Abnormal Sense of Agency in Patients with Schizophrenia: Evidence from Bimanual Coupling Paradigm

Pons-to-Cerebellum Hypoconnectivity Along the Psychosis Spectrum and Associations With Sensory Prediction and Hallucinations in Schizophrenia

BACKGROUND

Sensory prediction allows the brain to anticipate and parse incoming self-generated sensory information from externally generated signals. Sensory prediction breakdowns may contribute to perceptual and agency abnormalities in psychosis (hallucinations, delusions). The pons, a central node in a cortico-ponto-cerebellar-thalamo-cortical circuit, is thought to support sensory prediction. Examination of pons connectivity in schizophrenia and its role in sensory prediction abnormalities is lacking.

METHODS

We examined these relationships using resting-state functional magnetic resonance imaging and the electroencephalography-based auditory N1 event-related potential in 143 participants with psychotic spectrum disorders (PSPs) (with schizophrenia, schizoaffective disorder, or bipolar disorder); 63 first-degree relatives of individuals with psychosis; 45 people at clinical high risk for psychosis; and 124 unaffected comparison participants. This unique sample allowed examination across the psychosis spectrum and illness trajectory. Seeding from the pons, we extracted average connectivity values from thalamic and cerebellar clusters showing differences between PSPs and unaffected comparison participants. We predicted N1 amplitude attenuation during a vocalization task from pons connectivity and group membership. We correlated participant-level connectivity in PSPs and people at clinical high risk for psychosis with hallucination and delusion severity.

RESULTS

Compared to unaffected comparison participants, PSPs showed pons hypoconnectivity to 2 cerebellar clusters, and first-degree relatives of individuals with psychosis showed hypoconnectivity to 1 of these clusters. Pons-to-cerebellum connectivity was positively correlated with N1 attenuation; only PSPs with heightened pons-to-postcentral gyrus connectivity showed this pattern, suggesting a possible compensatory mechanism. Pons-to-cerebellum hypoconnectivity was correlated with greater hallucination severity specifically among PSPs with schizophrenia.

CONCLUSIONS

Deficient pons-to-cerebellum connectivity linked sensory prediction network breakdowns with perceptual abnormalities in schizophrenia. Findings highlight shared features and clinical heterogeneity across the psychosis spectrum.

Predicting the bodily self in space and time

To understand how the human brain distinguishes itself from external stimulation, it was examined if motor predictions enable healthy adult volunteers to infer self-location and to distinguish their body from the environment (and other agents). By uniquely combining a VR-setup with full-body motion capture, a full-body illusion paradigm (FBI) was developed with different levels of motion control: (A) a standard, passive FBI in which they had no motion control; (B) an active FBI in which they made simple, voluntary movements; and (C) an immersive game in which they real-time controlled a human-sized avatar in third person. Systematic comparisons between measures revealed a causal relationship between (i) motion control (prospective agency), (ii) self-other identification, and (iii) the ability to locate oneself. Healthy adults could recognise their movements in a third-person avatar and psychologically align with it (action observation); but did not lose a sense of place (self-location), time (temporal binding), nor who they are (self/other). Instead, motor predictions enabled them to localise their body and to distinguish self from other. In the future, embodied games could target and strengthen the brain's control networks in psychosis and neurodegeneration; real-time motion simulations could help advance neurorehabilitation techniques by fine-tuning and personalising therapeutic settings.

Sense of agency in schizophrenia: A reconciliation of conflicting findings through a theory-driven literature review

The sense of agency is the experience of being the author of self-generated actions and their outcomes. Both clinical manifestations and experimental evidence suggest that the agency experience and the mechanisms underlying agency attribution may be dysfunctional in schizophrenia. Yet, studies investigating the sense of agency in these patients show seemingly conflicting results: some indicated under-attribution of self-agency (coherently with certain positive symptoms), while others suggested over-attribution of self-agency. In this review, we assess whether recent theoretical frameworks can reconcile these divergent results. We examine whether the identification of agency abnormalities in schizophrenia might depend on the measure of self-agency considered (depending on the specific task requirements) and the available agency-related cues. We conclude that all these aspects are relevant to predict and characterize the type of agency misattribution that schizophrenia patients might show. We argue that one particular model, based on the predictive coding theory, can reconcile the interpretation of the multifarious phenomenology of agency manifestations in schizophrenia, paving the way for testing agency disorders in novel ways.

Agency in schizophrenia and autism: a systematic review

Introduction

Previous research suggests that altered experiences of agency are an underlying vulnerability in both schizophrenia and autism. Here, we explore agency as a potential transdiagnostic factor by conducting a systematic review of existing literature investigating agency in autism and schizophrenia individually and together.

Methods

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we conducted three systematic searches on PsycINFO, Embase, Medline, PubMed and Web of Science to identify studies that investigated (1) agency in schizophrenia, (2) agency in autism, and (3) agency in both schizophrenia and autism.

Results

A total of 31 articles met eligibility criteria for inclusion and data extraction, with 24 measuring agency in schizophrenia, 7 investigating agency in autism, and no articles comparing the two. Results show that, compared to control populations, agency is significantly different in every identified schizophrenia study and generally not significantly different in autism.

Discussion

Importantly, we identified a lack of studies using common tasks and a disproportionate number of studies investigating different dimensions of agency across the two conditions, resulting in limited grounds for valid comparison.

Systematic review registration

Prospero, CRD42021273373.

