Altered awareness of action in schizophrenia: a specific deficit in predicting action consequences

Looking forward: an impaired ability in patients with schizophrenia?

When two visual stimuli occur within 8 to 17 ms of one another, subjects cannot tell they are asynchronous, yet recent results show they are not processed as simultaneous. Two spatially separate squares were presented at an interval ranging from 0 to 92 ms and remained on the screen until subjects responded. Subjects pressed a right or left response key according to the judged simultaneity/asynchrony of the stimuli. We evaluated the Simon effect, i.e., the tendency to press the key on the same side as the stimulus. We found an effect even when the squares were displayed on opposite sides of the screen, with their onsets separated by less than 20 ms. Controls were biased towards the last stimulus, whereas patients with schizophrenia were biased towards the first. We investigate here whether the results are related to spatial or temporal processing. Using the same paradigm, we explored the impact of spatial grouping by comparing connected vs. unconnected stimuli and manipulating the predictability of the second stimulus location. We tested different groups of mildly symptomatic patients and matched controls in two studies. Under 20 ms, when stimuli were connected and the 2nd square location was predictable, patients tended to press the key to the side of the 1st square, whereas controls displayed the opposite tendency. The results suggest that controls put more emphasis on the last occurring event, but not patients with schizophrenia. This impairment is observed when spatial difficulties are removed, suggesting it is related to time rather than space.

Time, action and psychosis: using subjective time to investigate the effects of ketamine on sense of agency

Sense of agency refers to the experience of initiating and controlling actions in order to influence events in the outside world. A disturbed sense of agency is found in certain psychiatric and neurological disorders, most notably schizophrenia. Sense of agency is associated with a subjective compression of time: actions and their outcomes are perceived as bound together in time. This is known as 'intentional binding' and, in healthy adults, depends partly on advance prediction of action outcomes. Notably, this predictive contribution is disrupted in patients with schizophrenia. In the present study we aimed to characterise the psychotomimetic effect of ketamine, a drug model for psychosis, on the predictive contribution to intentional binding. It was shown that ketamine produced a disruption that closely resembled previous data from patients in the early, prodromal, stage of schizophrenic illness. These results are discussed in terms of established models of delusion formation in schizophrenia. The link between time and agency, more generally, is also considered.

Aberrant sense of agency in patients with schizophrenia: forward and backward over-attribution of temporal causality during intentional action

Self-disturbances in schizophrenia have been explained and studied from the standpoint of an abnormal sense of agency. We devised an agency-attribution task that evaluated explicit experiences of the temporal causal relations between an intentional action and an external event, without any confounding from sense of ownership of body movement. In each trial, a square piece appeared on the bottom of a computer screen and moved upward. Subjects were instructed to press a key when they heard a beep. When the key was pressed, the piece jumped with various temporal biases. Subjects were instructed to make an agency judgment for each trial. We demonstrated that an excessive sense of agency was observed in patients with schizophrenia compared with normal controls. Moreover, patient groups had a greater tendency to feel a sense of agency even when external events were programmed to precede their action. Therefore, patients felt both forward and backward exaggerated causal efficacy in the temporal event sequence during the intentional action. Confusion in the experience of temporal causal relations between the self and the external world may underlie self-disturbances in schizophrenia.

New frontiers in the neuroscience of the sense of agency

The sense that I am the author of my own actions, including the ability to distinguish my own from other people's actions, is a fundamental building block of our sense of self, on the one hand, and successful social interactions, on the other. Using cognitive neuroscience techniques, researchers have attempted to elucidate the functional basis of this intriguing phenomenon, also trying to explain pathological abnormalities of action awareness in certain psychiatric and neurological disturbances. Recent conceptual, technological, and methodological advances suggest several interesting and necessary new leads for future research on the neuroscience of agency. Here I will describe new frontiers for the field such as the need for novel and multifactorial paradigms, anatomically plausible network models for the sense of agency, investigations of the temporal dynamics during agentic processing and ecologically valid virtual reality (VR) applications.

