Rôle du sens de l’effort dans le syndrome d’influence

Centrally generated signals from premotor areas play a key role in voluntary muscle force perception. Indeed, sensations of effort, rather than sensations of intramuscular tension, make it possible to evaluate the intensity of willed muscle forces. We suggest that the sense of effort is involved in agency, the cognitive process by which one is aware of one’s actions. We argue that effort awareness accompanies each action and is the key component of the feeling of will. In delusions of alien control, patients with schizophrenia do not recognize some of their acts as their own and are convinced that they are under the control of someone else. Some experimental data suggest that delusions of control are related to an altered awareness of effort and an exaggerated awareness of afferent neural information, caused by neurological disorders in the frontal and parietal lobes. This impairment could lead to the inability to identify the author of an action. In this pathological condition, the cerebral state coding for “I intend to act” might move toward the state coding for “someone else intends to act”, even in the absence of another agent.     

Disorders of agency in schizophrenia correlate with an inability to compensate for the sensory consequences of actions

Psychopathological symptoms in schizophrenia patients suggest that the concept of self might be disturbed in these individuals [1]. Delusions of influence make them feel that someone else is guiding their actions, and certain kinds of their hallucinations seem to be misinterpretations of their own inner voice as an external voice, the common denominator being that self-produced information is perceived as if coming from outside. If this interpretation were correct, we might expect that schizophrenia patients might also attribute the sensory consequences of their own eye movements to the environment rather than to themselves, challenging the percept of a stable world. Indeed, this seems to be the case because we found a clear correlation between the strength of delusions of influence and the ability of schizophrenia patients to cancel out such self-induced retinal information in motion perception. This correlation reflects direct experimental evidence supporting the view that delusions of influence in schizophrenia might be due to a specific deficit in the perceptual compensation of the sensory consequences of one's own actions [1, 2, 3, 4, 5 and 6].     

Altered processing of sensorimotor feedback in schizophrenia

Schizophrenia is characterized by an altered sense of the reality, associated with hallucinations and delusions. Some theories suggest that schizophrenia is related to a deficiency of the system that generates information about the sensory consequences of the actions realized by the subject. This system monitors the reafferent information resulting from an action and allows its anticipation. In the present study, we examined visual-event-related potentials (ERPs) generated by a sensorimotor task in 15 patients with schizophrenia and 15 normal controls. The visual feedback from hand movements performed by the subjects was experimentally distorted. Behavioral results showed that patients were impaired in recognizing their own movements. The ERP signal in patients also differed from those of control subjects. In patients, the ERP waveform was affected during the early part of the response (200 ms). This early effect in schizophrenic patients reveals a modified processing of the visual consequence of their actions.     

Alien hand syndrome: neural correlates of movements without conscious will

Background

The alien hand syndrome is a striking phenomenon characterized by purposeful and autonomous movements that are not voluntarily initiated. This study aimed to examine neural correlates of this rare neurological disorder in a patient with corticobasal degeneration and alien hand syndrome of the left hand.

Methodology/Principal Findings

We employed functional magnetic resonance imaging to investigate brain responses associated with unwanted movements in a case study. Results revealed that alien hand movements involved a network of brain activations including the primary motor cortex, premotor cortex, precuneus, and right inferior frontal gyrus. Conscious and voluntary movements of the alien hand elicited a similar network of brain responses but lacked an activation of the inferior frontal gyrus. The results demonstrate that alien and unwanted movements may engage similar brain networks than voluntary movements, but also imply different functional contributions of prefrontal areas. Since the inferior frontal gyrus was uniquely activated during alien movements, the results provide further support for a specific role of this brain region in inhibitory control over involuntary motor responses.

Conclusions/Significance

We discuss the outcome of this study as providing evidence for a distributed neural network associated with unwanted movements in alien hand syndrome, including brain regions known to be related to movement execution and planning as well as areas that have been linked to inhibition control (inferior frontal gyrus) and experience of agency (precuneus).     

