Neural Correlates of Self-other Distinction in Patients with Schizophrenia Spectrum Disorders: The Roles of Agency and Hand Identity

Modelling sensory attenuation as Bayesian causal inference across two datasets

INTRODUCTION

To interact with the environment, it is crucial to distinguish between sensory information that is externally generated and inputs that are self-generated. The sensory consequences of one's own movements tend to induce attenuated behavioral- and neural responses compared to externally generated inputs. We propose a computational model of sensory attenuation (SA) based on Bayesian Causal Inference, where SA occurs when an internal cause for sensory information is inferred.

METHODS

Experiment 1investigates sensory attenuation during a stroking movement. Tactile stimuli on the stroking finger were suppressed, especially when they were predictable. Experiment 2 showed impaired delay detection between an arm movement and a video of the movement when participants were moving vs. when their arm was moved passively. We reconsider these results from the perspective of Bayesian Causal Inference (BCI). Using a hierarchical Markov Model (HMM) and variational message passing, we first qualitatively capture patterns of task behavior and sensory attenuation in simulations. Next, we identify participant-specific model parameters for both experiments using optimization.

RESULTS

A sequential BCI model is well equipped to capture empirical patterns of SA across both datasets. Using participant-specific optimized model parameters, we find a good agreement between data and model predictions, with the model capturing both tactile detections in Experiment 1 and delay detections in Experiment 2.

DISCUSSION

BCI is an appropriate framework to model sensory attenuation in humans. Computational models of sensory attenuation may help to bridge the gap across different sensory modalities and experimental paradigms and may contribute towards an improved description and understanding of deficits in specific patient groups (e.g. schizophrenia).

Disturbance at the self-other boundary in schizophrenia: Linking phenomenology to clinical neuroscience

In this selective review, we describe the current neuroscientific literature on disturbances of the self-other boundary in schizophrenia as they relate to structural and experiential aspects of the self. Within these two broad categories, the structural self includes body ownership and agency, and the experiential self includes self-reflection, source monitoring, and self-referential and autobiographical memory. Further, we consider how disturbances in these domains link to the phenomenology of schizophrenia. We identify faulty internal predictive coding as a potential mechanism of disturbance in body ownership and agency, which results in susceptibility to bias (over- or under-attributing outcomes to one's own actions or intentions). This is reflected in reduced activity in the temporoparietal junction (TPJ), a heteromodal association area implicated in several aspects of self-other processing, as well as reduced fronto-parietal functional connectivity. Deficits of the experiential self in schizophrenia may stem from a lack of salience of self-related information, whereby the mental representation of self is not as rich as in healthy controls and therefore does not result in the same level of privileged processing. As a result, memory for self-referential material and autobiographical memory processes is impaired, which hinders creation of a cohesive life narrative. Impairments of the experiential self implicate abnormal activation patterns along the cortical midline, including medial prefrontal cortex and posterior cingulate/precuneus, as well as TPJ. In fact, TPJ appears to be involved in all the reviewed aspects of the self-other disturbance. We conclude with suggestions for future work, including implications for interventions with critical timing considerations.

Global neural self-disturbance in schizophrenia: A systematic fMRI review

There is a general consensus that schizophrenia (SZ) is characterized by major changes in the sense of self. Phenomenological studies suggest that these changes in the sense of self stem from a basic disturbance, hence the term 'basic self-disturbance'. While imaging studies demonstrate changes in various regions during self-focused tasks, the exact neural correlates of such basic self-disturbances remain unclear. If the self-disturbance is indeed basic and thereby underlies all other symptoms, one would expect it to be related to more global rather than local changes in the brain. Testing this hypothesis, we conducted a systematic review of fMRI studies on self in SZ. Our main findings are 1. Abnormal activity related to the self can be observed in a variety of different regions ranging from higher-order transmodal to lower-order unimodal regions, 2. These findings hold true across different tasks including self-reflection, self-referentiality, and self-agency, and 3. The global neural abnormalities related to the self in SZ correspond to all layers of the self, predominantly the mental and exteroceptive self. Such global neural disturbance of self converges well with the basic self-disturbance as described in phenomenology.