Abnormal sense of agency in eating disorders

The feeling of controlling one's own actions and, through them, impacting the external environment (i.e. Sense of Agency-SoA) can be relevant in the eating disorders (EDs) symptomatology. Yet, it has been poorly investigated. This study aims to implicitly assess SoA exploiting the Sensory Attenuation paradigm in two groups of EDs patients (Anorexia Nervosa Restrictive and Anorexia Nervosa Binge-Purging or Bulimia Nervosa) compared to a control group. We find that controls perceive self-generated stimuli as less intense than other-generated ones showing the classic pattern of sensory attenuation. By contrast, EDs patients show the opposite pattern, with self-generated perceived as more intense than other-generated stimuli. This result indicates an alteration of the implicit component of the feeling of control in EDs patients, thus suggesting a potential implication of these results for the clinical practice and the treatment of EDs symptomatology.

An evolutionary account of impairment of self in cognitive disorders

Recent research has proposed that certain aspects of psychosis, as experienced in, e.g., schizophrenia (SCZ), but also aspects of other cognitive conditions, such as autism spectrum disorders (ASD) and synesthesia, can be related to a shattered sense of the notion of self. In this paper, our goal is to show that altered processing of self can be attributed to an abnormal functioning of cortico-striatal brain networks supporting, among other, one key human distinctive cognitive ability, namely cross-modality, which plays multiple roles in human cognition and language. Specifically, our hypothesis is that this cognitive mechanism sheds light both on some basic aspects of the minimal self and on some aspects related to higher forms of self, such as the narrative self. We further link the atypical functioning in these conditions to some recent evolutionary changes in our species, specifically, an atypical presentation of human self-domestication (HSD) features. In doing so, we also lean on previous work concerning the link between cognitive disorders and language evolution under the effects of HSD. We further show that this approach can unify both linguistic and non-linguistic symptoms of these conditions through deficits in the notion of self. Our considerations provide further support for the hypothesis that SCZ and ASD are diametrically opposed cognitive conditions, as well for the hypothesis that their etiology is associated with recent human evolution, leading to a deeper understanding of the causes and symptoms of these disorders, and providing new cues, which can be used for an earlier and more accurate diagnostics.

Flexible control as surrogate reward or dynamic reward maximization

The utility of a given experience, like interacting with a particular friend or tasting a particular food, fluctuates continually according to homeostatic and hedonic principles. Consequently, to maximize reward, an individual must be able to escape or attain outcomes as preferences change, by switching between actions. Recent work on human and artificial intelligence has defined such flexible instrumental control in information theoretic terms and postulated that it may serve as a reward surrogate. Another possibility, however, is that the adaptability afforded by flexible control is tacitly implemented by planning for dynamic changes in outcome values. In the current study, an expected utility model that computes decision values over a range of possible monetary gains and losses associated with sensory outcomes provided the best fit to behavioral choice data and performed best in terms of earned rewards. Moreover, consistent with previous work on perceived control and personality, individual differences in dimensional schizotypy were correlated with behavioral choice preferences in conditions with the greatest and lowest levels of flexible control. These results contribute to a growing literature on the role of instrumental control in goal-directed choice.

Reduced homotopic interhemispheric connectivity in psychiatric disorders: evidence for both transdiagnostic and disorder specific features

There is considerable interest in the significance of structural and functional connections between the two brain hemispheres in terms of both normal function and in relation to psychiatric disorders. In recent years, many studies have used voxel mirrored homotopic connectivity analysis of resting state data to investigate the importance of connectivity between homotopic regions in the brain hemispheres in a range of neuropsychiatric disorders. The current review summarizes findings from these voxel mirrored homotopic connectivity studies in individuals with autism spectrum disorder, addiction, attention deficit hyperactivity disorder, anxiety and depression disorders, and schizophrenia, as well as disorders such as Alzheimer's disease, mild cognitive impairment, epilepsy, and insomnia. Overall, other than attention deficit hyperactivity disorder, studies across psychiatric disorders report decreased homotopic resting state functional connectivity in the default mode, attention, salience, sensorimotor, social cognition, visual recognition, primary visual processing, and reward networks, which are often associated with symptom severity and/or illness onset/duration. Decreased homotopic resting state functional connectivity may therefore represent a transdiagnostic marker for general psychopathology. In terms of disorder specificity, the extensive decreases in homotopic resting state functional connectivity in autism differ markedly from attention deficit hyperactivity disorder, despite both occurring during early childhood and showing extensive co-morbidity. A pattern of more posterior than anterior regions showing reductions in schizophrenia is also distinctive. Going forward, more studies are needed to elucidate the functions of these homotopic functional connections in both health and disorder and focusing on associations with general psychopathology, and not only on disorder specific symptoms.

Consider the pons: bridging the gap on sensory prediction abnormalities in schizophrenia

A shared mechanism across species heralds the arrival of self-generated sensations, helping the brain to anticipate, and therefore distinguish, self-generated from externally generated sensations. In mammals, this sensory prediction mechanism is supported by communication within a cortico-ponto-cerebellar-thalamo-cortical loop. Schizophrenia is associated with impaired sensory prediction as well as abnormal structural and functional connections between nodes in this circuit. Despite the pons' principal role in relaying and processing sensory information passed from the cortex to cerebellum, few studies have examined pons connectivity in schizophrenia. Here, we first briefly describe how the pons contributes to sensory prediction. We then summarize schizophrenia-related abnormalities in the cortico-ponto-cerebellar-thalamo-cortical loop, emphasizing the dearth of research on the pons relative to thalamic and cerebellar connections. We conclude with recommendations for advancing our understanding of how the pons relates to sensory prediction failures in schizophrenia.