Investigating social gaze as an action-perception online performance

Gaze represents a major non-verbal communication channel in social interactions. In this respect, when facing another person, one's gaze should not be examined as a purely perceptive process but also as an action-perception online performance. However, little is known about processes involved in the real-time self-regulation of social gaze. The present study investigates the impact of a gaze-contingent viewing window on fixation patterns and the awareness of being the agent moving the window. In face-to-face scenarios played by a virtual human character, the task for the 18 adult participants was to interpret an equivocal sentence which could be disambiguated by examining the emotional expressions of the character speaking. The virtual character was embedded in naturalistic backgrounds to enhance realism. Eye-tracking data showed that the viewing window induced changes in gaze behavior, notably longer visual fixations. Notwithstanding, only half of the participants ascribed the window displacements to their eye movements. These participants also spent more time looking at the eyes and mouth regions of the virtual human character. The outcomes of the study highlight the dissociation between non-volitional gaze adaptation and the self-ascription of agency. Such dissociation provides support for a two-step account of the sense of agency composed of pre-noetic monitoring mechanisms and reflexive processes, linked by bottom-up and top-down processes. We comment upon these results, which illustrate the relevance of our method for studying online social cognition, in particular concerning autism spectrum disorders (ASD) where the poor pragmatic understanding of oral speech is considered linked to visual peculiarities that impede facial exploration.

Moving a Rubber Hand that Feels Like Your Own: A Dissociation of Ownership and Agency

During voluntary hand movement, we sense that we generate the movement and that the hand is a part of our body. These feelings of control over bodily actions, or the sense of agency, and the ownership of body parts are two fundamental aspects of the way we consciously experience our bodies. However, little is known about how these processes are functionally linked. Here, we introduce a version of the rubber hand illusion in which participants control the movements of the index finger of a model hand, which is in full view, by moving their own right index finger. We demonstrated that voluntary finger movements elicit a robust illusion of owning the rubber hand and that the senses of ownership and agency over the model hand can be dissociated. We systematically varied the relative timing of the finger movements (synchronous versus asynchronous), the mode of movement (active versus passive), and the position of the model hand (anatomically congruent versus incongruent positions). Importantly, asynchrony eliminated both ownership and agency, passive movements abolished the sense of agency but left ownership intact, and incongruent positioning of the model hand diminished ownership but did not eliminate agency. These findings provide evidence for a double dissociation of ownership and agency, suggesting that they represent distinct cognitive processes. Interestingly, we also noted that the sense of agency was stronger when the hand was perceived to be a part of the body, and only in this condition did we observe a significant correlation between the subjects' ratings of agency and ownership. We discuss this in the context of possible differences between agency over owned body parts and agency over actions that involve interactions with external objects. In summary, the results obtained in this study using a simple moving rubber hand illusion paradigm extend previous findings on the experience of ownership and agency and shed new light on their relationship.

The effect of dopamine agonists on adaptive and aberrant salience in Parkinson's disease

Clinical evidence suggests that after initiation of dopaminergic medications some patients with Parkinson's disease (PD) develop psychotic symptoms, such as hallucinations and delusions. Here, we tested the hypothesis that the neurocognitive basis of this phenomenon can be defined as the formation of arbitrary and illusory associations between conditioned stimuli and reward signals, called aberrant salience. Young, never-medicated PD patients and matched controls were assessed on a speeded reaction time task in which the probe stimulus was preceded by conditioned stimuli that could signal monetary reward by color or shape. The patients and controls were re-evaluated after 12 weeks during which the patients received a dopamine agonist (pramipexole or ropinirole). Results indicated that dopamine agonists increased both adaptive and aberrant salience in PD patients, that is, formation of real and illusory associations between conditioned stimuli and reward, respectively. This effect was present when associations were assessed by means of faster responding after conditioned stimuli signaling reward (implicit salience) and overt rating of stimulus-reward links (explicit salience). However, unusual feelings and experiences, which are subclinical manifestations of psychotic-like symptoms, were specifically related to irrelevant and illusory stimulus-reward associations (aberrant salience) in PD patients receiving dopamine agonists. The learning of relevant and real stimulus-reward associations (adaptive salience) was not related to unusual experiences. These results suggest that dopamine agonists may increase psychotic-like experiences in young patients with PD, possibly by facilitating dopaminergic transmission in the ventral striatum, which results in aberrant associations between conditioned stimuli and reward.

