strongly influences how a motor response is prepared, and the efficacy of triggering that response by a postural perturbation. When timing was certain, the motor plan was prepared within 150ms of the expected disturbance, and consistently released earlier by a perturbation than could be done voluntarily. Less predictable stimuli led to much earlier planning and a lower probability of releasing the plan early. These results clarify how uncertainty in when to move influences the planning and early release of perturbation-triggered responses, demonstrating an effect similar to previous reports on the planning of volitional movements.

How lovebirds maneuver through lateral gusts with minimal visual information

Flying birds maneuver effectively through lateral gusts, even when gust speeds are as high as flight speeds. What information birds use to sense gusts and how they compensate is largely unknown. We found that lovebirds can maneuver through 45° lateral gusts similarly well in forest-, lake-, and cave-like visual environments. Despite being diurnal and raised in captivity, the birds fly to their goal perch with only a dim point light source as a beacon, showing that they do not need optic flow or a visual horizon to maneuver. To accomplish this feat, lovebirds primarily yaw their bodies into the gust while fixating their head on the goal using neck angles of up to 30°. Our corroborated model for proportional yaw reorientation and speed control shows how lovebirds can compensate for lateral gusts informed by muscle proprioceptive cues from neck twist. The neck muscles not only stabilize the lovebirds' visual and inertial head orientations by compensating low-frequency body maneuvers, but also attenuate faster 3D wingbeat-induced perturbations. This head stabilization enables the vestibular system to sense the direction of gravity. Apparently, the visual horizon can be replaced by a gravitational horizon to inform the observed horizontal gust compensation maneuvers in the dark. Our scaling analysis shows how this minimal sensorimotor solution scales favorably for bigger birds, offering local wind angle feedback within a wingbeat. The way lovebirds glean wind orientation may thus inform minimal control algorithms that enable aerial robots to maneuver in similar windy and dark environments.

Touch as an auxiliary proprioceptive cue for movement control.

Recent studies extended the classical view that touch is mainly devoted to the perception of the external world. Perceptual tasks where the hand was stationary demonstrated that cutaneous stimuli from contact with objects provide the illusion of hand displacement. Here, we tested the hypothesis that touch provides auxiliary proprioceptive feedback for guiding actions. We used a well-established perceptual phenomenon to dissociate the estimates of reaching direction from touch and musculoskeletal proprioception. Participants slid their fingertip on a ridged plate to move toward a target without any visual feedback on hand location. Tactile motion estimates were biased by ridge orientation, inducing a systematic deviation in hand trajectories in accordance with our hypothesis. Results are in agreement with an ideal observer model, where motion estimates from different somatosensory cues are optimally integrated for the control of movement. These outcomes shed new light on the interplay between proprioception and touch in active tasks.

Central fatigue mechanisms are responsible for decreases in hand proprioceptive acuity following shoulder muscle fatigue

Muscle fatigue is a complex phenomenon, consisting of central and peripheral mechanisms which contribute to local and systemic changes in motor performance. In particular, it has been demonstrated that afferent processing in the fatigued muscle (e.g., shoulder), as well as in surrounding or distal muscles (e.g., hand) can be altered by fatigue. Currently, it is unclear how proximal muscle fatigue affects proprioceptive acuity of the distal limb. The purpose of the present study was to assess the effects of shoulder muscle fatigue on participants’ ability to judge the location of their hand using only proprioceptive cues. Participants’ (N = 16) limbs were moved outwards by a robot manipulandum and they were instructed to estimate the position of their hand relative to one of four visual reference targets (two near, two far). This estimation task was completed before and after a repetitive pointing task was performed to fatigue the shoulder muscles. To assess central versus peripheral effects of fatigue on the distal limb, the right shoulder was fatigued and proprioceptive acuity of the left and right hands were tested. Results showed that there was a significant decrease in the accuracy of proprioceptive estimates for both hands after the right shoulder was fatigued, with no change in the precision of proprioceptive estimates. A control experiment (N = 8), in which participants completed the proprioceptive estimation task before and after a period of quiet sitting, ruled out the possibility that the bilateral changes in proprioceptive accuracy were due to a practice effect. Together, these results indicate that shoulder muscle fatigue decreases proprioceptive acuity in both hands, suggesting that central fatigue mechanisms are primarily responsible for changes in afferent feedback processing of the distal upper limb.

