Internalizing agency of self-action: perception of one's own hand movements depends on an adaptable prediction about the sensory action outcome

Extensive work on learning in reaching and pointing tasks has demonstrated high degrees of plasticity in our ability to optimize goal-directed motor behavior. However, studies focusing on the perceptual awareness of our own actions during motor adaptation are still rare. Here we present the first simultaneous investigation of sensorimotor adaptation on both levels, i.e., action and action perception. We hypothesized that self-action perception relies on internal predictions about the sensory action outcome that are updated in a way similar to that of motor control. Twenty human subjects performed out-and-back pointing movements that were fed back visually. Feedback was initially presented in spatiotemporal correspondence with respect to the actual finger position, but later rotated by a constant angle. When distorted feedback was applied repetitively, subjects' perceived pointing direction shifted in the direction of the trajectory rotation. A comparable perceptual reinterpretation was observed in control trials without visual feedback, indicating that subjects learned to predict the new visual outcome of their actions based on nonvisual, internal information. The perception of the world, however, remained unchanged. The changes in perception of one's own movements were accompanied by adaptive changes in motor performance of the same amount, i.e., a secondary motor compensation opposite to the direction of the imposed visual rotation. Our results show that the perception of one's own actions depends on adaptable internal predictions about the sensory action outcome, allowing us to attribute new sensory consequences of our actions to our own agency. Furthermore, they indicate that the updated sensory prediction can be used to optimize motor control.     

Cue integration and the perception of action in intentional binding

‘Intentional binding’ describes the perceived temporal attraction between a voluntary action and its sensory consequence. Binding has been used in health and disease as an indirect measure of awareness of action or agency, that is, the sense that one controls one’s own actions. It has been proposed that binding results from cue integration, in which a voluntary action provides information about the timing of its consequences or vice versa. The perception of the timing of either event is then a weighted average, determined according to the reliability of each of these two cues. Here we tested the contribution of cue integration to the perception of action and its sensory effect in binding, that is, action and tone binding, by manipulating the sensory reliability of the outcome tone. As predicted, when tone reliability was reduced, action binding was diminished and tone binding was increased. However, further analyses showed that cue integration accounted for changes in action binding, but not tone binding. These findings establish a role for cue integration in action binding and support the growing evidence suggesting that action and tone binding are, at least in part, driven by distinct mechanisms.     

Phantom limb pain.

A phantom limb is universally experienced after a limb has been amputated or its sensory roots have been destroyed. A complete break of the spinal cord also often leads to a phantom body below the level of the break. Furthermore, phantom breasts, genitals and other body areas occur in a substantial number of people after surgical removal or denervation of the body part. The most astonishing feature of a phantom limb (or other body area) is its incredible "reality" to the person. An examination of phantom limb phenomena has led to a new theory. It is proposed that we are born with a widespread neural network--the "neuromatrix"--for the body-self, which is subsequently modified by experience. The neuromatrix imparts a pattern--the "neurosignature"--on all inputs from the body, so that experiences of one's own body have a quality of self and are imbued with affective tone and cognitive meaning. The theory is presented with supporting evidence as well as implications for research.     

Predicted sensory feedback derived from motor commands does not improve haptic sensitivity

Haptic perception is based on the integration of afferent proprioceptive and tactile signals. A further potential source of information during active touch is predicted sensory feedback (PSF) derived from a copy of efferent motor commands that give rise to the exploratory actions. There is substantial evidence that PSF is important for predicting the sensory consequences of action, but its role in perception is unknown. Theoretically, PSF leads to a higher redundancy of haptic information, which should improve sensitivity of the haptic sense. To investigate the effect of PSF on haptic precision, blindfolded subjects haptically explored the curved contour of a virtual object generated by a robotic manipulandum. They either actively moved their hand along the contour, or their hand was moved passively by the device along the same contour. In the active condition afferent sensory information and PSF were present, while in the passive condition subjects relied solely on afferent information. In each trial, two stimuli of different curvature were presented. Subjects needed to indicate which of the two was more “curved” (forced choice). For each condition, the detection and three discrimination thresholds were computed. The main finding is that absence of efference copy information did not systematically degrade haptic acuity. This indirectly implies that PSF does not aid or enhance haptic perception. We conclude that when maximum haptic sensitivity is required to explore novel objects, the perceptual system relies primarily on afferent tactile and proprioceptive information, and PSF has no added effect on the precision of the perceptual estimate.     