Out of touch with reality? Social perception in first-episode schizophrenia

Social dysfunction has been recognized as an elementary feature of schizophrenia, but it remains a crucial issue whether social deficits in schizophrenia concern the inter-subjective domain or primarily have their roots in disturbances of self-experience. Social perception comprises vicarious processes grounding an experiential inter-relationship with others as well as self-regulation processes allowing to maintain a coherent sense of self. The present study investigated whether the functional neural basis underlying these processes is altered in first-episode schizophrenia (FES). Twenty-four FES patients and 22 healthy control participants underwent functional magnetic resonance imaging during a social perception task requiring them to watch videos depicting other individuals' inanimate and animate/social tactile stimulations, and a tactile localizer condition. Activation in ventral premotor cortex for observed bodily tactile stimulations was reduced in the FES group and negatively correlated with self-experience disturbances. Moreover, FES patients showed aberrant differential activation in posterior insula for first-person tactile experiences and observed affective tactile stimulations. These findings suggest that social perception in FES at a pre-reflective level is characterized by disturbances of self-experience, including impaired multisensory representations and self-other distinction. However, the results also show that social perception in FES involves more complex alterations of neural activation at multiple processing levels.

An interoceptive predictive coding model of conscious presence

We describe a theoretical model of the neurocognitive mechanisms underlying conscious presence and its disturbances. The model is based on interoceptive prediction error and is informed by predictive models of agency, general models of hierarchical predictive coding and dopaminergic signaling in cortex, the role of the anterior insular cortex (AIC) in interoception and emotion, and cognitive neuroscience evidence from studies of virtual reality and of psychiatric disorders of presence, specifically depersonalization/derealization disorder. The model associates presence with successful suppression by top-down predictions of informative interoceptive signals evoked by autonomic control signals and, indirectly, by visceral responses to afferent sensory signals. The model connects presence to agency by allowing that predicted interoceptive signals will depend on whether afferent sensory signals are determined, by a parallel predictive-coding mechanism, to be self-generated or externally caused. Anatomically, we identify the AIC as the likely locus of key neural comparator mechanisms. Our model integrates a broad range of previously disparate evidence, makes predictions for conjoint manipulations of agency and presence, offers a new view of emotion as interoceptive inference, and represents a step toward a mechanistic account of a fundamental phenomenological property of consciousness.

Ketamine perturbs perception of the flow of time in healthy volunteers

RATIONALE

Disturbances in the subjective experience of time have been observed both in schizophrenia and following acute administration of ketamine. However, effects of ketamine on more objective timing tasks have not yet been measured in humans, nor has it been established that timing effects are not merely secondary to a more general dysfunction in working memory (WM).

OBJECTIVE AND METHODS

In a double-blind placebo-controlled crossover study, we characterised the effects of ketamine (100 ng/ml blood plasma level) on performance of perceptual timing and colour discrimination tasks, which were matched for WM and attentional demands. To test the ubiquity of ketamine's effects on timing, we also examined two distinct measures of temporal predictability.

RESULTS

Ketamine significantly distorted the subjective experience of time as measured by the Clinician-Administered Dissociative States Scales. Critically, ketamine also impaired accuracy on the perceptual timing task while having no effect on performance of the colour perception task. Although ketamine did not impair the ability to use prelearned temporal (or spatial) cues to predict target onset (or location), it did slow reaction times at long delays following non-informative neutral cues, suggesting an impaired ability to use the unidirectional flow of time itself to make temporal predictions.

CONCLUSIONS

Ketamine induced selective impairments in timing, which could not be explained by more fundamental effects on the ability to hold information in WM. Rather our collected findings suggest that ketamine may disturb timing by selectively impairing the way in which information is temporally manipulated within WM.