What is new with Artificial Intelligence? Human–agent interactions through the lens of social agency

In this article, we suggest that the study of social interactions and the development of a “sense of agency” in joint action can help determine the content of relevant explanations to be implemented in artificial systems to make them “explainable.” The introduction of automated systems, and more broadly of Artificial Intelligence (AI), into many domains has profoundly changed the nature of human activity, as well as the subjective experience that agents have of their own actions and their consequences – an experience that is commonly referred to as sense of agency. We propose to examine the empirical evidence supporting this impact of automation on individuals’ sense of agency, and hence on measures as diverse as operator performance, system explicability and acceptability. Because of some of its key characteristics, AI occupies a special status in the artificial systems landscape. We suggest that this status prompts us to reconsider human–AI interactions in the light of human–human relations. We approach the study of joint actions in human social interactions to deduce what key features are necessary for the development of a reliable sense of agency in a social context and suggest that such framework can help define what constitutes a good explanation. Finally, we propose possible directions to improve human–AI interactions and, in particular, to restore the sense of agency of human operators, improve their confidence in the decisions made by artificial agents, and increase the acceptability of such agents.

Predictive waves in the autism-schizophrenia continuum: A novel biobehavioral model

The brain is a predictive machine. Converging data suggests a diametric predictive strategy from autism spectrum disorders (ASD) to schizophrenic spectrum disorders (SSD). Whereas perceptual inference in ASD is rigidly shaped by incoming sensory information, the SSD population is prone to overestimate the precision of their priors' models. Growing evidence considers brain oscillations pivotal biomarkers to understand how top-down predictions integrate bottom-up input. Starting from the conceptualization of ASD and SSD as oscillopathies, we introduce an integrated perspective that ascribes the maladjustments of the predictive mechanism to dysregulation of neural synchronization. According to this proposal, disturbances in the oscillatory profile do not allow the appropriate trade-off between descending predictive signal, overweighted in SSD, and ascending prediction errors, overweighted in ASD. These opposing imbalances both result in an ill-adapted reaction to external challenges. This approach offers a neuro-computational model capable of linking predictive coding theories with electrophysiological findings, aiming to increase knowledge on the neuronal foundations of the two spectra features and stimulate hypothesis-driven rehabilitation/research perspectives.

Neural mechanisms underlying the Rubber Hand Illusion: A systematic review of related neurophysiological studies

INTRODUCTION

Many researchers took advantage of the well-established rubber hand illusion (RHI) paradigm to explore the link between the sense of body ownership and the different brain structures and networks. Here, we aimed to review the studies that have investigated this phenomenon by means of neurophysiological techniques.

METHODS

The MEDLINE, accessed by Pubmed and EMBASE electronic databases, was searched using the medical subject headings: "Rubber hand illusion" AND "Transcranial magnetic stimulation (TMS)" OR "Evoked potentials (EP)" OR "Event related potentials (ERP)" OR "Electroencephalography (EEG)".

RESULTS

Transcranial magnetic stimulation studies revealed a significant excitability drop in primary motor cortex hand circuits accompanying the disembodiment of the real hand during the RHI experience and that the perceived ownership over the rubber hand is associated with normal parietal-motor communication. Moreover, TMS provided causal evidence that the extrastriate body area is involved in the RHI and subsequently in body representation, while neuromodulation of ventral premotor area and the inferior parietal lobe did not result in an enhancement of embodiment. EP and ERP studies suggest that pre-existing body representations may affect larger stages of tactile processing and support predictive coding models of the functional architecture of multisensory integration in bodily perceptual experience. High-frequency oscillations on EEG play a role in the integrative processing of stimuli across modalities, and EEG activity in γ band activity in the parietal area reflects the visuotactile integration process. EEG studies also revealed that RHI is associated with the neural circuits underlying motor control and that premotor areas play a crucial role in mediating illusory body ownership.

CONCLUSION

Neurophysiological studies shed new light on our understanding of the different aspects that contribute to the formation of a coherent self-awareness in humans.

Bimanual coupling effect during a proprioceptive stimulation

Circle-line drawing paradigm is used to study bimanual coupling. In the standard paradigm, subjects are asked to draw circles with one hand and lines with the other hand; the influence of the concomitant tasks results in two "elliptical" figures. Here we tested whether proprioceptive information evoked by muscle vibration inducing a proprioceptive illusion (PI) of movement at central level, was able to affect the contralateral hand drawing circles or lines. A multisite 80 Hz-muscle vibration paradigm was used to induce the illusion of circle- and line-drawing on the right hand of 15 healthy participants. During muscle vibration, subjects had to draw a congruent or an incongruent figure with the left hand. The ovalization induced by PI was compared with Real and Motor Imagery conditions, which already have proved to induce bimanual coupling. We showed that the ovalization of a perceived circle over a line drawing during PI was comparable to that observed in Real and Motor Imagery condition. This finding indicates that PI can induce bimanual coupling, and proprioceptive information can influence the motor programs of the contralateral hand.

