The auditory dorsal stream plays a crucial role in projecting hallucinated voices into external space

Hallucination, imagery, dreaming: reassembling stimulus-independent perceptions based on Edmund Parish's classic misperception framework

Within the broad field of human perception lies the category of stimulus-independent perceptions, which draws together experiences such as hallucinations, mental imagery and dreams. Traditional divisions between medical and psychological sciences have contributed to these experiences being investigated separately. This review aims to examine their similarities and differences at the levels of phenomenology and underlying brain function and thus reassemble them within a common framework. Using Edmund Parish's historical work as a guiding tool and the latest research findings in the cognitive, clinical and computational sciences, we consider how different perspectives may be reconciled and help generate novel hypotheses for future research. This article is part of the theme issue 'Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation'.

Hallucinating schizophrenia patients have longer left arcuate fasciculus fiber tracks: a DTI tractography study

The arcuate fasciculus (AF) has been implicated in the pathology behind schizophrenia and auditory verbal hallucinations (AVHs). White matter tracts forming the arcuate fasciculus can be quantified and visualized using diffusion tensor imaging (DTI) tractography. Although there have been a number of studies on this topic, the results have been conflicting. Studying the underlying white matter structure of the AF could shed light on the constrains for interaction between temporal and frontal language areas in AVHs. The participants were 66 patients with a schizophrenia diagnosis, where AVHs were defined from the Positive and Negative Syndrome Scale (PANSS), and compared with a healthy control group. DTI was performed on a 3T MR scanner, and tensor estimation was done using deterministic streamline tractography. Statistical analysis of the data showed significantly longer reconstructed tracks along the AF in patients with severe and frequent AVHs, as well as an overall significant asymmetry with longer tracks in the left compared to the right side. In addition, there were significant positive correlations between PANSS scores and track length, track volume, and number of track streamlines for the posterior AF segment on the left side. It is concluded that the present DTI results may have implications for interpretations of functional imaging results.

The Self, Agency and Spatial Externalizations of Inner Verbal Thoughts, and Auditory Verbal Hallucinations

Aim: Auditory Verbal Hallucinations (AVH) are experienced as the "voices" of others (O-AVH) or self (S-AVH) in internal space/inside the head (IS-AVH) or external space (ES-AVH), and are considered to result from agency and spatial externalizations of inner speech. Both types of externalizations are conflated, and the relationship between these externalizations and AVH experiences is unclear. In this paper, I investigate the relationship between cognitive agency and spatial externalizations and between these externalizations and the types of AVH experience. Method: Twenty-five patients with history of AVH and 24 matched healthy controls performed agency and spatial distinction tasks: distinction between self-generated (read) (S) sentences and other-generated (O) sentences, and between sentences read silently (experienced in internal space, IS) and sentences read aloud (experienced in external space, ES). Regression analyses between misattribution biases (S-O vs. IS-ES, and O-S vs. ES-IS) were obtained. t tests were used to compare misattribution biases between AVH subtypes (S-AVH vs. O-AVH, and IS-AVH vs. ES-AVH). Results: Regressions suggest that agency distinction is independent from spatial distinction in both groups. O-AVH and S-AVH subgroups differed only with respect to S-O bias, and IS-AVH and ES-AVH subgroups differed only with respect to IS-ES bias. Conclusion: These results suggest that agency and spatial externalizations of inner speech are independent at phenomenological and cognitive and levels; and that these externalizations are co-related across levels. I discuss the implications of these findings in the wider context of research on AVH and on the experience of self.

Draining the pond and catching the fish: Uncovering the ecosystem of auditory verbal hallucinations