When moving without volition: implied self-causation enhances binding strength between involuntary actions and effects

The conscious awareness of voluntary action is associated with systematic changes in time perception: The interval between actions and outcomes is experienced as compressed in time. Although this temporal binding is thought to result from voluntary movement and provides a window to the sense of agency, recent studies challenge this idea by demonstrating binding in involuntary movement. We offer a potential account for these findings by proposing that binding between involuntary actions and effects can occur when self-causation is implied. Participants made temporal judgements concerning a key press and a tone, while they learned to consider themselves as the cause of the effect or not. Results showed that implied self-causation (vs. no implied self-causation) increased temporal binding. Since intrinsic motor cues of movement were absent, these results suggest that sensory evidence about the key press caused binding in retrospect and in line with the participant's sense of being an agent.

Temporal information processing in short- and long-term memory of patients with schizophrenia

Cognitive deficits of patients with schizophrenia have been largely recognized as core symptoms of the disorder. One neglected factor that contributes to these deficits is the comprehension of time. In the present study, we assessed temporal information processing and manipulation from short- and long-term memory in 34 patients with chronic schizophrenia and 34 matched healthy controls. On the short-term memory temporal-order reconstruction task, an incidental or intentional learning strategy was deployed. Patients showed worse overall performance than healthy controls. The intentional learning strategy led to dissociable performance improvement in both groups. Whereas healthy controls improved on a performance measure (serial organization), patients improved on an error measure (inappropriate semantic clustering) when using the intentional instead of the incidental learning strategy. On the long-term memory script-generation task, routine and non-routine events of everyday activities (e.g., buying groceries) had to be generated in either chronological or inverted temporal order. Patients were slower than controls at generating events in the chronological routine condition only. They also committed more sequencing and boundary errors in the inverted conditions. The number of irrelevant events was higher in patients in the chronological, non-routine condition. These results suggest that patients with schizophrenia imprecisely access temporal information from short- and long-term memory. In short-term memory, processing of temporal information led to a reduction in errors rather than, as was the case in healthy controls, to an improvement in temporal-order recall. When accessing temporal information from long-term memory, patients were slower and committed more sequencing, boundary, and intrusion errors. Together, these results suggest that time information can be accessed and processed only imprecisely by patients who provide evidence for impaired time comprehension. This could contribute to symptomatic cognitive deficits and strategic inefficiency in schizophrenia.

Sense of agency in health and disease: a review of cue integration approaches

Sense of agency (SoA) is a compelling but fragile experience that is augmented or attenuated by internal signals and by external cues. A disruption in SoA may characterise individual symptoms of mental illness such as delusions of control. Indeed, it has been argued that generic SoA disturbances may lie at the heart of delusions and hallucinations that characterise schizophrenia. A clearer understanding of how sensorimotor, perceptual and environmental cues complement, or compete with, each other in engendering SoA may prove valuable in deepening our understanding the agency disruptions that characterise certain focal neurological disorders and mental illnesses. Here we examine the integration of SoA cues in health and illness, describing a simple framework of this integration based on Bayesian principles. We extend this to consider how alterations in cue integration may lead to aberrant experiences of agency.

Ketamine administration in healthy volunteers reproduces aberrant agency experiences associated with schizophrenia

INTRODUCTION

Aberrant experience of agency is characteristic of schizophrenia. An understanding of the neurobiological basis of such experience is therefore of considerable importance for developing successful models of the disease. We aimed to characterise the effects of ketamine, a drug model for psychosis, on sense of agency (SoA). SoA is associated with a subjective compression of the temporal interval between an action and its effects: This is known as "intentional binding". This action-effect binding provides an indirect measure of SoA. Previous research has found that the magnitude of binding is exaggerated in patients with schizophrenia. We therefore investigated whether ketamine administration to otherwise healthy adults induced a similar pattern of binding.

METHODS

14 right-handed healthy participants (8 female; mean age 22.4 years) were given low-dose ketamine (100 ng/mL plasma) and completed the binding task. They also underwent structured clinical interviews.

