With hand on heart: A cardiac Rubber Hand Illusion.

Body illusions such as the Rubber Hand Illusion (RHI) have highlighted how multisensory integration underpins the sense of one's own body. Much of this research has focused on senses arising from outside the body (e.g. vision and touch), but sensations from within the body may also play a role. In a pre-registered study, participants completed a cardiac variation of the RHI, where taps to the finger occurred in or out of time with the heartbeat. We replicated the RHI effect, showing that synchronous but not asynchronous taps to the real and rubber hand increased sensations of embodiment over the rubber hand and caused a shift in the perceived hand location. However, there were no significant influences of cardiac timing on embodiment, nor did it interact with visuo-tactile synchrony. An exploratory analysis found a three-way interaction between synchrony, cardiac timing and interoceptive accuracy as measured by a heartbeat counting task, such that greater interoceptive accuracy was associated with lower embodiment ratings in the systole condition compared to diastole, but only during synchronous stimulation. Although our novel methodology successfully replicated the RHI, our findings suggest that the cooccurence of vision and touch with cardiac signals may make little contribution to the sense of one's body.

Varieties of felt presence? Three surveys of presence phenomena and their relations to psychopathology.

BACKGROUND: Experiences of felt presence (FP) are well documented in neurology, neuropsychology and bereavement research, but systematic research in relation to psychopathology is limited. FP is a feature of sensorimotor disruption in psychosis, hypnagogic experiences, solo pursuits and spiritual encounters, but research comparing these phenomena remains rare. A comparative approach to the phenomenology of FP has the potential to identify shared and unique processes underlying the experience across these contexts, with implications for clinical understanding and intervention. METHODS: We present a mixed-methods analysis from three online surveys comparing FP across three diverse contexts: a population sample which included people with experience of psychosis and voice-hearing (study 1, N = 75), people with spiritual and spiritualist beliefs (study 2, N = 47) and practitioners of endurance/solo pursuits (study 3, N = 84). Participants were asked to provide descriptions of their FP experiences and completed questionnaires on FP frequency, hallucinatory experiences, dissociation, paranoia, social inner speech and sleep. Data and code for the study are available via OSF. RESULTS: Hierarchical linear regression analysis indicated that FP frequency was predicted by a general tendency to experience hallucinations in all three studies, although paranoia and gender (female > male) were also significant predictors in sample 1. Qualitative analysis highlighted shared and diverging phenomenology of FP experiences across the three studies, including a role for immersive states in FP. CONCLUSIONS: These data combine to provide the first picture of the potential shared mechanisms underlying different accounts of FP, supporting a unitary model of the experience.

Continuities and Discontinuities in the Cognitive Mechanisms Associated With Clinical and Nonclinical Auditory Verbal Hallucinations.

Auditory verbal hallucinations (AVHs) are typically associated with schizophrenia but also occur in individuals without any need for care (nonclinical voice hearers [NCVHs]). Cognitive models of AVHs posit potential biases in source monitoring, top-down processes, or a failure to inhibit intrusive memories. However, research across clinical/nonclinical groups is limited, and the extent to which there may be continuity in cognitive mechanism across groups, as predicted by the psychosis-continuum hypothesis, is unclear. We report two studies in which voice hearers with psychosis (n = 31) and NCVH participants reporting regular spiritual voices (n = 26) completed a battery of cognitive tasks. Compared with non-voice-hearing groups (ns = 33 and 28), voice hearers with psychosis showed atypical performance on signal detection, dichotic listening, and memory-inhibition tasks but intact performance on the source-monitoring task. NCVH participants, however, showed only atypical signal detection, which suggests differences between clinical and nonclinical voice hearers potentially related to attentional control and inhibition. These findings suggest that at the level of cognition, continuum models of hallucinations may need to take into account continuity but also discontinuity between clinical and nonclinical groups.

Susceptibility to auditory hallucinations is associated with spontaneous but not directed modulation of top-down expectations for speech.

Auditory verbal hallucinations (AVHs)-or hearing voices-occur in clinical and non-clinical populations, but their mechanisms remain unclear. Predictive processing models of psychosis have proposed that hallucinations arise from an over-weighting of prior expectations in perception. It is unknown, however, whether this reflects (i) a sensitivity to explicit modulation of prior knowledge or (ii) a pre-existing tendency to spontaneously use such knowledge in ambiguous contexts. Four experiments were conducted to examine this question in healthy participants listening to ambiguous speech stimuli. In experiments 1a (n = 60) and 1b (n = 60), participants discriminated intelligible and unintelligible sine-wave speech before and after exposure to the original language templates (i.e. a modulation of expectation). No relationship was observed between top-down modulation and two common measures of hallucination-proneness. Experiment 2 (n = 99) confirmed this pattern with a different stimulus-sine-vocoded speech (SVS)-that was designed to minimize ceiling effects in discrimination and more closely model previous top-down effects reported in psychosis. In Experiment 3 (n = 134), participants were exposed to SVS without prior knowledge that it contained speech (i.e. naïve listening). AVH-proneness significantly predicted both pre-exposure identification of speech and successful recall for words hidden in SVS, indicating that participants could actually decode the hidden signal spontaneously. Altogether, these findings support a pre-existing tendency to spontaneously draw upon prior knowledge in healthy people prone to AVH, rather than a sensitivity to temporary modulations of expectation. We propose a model of clinical and non-clinical hallucinations, across auditory and visual modalities, with testable predictions for future research.