Analgesia induced by self‐initiated electrotactile sensation is mediated by top‐down modulations

It is well known that sensory perception can be attenuated when sensory stimuli are controlled by self‐initiated actions. This phenomenon is explained by the consistency between forward models of anticipated action effects and actual sensory feedback. Specifically, the brain state related to the binding between motor processing and sensory perception would have inhibitory function by gating sensory information via top‐down control. Since the brain state could casually influence the perception of subsequent stimuli of different sensory modalities, we hypothesize that pain evoked by nociceptive stimuli following the self‐initiated tactile stimulation would be attenuated as compared to that following externally determined tactile stimulation. Here, we compared psychophysical and neurophysiological responses to identical nociceptive‐specific laser stimuli in two different conditions: self‐initiated tactile sensation condition (STS) and nonself‐initiated tactile sensation condition (N‐STS). We observed that pain intensity and unpleasantness, as well as laser‐evoked brain responses, were significantly reduced in the STS condition compared to the N‐STS condition. In addition, magnitudes of alpha and beta oscillations prior to laser onset were significantly larger in the STS condition than in the N‐STS condition. These results confirmed that pain perception and pain‐related brain responses were attenuated when the tactile stimulation was initiated by subjects’ voluntary actions, and exploited neural oscillations reflecting the binding between motor processing and sensory feedback. Thus, our study elaborated the understanding of underlying neural mechanisms related to top‐down modulations of the analgesic effect induced by self‐initiated tactile sensation, which provided theoretical basis to improve the analgesic effect in various clinical applications.     

The role of fearful beliefs in the relationship between situational self‐awareness and report of breathing‐related sensations

Background and aims. Gating models of sensory perception suggest that increased attention towards the self leads to more on‐line processing of sensory information and less report bias. However, little is known about the interaction of self‐awareness with fearful beliefs about bodily sensations. In the present study, we explored report bias of breathing‐related sensation under increased self‐awareness compared to increased focus on external cues related to breathlessness. We expected report bias under internal focus to be lower than under external focus. However, we expected this effect of internal focus to be moderated by fearful beliefs about bodily sensations. Methods. Thirty participants completed two appointments in which attention was directed either towards the self or towards the surroundings. On both sessions, participants' detection threshold for inspiratory loads, negative mood, and fear of bodily sensations was assessed. Changes in threshold were tested using repeated measures ANOVA. The role of fear of bodily sensations was tested in a within‐subject moderation analysis. Results and conclusion. Relative over report of sensations was lower under internal focus compared to external focus. However, this effect was moderated by fear of bodily sensations: the greater fear of bodily sensations was, the lower the effect of self‐awareness. Results encourage research on the interaction of self‐awareness and fearful beliefs in the top‐down modulation of perception.     

Unmyelinated visceral afferents exhibit frequency dependent action potential broadening while myelinated visceral afferents do not

Sensory information arising from visceral organ systems is encoded into action potential trains that propagate along afferent fibers to target nuclei in the central nervous system. These information streams range from tight patterns of action potentials that are well synchronized with the sensory transduction event to irregular, patternless discharge with no clear correlation to the sensory input. In general terms these afferent pathways can be divided into unmyelinated and myelinated fiber types. Our laboratory has a long standing interest in the functional differences between these two types of afferents in terms of the preprocessing of sensory information into action potential trains (synchrony, frequency, duration, etc.), the reflexogenic consequences of this sensory input to the central nervous system and the ionic channels that give rise to the electrophysiological properties of these unique cell types. The aim of this study was to determine whether there were any functional differences in the somatic action potential characteristics of unmyelinated and myelinated vagal afferents in response to different rates of sensory nerve stimulation. Our results showed that activity and frequency-dependent widening of the somatic action potential was quite prominent in unmyelinated but not myelinated vagal afferents. Spike broadening often leads to increased influx of Ca(2+) ions that has been associated with a diverse range of modulatory mechanisms both at the cell body and central synaptic terminations (e.g. increased neurotransmitter release.) We conclude that our observations are indicative of fundamentally different mechanisms for neural integration of sensory information arising from unmyelinated and myelinated vagal afferents.     