The various models proposed for the mediation of auditory verbal hallucinations (AVH) implicate a considerable number of brain areas and mechanisms. To establish which of those mechanisms are actually involved in the mediation of AVH, we developed a novel method to analyze functional MRI data, which allows for the detection of the full network of mutually interacting brain states, and the identification of those states that are relevant to the mediation of AVH, while applying a minimum number of preconceived assumptions. This method is comparable to the draining of a pond to lay bare the full ecosystem that affects the presence of a particular fish species. We used this model to analyze the fMRI data of 85 psychotic patients experiencing AVH. The data were decomposed into 98 independent components (ICs) representing all major functions active in the brain during scanning. ICs involved in mediating AVH were identified by associating their time series with the hallucination time series as provided by subjects within the scanner. Using graph theory, a network of interacting ICs was created, which was clustered into IC modules. We used causal reasoning software to determine the direction of links in this network, and discover the chain of events that leads to the conscious experience of hallucinations. Hallucinatory activity was linked to three of the seven IC clusters and 11 of the 98 ICs. ICs with the most influential roles in producing AVH-related activity were those within the so-called salience network (comprising the anterior cingulate gyrus, right insula, Broca's homologue, premotor cortex, and supramarginal gyrus). Broca's area and the cerebellar regions were significantly, but more distantly involved in the mediation of AVH. These results support the notion that AVH are largely mediated by the salience network. We therefore propose that the mediation of AVH in the context of schizophrenia spectrum disorders involves the attribution of an excess of negative salience by anterior-cingulate areas to linguistic input from Broca's right homologue, followed by subsequent processing errors in areas further 'downstream' the causal chain of events. We provide a detailed account of the origin of AVH for this patient group, and make suggestions for selective interventions directed at the most relevant brain areas.

Are there clinical differences between inner, outer or dual spatial locations of auditory verbal hallucinations?

The aim of the present exploratory study was to examine the clinical differences of Auditory Verbal Hallucinations (AVHs) according to their spatial localization. Sixty-six outpatients were divided into three separate groups: inner, external and dual AVHs. The three groups were compared on sociodemographic variables (age, gender, education, marital status, living situation, employment, social disability), on clinical psychiatric characteristics (diagnosis, medication, comorbidities, illness onset, illness duration and hospitalizations) and on the measure yielded by the clinical assessments (Brief Psychiatric Rating Scale-Expanded, version 4.0; Maastricht Voices Interview for Adults; Belief About Voices Questionnaire Revised, the Clinical Global Impression, the Global Assessment Functioning Self-Esteem Rating Short Form, the World Health Organisation Quality of Life-Bref). Gender, living situation, social quality of life and some items regarding beliefs about AVHs raised significant difference, however most of the other comparisons failed to reach significance. Taken together, our findings suggest that all AVHs subtypes have equal clinical significance in patients presenting a chronic mental illness. However, the power of the study limits the generalization of the findings. Clinical implications of the findings are proposed.

Positive symptoms associate with cortical thinning in the superior temporal gyrus via the ENIGMA Schizophrenia consortium

OBJECTIVE

Based on the role of the superior temporal gyrus (STG) in auditory processing, language comprehension and self-monitoring, this study aimed to investigate the relationship between STG cortical thickness and positive symptom severity in schizophrenia.

METHOD

This prospective meta-analysis includes data from 1987 individuals with schizophrenia collected at seventeen centres around the world that contribute to the ENIGMA Schizophrenia Working Group. STG thickness measures were extracted from T1-weighted brain scans using FreeSurfer. The study performed a meta-analysis of effect sizes across sites generated by a model predicting left or right STG thickness with a positive symptom severity score (harmonized SAPS or PANSS-positive scores), while controlling for age, sex and site. Secondary models investigated relationships between antipsychotic medication, duration of illness, overall illness severity, handedness and STG thickness.

RESULTS

Positive symptom severity was negatively related to STG thickness in both hemispheres (left: β_std = -0.052; P = 0.021; right: β_std = -0.073; P = 0.001) when statistically controlling for age, sex and site. This effect remained stable in models including duration of illness, antipsychotic medication or handedness.

CONCLUSION

Our findings further underline the important role of the STG in hallmark symptoms in schizophrenia. These findings can assist in advancing insight into symptom-relevant pathophysiological mechanisms in schizophrenia.

Understanding auditory verbal hallucinations: a systematic review of current evidence

OBJECTIVE

Auditory verbal hallucinations (AVHs) are core features of psychotic illness and remain significant in predicting poor outcome and risk. There has been a wide range of approaches to understanding these experiences.

METHOD

A systematic literature review summarizing different methods of investigation and their results; phenomenology, descriptive psychopathology, psychological, cognitive neurobiology, and neuroimaging.

RESULTS

A number of 764 papers and texts were screened and 113 reviewed. Phenomenological studies are comparably few in number, and psychopathology remains based on concepts defined in the early 20th century. Psychological models focus on voice content and emotional reaction, and suggest a continuum of AVHs from normal experience. Neuropsychological models include AVHs as misattribution of inner speech, whilst functional neuroimaging studies focus on the spontaneous activity and connectivity of auditory networks.