The neural network of sensory attenuation: A neuroimaging meta-analysis

Sensory attenuation refers to the reduction in sensory intensity resulting from self-initiated actions compared to stimuli initiated externally. A classic example is scratching oneself without feeling itchy. This phenomenon extends across various sensory modalities, including visual, auditory, somatosensory, and nociceptive stimuli. The internal forward model proposes that during voluntary actions, an efferent copy of the action command is sent out to predict sensory feedback. This predicted sensory feedback is then compared with the actual sensory feedback, leading to the suppression or reduction of sensory stimuli originating from self-initiated actions. To further elucidate the neural mechanisms underlying sensory attenuation effect, we conducted an extensive meta-analysis of functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) studies. Utilizing activation likelihood estimation (ALE) analysis, our results revealed significant activations in a prominent cluster encompassing the right superior temporal gyrus (rSTG), right middle temporal gyrus (rMTG), and right insula when comparing external-generated with self-generated conditions. Additionally, significant activation was observed in the right anterior cerebellum when comparing self-generated to external-generated conditions. Further analysis using meta-analytic connectivity modeling (MACM) unveiled distinct brain networks co-activated with the rMTG and right cerebellum, respectively. Based on these findings, we propose that sensory attenuation arises from the suppression of reflexive inputs elicited by self-initiated actions through the internal forward modeling of a cerebellum-centered action prediction network, enabling the "sensory conflict detection" regions to effectively discriminate between inputs resulting from self-induced actions and those originating externally.

Temporal recalibration in response to delayed visual feedback of active versus passive actions: an fMRI study

The brain can adapt its expectations about the relative timing of actions and their sensory outcomes in a process known as temporal recalibration. This might occur as the recalibration of timing between the sensory (e.g. visual) outcome and (1) the motor act (sensorimotor) or (2) tactile/proprioceptive information (inter-sensory). This fMRI recalibration study investigated sensorimotor contributions to temporal recalibration by comparing active and passive conditions. Subjects were repeatedly exposed to delayed (150 ms) or undelayed visual stimuli, triggered by active or passive button presses. Recalibration effects were tested in delay detection tasks, including visual and auditory outcomes. We showed that both modalities were affected by visual recalibration. However, an active advantage was observed only in visual conditions. Recalibration was generally associated with the left cerebellum (lobules IV, V and vermis) while action related activation (active > passive) occurred in the right middle/superior frontal gyri during adaptation and test phases. Recalibration transfer from vision to audition was related to action specific activations in the cingulate cortex, the angular gyrus and left inferior frontal gyrus. Our data provide new insights in sensorimotor contributions to temporal recalibration via the middle/superior frontal gyri and inter-sensory contributions mediated by the cerebellum.

Facilitation of sensorimotor temporal recalibration mechanisms by cerebellar tDCS in patients with schizophrenia spectrum disorders and healthy individuals

Core symptoms in patients with schizophrenia spectrum disorders (SSD), like hallucinations or ego-disturbances, have been associated with a failure of internal forward models to predict the sensory outcomes of self-generated actions. Importantly, forward model predictions must also be able to flexibly recalibrate to changing environmental conditions, for example to account for additional delays between action and outcome. We investigated whether transcranial direct current stimulation (tDCS) can be used to improve these sensorimotor temporal recalibration mechanisms in patients and healthy individuals. While receiving tDCS on the cerebellum, temporo-parietal junction, supplementary motor area, or sham stimulation, patients with SSD and healthy control participants were repeatedly exposed to delays between actively or passively elicited button presses and auditory outcomes. Effects of this procedure on temporal perception were assessed with a delay detection task. Similar recalibration outcomes and faciliatory effects of cerebellar tDCS on recalibration were observed in SSD and healthy individuals. Our findings indicate that sensorimotor recalibration mechanisms may be preserved in SSD and highlight the importance of the cerebellum in both patients and healthy individuals for this process. They further suggest that cerebellar tDCS could be a promising tool for addressing deficits in action-outcome monitoring and related adaptive sensorimotor processes in SSD.

Pre-movement event-related potentials and multivariate pattern of EEG encode action outcome prediction