New measures of agency from an adaptive sensorimotor task

Self-agency, the sense that one is the author or owner of one’s behaviors, is impaired in multiple psychological and neurological disorders, including functional movement disorders, Parkinson’s Disease, alien hand syndrome, schizophrenia, and dystonia. Existing assessments of self-agency, many of which focus on agency of movement, can be prohibitively time-consuming and often yield ambiguous results. Here, we introduce a short online motion tracking task that quantifies movement agency through both first-order perceptual and second-order metacognitive judgments. The task assesses the degree to which a participant can distinguish between a motion stimulus whose trajectory is influenced by the participant’s cursor movements and a motion stimulus whose trajectory is random. We demonstrate the task’s reliability in healthy participants and discuss how its efficiency, reliability, and ease of online implementation make it a promising new tool for both diagnosing and understanding disorders of agency.

Disrupted Sense of Agency as a State Marker of First-Episode Schizophrenia: A Large-Scale Follow-Up Study

Background: Schizophrenia is often characterized by a general disruption of self-processing and self-demarcation. Previous studies have shown that self-monitoring and sense of agency (SoA, i.e., the ability to recognize one's own actions correctly) are altered in schizophrenia patients. However, research findings are inconclusive in regards to how SoA alterations are linked to clinical symptoms and their severity, or cognitive factors. Methods: In a longitudinal study, we examined 161 first-episode schizophrenia patients and 154 controls with a continuous-report SoA task and a control task testing general cognitive/sensorimotor processes. Clinical symptoms were assessed with the Positive and Negative Syndrome Scale (PANSS). Results: In comparison to controls, patients performed worse in terms of recognition of self-produced movements even when controlling for confounding factors. Patients' SoA score correlated with the severity of PANSS-derived "Disorganized" symptoms and with a priori defined symptoms related to self-disturbances. In the follow-up, the changes in the two subscales were significantly associated with the change in SoA performance. Conclusion: We corroborated previous findings of altered SoA already in the early stage of schizophrenia. Decreased ability to recognize self-produced actions was associated with the severity of symptoms in two complementary domains: self-disturbances and disorganization. While the involvement of the former might indicate impairment in self-monitoring, the latter suggests the role of higher cognitive processes such as information updating or cognitive flexibility. The SoA alterations in schizophrenia are associated, at least partially, with the intensity of respective symptoms in a state-dependent manner.

Drawing lines and circles in Parkinson's Disease: The lateralized symptoms interfere with the movements of the unaffected hand

INTRODUCTION

Evidence about altered bimanual coordination has been reported in Parkinson's Disease. However, no previous study has explored such an alteration quantifying the interference effect that the trajectory of each hand might impose on the other one. Thus, in the present research, we applied the traditional Circles-Lines Coupling Task, which allowed assessing the motor coordination of the two hands, in the context of Parkinson's Disease.

METHODS

Thirty-six individuals affected by Parkinson's Disease were consecutively recruited and assigned to two groups according to their symptoms' lateralization. Moreover, eighteen age-matched healthy controls participated in the study. We capitalized on the Circles-Lines Coupling Task, in which the performance during incongruent movements (drawing lines with one hand and circles with the other hand) was compared with the performance during congruent movements (drawing lines with both hands). A bimanual coupling index was computed to compare the interference effect of each hand on the other one.

RESULTS

In healthy controls, the bimanual coupling index did not differ between the two hands. Crucially, in both groups of individuals affected by Parkinson's Disease, the less affected hand showed a significantly higher bimanual coupling index, due to the abnormal interference exerted by the most affected one, than vice versa.

CONCLUSIONS

Our results highlighted an altered spatial bimanual coupling in Parkinson's disease, depending on the symptoms' lateralization. We offered different explanations of our results according to the theoretical frameworks about the mechanisms subserving bimanual coordination.

Social Agency as a continuum

Sense of Agency, the phenomenology associated with causing one's own actions and corresponding effects, is a cornerstone of human experience. Social Agency can be defined as the Sense of Agency experienced in any situation in which the effects of our actions are related to a conspecific. This can be implemented as the other's reactions being caused by our action, joint action modulating our Sense of Agency, or the other's mere social presence influencing our Sense of Agency. It is currently an open question how such Social Agency can be conceptualized and how it relates to its nonsocial variant. This is because, compared with nonsocial Sense of Agency, the concept of Social Agency has remained oversimplified and underresearched, with disparate empirical paradigms yielding divergent results. Reviewing the empirical evidence and the commonalities and differences between different instantiations of Social Agency, we propose that Social Agency can be conceptualized as a continuum, in which the degree of cooperation is the key dimension that determines our Sense of Agency, and how it relates to nonsocial Sense of Agency. Taking this perspective, we review how the different factors that typically influence Sense of Agency affect Social Agency, and in the process highlight outstanding empirical questions within the field. Finally, concepts from wider research areas are discussed in relation to the ecological validity of Social Agency paradigms, and we provide recommendations for future methodology.