CONCLUSION

There has been a large growth in research on AVHs in recent decades dominated by neurobiological and neuroimaging studies. Future research should include focus on phenomenological aspects and AVHs change over the course of developing illness. Integration between branches of enquiry is needed, and the risk is that without this, models are proposed and investigated that bear scant relevance to the symptom itself.

[Multidimensionality of inner speech and its relationship with abnormal perceptions]

BACKGROUND

Inner speech is a common human experience. Recently, there have been studies linking this experience with cognitive functions, such as problem solving, reading, writing, autobiographical memory, and some disorders, such as anxiety and depression. In addition, inner speech is recognised as the main source of auditory hallucinations.

OBJECTIVES

The main purpose of this study is to establish the factor structure of Varieties of Inner Speech Questionnaire (VISQ) in a sample of the Colombian population. Furthermore, it aims at establishing a link between VISQ and abnormal perceptions.

METHOD

This was a cross-sectional study in which 232 college students were assessed using the VISQ and the Cardiff Anomalous Perceptions Scale (CAPS).

RESULTS

Through an exploratory factor analysis, a structure of three factors was found: Other Voices in the Internal Speech, Condensed Inner speech, and Dialogical/Evaluative Inner speech, all of them with acceptable levels of reliability. Gender differences were found in the second and third factor, with higher averages for women. Positive correlations were found among the three VISQ and the two CAPS factors: Multimodal Perceptual Alterations and Experiences Associated with the Temporal Lobe.

CONCLUSIONS

The results are consistent with previous findings linking the factors of inner speech with the propensity to auditory hallucination, a phenomenon widely associated with temporal lobe abnormalities. The hallucinations associated with other perceptual systems, however, are still weakly explained.

Auditory verbal hallucinations in first-episode psychosis: a phenomenological investigation

BACKGROUND

In dimensional understanding of psychosis, auditory verbal hallucinations (AVH) are unitary phenomena present on a continuum from non-clinical voice hearing to severe mental illness. There is mixed evidence for this approach and a relative absence of research into subjective experience of AVH in early psychosis.

AIMS

To conduct primary research into the nature of subjective experience of AVH in first-episode psychosis.

METHOD

A phenomenological study using diary and photo-elicitation qualitative techniques investigating the subjective experience of AVH in 25 young people with first-episode psychosis.

RESULTS

AVH are characterised by: (a) entity, as though from a living being with complex social interchange; and (b) control, exerting authority with ability to influence. AVH are also received with passivity, often accompanied by sensation in other modalities.

CONCLUSIONS

A modern detailed phenomenological investigation, without presupposition, gives results that echo known descriptive psychopathology. However, novel findings also emerge that may be features of AVH in psychosis not currently captured with standardised measures.

DECLARATION OF INTEREST

None.

COPYRIGHT AND USAGE

© The Royal College of Psychiatrists 2016. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) licence.

"Who is talking to me?" - Self-other attribution of auditory hallucinations and sulcation of the right temporoparietal junction

Brain imaging research in schizophrenia has provided a better understanding of the neural basis of auditory hallucinations (AH). Recently, renewed interest in the phenomenology of AH raised questions related to their neural substrates. Hence, the neural basis of AH self/other attribution have yet to be investigated as beliefs regarding the origin of the voices is a cardinal feature of AH phenomenology. As the right temporoparietal junction (TPJ) and the inferior parietal lobule (IPL) play a key role in disentangling the origin of sensory events and in self/other distinction, we tested the hypothesis that the morphology of the IPL/TPJ area may be involved in AH self/other attribution. Magnetic resonance images of 39 right-handed patients with persistent auditory hallucinations and 19 healthy subjects were analyzed with sulcus-based morphometry. AH self-other attribution were found to be associated with the sulcal pattern of the posterior part of the Sylvian fissure, encompassing the IPL/TPJ area. The preference for the attribution of AH to self or to others could be associated with early neurodevelopmental events as the sulcal pattern is determined during fetal life and is stable after birth. Our study also raises basic cognitive questions regarding self-consciousness and suggest that impairments at a pre-reflexive level, leading to hearing his/her thoughts as voices ('I' level or feeling of agency), and a reflexive level leading to attribution belief ('Me' level or judgment of agency) are likely involved in AH.