Self-initiated movements are accompanied by an efference copy, a motor command sent from motor regions to the sensory cortices, containing a prediction of the movement's sensory outcome. Previous studies have proposed pre-motor event-related potentials (ERPs), including the readiness potential (RP) and its lateralized sub-component (LRP), as potential neural markers of action feedback prediction. However, it is not known how specific these neural markers are for voluntary (active) movements as compared to involuntary (passive) movements, which produce much of the same sensory feedback (tactile, proprioceptive) but are not accompanied by an efference copy. The goal of the current study was to investigate how active and passive movements are distinguishable from premotor electroencephalography (EEG), and to examine if this change of neural activity differs when participants engage in tasks that differ in their expectation of sensory outcomes. Participants made active (self-initiated) or passive (finger moved by device) finger movements that led to either visual or auditory stimuli (100 ms delay), or to no immediate contingency effects (control). We investigated the time window before the movement onset by measuring pre-movement ERPs time-locked to the button press. For RP, we observed an interaction between task and movement. This was driven by movement differences in the visual and auditory but not the control conditions. LRP conversely only showed a main effect of movement. We then used multivariate pattern analysis to decode movements (active vs. passive). The results revealed ramping decoding for all tasks from around -800 ms onwards up to an accuracy of approximately 85% at the movement. Importantly, similar to RP, we observed lower decoding accuracies for the control condition than the visual and auditory conditions, but only shortly (from -200 ms) before the button press. We also decoded visual vs. auditory conditions. Here, task is decodable for both active and passive conditions, but the active condition showed increased decoding shortly before the button press. Taken together, our results provide robust evidence that pre-movement EEG activity may represent action-feedback prediction in which information about the subsequent sensory outcome is encoded.

Patterns of multiple brain network activation in dot perspective task

In this functional MRI (fMRI) study on 82 healthy adults using the dot perspective task, inconsistency of perspectives was associated with a significant increase of the mean reaction time and number of errors both in Self and Other conditions. Unlike the Arrow (non-mentalizing), the Avatar (mentalizing) paradigm was characterized by the recruitment of parts of the mentalizing and salience networks. These data provide experimental evidence supporting the fMRI distinction between mentalizing and non-mentalizing stimuli. A widespread activation of classical theory of mind (ToM) areas but also of salience network and decision making areas was observed in the Other compared to Self-conditions. Compared to Self-Consistent, Self-Inconsistent trials were related to increased activation in the lateral occipital cortex, right supramarginal and angular gyrus as well as inferior, superior and middle frontal gyri. Compared to the Other-Consistent, Other-Inconsistent trials yielded strong activation in the lateral occipital cortex, precuneus and superior parietal lobule, middle and superior precentral gyri and left frontal pole. These findings reveal that altercentric interference relies on areas involved in self-other distinction, self-updating and central executive functions. In contrast, egocentric interference needs the activation of the mirror neuron system and deductive reasoning, much less related to pure ToM abilities.

Perception of self-generated and externally-generated visual stimuli: Evidence from EEG and behavior

Efference copy-based forward model mechanisms may help us to distinguish between self-generated and externally-generated sensory consequences. Previous studies have shown that self-initiation modulates neural and perceptual responses to identical stimulation. For example, event-related potentials (ERPs) elicited by tones that follow a button press are reduced in amplitude relative to ERPs elicited by passively attended tones. However, previous EEG studies investigating visual stimuli in this context are rare, provide inconclusive results, and lack adequate control conditions with passive movements. Furthermore, although self-initiation is known to modulate behavioral responses, it is not known whether differences in the amplitude of ERPs also reflect differences in perception of sensory outcomes. In this study, we presented to participants visual stimuli consisting of gray discs following either active button presses, or passive button presses, in which an electromagnet moved the participant's finger. Two discs presented visually 500-1250 ms apart followed each button press, and participants judged which of the two was more intense. Early components of the primary visual response (N1 and P2) over the occipital electrodes were suppressed in the active condition. Interestingly, suppression in the intensity judgment task was only correlated with suppression of the visual P2 component. These data support the notion of efference copy-based forward model predictions in the visual sensory modality, but especially later processes (P2) seem to be perceptually relevant. Taken together, the results challenge the assumption that N1 differences reflect perceptual suppression and emphasize the relevance of the P2 ERP component.

Blots and brains. A note on the centenary of Hermann Rorschach's death

This historical note is a commemorial of Rorschach, the person, and Rorschach the test. Hermann Rorschach died 100 years ago, not quite a year after the publication of his book containing the 10 inkblots. These have reached an iconic status, but the "Rorschach Test" as used in psychiatry, legal organizations and aptitude assessments is not quite what Hermann Rorschach designed it for in the first line. A first section of this article introduces Hermann Rorschach as a man with very broad interests and an inclination to ask cognitive science questions that are still challenging today. A second section provides a critical summary of the fate of the ten inkblots after Rorschach's death - how they conquered the whole world in a time with a pronouced "psychometric attitude", and also how they failed in some attempts to measure personality traits in special populations. A final section focuses on recent research on one particular aspect of a testee's associations to the inkblots: "movement responses", i.e. the perception of implied motion. Here, neural and behavioral correlates have been demonstrated by modern neuroimaging techniques. One study, which set out to validate both the Rorschach as a personality test and the view that the two cerebral hemispheres correspond to divergent "personalities" is also summarized. The viewpoint concludes by suggesting that future work with inkblots should consider Rorschach's original intention to use inkblots to uncover basic laws of perception. Modern applications of computer-generated pseudorandom stimuli (random dot arrays or stochastic noise) would have been embraced by Hermann Rorschach as he appreciated the impact of visual noise for the study of vision and visual cognition.