Altered postural timing and abnormally low use of proprioception in lumbar spinal stenosis pre- and post- surgical decompression

BackgroundLumbar spinal stenosis (LSS) is frequently associated with postural instability. Although several studies evaluated patients’ functional impairments, underlying sensorimotor mechanisms are still poorly understood. We aimed to assess the specific set of postural control deficits associated with LSS during spontaneous and externally perturbed stance and evaluated post-surgical changes in postural behavior.MethodsWe analyzed postural control in eleven LSS patients (age 69 ± 8 years) pre- and post-laminectomy, correlated experimental data with functional tests and patient-reported outcomes, and compared findings to 15 matched, healthy control subjects (age 70 ± 6 years). Postural control was characterized by spontaneous sway measures and measures of perturbed stance. Perturbations were induced by anterior-posterior pseudorandom tilts of the body support surface. We used an established postural control model to extract specific postural control parameters.ResultsSpontaneous sway amplitude, velocity and frequency were abnormally large in LSS patients. Furthermore, patients’ postural reactions to platform tilts, represented by GAIN and PHASE were significantly altered. Based on simple feedback model simulations, we found that patients rely less on proprioceptive cues for stance regulation than healthy subjects. Moreover, their postural reactions’ timing is altered. After surgery, patients’ spontaneous sway amplitude was significantly reduced and their postural timing approximated the behavior of healthy subjects.ConclusionThe reduction in proprioceptive input for stance control due to stenosis-caused afferent dysfunction is a functional disadvantage for LSS patients – and may be the basis of increased spontaneous sway. This disadvantage may cause the timing of postural reactions to alter, with the intent of preventing rapid changes in stance regulation for safety reasons. After surgery, patients’ postural timing approximated those of healthy subjects, while the abnormally low use of proprioception remained unchanged. We suggest the post-surgery rehabilitation of proprioception, eg through balance exercises on unstable surfaces and reduced visual input.

A Haptic Object to Quantify the Effect of Feedback Modality on Prosthetic Grasping

Upper limb prostheses do not provide proprioceptive cues to their users, which impedes performance in grasp and manipulation tasks. Various sensory substitution methods have been developed to provide prosthesis users with a sense of the device's position, orientation, and terminal device aperture. However, the impact of these technologies on manipulation dexterity has not been systematically assessed and these technologies have not been widely adopted by prosthesis users. Researchers have previously used visually rendered virtual objects and virtual prostheses, which do not provide cues associated with physical interactions involved in grasping and manipulation. Other studies use a physical object and a physical prosthesis, but these methods lack the benefit of programmable conditions, systematic experiment setup, and direct evaluation of performance in addition to issues of consistent application across different types of prostheses. In order to address these concerns, we suggest a new method to evaluate different types of feedback with the use of a haptic device that renders physical properties through motors to a hand or a physical prosthesis. Ten users without amputation were asked to match hand aperture to a target using various feedback modalities (visual, vibration, and soft force-wall feedback). Participants interacted with the haptic device either through their natural hand or using a body-powered prosthetic emulator. In addition, three prosthesis users were recruited to complete the same task, each using their own prosthesis. Trials performed under conditions with visual and vibration feedback showed similar improvements in position accuracy, compared to trials without feedback.

Postural Control and Verbal and Visual Working Memory Correlates in Nonclinical Psychosis

Introduction: Motor and cognitive abnormalities are well documented in psychosis spectrum disorders. Evidence suggests these deficits could be pronounced because of disruptions in the cerebellar-thalamic-cortical-cerebellar (CTCC) circuit, a network thought to be heavily implicated in motor and higher cognitive functioning. Although significant research has been done on this topic in individuals with schizophrenia and those at a clinical high risk for psychosis, much less is known about deficits at the lower end of the spectrum. Methods: In this study, we extended the understanding of motor abnormalities across the psychosis continuum by examining postural sway deficits in the nonclinical psychosis (NCP) population. Furthermore, we linked these deficits to verbal and visual working memory. High-NCP (n = 37) and low-NCP control (n = 31) participants completed an instrumental balance task, highly sensitive to subtle variations in postural sway, along with a brief working memory battery. Results: We found that high-NCP participants presented with increased postural sway area (i.e., worse postural control) relative to low-NCP controls on a difficult condition (with limited proprioceptive cues), but not on an easier condition. Furthermore, results indicated that the sway area was correlated with poorer performance on working memory tasks in the high-NCP group. Conclusion: These findings suggest that CTCC circuit abnormalities are present across the lower end of the psychosis spectrum and that they may be contributing to a range of motor and cognitive behaviors seen in the population. However, evidence suggests that the signs are subtle, and that sensitive assessment devices and challenging conditions may be necessary for detection.