Abnormalities in the awareness and control of action

Much of the functioning of the motor system occurs without awareness. Nevertheless, we are aware of some aspects of the current state of the system and we can prepare and make movements in the imagination. These mental representations of the actual and possible states of the system are based on two sources: sensory signals from skin and muscles, and the stream of motor commands that have been issued to the system. Damage to the neural substrates of the motor system can lead to abnormalities in the awareness of action as well as defects in the control of action. We provide a framework for understanding how these various abnormalities of awareness can arise. Patients with phantom limbs or with anosognosia experience the illusion that they can move their limbs. We suggest that these representations of movement are based on streams of motor commands rather than sensory signals. Patients with utilization behaviour or with delusions of control can no longer properly link their intentions to their actions. In these cases the impairment lies in the representation of intended movements. The location of the neural damage associated with these disorders suggests that representations of the current and predicted state of the motor system are in parietal cortex, while representations of intended actions are found in prefrontal and premotor cortex.     

Using Hypnotic Suggestion to Model Loss of Control and Awareness of Movements: An Exploratory fMRI Study

The feeling of voluntary control and awareness of movement is fundamental to our notions of selfhood and responsibility for actions, yet can be lost in neuropsychiatric syndromes (e.g. delusions of control, non-epileptic seizures) and culturally influenced dissociative states (e.g. attributions of spirit possession). The brain processes involved remain poorly understood. We used suggestion and functional magnetic resonance imaging (fMRI) to investigate loss of control and awareness of right hand movements in 15 highly hypnotically suggestible subjects. Loss of perceived control of movements was associated with reduced connectivity between supplementary motor area (SMA) and motor regions. Reduced awareness of involuntary movements was associated with less activation in parietal cortices (BA 7, BA 40) and insula. Collectively these results suggest that the sense of voluntary control of movement may critically depend on the functional coupling of SMA with motor systems, and provide a potential neural basis for the narrowing of awareness reported in pathological and culturally influenced dissociative phenomena.     

Visual Feedback Dominates the Sense of Agency for Brain-Machine Actions

Recent advances in neuroscience and engineering have led to the development of technologies that permit the control of external devices through real-time decoding of brain activity (brain-machine interfaces; BMI). Though the feeling of controlling bodily movements (sense of agency; SOA) has been well studied and a number of well-defined sensorimotor and cognitive mechanisms have been put forth, very little is known about the SOA for BMI-actions. Using an on-line BMI, and verifying that our subjects achieved a reasonable level of control, we sought to describe the SOA for BMI-mediated actions. Our results demonstrate that discrepancies between decoded neural activity and its resultant real-time sensory feedback are associated with a decrease in the SOA, similar to SOA mechanisms proposed for bodily actions. However, if the feedback discrepancy serves to correct a poorly controlled BMI-action, then the SOA can be high and can increase with increasing discrepancy, demonstrating the dominance of visual feedback on the SOA. Taken together, our results suggest that bodily and BMI-actions rely on common mechanisms of sensorimotor integration for agency judgments, but that visual feedback dominates the SOA in the absence of overt bodily movements or proprioceptive feedback, however erroneous the visual feedback may be.     

When Passive Feels Active - Delusion-Proneness Alters Self-Recognition in the Moving Rubber Hand Illusion

Psychotic patients have problems with bodily self-recognition such as the experience of self-produced actions (sense of agency) and the perception of the body as their own (sense of ownership). While it has been shown that such impairments in psychotic patients can be explained by hypersalient processing of external sensory input it has also been suggested that they lack normal efference copy in voluntary action. However, it is not known how problems with motor predictions like efference copy contribute to impaired sense of agency and ownership in psychosis or psychosis-related states. We used a rubber hand illusion based on finger movements and measured sense of agency and ownership to compute a bodily self-recognition score in delusion-proneness (indexed by Peters’ Delusion Inventory - PDI). A group of healthy subjects (n=71) experienced active movements (involving motor predictions) or passive movements (lacking motor predictions). We observed a highly significant correlation between delusion-proneness and self-recognition in the passive conditions, while no such effect was observed in the active conditions. This was seen for both ownership and agency scores. The result suggests that delusion-proneness is associated with hypersalient external input in passive conditions, resulting in an abnormal experience of the illusion. We hypothesize that this effect is not present in the active condition because deficient motor predictions counteract hypersalience in psychosis proneness.     

