Have we overlooked the significance of multinodal hallucinations in schizophrenia?

Examining the relationships between cognition and auditory hallucinations: A systematic review

OBJECTIVE

Auditory hallucinations (hearing voices) have been associated with a range of altered cognitive functions, pertaining to signal detection, source-monitoring, memory, inhibition and language processes. Yet, empirical results are inconsistent. Despite this, several theoretical models of auditory hallucinations persist, alongside increasing emphasis on the utility of a multidimensional framework. Thus, clarification of current evidence across the broad scope of proposed mechanisms is warranted.

METHOD

A systematic search of the Web of Science, PubMed and Scopus databases was conducted. Records were screened to confirm the use of an objective behavioural cognitive task, and valid measurement of hallucinations specific to the auditory modality.

RESULTS

Auditory hallucinations were primarily associated with difficulties in perceptual decision-making (i.e. reduced sensitivity/accuracy for signal-noise discrimination; liberal responding to ambiguity), source-monitoring (i.e. self-other and temporal context confusion), working memory and language function (i.e. reduced verbal fluency). Mixed or limited support was observed for perceptual feature discrimination, imagery vividness/illusion susceptibility, source-monitoring for stimulus form and spatial context, recognition and recall memory, executive functions (e.g. attention, inhibition), emotion processing and language comprehension/hemispheric organisation.

CONCLUSIONS

Findings were considered within predictive coding and self-monitoring frameworks. Of concern was the portion of studies which - despite offering auditory-hallucination-specific aims and inferences - employed modality-general measures, and/or diagnostic-based contrasts with psychologically healthy individuals. This review highlights disparities within the literature between theoretical conceptualisations of auditory hallucinations and the body of rigorous empirical evidence supporting such inferences. Future cognitive investigations, beyond the schizophrenia-spectrum, which explicitly define and measure the timeframe and sensory modality of hallucinations, are recommended.

Multi-modal hallucinations across diagnoses: What relationships do they have with voice-related distress?

BACKGROUND

Research into hallucinatory experiences has focused primarily upon hallucinations within the auditory modality, to the relative neglect of other modalities. Furthermore, the exploration of auditory hallucinations (or 'voices') has focused primarily upon the experiences of people with a diagnosis of psychosis. The presence of multi-modal hallucinations may have implications across diagnoses for levels of distress, formulation and the targeting of psychological interventions.

METHODS

This study presents a cross-sectional analysis of observational data from the PREFER survey (N = 335). Linear regression was used to explore the relationships between voice-related distress and the presence, number, type and timing of multi-modal hallucinations.

RESULTS

Simple relationships were not found between distress and the presence of hallucinations in visual, tactile, olfactory or gustatory modalities, or in the number of modalities experienced. When considering the degree to which another modality hallucination was experienced simultaneously with voices, there was some evidence that the degree of co-occurrence with visual hallucinations was predictive of distress.

CONCLUSIONS

The co-occurrence of voices with visual hallucinations may be associated with relatively greater distress, but not consistently, and the association between multimodal hallucinations and clinical impact appear complex and potentially variable from individual to individual. Further study of associated variables such as perceived voice power may further illuminate these relationships.

Experiencing hallucinations in daily life: The role of metacognition

BACKGROUND

Hallucinations have been linked to failures in metacognitive reflection suggesting an association between hallucinations and overestimation of performance, although the cross-sectional findings are inconsistent. This inconsistency may relate to the fluctuating hallucinatory experiences that are not captured in cross-sectional studies. Ecological Momentary Assessment (EMA) captures in-the-moment experiences over time so can identify causal relationships between variables such as the associations between metacognition and hallucinatory experience in daily life and overcome problems in cross-sectional designs.

METHODS

Participants (N = 41) experiencing daily hallucinations completed baseline questionnaires and smartphone surveys 7 times per day for 14 days. They were prompted to identify a task they would complete in the next 4 h and to make metacognitive predictions around the likelihood of completing the task, the difficulty of the task, and how well they would complete it (standard of completion).

RESULTS

76 % finished the 14-days of assessment with an average of 42.2 % survey completion. Less accurate metacognition was associated with more hallucinations, but less accurate likelihood and standard of completion was associated with fewer hallucinations. Using a cross-lagged analysis, metacognitive predictions around the likelihood of completion (p < .001) and standard of completion (p = .01) predicted hallucination intensity at the following timepoint, and metacognitive predictions regarding likelihood of completion (p = .02) predicted hallucination control at the following timepoint.

DISCUSSION

Interventions that aim to improve metacognitive ability in-the-moment may serve to reduce the intensity and increase the control of hallucinations.