A Neuropsychological Approach to Auditory Verbal Hallucinations and Thought Insertion - Grounded in Normal Voice Perception

A neuropsychological perspective on auditory verbal hallucinations (AVH) links key phenomenological features of the experience, such as voice location and identity, to functionally separable pathways in normal human audition. Although this auditory processing stream (APS) framework has proven valuable for integrating research on phenomenology with cognitive and neural accounts of hallucinatory experiences, it has not yet been applied to other symptoms presumed to be closely related to AVH – such as thought insertion (TI). In this paper, I propose that an APS framework offers a useful way of thinking about the experience of TI as well as AVH, providing a common conceptual framework for both. I argue that previous self-monitoring theories struggle to account for both the differences and similarities in the characteristic features of AVH and TI, which can be readily accommodated within an APS framework. Furthermore, the APS framework can be integrated with predictive processing accounts of psychotic symptoms; makes predictions about potential sites of prediction error signals; and may offer a template for understanding a range of other symptoms beyond AVH and TI.

The role of the superior temporal lobe in auditory false perceptions: a transcranial direct current stimulation study

Neuroimaging has shown that a network of cortical areas, which includes the superior temporal gyrus, is active during auditory verbal hallucinations (AVHs). In the present study, healthy, non-hallucinating participants (N=30) completed an auditory signal detection task, in which participants were required to detect a voice in short bursts of white noise, with the variable of interest being the rate of false auditory verbal perceptions. This paradigm was coupled with transcranial direct current stimulation, a noninvasive brain stimulation technique, to test the involvement of the left posterior superior temporal gyrus in the creation of auditory false perceptions. The results showed that increasing the levels of excitability in this region led to a higher rate of ‘false alarm’ responses than when levels of excitability were decreased, with false alarm responses under a sham stimulation condition lying at a mid-point between anodal and cathodal stimulation conditions. There were also corresponding changes in signal detection parameters. These results are discussed in terms of prominent cognitive neuroscientific theories of AVHs, and potential future directions for research are outlined.

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Investigated role of left STG in false perceptions of voices in white noise.

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Used noninvasive brain stimulation whilst participants listened to white noise.

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Tested whether number of false perceptions was affected by stimulation of STG.

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Higher false alarm rate when excitability increased than when decreased.

Better than mermaids and stray dogs? Subtyping auditory verbal hallucinations and its implications for research and practice

The phenomenological diversity of auditory verbal hallucinations (AVH) is not currently accounted for by any model based around a single mechanism. This has led to the proposal that there may be distinct AVH subtypes, which each possess unique (as well as shared) underpinning mechanisms. This could have important implications both for research design and clinical interventions because different subtypes may be responsive to different types of treatment. This article explores how AVH subtypes may be identified at the levels of phenomenology, cognition, neurology, etiology, treatment response, diagnosis, and voice hearer's own interpretations. Five subtypes are proposed; hypervigilance, autobiographical memory (subdivided into dissociative and nondissociative), inner speech (subdivided into obsessional, own thought, and novel), epileptic and deafferentation. We suggest other facets of AVH, including negative content and form (eg, commands), may be best treated as dimensional constructs that vary across subtypes. After considering the limitations and challenges of AVH subtyping, we highlight future research directions, including the need for a subtype assessment tool.

Auditory verbal hallucinations as atypical inner speech monitoring, and the potential of neurostimulation as a treatment option

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We discuss ‘inner speech’ theories of auditory verbal hallucinations.

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Atypical self-monitoring may lead to the experience of inner speech as external.

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We summarize research into the use of neurostimulation to treat hallucinations.

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Effects of neurostimulation may be due to modulation of self-monitoring networks.

Auditory verbal hallucinations (AVHs) are the experience of hearing voices in the absence of any speaker, often associated with a schizophrenia diagnosis. Prominent cognitive models of AVHs suggest they may be the result of inner speech being misattributed to an external or non-self source, due to atypical self- or reality monitoring. These arguments are supported by studies showing that people experiencing AVHs often show an externalising bias during monitoring tasks, and neuroimaging evidence which implicates superior temporal brain regions, both during AVHs and during tasks that measure verbal self-monitoring performance. Recently, efficacy of noninvasive neurostimulation techniques as a treatment option for AVHs has been tested. Meta-analyses show a moderate effect size in reduction of AVH frequency, but there has been little attempt to explain the therapeutic effect of neurostimulation in relation to existing cognitive models. This article reviews inner speech models of AVHs, and argues that a possible explanation for reduction in frequency following treatment may be modulation of activity in the brain regions involving the monitoring of inner speech.