A causal role for the right angular gyrus in self-location mediated perspective taking

Recent theories suggest that self-consciousness, in its most elementary form, is functionally disconnected from the phenomenal body. Patients with psychosis frequently misattribute their thoughts and actions to external sources; and in certain out-of-body experiences, lucid states, and dreams body-ownership is absent but self-identification is preserved. To explain these unusual experiences, we hypothesized that self-identification depends on inferring self-location at the right angular gyrus (i.e., perspective-taking). This process relates to the discrimination of self-produced signals (endogenous attention) from environmental stimulation (exogenous attention). Therefore, when this mechanism fails, this causes altered sensations and perceptions. We combined a Full-body Illusion paradigm with brain stimulation (HD-tDCS) and found a clear causal association between right angular gyrus activation and alterations in self-location (perspective-taking). Anodal versus sham HD-tDCS resulted in: a more profound out-of-body shift (with reduced sense of agency); and a weakened ability to discriminate self from other perspectives. We conclude that self-identification is mediated in the brain by inferring self-location (i.e., perspective-taking). Self-identification can be decoupled from the bodily self, explaining phenomena associated with disembodiment. These findings present novel insights into the relationship between mind and body, and may offer important future directions for treating psychosis symptoms and rehabilitation programs to aid in the recovery from a nervous system injury. The brain's ability to locate itself might be the key mechanism for self-identification and distinguishing self from other signals (i.e., perspective-taking).

Visual-Tactile Spatial Multisensory Interaction in Adults With Autism and Schizophrenia

Background: Individuals with autism spectrum disorder (ASD) and schizophrenia (SZ) exhibit multisensory processing difficulties and social impairments, with growing evidence that the former contributes to the latter. However, this work has largely reported on separate cohorts, introducing method variance as a barrier to drawing broad conclusions across studies. Further, very few studies have addressed touch, resulting in sparse knowledge about how these two clinical groups may integrate somatic information with other senses. Methods: In this study, we compared adults with ASD (n = 29), SZ (n = 24), and typical developmental histories (TD, n = 37) on two tasks requiring visual-tactile spatial multisensory processing. In the first task (crossmodal congruency), participants judged the location of a tactile stimulus in the presence or absence of simultaneous visual input that was either spatially congruent or incongruent, with poorer performance for incongruence an index of spatial multisensory interaction. In the second task, participants reacted to touch in the presence or absence of dynamic visual stimuli that appeared to approach or recede from the body. Within a certain radius around the body, defined as peripersonal space (PPS), an approaching visual or auditory stimulus reliably speeds reaction times (RT) to touch; outside of this radius, in extrapersonal space (EPS), there is no multisensory effect. PPS can be defined both by its size (radius) and slope (sharpness of the PPS-EPS boundary). Clinical measures were administered to explore relations with visual-tactile processing. Results: Neither clinical group differed from controls on the crossmodal congruency task. The ASD group had significantly smaller and more sharply-defined PPSs compared to the other two groups. Small PPS size was related to social symptom severity across groups, but was largely driven by the TD group, without significant effects in either clinical group. Conclusions: These results suggest that: (1) spatially static visual-tactile facilitation is intact in adults with ASD and SZ, (2) spatially dynamic visual-tactile facilitation impacting perception of the body boundary is affected in ASD but not SZ, and (3) body boundary perception is related to social-emotional function, but not in a way that maps on to clinical status.

Embodied Predictions, Agency, and Psychosis

Psychotic symptoms, i.e., hallucinations and delusions, involve gross departures from conscious apprehension of consensual reality; respectively, perceiving and believing things that, according to same culture peers, do not obtain. In schizophrenia, those experiences are often related to abnormal sense of control over one's own actions, often expressed as a distorted sense of agency (i.e., passivity symptoms). Cognitive and computational neuroscience have furnished an account of these experiences and beliefs in terms of the brain's generative model of the world, which underwrites inferences to the best explanation of current and future states, in order to behave adaptively. Inference then involves a reliability-based trade off of predictions and prediction errors, and psychotic symptoms may arise as departures from this inference process, either an over- or under-weighting of priors relative to prediction errors. Surprisingly, there is empirical evidence in favor of both positions. Relatedly, there is evidence for both an enhanced and a diminished sense of agency in schizophrenia. How can this be? We argue that there is more than one generative model in the brain, and that ego- and allo-centric models operate in tandem. In brief, ego-centric models implement corollary discharge signals that cancel out the effects of self-generated actions while allo-centric models compare several hypothesis regarding the causes of sensory inputs (including the self among the potential causes). The two parallel hierarchies give rise to different levels of agency, with ego-centric models subserving "feelings of agency" and allo-centric predictions giving rise to "judgements of agency." Those two components are weighted according to their reliability and combined, generating a higher-level "sense of agency." We suggest that in schizophrenia a failure of corollary discharges to suppress self-generated inputs results in the absence of a "feeling of agency" and in a compensatory enhancement of allo-centric priors, which might underlie hallucinations, delusions of control but also, under certain circumstances, the enhancement of "judgments of agency." We discuss the consequences of such a model, and potential courses of action that could lead to its falsification.