Yawning: unsuspected avenue for a better understanding of arousal and interoception

Almost all the vertebrates yawn, testifying the phylogenetic old origins of this behavior. Correlatively speaking, yawning shows an ontogenical precociousness since it occurs as early as 12 weeks after conception and remains relatively unchanged throughout life. Thus, it is contended that these common characteristics and their diencephalic origin allow to model an approach from which emerges a pivotal link between yawning and REM sleep. Yawning and stretching reverse the muscular atonia of the REM-sleep and reopen the collapsed airways. Yawning appears as a powerful muscular stretch, recruiting specific control systems particularly the paraventricular nucleus of the hypothalamus, the locus coeruleus and the reticular activating system from which the vigor of this ancestral vestige, surviving throughout evolution with little variation, may increase arousal. On the other hand, the James-Lange theory proposes that afferent feedback from muscles and viscera provides the brain with a feeling that characterizes the active motivational state and arousal. On this basis and using selected supporting findings from the literature and from data provided by daily life, it is contended that yawning takes part in interoceptiveness by its capacity to increase arousal and self-awareness. Adaptative behaviors depend on interactions among the nervous system and the body by a continuous feedback between them. The body's schema is a main component of the self, and interoceptive process is essential to awareness of the body and arousal. Yawning contributes to bodily consciousness as a behavior affiliating a sensory motor act and his perception from which pleasure is derived. Yawning can be seen as a proprioceptive performance awareness which inwardly provides a pre-reflective sense of one's body and a reappraisal of the body schema. The behavioral consequences of adopting specific regulatory strategies and the neural systems involved act upon attention and cognitive changes.Thus, it is proposed that yawning is a part of interoceptiveness by its capacity to increase arousal and self-awareness.     

Voluntary action and conscious awareness

Humans have the conscious experience of 'free will': we feel we can generate our actions, and thus affect our environment. Here we used the perceived time of intentional actions and of their sensory consequences as a means to study consciousness of action. These perceived times were attracted together in conscious awareness, so that subjects perceived voluntary movements as occurring later and their sensory consequences as occurring earlier than they actually did. Comparable involuntary movements caused by magnetic brain stimulation reversed this attraction effect. We conclude that the CNS applies a specific neural mechanism to produce intentional binding of actions and their effects in conscious awareness.     

Effect of ageing on tactile transduction processes

With advancing age, a decline in the main sensory modalities including touch sensation and perception is well reported to occur. This review mainly outlines the peripheral components of touch perception highlighting ageing influences on morphological and functional features of cutaneous mechanical transducers and mechanosensitive ion channels, sensory innervation, neurotransmitters and even vascular system required to ensure efferent function of the afferent nerve fibres in the skin. This, in conjunction with effect of ageing on the skin per se and central nervous system, could explain the tactile deficit seen among the ageing population. We also discuss appropriate tools and experimental models available to study the age-related tactile decline.     

Detecting delay in visual feedback of an action as a monitor of self recognition

How do we distinguish “self” from “other”? The correlation between willing an action and seeing it occur is an important cue. We exploited the fact that this correlation needs to occur within a restricted temporal window in order to obtain a quantitative assessment of when a body part is identified as “self”. We measured the threshold and sensitivity (d′) for detecting a delay between movements of the finger (of both the dominant and non-dominant hands) and visual feedback as seen from four visual perspectives (the natural view, and mirror-reversed and/or inverted views). Each trial consisted of one presentation with minimum delay and another with a delay of between 33 and 150 ms. Participants indicated which presentation contained the delayed view. We varied the amount of efference copy available for this task by comparing performances for discrete movements and continuous movements. Discrete movements are associated with a stronger efference copy. Sensitivity to detect asynchrony between visual and proprioceptive information was significantly higher when movements were viewed from a “plausible” self perspective compared with when the view was reversed or inverted. Further, we found differences in performance between dominant and non-dominant hand finger movements across the continuous and single movements. Performance varied with the viewpoint from which the visual feedback was presented and on the efferent component such that optimal performance was obtained when the presentation was in the normal natural orientation and clear efferent information was available. Variations in sensitivity to visual/non-visual temporal incongruence with the viewpoint in which a movement is seen may help determine the arrangement of the underlying visual representation of the body.     

Transmitter diversity in carotid body afferent neurons: dopaminergic and peptidergic phenotypes.