Item-specific overlap between hallucinatory experiences and cognition in the general population: A three-step multivariate analysis of international multi-site data.

Hallucinatory experiences (HEs) can be pronounced in psychosis, but similar experiences also occur in nonclinical populations. Cognitive mechanisms hypothesized to underpin HEs include dysfunctional source monitoring, heightened signal detection, and impaired attentional processes. Using data from an international multisite study on non-clinical participants (N = 419), we described the overlap between two sets of variables - one measuring cognition and the other HEs - at the level of individual items. We used a three-step method to extract and examine item-specific signal, which is typically obscured when summary scores are analyzed using traditional methodologies. The three-step method involved: (1) constraining variance in cognition variables to that which is predictable from HE variables, followed by dimension reduction, (2) determining reliable HE items using split-halves and permutation tests, and (3) selecting cognition items for interpretation using a leave-one-out procedure followed by repetition of Steps 1 and 2. The results showed that the overlap between HEs and cognition variables can be conceptualized as bi-dimensional, with two distinct mechanisms emerging as candidates for separate pathways to the development of HEs: HEs involving perceptual distortions on one hand (including voices), underpinned by a low threshold for signal detection in cognition, and HEs involving sensory overload on the other hand, underpinned by reduced laterality in cognition. We propose that these two dimensions of HEs involving distortions/liberal signal detection, and sensation overload/reduced laterality may map onto psychosis-spectrum and dissociation-spectrum anomalous experiences, respectively.

Correlates of Hallucinatory Experiences in the General Population: An International Multisite Replication Study.

Hallucinatory experiences can occur in both clinical and nonclinical groups. However, in previous studies of the general population, investigations of the cognitive mechanisms underlying hallucinatory experiences have yielded inconsistent results. We ran a large-scale preregistered multisite study, in which general-population participants (N = 1,394 across 11 data-collection sites and online) completed assessments of hallucinatory experiences, a measure of adverse childhood experiences, and four tasks: source memory, dichotic listening, backward digit span, and auditory signal detection. We found that hallucinatory experiences were associated with a higher false-alarm rate on the signal detection task and a greater number of reported adverse childhood experiences but not with any of the other cognitive measures employed. These findings are an important step in improving reproducibility in hallucinations research and suggest that the replicability of some findings regarding cognition in clinical samples needs to be investigated.

Inner experience differs in rumination and distraction without a change in electromyographical correlates of inner speech.

Ruminative thought is a style of thinking which involves repetitively focusing upon one's own negative mood, its causes and its consequences. The negative effects of rumination are well-documented, but comparatively little is known about how rumination is experienced. The evaluative nature of rumination suggests that it could involve more inner speech than non-ruminative states. The present study (N = 31) combined facial electromyography and self-report questionnaires to determine the type of inner experience that occurs in rumination. The results showed that induced rumination involved similar levels of muscle activity related to inner speech as periods of induced distraction. However, experience sampling and questionnaire responses showed that rumination involved more verbal thought, and also involved more evaluative and dialogic inner speech than distraction. These findings contribute to the understanding of inner speech as a flexible phenomenon and confirms the importance of employing multiple methods to investigate inner speech. Future research should clarify the link between inner speech in rumination and its negative effects on wellbeing.

Modeling perception and behavior in individuals at clinical high risk for psychosis: Support for the predictive processing framework.

Early intervention in psychotic spectrum disorders is critical for maximizing key clinical outcomes. While there is some evidence for the utility of intervention during the prodromal phase of the illness, efficacy of interventions is difficult to assess without appropriate risk stratification. This will require biomarkers that robustly help to identify risk level and are also relatively easy to obtain. Recent work highlights the utility of computer-based behavioral tasks for understanding the pathophysiology of psychotic symptoms. Computational modeling of performance on such tasks may be particularly useful because they explicitly and formally link performance and symptom expression. Several recent studies have successfully applied principles of Bayesian inference to understanding the computational underpinnings of hallucinations. Within this framework, hallucinations are seen as arising from an over-weighting of prior beliefs relative to sensory evidence. This view is supported by recently-published data from two tasks: the Conditioned Hallucinations (CH) task, which determines the degree to which participants use expectations in detecting a target tone; and a Sine-Vocoded Speech (SVS) task, in which participants can use prior exposure to speech samples to inform their understanding of degraded speech stimuli. We administered both of these tasks to two samples of participants at clinical high risk for psychosis (CHR; N = 19) and healthy controls (HC; N = 17). CHR participants reported both more conditioned hallucinations and more pre-training SVS detection. In addition, relationships were found between participants' performance on both tasks. On computational modeling of behavior on the CH task, CHR participants demonstrate significantly poorer recognition of task volatility as well as a trend toward higher weighting of priors. A relationship was found between this latter effect and performance on both tasks. Taken together, these results support the assertion that these two tasks may be driven by similar latent factors in perceptual inference, and highlight the potential utility of computationally-based tasks in identifying risk.