Understanding visual hallucinations: a new synthesis

Despite decades of research, we do not definitively know how people sometimes see things that are not there. Eight models of complex visual hallucinations have been published since 2000, including Deafferentation, Reality Monitoring, Perception and Attention Deficit, Activation, Input, and Modulation, Hodological, Attentional Networks, Active inference, and Thalamocortical Dysrhythmia Default Mode Network Decoupling. Each was derived from different understandings of brain organisation. To reduce this variability, representatives from each research group agreed an integrated Visual Hallucination Framework that is consistent with current theories of veridical and hallucinatory vision. The Framework delineates cognitive systems relevant to hallucinations. It allows a systematic, consistent, investigation of relationships between the phenomenology of visual hallucinations and changes in underpinning cognitive structures. The episodic nature of hallucinations highlights separate factors associated with the onset, persistence, and end of specific hallucinations suggesting a complex relationship between state and trait markers of hallucination risk. In addition to a harmonised interpretation of existing evidence, the Framework highlights new avenues of research, and potentially, new approaches to treating distressing hallucinations.

Prevalence and nature of multi-sensory and multi-modal hallucinations in people with first episode psychosis

Hallucinations can occur in single or multiple sensory modalities. This study explored how common these experiences were in people with first episode of psychosis (n = 82). Particular attention was paid to the number of modalities reported and whether the experiences were seen to be linked temporally and thematically. It was predicted that those people reporting a greater number of hallucinations would report more delusional ideation, greater levels of distress generally and lower functioning. All participants reported hallucinations in the auditory domain, given the nature of the recruitment. The participants also reported a range of other unusual sensory experiences, with visual and tactile hallucinations being reported by over half. Moreover, single sensory experiences or unimodal hallucinations were less common than two or more hallucination modalities which was reported by 78% of the participants. The number of hallucinations was significantly associated with greater delusional ideation and higher levels of general distress, but not with reduced functioning. It is clear there is a need to refine psychological treatments so that they are better matched to the actual experiences reported by people with psychosis. Theoretical implications are also considered.

Visual phenomenology in schizophrenia and post-traumatic stress disorder: an exploratory study

BACKGROUND

Visual experiences such as hallucinations are commonly reported by people with psychosis, psychological trauma and dissociative states, although questions remain about their similarities and differences. For diagnostic and therapeutic purposes, clinical research must better delineate and compare the characteristics of these experiences in post-traumatic stress disorder (PTSD) and in schizophrenia.

AIMS

To compare visual phenomena and dissociation in participants with a primary psychotic illness and those with a trauma diagnosis.

METHOD

A quantitative group design study comparing visual phenomena in three participant groups who also have a history of hearing voices: schizophrenia and no trauma history (n = 19), PTSD with dissociation (n = 17) and comorbid schizophrenia and PTSD (n = 20). Validated clinical measures included the North-East Visual Hallucination Interview, PTSD Symptoms Scale Interview, Clinician Administered Dissociative States Scale, Psychotic Symptoms Rating Scales and Positive and Negative Syndrome Scale.

RESULTS

There was a remarkable similarity in visual experiences, including rates of complex visual hallucinations, between the three diagnostic groups. There were no significant differences in the severity or components of distress surrounding the visual experiences. Dissociation predicted visual hallucination severity for the comorbid schizophrenia and PTSD group, but not for PTSD or schizophrenia alone.

CONCLUSIONS

Visual experiences in PTSD can include visual hallucinations that are indistinguishable from those experienced in schizophrenia. Multimodal hallucinations are frequently observed in both schizophrenia and PTSD. A model for visual hallucinations in PTSD is suggested, following two separate neurobiological pathways based on distinct responses to trauma.

Distinguishing multimodal versus multisensory hallucinations in psychosis: Key definitions and a way forward

The study of hallucinations across multiple senses in psychosis has garnered renewed interest. Recent studies have adopted the term multimodal hallucinations to describe these experiences, yet some appear to be investigating a different, but related, phenomenon. In the current paper, we suggest use of the terms multimodal hallucinations and multisensory hallucinations to categorise distinct events that involve unusual sensory experiences across multiple domains. We propose that the constructs of temporality and relatedness are critical to delineating these experiences, where multimodal hallucinations refer to hallucinations in two or more sensory modes occurring concurrently in time and/or with significant thematic overlaps. Multisensory hallucinations conversely denote similar multisensory experiences, but with no temporal or relatedness constraints. This is accompanied by a decision-making framework for identifying whether a set of unusual perceptual experiences constitutes multimodal hallucinations or otherwise. We conclude by suggesting several priorities for future research, including empirical validation of our proposed model, further investigation of phenomenology, developing appropriate assessment tools and investigating underlying cognitive and other aetiological mechanisms.

Multimodal versus unimodal auditory hallucinations in clinical practice: Clinical characteristics and treatment outcomes

Psychological treatments for hallucinations typically target auditory verbal hallucinations (AVH) but neglect the influence of hallucinations in other sensory modalities. This study compared the baseline clinical characteristics and therapeutic outcomes (following brief Coping Strategy Enhancement) of adult clients (N = 100) with multimodal or unimodal (auditory) hallucinations attending an outpatient service for distressing AVH. The results showed that 72.1% of clients reported multimodal hallucinations in the past month. Group comparisons of most baseline clinical characteristics (AVH features, beliefs about AVH, number of traumatic events, personal and social functioning, negative affect) were non-significant. However, in the subgroup (N = 65) reporting ongoing effects of traumatic events, those with multimodal hallucinations reported significantly higher posttraumatic stress symptoms (d = 0.62). Notably, both multimodal and unimodal hallucination groups showed improvement in AVH distress and frequency post-treatment, but group differences in treatment outcomes were not significant. These findings, in a naturalistic service setting, confirm that multimodal hallucinations are common in people seeking help for distressing AVH and may be associated with higher levels of posttraumatic stress symptoms. Importantly, they also suggest that psychological therapy may be suitable and effective for clients experiencing AVH - irrespective of the presence of hallucinations in other sensory modalities.