Hypoxic stimulation of carotid body chemoreceptors is conveyed to the brainstem by primary sensory neurons whose peripheral axons run in the carotid sinus nerve. While considerable attention has focused on defining chemical neuroregulators released by glomus cells in the carotid body, our understanding of the morphology, distribution and transmitter phenotype of these carotid body afferent neurons remains limited. Carotid body afferent neurons were labeled by microinjection of the retrograde tracer, Fluorogold, into the vascularly isolated rat carotid body. In addition, immunoelectron microscopy was used to correlate transmitter phenotype with ultrastructural features of afferent terminals in the carotid body. Our results indicate that 41% of all carotid body afferent neurons express tyrosine hydroxylase, the rate-limiting enzyme in catecholamine biosynthesis, whereas 7% contain substance P. Tyrosine hydroxylase- and substance P-positive neurons constitute separate subpopulations of carotid body afferents, as these two phenotypes were not colocalized. Most of the tyrosine hydroxylase-containing carotid body afferent neurons were small- or medium-sized (mean cell diameter 15-20 microns) and located in the distal petrosal ganglion, whereas the majority of substance P-containing carotid body afferent neurons were medium- to large-sized (mean cell diameter 20-29 microns) and located in the proximal petrosal ganglion and jugular ganglion. These differences strengthen the notion that these catecholaminergic and peptidergic carotid body afferent neurons give rise to functionally distinct subsets of chemoafferent fibers. To further characterize the catecholaminergic phenotype expressed by tyrosine hydroxylase-positive cells in the petrosal ganglion, we examined the colocalization of tyrosine hydroxylase and DOPA decarboxylase, the dopamine-synthesizing enzyme. Eighty-six per cent of tyrosine hydroxylase-positive neurons in the distal petrosal ganglion also contained DOPA decarboxylase; as these cells do not express the norepinephrine-synthesizing enzyme, dopamine beta-hydroxylase, these data indicate that the catecholaminergic carotid body afferent neurons are dopaminergic. Finally, ultrastructural analysis of the peripheral processes of tyrosine hydroxylase-positive afferent terminals in the carotid body demonstrated endings in close opposition to Type I glomus cells, consistent with a role for dopaminergic afferent neurons in carotid body chemoreception. One possibility is that these cells, in addition to their role as afferents, constitute a morphologic substrate for dopaminergic "efferent" inhibition in the carotid body.     

I can feel my heartbeat: Dancers have increased interoceptive accuracy

Interoception is the process of perceiving afferent signals arising from within the body including heart rate (HR), gastric signals, etc., and has been described as a mechanism crucially involved in the creation of self‐awareness and selfhood. The heartbeat perception task is a tool to measure individuals' interoceptive accuracy (IAcc). IAcc correlates positively with measures of self‐awareness and with attributes including emotional sensitivity, empathy, prosocial behavior, and efficient decision making. IAcc is only moderate in the general population, and attempts to identify groups of people who might have higher IAcc due to their specific training (e.g., yoga, meditation) have not been successful. However, a recent study with musicians suggests that those trained in the arts might exhibit high IAcc. Here, we tested IAcc in 20 professional dancers and 20 female control participants on a heartbeat perception task. Dancers had a higher IAcc, and this effect was independent of their lower heart rates (a proxy measure of physical fitness), counting ability, and knowledge about HR. An additional between‐groups analysis after a median split in the dancer group (based on years of dance experience) showed that junior dancers' IAcc differed from controls, and senior dancers' IAcc was higher than both junior dancers and controls. General art experience correlated positively with IAcc. No correlations were found between IAcc and questionnaire measures of empathy, emotional experience, and alexithymia. These findings are discussed in the context of current theories of interoception and emotion—highlighting the features of arts training that might be related to IAcc.     

Pain response in depersonalization: a functional imaging study using hypnosis in healthy subjects

BACKGROUND: Depersonalization (DP) is characterized by persistent or recurrent episodes of detachment from one's self with reduced pain perception being a common feature. Alterations in the body schema similar to the cortico-limbic disconnection syndrome of pain asymbolia are suggested to be responsible for DP. In this study we used hypnosis to induce DP in healthy subjects and to examine neural patterns of pain perception in the state of DP by means of functional magnetic resonance imaging (fMRI). METHODS: Pain perception was investigated in 7 healthy subjects with high susceptibility to hypnosis in three different mental states: waking state (N-W), hypnotic relaxation (H-R) and hypnotic DP (H-DP). Pain was induced with electrical stimulation to the median nerve at the right wrist. fMRI measurements were performed during all states. RESULTS: Nociceptive stimuli led to an activation of the well described pain network including somatosensory and insular regions and the cerebellum. Activation was markedly reduced in the contralateral somatosensory cortex, parietal cortex (Brodmann area 40, BA40), prefrontal cortex (BA9), putamen and the ipsilateral amygdala during H-DP. Subjects also reported a significant decrease in pain intensity from N-W to H-DP. CONCLUSION: Pain response during H-DP was reduced in sensory and affective pain-related areas, reflecting the diminished intensity of the perceived pain. Moreover, a network of cortical and subcortical areas that have been implicated in the perception of the own body was less responsive during DP, which might point to a specific neural mechanism underlying the 'out-of-body' experience. Although the small number of subjects does not allow a generalization of our findings, H-DP seems to be a promising tool for the investigation of psychological and biological mechanisms of self-inflicted injuries as well as the mind-body interplay within the realm of psychosomatic disorders.     