Self-Harming and Sense of Agency in Patients With Borderline Personality Disorder

Self-harm is considered a pervasive problem in several psychopathologies, and especially in Borderline Personality Disorder (BPD). Self-harming behaviors may be enacted for many purposes for example to regulate emotions and to reduce dissociation. BPD patients often report dissociative episodes, which may be related to an altered body awareness, and in particular to an altered awareness of the sense of agency. The sense of agency draws in part upon perceptions of being in control of our bodies and our physical movements, of being able to act upon environments. In this study, we aim to investigate whether dissociative experiences of BPD patients may be linked to an altered sense of agency and whether self-injurious actions may, through strong sensorial stimulation, constitute a coping strategy for the reduction of the distress associated with these dissociative experiences. A group of 20 BPD patients, of whom 9 presented self-harming behaviors, took part in the study and were compared with an age-matched control group of 20 healthy individuals. Sense of agency was evaluated through the Sensory Attenuation paradigm. In this paradigm, in a comparison with externally generated sensations, the degree to which perceived intensity of self-generated sensations is reduced is considered an implicit measure of sense of agency. As we expected, we found a significant difference in the perceptions of the two groups. The attenuation effect appeared to be absent in the BPD group while it was present in the control group. However, further analysis revealed that those BPD patients who engaged in self-harming behaviors presented a degree of attenuation which was similar to that of the control group. These results confirm the hypothesis that self-injurious actions constitute a coping strategy for increasing the sense of agency. We finally discuss the correlation of these experimental results with some clinical self-evaluation measures assessing dissociation, anxiety, depression, and affective dysregulation.

From Freedom From to Freedom To: New Perspectives on Intentional Action

There are few concepts as relevant as that of intentional action in shaping our sense of self and the interaction with the environment. At the same time, few concepts are so elusive. Indeed, both conceptual and neuroscientific accounts of intentional agency have proven to be problematic. On the one hand, most conceptual views struggle in defining how agents can adequately exert control over their actions. On the other hand, neuroscience settles for definitions by exclusion whereby key features of human intentional actions, including goal-directness, remain underspecified. This paper reviews the existing literature and sketches how this gap might be filled. In particular, we defend a gradualist notion of intentional behavior, which revolves around the following key features: autonomy, flexibility in the integration of causal vectors, and control.

Losing my hand. Body ownership attenuation after virtual lesion of the primary motor cortex

A fundamental component of the self-awareness is the sensation that we are acting with our own body. Thus, a coherent sense of self implies the existence of a tight link between the sense of body ownership and the motor system. Here, we investigated this issue by taking advantage of a well-known experimental manipulation of body ownership, i.e., the rubber hand illusion (RHI), during which the subjects perceive a fake hand as part of their own body. To test the effect of the motor system down-regulation on the RHI susceptibility, we designed a sham-controlled study, where the primary motor cortex (M1) excitability was modulated by off-line low-frequency repetitive transcranial magnetic stimulation (rTMS). After rTMS (real or sham), subjects underwent the RHI either on the right hand, contralateral to the inhibited hemisphere (Experiment 1), or on the left hand, ipsilateral to the inhibited hemisphere (Experiment 2). Only in Experiment 1, the procedure strengthened the illusory experience, as proved by a significant increase, in rTMS compared to Sham, of both subjective (Embodiment/Disembodiment Questionnaires) and objective (Proprioceptive Drift) RHI measures. This evidence demonstrates that, when the M1 activity is down-regulated, the sense of body ownership is attenuated and the subjects become more prone to incorporate an alien body part. This, in turn, supports the existence of a mutual interaction between the sense of body ownership and the motor system, shedding new light on the construction of a coherent sense of self as an acting body.

On the relation between body ownership and sense of agency: A link at the level of sensory-related signals

The relation between sense of body ownership and sense of agency is still highly debated. Here we investigated in a large sample of healthy participants the associations between several implicit and explicit indexes of the two senses. Specifically, we examined the correlations between proprioceptive shift (implicit measure) and questionnaire on the subjective experience of ownership (explicit measure) within the rubber hand illusion paradigm (body ownership), and intentional binding (implicit measure), attenuation of the intensity of auditory outcomes of actions (implicit measure) and questionnaire on the subjective experience of authorship (explicit measure) within the Libet's clock paradigm (sense of agency). Our results showed that proprioceptive shift was positively correlated with the attenuation of auditory outcomes. No significant correlations were found between the explicit measures of the two senses. We argue that the individual spatiotemporal constraints subserving the integration of sensory-related signals (implicit signature) would be common to both senses, whereas their subjective experience (explicit signature) would rely on additional processes specific for any given sense.

A Delusion of Control - What happens to a sense of Agency in Schizophrenic patients?

The sense of agency is known to be disrupted in Schizophrenia. This article explores the transition from the comparator model to the two-step model of agency, in order to review the paper ‘In and out of control: brain mechanisms linking fluency of action selection to self-agency in patients with Schizophrenia’1. A sense of agency involves using retrospective cues to make causal inferences, but this paper also introduces a new, prospective aspect. This paper shows that subliminal priming, a prospective cue, increases the reported sense of agency over a subsequent action outcome. It also shows that in schizophrenic patients, retrospective cues had more of an influence on their reported sense of agency, while conversely, prospective cues had less influence. This may reflect a greater reliance on retrospective cues in schizophrenia, which could be one of the underlying factors for some of the delusions seen in schizophrenia. Using fMRI measurements during the task, results suggest that angular gyrus activation reflects the experience of non-agency. In healthy controls, they saw altered connectivity between frontal areas and the angular gyrus associated with priming. In schizophrenic patients, there was no effect of priming on activation of the angular gyrus, or frontoparietal connectivity. In our review, we have introduced a putative schema that suggests that the action selection signals from the frontal lobes into the angular gyrus represent the prospective aspect of agency. This connection is disrupted In schizophrenia, and that may be why prospective agency is impaired.

