Voice identity recognition failure in patients with schizophrenia

Altered Auditory Self-recognition in People with Schizophrenia

Self-recognition is of great significance to our sense of self. To date, disturbances in the processing of visual self-recognition are well studied in people with schizophrenia, whereas relatively few studies have focused on the processing of self in other domains, such as auditory. An investigation of auditory self-recognition contributes to delineate changes related to self and the potential roots of the described psychopathological aspects connoting schizophrenia. By applying unimodal task and multisensory test, this study investigated auditory self-recognition in people with schizophrenia under unimodal and bimodal circumstances. Forty-six adults diagnosed with schizophrenia and thirty-two healthy controls were involved in this study. Results suggested that people with schizophrenia seemed to have significantly lower perceptual sensitivity in detecting self-voice, and also showed stricter judgment criteria in self-voice decision. Furthermore, in the presentation of stimuli that combined the stimulation of others' faces with one's own voice, people with schizophrenia mistakenly attributed the voices of others as their own. In conclusion, altered auditory self-recognition in people with schizophrenia was found.

Abnormal Local Activity and Functional Dysconnectivity in Patients with Schizophrenia Having Auditory Verbal Hallucinations

Auditory verbal hallucination (AVH) is emphasized as a pathological hallmark of schizophrenia. Neuroimaging studies provide evidence linking AVH to overlapping functional abnormalities in distributed networks. However, no clear conclusion has still been reached. This study aimed to further explore the brain activity of patients with schizophrenia having AVH from both local activity (LA) and functional connectivity (FC) insights, while excluding confounding factors from other positive symptoms. A total of 42 patients with AVH (AVH patients group, APG), 26 without AVH (non-AVH patients group, NPG), and 82 normal controls (NC) underwent resting-state functional magnetic resonance imaging (fMRI). LA measures, including regional homogeneity (ReHo) and fractional amplitude of low-frequency fluctuations (fALFF), and FC measures were evaluated to understand the neuroimaging mechanism of AVH. APG showed increased ReHo and fALFF in the bilateral putamen (Put) compared with NPG and NC. FC analysis (using bilateral putamen as seeds) revealed that all patients showed abnormal FC of multiple resting-state network regions, including the anterior and post cingulate cortex, middle frontal gyrus, inferior parietal gyrus, and left angular gyrus. Interestingly, APG showed significantly decreased FC of insula extending to the superior temporal gyrus and inferior frontal gyrus compared with NPG and NC. The present findings suggested a significant correlation of abnormal LA and dysfunctional putamen-auditory cortical connectivity with the neuropathological mechanism of AVH, providing evidence for the functional disconnection hypothesis of schizophrenia.

Intranasal oxytocin modulates brain responses to voice-identity recognition in typically developing individuals, but not in ASD

Faces and voices are prominent cues for person-identity recognition. Face recognition behavior and associated brain responses can be enhanced by intranasal administration of oxytocin. It is unknown whether oxytocin can also augment voice-identity recognition mechanisms. To find it out is particularly relevant for individuals who have difficulties recognizing voice identity such as individuals diagnosed with autism spectrum disorder (ASD). We conducted a combined behavioral and functional magnetic resonance imaging (fMRI) study to investigate voice-identity recognition following intranasal administration of oxytocin or placebo in a group of adults diagnosed with ASD (full-scale intelligence quotient > 85) and pairwise-matched typically developing (TD) controls. A single dose of 24 IU oxytocin was administered in a randomized, double-blind, placebo-controlled and cross-over design. In the control group, but not in the ASD group, administration of oxytocin compared to placebo increased responses to recognition of voice identity in contrast to speech in the right posterior superior temporal sulcus/gyrus (pSTS/G) - a region implicated in the perceptual analysis of voice-identity information. In the ASD group, the right pSTS/G responses were positively correlated with voice-identity recognition accuracy in the oxytocin condition, but not in the placebo condition. Oxytocin did not improve voice-identity recognition performance at the group level. The ASD compared to the control group had lower right pSTS/G responses to voice-identity recognition. Since ASD is known to have atypical pSTS/G, the results indicate that the potential of intranasal oxytocin to enhance mechanisms for voice-identity recognition might be variable and dependent on the functional integrity of this brain region.