Sense of body ownership and body agency in schizophrenia

Recent research suggests that embodiment sensations (sense of body ownership and sense of body agency) are altered in schizophrenia. Using a mirror box illusion setup, we tested if the anomalous embodiment experience depends on deficient processing of visuomotor synchrony, disrupted processing of movement mode, or both. The task required participants to press a lever with their index while looking at the image of the experimenter's hand moving on a similar lever. The illusion of embodiment could arise because looking toward the direction of their own hand the participant saw the reflection of the experimenter's hand visually superimposed to his own one through a mirror. During the illusion induction, we systematically varied visuomotor asynchrony (4 delays were imposed on the movement of the experimenter's hand) and the mode of movement (the participant could perform active vs. passive movements). The strength of the illusion of embodiment of the external hand was assessed with explicit judgments of ownership and agency. Patients' data showed an anomalous modulation of ownership with respect to visuomotor synchrony manipulation and an altered modulation of agency with respect to both visuomotor synchrony and movement mode manipulations. Results from the present study suggest that impairments affecting both the processing of temporal aspects of visuomotor signals and the processing of type of movement underlie anomalous embodiment sensations in schizophrenia. Hypotheses about potential deficits accounting for our results are proposed.

Induced feelings of external influence during instructed imaginations in healthy subjects

The psychopathological phenomenon of delusions of influence comprises variable disturbances of the self-environment-border leading to the feeling of external influence on thoughts, feelings, impulses or behaviors. Delusions of influence are a hallmark in psychotic illness, but nevertheless, attenuated forms can also appear in healthy individuals. Here we present a newly developed paradigm to induce and assess feelings of external influence during instructed imaginations in healthy individuals. In the current study, we asked 60 healthy individuals to visually imagine different objects. To induce feelings of external influence, we applied one of three different physical setups (low-amplitude transcranial direct current stimulation, eye contact, or skin-to-skin hand touch), and informed the participants whether or not an external influence was attempted during the respective trial. The physical setup (setup vs. no setup, Z = -3.847, p < 0.001, r = 0.497) as well as the information given to the participants (confirmation vs. negation, Z = -5.218, p < 0.001, r = 0.674) alone were able to modulate the feeling of external influence in all three interventions. The impact of information (whether influence was attempted or not attempted) significantly exceeded the impact of the physical setup on the ratings of experienced external influence (Z = -2.394, p = 0.016, r = 0.310). Moreover, the response latency correlated with the estimated feeling of external influence (r _S = 0.392, p = 0.002). Additional analyses addressed the influence of the emotional content of imagined objects and examined the intensity and emotional valence of the imaginations. Further supplemental analyses correlated external influence estimation of the participants with other psychopathological measures (trait markers for supernatural beliefs, proneness to hallucinations, and delusions and attributional style). In conclusion, this study endorses a quantitative model of psychopathological characteristics, in this case feelings of external influence that can be induced by external cues.

Action-based predictions affect visual perception, neural processing, and pupil size, regardless of temporal predictability

Sensory consequences of one's own action are often perceived as less intense, and lead to reduced neural responses, compared to externally generated stimuli. Presumably, such sensory attenuation is due to predictive mechanisms based on the motor command (efference copy). However, sensory attenuation has also been observed outside the context of voluntary action, namely when stimuli are temporally predictable. Here, we aimed at disentangling the effects of motor and temporal predictability-based mechanisms on the attenuation of sensory action consequences. During fMRI data acquisition, participants (N = 25) judged which of two visual stimuli was brighter. In predictable blocks, the stimuli appeared temporally aligned with their button press (active) or aligned with an automatically generated cue (passive). In unpredictable blocks, stimuli were presented with a variable delay after button press/cue, respectively. Eye tracking was performed to investigate pupil-size changes and to ensure proper fixation. Self-generated stimuli were perceived as darker and led to less neural activation in visual areas than their passive counterparts, indicating sensory attenuation for self-generated stimuli independent of temporal predictability. Pupil size was larger during self-generated stimuli, which correlated negatively with the blood oxygenation level dependent (BOLD) response: the larger the pupil, the smaller the BOLD amplitude in visual areas. Our results suggest that sensory attenuation in visual cortex is driven by action-based predictive mechanisms rather than by temporal predictability. This effect may be related to changes in pupil diameter. Altogether, these results emphasize the role of the efference copy in the processing of sensory action consequences.