Arcuate fasciculus abnormalities and their relationship with psychotic symptoms in schizophrenia

Disruption of fronto-temporal connections involving the arcuate fasciculus (AF) may underlie language processing anomalies and psychotic features such as auditory hallucinations in schizophrenia. No study to date has specifically investigated abnormalities of white matter integrity at particular loci along the AF as well as its regional lateralization in schizophrenia. We examined white matter changes (fractional anisotropy (FA), axial diffusivity (AD), asymmetry indices) along the whole extent of the AF and their relationship with psychotic symptoms in 32 males with schizophrenia and 44 healthy males. Large deformation diffeomorphic metric mapping and Fiber Assignment Continuous Tracking were employed to characterize FA and AD along the geometric curve of the AF. Our results showed that patients with schizophrenia had lower FA in the frontal aspects of the left AF compared with healthy controls. Greater left FA and AD lateralization in the temporal segment of AF were associated with more severe positive psychotic symptoms such as delusions and hallucinations in patients with schizophrenia. Disruption of white matter integrity of the left frontal AF and accentuation of normal left greater than right asymmetry of FA/AD in the temporal AF further support the notion of aberrant fronto-temporal connectivity in schizophrenia. AF pathology can affect corollary discharge of neural signals from frontal speech/motor initiation areas to suppress activity of auditory cortex that may influence psychotic phenomena such as auditory hallucinations and facilitate elaboration of delusional content.     

Dominance of Objects over Context in a Mediotemporal Lobe Model of Schizophrenia

Background

A large body of evidence suggests impaired context processing in schizophrenia. Here we propose that this impairment arises from defective integration of mediotemporal ‘what’ and ‘where’ routes, carrying object and spatial information to the hippocampus.

Methodology and Findings

We have previously shown, in a mediotemporal lobe (MTL) model, that the abnormal connectivity between MTL regions observed in schizophrenia can explain the episodic memory deficits associated with the disorder. Here we show that the same neuropathology leads to several context processing deficits observed in patients with schizophrenia: 1) failure to choose subordinate stimuli over dominant ones when the former fit the context, 2) decreased contextual constraints in memory retrieval, as reflected in increased false alarm rates and 3) impaired retrieval of contextual information in source monitoring. Model analyses show that these deficits occur because the ‘schizophrenic MTL’ forms fragmented episodic representations, in which objects are overrepresented at the expense of spatial contextual information.

Conclusions and Significance

These findings highlight the importance of MTL neuropathology in schizophrenia, demonstrating that it may underlie a broad spectrum of deficits, including context processing and memory impairments. It is argued that these processing deficits may contribute to central schizophrenia symptoms such as contextually inappropriate behavior, associative abnormalities, conversational drift, concreteness and delusions.     

It’s Not My Fault: Postdictive Modulation of Intentional Binding by Monetary Gains and Losses

Sense of agency refers to the feeling that one’s voluntary actions caused external events. Past studies have shown that compression of the subjective temporal interval between actions and external events, called intentional binding, is closely linked to the experience of agency. Current theories postulate that the experience of agency is constructed via predictive and postdictive pathways. One remaining problem is the source of human causality bias; people often make misjudgments on the causality of voluntary actions and external events depending on their rewarding or punishing outcomes. Although human causality bias implies that sense of agency can be modified by post-action information, convincing empirical findings for this issue are lacking. Here, we hypothesized that sense of agency would be modified by affective valences of action outcomes. To examine this issue, we investigated how rewarding and punishing outcomes following voluntary action modulate behavioral measures of agency using intentional binding paradigm and classical conditioning procedures. In the acquisition phase, auditory stimuli were paired with positive, neutral or negative monetary outcomes. Tone-reward associations were evaluated using reaction times and preference ratings. In the experimental session, participants performed a variant of intentional binding task, where participants made timing judgments for onsets of actions and sensory outcomes while playing simple slot games. Our results showed that temporal binding was modified by affective valences of action outcomes. Specifically, intentional binding was attenuated when negative outcome occurred, consistent with self-serving bias. Our study not only provides evidence for postdictive modification of agency, but also proposes a possible mechanism of human causality bias.     

The Sense of Agency during Continuous Action: Performance Is More Important than Action-Feedback Association

The sense of agency refers to the feeling that one is controlling events through one’s own behavior. This study examined how task performance and the delay of events influence one’s sense of agency during continuous action accompanied by a goal. The participants were instructed to direct a moving dot into a square as quickly as possible by pressing the left and right keys on a keyboard to control the direction in which the dot traveled. The interval between the key press and response of the dot (i.e., direction change) was manipulated to vary task difficulty. Moreover, in the assisted condition, the computer ignored participants’ erroneous commands, resulting in improved task performance but a weaker association between the participants’ commands and actual movements of the dot relative to the condition in which all of the participants’ commands were executed (i.e., self-control condition). The results showed that participants’ sense of agency increased with better performance in the assisted condition relative to the self-control condition, even though a large proportion of their commands were not executed. We concluded that, when the action-feedback association was uncertain, cognitive inference was more dominant relative to the process of comparing predicted and perceived information in the judgment of agency.     