RESULTS

Ketamine mimicked the performance of schizophrenia patients on the intentional binding task, significantly increasing binding relative to placebo. The size of this effect also correlated with aberrant bodily experiences engendered by the drug.

CONCLUSIONS

These data suggest that ketamine may be able to mimic certain aberrant agency experiences that characterise schizophrenia. The link to individual changes in bodily experience suggests that the fundamental change produced by the drug has wider consequences in terms of individuals' experiences of their bodies and movements.

Altered sense of agency in schizophrenia and the putative psychotic prodrome

The mechanisms underlying distortions in sense of agency, i.e. the experience of controlling one's own actions and their consequences, in schizophrenia are not fully understood and have barely been investigated in patients classified as being in a putative psychotic prodrome. This study aims to expound the contribution of early and late illness-related processes. Thirty schizophrenia patients, 30 putatively prodromal patients and 30 healthy controls were instructed to reproduce a computer-generated series of drum sounds on a drum pad. While tapping, subjects heard either their self-produced tones or a computer-controlled reproduction of the drum tone series that used either exactly the same, an accelerated or decelerated tempo. Subjects had to determine the source of agency. Results show similar significant impairments in assigning the source of agency under ambiguous conditions in schizophrenia and putatively prodromal patients and an exaggerated self-attribution bias, both of which were significantly correlated with increased (ego-)psychopathology. Patient groups, however, benefited significantly more than controls from additional sensorimotor cues to agency. Sensorimotor input seems to be a compensatory mechanism involved in correctly attributing agency. We deduce that altered awareness of agency may hold promise as an additional risk factor for psychosis.

Sense of agency is altered in patients with a putative psychotic prodrome

BACKGROUND

Sense of agency (SoAg)--the experience of controlling one's own actions and their consequences--has been studied in schizophrenia but not in the earlier stages of the disease, i.e. in patients with a putative psychotic prodrome (PP). Previous research has shown that time judgments of voluntary actions can provide an implicit measure of the SoAg.

METHOD

30 PP patients and 30 healthy controls performed voluntary key presses while watching a rotating clock hand on a monitor. After each key press they had to estimate the time of the action (based on the perceived position of the clock hand at the time of the key press). By varying the probability with which the simple manual action was followed by a tone, we investigated whether shifts in perceptual estimates of the operant action towards a resulting effect depended on the actual occurrence of the effect (retrospective process) or on the prediction that the effect will occur.

RESULTS

PP patients differed from healthy controls but their results did not resemble previous findings in schizophrenia patients. PP patients showed numerically--but not significantly--stronger temporal linkage between action and consequence than healthy controls. Retrospective and predictive influences on action binding were stronger in PP patients. Furthermore, the altered influence of prediction was significantly correlated to ego-psychopathology.

DISCUSSION

Distortions of agency constitute a core feature of the disease that is already present in the PP but may evolve further with progression of the illness. Distortions of agency may thus represent a promising additional predictive risk factor for transition to psychosis in PP patients.

Different brain structures related to self- and external-agency attribution: a brief review and meta-analysis

Several neuroimaging studies have consistently shown activations of areas surrounding the temporo-parietal junction (TPJ) during tasks exploring the sense of agency. Beyond TPJ, activations in different structures, such as the dorsolateral prefrontal cortex (dLPFC), the pre-supplementary motor area (pre-SMA), the insula and the precuneus have been reported. Moreover, a possible dissociation between self- and external-agency attribution has been suggested. To test the hypothesis of distinct neural correlates for self- and external-agency attribution a quantitative meta-analysis, based on activation likelihood estimation (ALE) method, across 15 PET and fMRI studies (228 subjects) was conducted. Results show converging activations including the TPJ, pre-SMA, precuneus and dorsomedial prefrontal cortex (dMPFC) in external-agency, while insula activation was related to self-agency. We discuss these findings, highlighting the role of the insula, and calling for the use of alternative paradigms such as intentional binding and interactive imitation to study agency.