The effect of self-generated versus externally generated actions on timing, duration, and amplitude of blood oxygen level dependent response for visual feedback processing

It has been widely assumed that internal forward models use efference copies to create predictions about the sensory consequences of our own actions. While these predictions have frequently been associated with a reduced blood oxygen level dependent (BOLD) response in sensory cortices, the timing and duration of the hemodynamic response for the processing of video feedback of self‐generated (active) versus externally generated (passive) movements is poorly understood. In the present study, we tested the hypothesis that predictive mechanisms for self‐generated actions lead to early and shorter neural processing compared with externally generated movements. We investigated active and passive movements using a custom‐made fMRI‐compatible movement device. Visual video feedback of the active and passive movements was presented in real time or with variable delays. Participants had to judge whether the feedback was delayed. Timing and duration of BOLD impulse response was calculated using a first (temporal derivative [TD]) and second‐order (dispersion derivative [DD]) Taylor approximation. Our reanalysis confirmed our previous finding of reduced BOLD response for active compared to passive movements. Moreover, we found positive effects of the TD and DD in the supplementary motor area, cerebellum, visual cortices, and subcortical structures, indicating earlier and shorter hemodynamic responses for active compared to passive movements. Furthermore, earlier activation in the putamen for active compared to passive conditions was associated with reduced delay detection performance. These findings indicate that efference copy‐based predictive mechanisms enable earlier processing of action feedback, which might have reduced the ability to detect short delays between action and feedback.

The impact of cerebellar transcranial direct current stimulation (tDCS) on sensorimotor and inter-sensory temporal recalibration

The characteristic temporal relationship between actions and their sensory outcomes allows us to distinguish self- from externally generated sensory events. However, the complex sensory environment can cause transient delays between action and outcome calling for flexible recalibration of predicted sensorimotor timing. Since the neural underpinnings of this process are largely unknown this study investigated the involvement of the cerebellum by means of cerebellar transcranial direct current stimulation (ctDCS). While receiving anodal, cathodal, dual-hemisphere or sham ctDCS, in an adaptation phase, participants were exposed to constant delays of 150 ms between actively or passively generated button presses and visual sensory outcomes. Recalibration in the same (visual outcome) and in another sensory modality (auditory outcome) was assessed in a subsequent test phase during which variable delays between button press and visual or auditory outcome had to be detected. Results indicated that temporal recalibration occurred in audition after anodal ctDCS while it was absent in vision. As the adaptation modality was visual, effects in audition suggest that recalibration occurred on a supra-modal level. In active conditions, anodal ctDCS improved sensorimotor recalibration at the delay level closest to the adaptation delay, suggesting a precise cerebellar-dependent temporal recalibration mechanism. In passive conditions, the facilitation of inter-sensory recalibration by anodal ctDCS was overall stronger and tuned to larger delays. These findings point to a role of the cerebellum in supra-modal temporal recalibration across sensorimotor and perceptual domains, but the differential manifestation of the effect across delay levels in active and passive conditions points to differences in the underlying mechanisms depending on the availability of action-based predictions. Furthermore, these results suggest that anodal ctDCS can be a promising tool for facilitating effects of temporal recalibration in sensorimotor and inter-sensory contexts.

The Transdiagnostic Relevance of Self-Other Distinction to Psychiatry Spans Emotional, Cognitive and Motor Domains

Self-other distinction refers to the ability to distinguish between our own and other people's physical and mental states (actions, perceptions, emotions etc.). Both the right temporo-parietal junction and brain areas associated with the human mirror neuron system are likely to critically influence self-other distinction, given their respective contributions to theory of mind and embodied empathy. The degree of appropriate self-other distinction will vary according to the exact social situation, and how helpful it is to feel into, or remain detached from, another person's mental state. Indeed, the emotional resonance that we can share with others affords the gift of empathy, but over-sharing may pose a downside, leading to a range of difficulties from personal distress to paranoia, and perhaps even motor tics and compulsions. The aim of this perspective paper is to consider how evidence from behavioral and neurophysiological studies supports a role for problems with self-other distinction in a range of psychiatric symptoms spanning the emotional, cognitive and motor domains. The various signs and symptoms associated with problematic self-other distinction comprise both maladaptive and adaptive (compensatory) responses to dysfunction within a common underlying neuropsychological mechanism, compelling the adoption of more holistic transdiagnostic therapeutic approaches within Psychiatry.