Interplay of Agency and Ownership: The Intentional Binding and Rubber Hand Illusion Paradigm Combined

The sense of agency (SoA) refers to the phenomenal experience of initiating and controlling an action, whereas the sense of ownership (SoO) describes the feeling of myness an agent experiences towards his or her own body parts. SoA has been investigated with intentional binding paradigms, and the sense of ownership (SoO) with the rubber-hand illusion (RHI). We investigated the relationship between SoA and SoO by incorporating intentional binding into the RHI. Explicit and implicit measures of agency (SoA-questionnaire, intentional binding) and ownership (SoO-questionnaire, proprioceptive drift) were used. Artificial hand position (congruent/incongruent) and mode of agent (self-agent/other-agent) were systematically varied. Reported SoO varied mainly with position (higher in congruent conditions), but also with agent (higher in self-agent conditions). Reported SoA was modulated by agent (higher in self-agent conditions), and moderately by position (higher in congruent conditions). Implicit and explicit agency measures were not significantly correlated. Finally, intentional binding tended to be stronger in self-generated than observed voluntary actions. Results provide further evidence for a partial double dissociation between SoA and SoO, empirically distinct agency levels, and moderate intentional binding differences between self-generated and observed voluntary actions.     

Other faces in the mirror: a perspective on schizophrenia

A patient with schizophrenia may generate an action (whether manual or verbal), but not attribute the generation of that action to himself. We distinguish self-monitoring and attribution of agency, relating only the former to forward models and the mirror system. We suggest that alien hand experiences occur when an action progresses through hand control pathways with no record of disinhibition having been kept and is then seen but dismissed as external. Analogously, auditory pathways are active during verbal hallucinations and produce a subvocal verbal process, but since no record is kept of the words being created, they are treated as external. The subject then proceeds to confabulate, to provide an account for the agency.     

Neural Substrates for Judgment of Self-Agency in Ambiguous Situations

The sense of agency is the attribution of oneself as the cause of one’s own actions and their effects. Accurate agency judgments are essential for adaptive behaviors in dynamic environments, especially in conditions of uncertainty. However, it is unclear how agency judgments are made in ambiguous situations where self-agency and non-self-agency are both possible. Agency attribution is thus thought to require higher-order neurocognitive processes that integrate several possibilities. Furthermore, neural activity specific to self-attribution, as compared with non-self-attribution, may reflect higher-order critical operations that contribute to constructions of self-consciousness. Based on these assumptions, the present study focused on agency judgments under ambiguous conditions and examined the neural correlates of this operation with functional magnetic resonance imaging. Participants performed a simple but demanding agency-judgment task, which required them to report on whether they attributed their own action as the cause of a visual stimulus change. The temporal discrepancy between the participant’s action and the visual events was adaptively set to be maximally ambiguous for each individual on a trial-by-trial basis. Comparison with results for a control condition revealed that the judgment of agency was associated with activity in lateral temporo-parietal areas, medial frontal areas, the dorsolateral prefrontal area, and frontal operculum/insula regions. However, most of these areas did not differentiate between self- and non-self-attribution. Instead, self-attribution was associated with activity in posterior midline areas, including the precuneus and posterior cingulate cortex. These results suggest that deliberate self-attribution of an external event is principally associated with activity in posterior midline structures, which is imperative for self-consciousness.     

Sampling inspection to prevent the invasion of alien pests: statistical theory of import plant quarantine systems in Japan

The establishment of appropriate import quarantine systems is the best known method for preventing the unintentional introduction of invasive alien pests. However, quarantine systems are sometimes judged as non-tariff barriers against trade by the World Trade Organization. The construction of a common scientific theory for quarantine systems is thus extremely important to prevent invasion without causing international conflict. We explain several statistical theories that have been adopted in import plant quarantine systems in Japan. Quarantine systems include three major components: (1) import sampling inspection, (2) early detection procedures, and (3) emergency control. We first explain the principle of risk management that was commonly adopted in these components. Then, we explain the method for calculating the required sample size in the import sampling inspection. We then explain hierarchical sampling inspection for detecting alien pests inside Japan. We further explain the theory for declaring the eradication of invasive alien pests as an emergency control. Actual examples of quarantine actions against the invasion of plum pox virus disease and citrus huanglongbing are discussed.     