Comparing Primary Voice-Hearers with and without Hallucinations in Other Sensory Modalities

There has been burgeoning interest in studying hallucinations in psychosis occurring across multiple sensory modalities. The current study aimed to characterize the auditory hallucination and delusion profiles in patients with auditory hallucinations only versus those with multisensory hallucinations. Participants with psychosis were partitioned into groups with voices only (AVH; n = 50) versus voices plus hallucinations in at least one other sensory modality (AVH+; n = 50), based on their responses on the Scale for the Assessment of Positive Symptoms (SAPS). Basic demographic and clinical information was collected, and the Questionnaire for Psychotic Experiences (QPE) was used to assess psychosis phenomenology. Relative to the AVH group, greater compliance to perceived commands, auditory illusions, and sensed presences was significantly elevated in the AVH+ group. The latter group also had greater levels of delusion-related distress and functional impairment and was more likely to endorse delusions of reference and misidentification. This preliminary study uncovered important phenomenological differences in those with multisensory hallucinations. Future hallucination research extending beyond the auditory modality is needed.

A Review of Multimodal Hallucinations: Categorization, Assessment, Theoretical Perspectives, and Clinical Recommendations

Hallucinations can occur in different sensory modalities, both simultaneously and serially in time. They have typically been studied in clinical populations as phenomena occurring in a single sensory modality. Hallucinatory experiences occurring in multiple sensory systems-multimodal hallucinations (MMHs)-are more prevalent than previously thought and may have greater adverse impact than unimodal ones, but they remain relatively underresearched. Here, we review and discuss: (1) the definition and categorization of both serial and simultaneous MMHs, (2) available assessment tools and how they can be improved, and (3) the explanatory power that current hallucination theories have for MMHs. Overall, we suggest that current models need to be updated or developed to account for MMHs and to inform research into the underlying processes of such hallucinatory phenomena. We make recommendations for future research and for clinical practice, including the need for service user involvement and for better assessment tools that can reliably measure MMHs and distinguish them from other related phenomena.

Characteristics of non-clinical hallucinations: A mixed-methods analysis of auditory, visual, tactile and olfactory hallucinations in a primary voice-hearing cohort

Phenomenological studies involving hallucinations in non-clinical populations have been relatively neglected, especially within the non-auditory realm. Relevant knowledge would help further a more nuanced understanding of the psychosis continuum. Participants (N=33) were non-clinical voice-hearers, who have experienced auditory verbal hallucinations, but with no known mental health diagnosis and not taking any prescribed psychiatric medications. A comprehensive hallucinations phenomenology interview was conducted to assess physical, cognitive and emotional characteristics of hallucinatory experiences across sensory domains. Mixed methods analysis was employed. Characteristics of reported AVHs were mostly in agreement with existing knowledge, though some deviations did exist (e.g. controllability). In addition, 50%, 24% and 29% of our voice-hearing sample experienced hallucinations in the visual, tactile and olfactory domains at least once a week. In contrast, delusions and disordered thinking were rare. Qualitative thematic analysis yielded added phenomenological insights into contextual triggers as well as the content and perceived purpose(s) of multisensory hallucinations. Our findings highlight lesser-reported data that hallucinations in non-auditory domains are relatively frequent in non-clinical voice-hearers. However, other psychotic-like symptoms (i.e. delusions and thought disorder) seem less common. These insights should be considered in the context of the psychosis continuum argument.

Quantifying auditory impressions in dreams in order to assess the relevance of dreaming as a model for psychosis

A long noted hypothesis is that mechanisms of dreaming play a role in psychotic hallucinations. One challenge for this hypothesis is that while psychotic hallucinations primarily are auditory, dreaming most characteristically is visual. At the same time, previous studies have not explicitly examined auditory impressions in dreaming. Here, we mapped the prevalence and characteristics of auditory impressions in 130 dreams reported after spontaneous awakenings from sleep in 13 normal, healthy people. We instructed participants to report any dream they could recall and to pay particular attention to possible auditory impressions. The participants reported auditory impressions in 93.9% of their dreams on average. The most prevalent auditory type was other people speaking (83.9% of participants’ dreams), followed by the dreamer speaking (60.0%), and other types of sounds (e.g. music, 33.1%). Of altogether 407 instances of auditory impressions in the 130 dreams, auditory quality was judged comparable to waking in 46.4%, indeterminate in 50.6%, and absent or only thought-like in 2.9%. The results suggest that also internally generated auditory (verbal) sensations are a central component of dreaming, typically occurring several times every night in normal, healthy people.