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.

Obligatory and facultative brain regions for voice-identity recognition

Recognizing the identity of others by their voice is an important skill for social interactions. To date, it remains controversial which parts of the brain are critical structures for this skill. Based on neuroimaging findings, standard models of person-identity recognition suggest that the right temporal lobe is the hub for voice-identity recognition. Neuropsychological case studies, however, reported selective deficits of voice-identity recognition in patients predominantly with right inferior parietal lobe lesions. Here, our aim was to work towards resolving the discrepancy between neuroimaging studies and neuropsychological case studies to find out which brain structures are critical for voice-identity recognition in humans. We performed a voxel-based lesion-behaviour mapping study in a cohort of patients (n = 58) with unilateral focal brain lesions. The study included a comprehensive behavioural test battery on voice-identity recognition of newly learned (voice-name, voice-face association learning) and familiar voices (famous voice recognition) as well as visual (face-identity recognition) and acoustic control tests (vocal-pitch and vocal-timbre discrimination). The study also comprised clinically established tests (neuropsychological assessment, audiometry) and high-resolution structural brain images. The three key findings were: (i) a strong association between voice-identity recognition performance and right posterior/mid temporal and right inferior parietal lobe lesions; (ii) a selective association between right posterior/mid temporal lobe lesions and voice-identity recognition performance when face-identity recognition performance was factored out; and (iii) an association of right inferior parietal lobe lesions with tasks requiring the association between voices and faces but not voices and names. The results imply that the right posterior/mid temporal lobe is an obligatory structure for voice-identity recognition, while the inferior parietal lobe is only a facultative component of voice-identity recognition in situations where additional face-identity processing is required.

Auditory Hallucinations as Translational Psychiatry: Evidence from Magnetic Resonance Imaging

In this invited review article, I present a translational perspective and overview of our research on auditory hallucinations in schizophrenia at the University of Bergen, Norway, with a focus on the neuronal mechanisms underlying the phenomenology of experiencing “hearing voices”. An auditory verbal hallucination (i.e. hearing a voice) is defined as a sensory experience in the absence of a corresponding external sensory source that could explain the phenomenological experience. I suggest a general frame or scheme for the study of auditory verbal hallucinations, called Levels of Explanation. Using a Levels of Explanation approach, mental phenomena can be described and explained at different levels (cultural, clinical, cognitive, brain-imaging, cellular and molecular). Another way of saying this is that, to advance knowledge in a research field, it is not only necessary to replicate findings, but also to show how evidence obtained with one method, and at one level of explanation, converges with evidence obtained with another method at another level. To achieve breakthroughs in our understanding of auditory verbal hallucinations, we have to advance vertically through the various levels, rather than the more common approach of staying at our favourite level and advancing horizontally (e.g., more advanced techniques and data acquisition analyses). The horizontal expansion will, however, not advance a deeper understanding of how an auditory verbal hallucination spontaneously starts and stops. Finally, I present data from the clinical, cognitive, brain-imaging, and cellular levels, where data from one level validate and support data at another level, called converging of evidence. Using a translational approach, the current status of auditory verbal hallucinations is that they implicate speech perception areas in the left temporal lobe, impairing perception of and attention to external sounds. Preliminary results also show that amygdala is implicated in the emotional «colouring» of the voices and that excitatory neurotransmitters might be involved. What we do not know is why hallucinatory episodes occur spontaneously, why they fluctuate over time, and what makes them spontaneously stop. Moreover, is voice hearing a category or dimension in its own right, independent of diagnosis, and why is the auditory modality predominantly implicated in psychotic disorders, while the visual modality dominates in, for example, neurological diseases?