北京女大学生瘦身倾向的影响因素

目的：考察北京女大学生瘦身倾向的影响因素。方法：采用进食障碍问卷(EDI)的瘦身倾向分量表、青少年及成人身体自尊量表和BMI体象量表(BMI-SMT)测查了499名北京女大学生。结果：对自身体形的期望偏差、身体自尊状况以及对自身体形的认识偏差对于个体的瘦身倾向状况具有预测作用；体形指数属正常组的个体对自身体形的认识偏差、期望偏差显著高于偏瘦、过瘦组，身体自尊显著低于偏瘦、过瘦组，瘦身倾向显著高于偏瘦、过瘦组。结论：女大学生对自身体形的歪曲认识、不合理的期望及较低的身体自尊是影响瘦身倾向进而引发进食障碍的重要因素。     

Psychotherapist and expansion of awareness

The author emphasizes the therapist's well-integrated and matured personality as the crucial element for being a good psychotherapist; therefore, it is essential for a psychotherapist to make ceaseless efforts regarding his own personality growth with his ongoing therapeutic experiences. Nevertheless, nowadays students are apt to satisfy themselves with or cling to the theories and techniques of psychotherapy, neglecting their own personality growth. The author attributes such a tendency, on the one hand, to the contemporary thought of 'technology first and convenience first', on the other, to the current system of medical education which is extremely faithful to scientism. He warns that concepts or theories sometimes serve as a barrier in one's mind and falsify the reality. He reiterates the importance of the therapist's own maturity and expansion of awareness. In this context, the author recommends Zen meditation or Theravada meditation as one of the advanced courses of training for psychotherapists. He elucidates a way of promoting one's awareness in Zen meditation and what the ultimate state of "no-self" of Zen should be, based on his own experience of Zen practices.     

The central nervous system efferent control of the organs of balance and equilibrium.

The vestibular labyrinth is innervated by both primary afferent nerves and efferent axons with cell bodies located in the central nervous system. Efferent terminals are found on both hair cells and on primary afferent axons. Acetylcholine is the major efferent transmitter, but enkephalin and calcitonin gene-related peptide (CGRP) have also been localized to efferent terminals and somata. The efferent vestibular nuclei are bilaterally organized in the majority of species. Semicircular canal primary afferents have been classified by their sensitivity and phase in response to rotation. Electrical activation of efferents in monkey and fish increases afferent resting discharge and reduces afferent gain to adequate stimulation. Effects are most profound on high-gain, phase-advanced (re. velocity) afferents. Experiments in alert animals indicate that multiple sensory modalities can activate the efferent system.     

Sensorimotor attenuation by central motor command signals in the absence of movement

Voluntary actions typically produce suppression of afferent sensation from the moving body part. We used transcranial magnetic stimulation to delay the output of motor commands from the motor cortex during voluntary movement. We show attenuation of sensation during this delay, in the absence of movement. We conclude that sensory suppression mainly relies on central signals related to the preparation for movement and that these signals are upstream of primary motor cortex.     

Strategies for providing upper extremity amputees with tactile and hand position feedback--moving closer to the bionic arm.

A continuing challenge for prostheses developers is to replace the sensory function of the hand. This includes tactile sensitivity such as finger contact, grip force, object slippage, surface texture and temperature, as well as proprioceptive sense. One approach is sensory substitution whereby an intact sensory system such as vision, hearing or cutaneous sensation elsewhere on the body is used as an input channel for information related to the prosthesis. A second technique involves using electrical stimulation to deliver sensor derived information directly to the peripheral afferent nerves within the residual limb. Stimulation of the relevant afferent nerves can ultimately come closest to restoring the original sensory perceptions of the hand, and to this end, researchers have already demonstrated some degree of functionality of the transected sensory nerves in studies with amputee subjects. This paper provides an overview of different types of nerve interface components and the advantages and disadvantages of employing each of them in sensory feedback systems. Issues of sensory perception, neurophysiology and anatomy relevant to hand sensation and function are discussed with respect to the selection of the different types of nerve interfaces. The goal of this paper is to outline what can be accomplished for implementing sensation into artificial arms in the near term by applying what is present or presently attainable technology.