Preserved multisensory body representations in advanced age

The internal representation of the body emerges via the integration of multisensory body cues. Sensory signal transfer and the ability to integrate multisensory information deteriorate significantly with increasing age. However, there is little empirical evidence on age-related changes in body representations based on multisensory integration. Here, we used a standard paradigm for evaluating body representations based on multisensory integration, the rubber hand illusion, and compared the amount of proprioceptive drift and changes in perceived body ownership triggered by the integration of visual, tactile, and proprioceptive cues between younger and older adults. To account for potential age-related differences in the temporal stability of the illusion, proprioceptive drift was measured at five different time points. Our results show that older adults used synchronous visuo-tactile cues similarly to younger adults to update both the position of their own hand, and their feeling of ownership over the artificial hand. Independent of visuo-tactile synchrony, older adults perceived their hand as closer to their body than younger adults did, and showed a less stable representation of this in-depth hand position. This proprioceptive bias towards the body did not correlate with the strength of the illusion. Our results indicate that the integration of visual and tactile cues is largely preserved in advanced age when used to update limb position, whereas proprioception worsens with age. This may be linked to two different pathways that underlie changes in body representations over the life span.

Attenuation of access to internal states in high obsessive-compulsive individuals might increase susceptibility to false feedback: Evidence from a visuo-motor hand-reaching task

Background and objectivesThe Seeking Proxies for Internal States (SPIS) model of obsessive-compulsive disorder (OCD) posits that obsessive-compulsive (OC) individuals have attenuated access to their internal states. Hence, they seek and rely on proxies, or discernible substitutes for these internal states. In previous studies, participants with high OC tendencies and OCD patients, compared to controls, showed increased reliance on external proxies and were more influenced by false feedback when judging their internal states. This study is the first to examine the effects of false feedback on performance of hand movements in participants with high and low OC tendencies. MethodThirty-four participants with high OC tendencies and 34 participants with low OC tendencies were asked to perform accurate hand reaches without visual feedback in two separate sessions of a computerized hand-reaching task: once after valid feedback training of their hand location and once with false-rotated feedback. We assessed the accuracy and directional adaptation of participants’ reaches. ResultsAs predicted, high OC participants evidenced a larger decrease in their hand positioning accuracy after training with false feedback compared to low OC participants. LimitationsThe generalization of our findings to OCD requires replication with a clinical sample. ConclusionsThese results suggest that in addition to self-perceptions, motor performance of OC individuals is prone to be overly influenced by false feedback, possibly due to attenuated access to proprioceptive cues. These findings may be particularly relevant to understanding the distorted sense of agency in OCD.

Remembering actions without proprioception

It has been suggested that agency signals generated by enactment provide memories with an enduring episodic marker that can successively be exploited to facilitate recall. Current theories of motor awareness highlight the role of prospective and retrospective sensorimotor cues in the construction of sense of agency (SA). To explore how these signals impact on memory for actions, we studied the effect of enactment in a patient with complete loss of somatic sensation below nose level, and compared her performance to that of a group of neurologically intact individuals. A memory advantage for enacted material was clearly detectable in the control group and, interestingly, also in sensory deafferented patient GL. This novel finding shows that robust memory for actions can be obtained even in the absence of somatosensory reafferences. We hypothesize that the neural processes evoked by intention to move, together with visual experience about one's actions, provide the long-lasting agency signals that are responsible for the special quality of self-performed actions and may support autobiographical experience. Proprioceptive cues, being more time-constrained, are critical to online SA but do not necessarily partake in offline action representations.

Response Properties of Interneurons and Pyramidal Neurons in Macaque MSTd and VPS Areas During Self-Motion.

To perceive self-motion perception, the brain needs to integrate multi-modal sensory signals such as visual, vestibular and proprioceptive cues. Self-motion perception is very complex and involves multi candidate areas. Previous studies related to self-motion perception during passive motion have revealed that some of the areas show selective response to different directions for both visual (optic flow) and vestibular stimuli, such as the dorsal subdivision of the medial superior temporal area (MSTd) and the visual posterior sylvian fissure (VPS), although MSTd is dominated by visual signals and VPS is dominated by vestibular signals. However, none of studies related to self-motion perception have distinguished the different neuron types with distinct neuronal properties in cortical microcircuitry, which limited our understanding of the local circuits for self-motion perception. In the current study, we classified the recorded MSTd and VPS neurons into putative pyramidal neurons and putative interneurons based on the extracellular action potential waveforms and spontaneous firing rates. We found that: (1) the putative interneurons exhibited obviously broader direction tuning than putative pyramidal neurons in response to their dominant (visual for MSTd; vestibular for VPS) stimulation type; (2) either in visual or vestibular condition, the putative interneurons were more responsive but with larger variability than the putative pyramidal neurons for both MSTd and VPS areas; and (3) the timing of vestibular and visual peak directional tuning was earlier in the putative interneurons than that of the putative pyramidal neurons for both MSTd and VPS areas. Based on these findings we speculated that, within the microcircuitry, several adjacent putative interneurons with broad direction tuning receive earlier strong but variable signals, which might act feedforward input to shape the direction tuning of the target putative pyramidal neuron, but each interneuron may participate in several microcircuitries, targeting different output neurons.