Responsibility and the sense of agency enhance empathy for pain

Being held responsible for our actions strongly determines our moral judgements and decisions. This study examined whether responsibility also influences our affective reaction to others'' emotions. We conducted two experiments in order to assess the effect of responsibility and of a sense of agency (the conscious feeling of controlling an action) on the empathic response to pain. In both experiments, participants were presented with video clips showing an actor''s facial expression of pain of varying intensity. The empathic response was assessed with behavioural (pain intensity estimation from facial expressions and unpleasantness for the observer ratings) and electrophysiological measures (facial electromyography). Experiment 1 showed enhanced empathic response (increased unpleasantness for the observer and facial electromyography responses) as participants'' degree of responsibility for the actor''s pain increased. This effect was mainly accounted for by the decisional component of responsibility (compared with the execution component). In addition, experiment 2 found that participants'' unpleasantness rating also increased when they had a sense of agency over the pain, while controlling for decision and execution processes. The findings suggest that increased empathy induced by responsibility and a sense of agency may play a role in regulating our moral conduct.     

Whodunnit? Electrophysiological Correlates of Agency Judgements

Sense of agency refers to the feeling that "I" am responsible for those external events that are directly produced by one's own voluntary actions. Recent theories distinguish between a non-conceptual "feeling" of agency linked to changes in the processing of self-generated sensory events, and a higher-order judgement of agency, which attributes sensory events to the self. In the current study we explore the neural correlates of the judgement of agency by means of electrophysiology. We measured event-related potentials to tones that were either perceived or not perceived as triggered by participants' voluntary actions and related these potentials to later judgements of agency over the tones. Replicating earlier findings on predictive sensory attenuation, we found that the N1 component was attenuated for congruent tones that corresponded to the learned action-effect mapping as opposed to incongruent tones that did not correspond to the previously acquired associations between actions and tones. The P3a component, but not the N1, directly reflected the judgement of agency: deflections in this component were greater for tones judged as self-generated than for tones judged as externally produced. The fact that the outcome of the later agency judgement was predictable based on the P3a component demonstrates that agency judgements incorporate early information processing components and are not purely reconstructive, post-hoc evaluations generated at time of judgement.     

Disturbances in body ownership in schizophrenia: evidence from the rubber hand illusion and case study of a spontaneous out-of-body experience

Background

A weakened sense of self may contribute to psychotic experiences. Body ownership, one component of self-awareness, can be studied with the rubber hand illusion (RHI). Watching a rubber hand being stroked while one''s unseen hand is stroked synchronously can lead to a sense of ownership over the rubber hand, a shift in perceived position of the real hand, and a limb-specific drop in stimulated hand temperature. We aimed to assess the RHI in schizophrenia using quantifiable measures: proprioceptive drift and stimulation-dependent changes in hand temperature.

Methods

The RHI was elicited in 24 schizophrenia patients and 21 matched controls by placing their unseen hand adjacent to a visible rubber hand and brushing real and rubber hands synchronously or asynchronously. Perceived finger location was measured before and after stimulation. Hand temperature was taken before and during stimulation. Subjective strength of the illusion was assessed by a questionnaire.

Results

Across groups, the RHI was stronger during synchronous stimulation, indicated by self-report and proprioceptive drift. Patients reported a stronger RHI than controls. Self-reported strength of RHI was associated with schizotypy in controls Proprioceptive drift was larger in patients, but only following synchronous stimulation. Further, we observed stimulation-dependent changes in skin temperature. During right hand stimulation, temperature dropped in the stimulated hand and rose in the unstimulated hand. Interestingly, induction of RHI led to an out-of-body experience in one patient, linking body disownership and psychotic experiences.

Conclusions

The RHI is quantitatively and qualitatively stronger in schizophrenia. These findings suggest that patients have a more flexible body representation and weakened sense of self, and potentially indicate abnormalities in temporo-parietal networks implicated in body ownership. Further, results suggest that these body ownership disturbances might be at the heart of a subset of the pathognomonic delusions of passivity.