Who Has Done It? Exploring Gaze Agency in Obsessive-Compulsive Checkers

The sense of agency (SoA) is a multifaceted construct, which can be defined as the ability to understand the causal relationships between our actions and sensory events. Obsessive-Compulsive Disorder (OCD) patients with checking compulsions often report a "lack of action completion" sensations, which has been conceptualized in the so-called "Not Just Right Experiences" construct. An intriguing explanation of this phenomenon comes from Belayachi and Van der Linden (2009, 2010), who suggest that OCD-checking patients are more prone to specify their action in a relatively molecular and inflexible way. Currently, there are no studies in literature which address this issue in OCD patients, except for the one of Gentsch et al. (2012), who suggested an altered SoA in these patients. Here we exploited a novel construct, gaze agency, to evaluate causal attribution capabilities in a group of 21 OCD patients (checkers) and matched healthy controls (HCs). Basically, two tasks targeted observers' capability to identify their own eye movements as the cause of concurrently presented beeps, which allowed us to measure agency sensitivity as well as subtle agency alterations in an ecological setting. We found a poorer performance in OCD patients as compared to HCs in many parameters of our tasks, suggesting a difficulty with causal attribution possibly due to both a reduced cognitive flexibility and a less functional gaze agency in OCD patients.

Dissociation between executed and imagined bimanual movements in autism spectrum conditions

Autism spectrum conditions (ASC) are characterized by social-communicative deficits and repetitive stereotyped behaviors. Altered motor coordination is also observed and a dysfunction of motor imagery has been recently reported on implicit tasks. However, no information on explicit motor imagery abilities is available in ASC. Here, we employed a spatial bimanual task to concurrently assess motor coordination and explicit motor imagery in autism. A secondary objective of the study was to evaluate these abilities across two populations of ASC, namely adolescents and adults with ASC. To this aim, we took advantage of the circles-lines task in which where participants were asked to continuously draw: right hand lines (unimanual condition); right hand lines and left hand circles (bimanual condition); right hand lines while imagining to draw left hand circles (imagery condition). For each participant, an Ovalization Index (OI) was calculated as a deviation of the right hand drawing trajectory from an absolute vertical axis. Results showed a significant and similar coupling effect in the bimanual condition (i.e., a significant increase of the OI values with respect to the unimanual condition) in both controls and ASC participants. On the contrary, in the imagery condition, a significant coupling effect was found only in controls. Furthermore, adult controls showed a significantly higher imagery coupling effect in comparison to all the other groups. These results demonstrate that atypical motor imagery processes in ASC are not limited to implicit tasks and suggest that development of neural structures involved in motor imagery are immature in ASC. Autism Res 2018, 11: 376-384. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

LAY SUMMARY

Autism spectrum conditions (ASC) are characterized by social-communicative and motor coordination difficulties but in many cases also by an impaired capability to imagine movements. In this study we found that while two handed coordination in ASC can be developed as well as in typically developed persons, the development of motor imagery could still be immature in ASC, leading to difficulties in imagining, understanding as well as programming and coordinating complex movements.

Altered awareness of action in Parkinson's disease: evaluations by explicit and implicit measures

Deficits in the integration of motor prediction and its feedback have been reported in Parkinson’s disease. Conscious awareness of action is proposed to emerge under the integration of motor prediction and its feedback. Thus, it may lead to changes in the awareness of the authorship of action (in other words, the sense of agency) in Parkinson’s disease. We have employed both explicit and implicit measures to assess the awareness of action in Parkinson’s disease and matched controls. As an explicit measure, an action recognition task requiring explicit judgments was used. Patients showed less attribution of their movements to non-biased and angular-biased visual feedbacks. As an implicit measure, the temporal attraction between the perceived time of actions and their effects, which is known as intentional binding task, was used. While action-effect association was observed in the control group, actions were not experienced as having shifted towards their subsequent effects in the patient group. These tendencies were consistent regardless of the side of the asymmetrical motor symptoms. These results may reflect an underlying abnormality in the awareness of voluntary action in Parkinson’s disease.

Drawn together: When motor representations ground joint actions

What enables individuals to act together? Recent discoveries suggest that a variety of mechanisms are involved. But something fundamental is yet to be investigated. In joint action, agents represent a collective goal, or so it is often assumed. But how, if at all, are collective goals represented in joint action and how do such representations impact performance? To investigate this question we adapted a bimanual paradigm, the circle-line drawing paradigm, to contrast two agents acting in parallel with two agents performing a joint action. Participants were required to draw lines or circles while observing circles or lines being drawn. The findings indicate that interpersonal motor coupling may occur in joint but not parallel action. This suggests that participants in joint actions can represent collective goals motorically.

Toward a Molecular Profile of Self-Representation

Feeling embodiment over our body or body part has a major role in the understanding of the self and control of self-actions. Even though it is crucial in our daily life, embodiment is not an homogenous phenotype across population, as quantified by implicit and explicit measures (i.e., neuroimaging or self-reports). Studies have shown differences in neuropathological conditions compared to healthy controls, but also across healthy individuals. We discuss examples of self-perception differences, and the molecular origin of embodiment, focusing on clinical cases, during the first and second section. We then discuss two important questions in this molecular-to-embodiment relationship: (i) which are the molecular levels (and their associated techniques) that can be relevant to embodiment, and (ii) which are the most adequate experiments to correlate molecular profiles and embodiment quantification across individuals. Potential answers for both questions will be outlined during the third and fourth sections, respectively, in order to design a framework to study the molecular profile of body embodiment.