Processing Speech and Thoughts during Silent Reading: Direct Reference Effects for Speech by Fictional Characters in Voice-Selective Auditory Cortex and a Theory-of-Mind Network.

Stories transport readers into vivid imaginative worlds, but understanding how readers create such worlds-populating them with characters, objects, and events-presents serious challenges across disciplines. Auditory imagery is thought to play a prominent role in this process, especially when representing characters' voices. Previous research has shown that direct reference to speech in stories (e.g., He said, "I'm over here") may prompt spontaneous activation of voice-selective auditory cortex more than indirect speech [Yao, B., Belin, P., & Scheepers, C. Silent reading of direct versus indirect speech activates voice-selective areas in the auditory cortex. Journal of Cognitive Neuroscience, 23, 3146-3152, 2011]. However, it is unclear whether this effect reflects differential processing of speech or differences in linguistic content, source memory, or grammar. One way to test this is to compare direct reference effects for characters speaking and thinking in a story. Here, we present a multidisciplinary fMRI study of 21 readers' responses to characters' speech and thoughts during silent reading of short fictional stories. Activations relating to direct and indirect references were compared for both speaking and thinking. Eye-tracking and independent localizer tasks (auditory cortex and theory of mind [ToM]) established ROIs in which responses to stories could be tracked for individuals. Evidence of elevated auditory cortex responses to direct speech over indirect speech was observed, replicating previously reported effects; no reference effect was observed for thoughts. Moreover, a direct reference effect specific to speech was also evident in regions previously associated with inferring intentions from communication. Implications are discussed for the spontaneous representation of fictional characters and the potential roles of inner speech and ToM in this process.

Reading characters in voices: Ratings of personality characteristics from voices predict proneness to auditory verbal hallucinations.

People rapidly make first impressions of others, often based on very little information-minimal exposure to faces or voices is sufficient for humans to make up their mind about personality of others. While there has been considerable research on voice personality perception, much less is known about its relevance to hallucination-proneness, despite auditory hallucinations being frequently perceived as personified social agents. The present paper reports two studies investigating the relation between voice personality perception and hallucination-proneness in non-clinical samples. A voice personality perception task was created, in which participants rated short voice recordings on four personality characteristics, relating to dimensions of the voice's perceived Valence and Dominance. Hierarchical regression was used to assess contributions of Valence and Dominance voice personality ratings to hallucination-proneness scores, controlling for paranoia-proneness and vividness of mental imagery. Results from Study 1 suggested that high ratings of voices as dominant might be related to high hallucination-proneness; however, this relation seemed to be dependent on reported levels of paranoid thinking. In Study 2, we show that hallucination-proneness was associated with high ratings of voice dominance, and this was independent of paranoia and imagery abilities scores, both of which were found to be significant predictors of hallucination-proneness. Results from Study 2 suggest an interaction between gender of participants and the gender of the voice actor, where only ratings of own gender voices on Dominance characteristics are related to hallucination-proneness scores. These results are important for understanding the perception of characterful features of voices and its significance for psychopathology.

Intentional inhibition but not source memory is related to hallucination-proneness and intrusive thoughts in a university sample.

Proneness to unusual perceptual states - such as auditory or visual hallucinations - has been proposed to exist on a continuum in the general population, but whether there is a cognitive basis for such a continuum remains unclear. Intentional cognitive inhibition (the ability to wilfully control thoughts and memories) is one mechanism that has been linked to auditory hallucination susceptibility, but most evidence to date has been drawn from clinical samples only. Moreover, such a link has yet to be demonstrated over and above relations to other cognitive skills (source monitoring) and cognitive states (intrusive thoughts) that often correlate with both inhibition and hallucinations. The present study deployed two tests of intentional inhibition ability - the Inhibition of Currently Irrelevant Memories (ICIM) task and Directed Forgetting (DF) task - and one test of source monitoring (a source memory task) to examine how cognitive task performance relates to self-reported i) auditory hallucination-proneness and ii) susceptibility to intrusive thoughts in a non-clinical student sample (N = 76). Hierarchical regression analyses were used to assess the independent and combined contributions of task performance to proneness scores. ICIM performance but not DF or source memory scores were significantly related to both hallucination-proneness and intrusive thoughts. Further analysis suggested that intrusive thoughts may mediate the link between intentional inhibition skills and auditory hallucination-proneness, suggesting a potential pathway from inhibition to perception via intrusions in cognition. The implications for studying cognitive mechanisms of hallucination and their role in "continuum" views of psychosis-like experiences are discussed.