Decreased motor cortex excitability mirrors own hand disembodiment during the rubber hand illusion

During the rubber hand illusion (RHI), subjects experience an artificial hand as part of their own body, while the real hand is subject to a sort of 'disembodiment'. Can this altered belief about the body also affect physiological mechanisms involved in body-ownership, such as motor control? Here we ask whether the excitability of the motor pathways to the real (disembodied) hand are affected by the illusion. Our results show that the amplitude of the motor-evoked potentials recorded from the real hand is significantly reduced, with respect to baseline, when subjects in the synchronous (but not in the asynchronous) condition experience the fake hand as their own. This finding contributes to the theoretical understanding of the relationship between body-ownership and motor system, and provides the first physiological evidence that a significant drop in motor excitability in M1 hand circuits accompanies the disembodiment of the real hand during the RHI experience.

DOI:http://dx.doi.org/10.7554/eLife.14972.001

The feeling of body ownership — that the various parts of your body are all part of you — is something that we typically take for granted. However, brain damage can disrupt this sensation and leave individuals convinced that an arm or a leg is no longer their own. Even in healthy people, the ‘rubber hand illusion’ can temporarily produce a similar phenomenon. Individuals watch a lifelike rubber hand being touched while their own hand – which is hidden from view – is touched at the same time. This creates the feeling that the artificial hand has become part of their body, while their real hand is left in a ‘disembodied’ state.

How does the brain generate this illusory sense of ownership and accompanying sense of disembodiment? A person’s ability to move their body is thought to contribute to their feeling of body ownership. Therefore, della Gatta, Garbarini et al. asked whether the brain’s ability to move the real hand changes during the rubber hand illusion.

In the experiments, the region of the brain that controls hand movement was artificially stimulated in a number of volunteers. When an individual had been primed by the rubber hand illusion to perceive a fake hand as part of their own body, their brain was temporarily less able to activate the muscles of their real hand. This is as if the brain no longer considered the real hand as part of the body. Thus, the altered sense of body ownership experienced during the rubber hand illusion is not a bizarre fantasy, but corresponds to a physiological reaction that accompanies changes in brain activity.

The next step is to further define and quantify the relationship between the sense of body ownership and the control of body movement. Specifically, how does activity in the brain areas that control movement contribute to the sense of body ownership? And how do these brain regions communicate with one another to generate a sense of self?

DOI:http://dx.doi.org/10.7554/eLife.14972.002

Anomalous bodily experiences and perceived social isolation in schizophrenia: An extension of the Social Deafferentation Hypothesis

BACKGROUND

Disturbances of the bodily self are fundamental to the phenomenological experience of individuals with schizophrenia, a population at risk for social isolation. Both proprioception and exteroception contribute to a sense of consistent body boundary that contains the self across time and space, and this process is influenced by self-other (social) interactions. However, the relationship between social isolation, exteroception, and in-the-moment changes in body representation has not been elucidated. We investigated susceptibility to anomalous bodily experiences with a phantom nose induction procedure that elicits a sensation that one's nose is changing (Pinocchio Illusion: PI) in relation to exteroceptive awareness and social isolation.

METHODS

25 individuals with schizophrenia (SZ) and 15 matched controls (CO) participated in a PI induction procedure to quantify susceptibility to bodily aberrations and a tactile discrimination task to assess exteroception. Clinical symptoms in SZ and schizotypy in CO were assessed, in addition to a self-report measure of perceived social isolation.

RESULTS

Compared to CO, SZ showed increased PI and impaired tactile discriminability. SZ reported greater loneliness than CO. PI scores were correlated with increased loneliness and decreased tactile discriminability.

CONCLUSIONS

Greater susceptibility to anomalous bodily experiences, together with reduced exteroceptive awareness and increased loneliness, is compatible with the framework of Hoffman's Social Deafferentation Hypothesis, which posits that a functional "amputation" from one's social environment could lead to a reorganization of the social brain network, resulting in hallucinations and delusions. These findings underscore the importance of the relationship between social isolation and self-disturbances in schizophrenia.

Bodily Experience in Schizophrenia: Factors Underlying a Disturbed Sense of Body Ownership

Emerging evidence is now challenging the view that patients diagnosed with schizophrenia experience a selective deficit in their sense of agency. Additional disturbances seem to exist in their sense of body ownership. However, the factors underlying this disturbance in body ownership remain elusive. Knowledge of these factors, and increased understanding of how body ownership is related to other abnormalities seen in schizophrenia, could ultimately advance development of new treatments. Research on body ownership in schizophrenia has mainly been investigated with the rubber hand illusion (RHI). Schizophrenia patients show higher susceptibility to the RHI, which may be explained by a stronger reliance on multisensory information over weaker stored body representations. This review shows that a coherent sense of body ownership arises from the integration of both bottom-up sensory processes and higher order, top-down bodily- and perceptual representations. Multisensory integration, temporal binding, anticipation, intention and efferent signals all partly modulate the complex experience of body ownership. Specifically, we propose that patients with schizophrenia have weaker stored body representations, and rely to a greater extent on external stimuli, such as visual information, due to imprecise or highly variable internal predictions. Moreover, the reduced sense of agency in schizophrenia may additionally contribute to the disturbed sense of body ownership, as evidence from healthy participants suggests that agency and body ownership are interrelated. Vice versa, a reduced sense of body ownership may also contribute to a reduced sense of agency. Future studies should explicitly target the precise relationship between the two in schizophrenia.