Drawing a distinction between familiar and unfamiliar voice processing: A review of neuropsychological, clinical and empirical findings

Thirty years on from their initial observation that familiar voice recognition is not the same as unfamiliar voice discrimination (van Lancker and Kreiman, 1987), the current paper reviews available evidence in support of a distinction between familiar and unfamiliar voice processing. Here, an extensive review of the literature is provided, drawing on evidence from four domains of interest: the neuropsychological study of healthy individuals, neuropsychological investigation of brain-damaged individuals, the exploration of voice recognition deficits in less commonly studied clinical conditions, and finally empirical data from healthy individuals. All evidence is assessed in terms of its contribution to the question of interest - is familiar voice processing distinct from unfamiliar voice processing. In this regard, the evidence provides compelling support for van Lancker and Kreiman's early observation. Two considerations result: First, the limits of research based on one or other type of voice stimulus are more clearly appreciated. Second, given the demonstration of a distinction between unfamiliar and familiar voice processing, a new wave of research is encouraged which examines the transition involved as a voice is learned.

Abnormal Degree Centrality of Bilateral Putamen and Left Superior Frontal Gyrus in Schizophrenia with Auditory Hallucinations: A Resting-state Functional Magnetic Resonance Imaging Study

BACKGROUND

Dysconnectivity hypothesis of schizophrenia has been increasingly emphasized. Recent researches showed that this dysconnectivity might be related to occurrence of auditory hallucination (AH). However, there is still no consistent conclusion. This study aimed to explore intrinsic dysconnectivity pattern of whole-brain functional networks at voxel level in schizophrenic with AH.

METHODS

Auditory hallucinated patients group (n = 42 APG), no hallucinated patients group (n = 42 NPG) and normal controls (n = 84 NCs) were analyzed by resting-state functional magnetic resonance imaging. The functional connectivity metrics index (degree centrality [DC]) across the entire brain networks was calculated and evaluated among three groups.

RESULTS

DC decreased in the bilateral putamen and increased in the left superior frontal gyrus in all the patients. However, in APG, the changes of DC were more obvious compared with NPG. Symptomology scores were negatively correlated with the DC of bilateral putamen in all patients. AH score of APG positively correlated with the DC in left superior frontal gyrus but negatively correlated with the DC in bilateral putamen.

CONCLUSION

Our findings corroborated that schizophrenia was characterized by functional dysconnectivity, and the abnormal DC in bilateral putamen and left superior frontal gyrus might be crucial in the occurrence of AH.

Is this my voice or yours? The role of emotion and acoustic quality in self-other voice discrimination in schizophrenia

INTRODUCTION

Impairments in self-other voice discrimination have been consistently reported in schizophrenia, and associated with the severity of auditory verbal hallucinations (AVHs). This study probed the interactions between voice identity, voice acoustic quality, and semantic valence in a self-other voice discrimination task in schizophrenia patients compared with healthy subjects. The relationship between voice identity discrimination and AVH severity was also explored.

METHODS

Seventeen chronic schizophrenia patients and 19 healthy controls were asked to read aloud a list of adjectives characterised by emotional or neutral content. Participants' voice was recorded in the first session. In the behavioural task, 840 spoken words differing in identity (self/non-self), acoustic quality (undistorted/distorted), and semantic valence (negative/positive/neutral) were presented. Participants indicated if the words were spoken in their own voice, another person's voice, or were unsure.

RESULTS

Patients were less accurate than controls in the recognition of self-generated speech with negative content only. Impaired recognition of negative self-generated speech was associated with AVH severity ("voices conversing").

CONCLUSIONS

These results suggest that abnormalities in higher order processes (evaluation of the salience of a speech stimulus) modulate impaired self-other voice discrimination in schizophrenia. Abnormal processing of negative self-generated speech may play a role in the experience of AVH.

A Cognitive Neuroscience View of Voice-Processing Abnormalities in Schizophrenia: A Window into Auditory Verbal Hallucinations?

Auditory verbal hallucinations (AVH) are a core symptom of schizophrenia. Like "real" voices, AVH carry a rich amount of linguistic and paralinguistic cues that convey not only speech, but also affect and identity, information. Disturbed processing of voice identity, affective, and speech information has been reported in patients with schizophrenia. More recent evidence has suggested a link between voice-processing abnormalities and specific clinical symptoms of schizophrenia, especially AVH. It is still not well understood, however, to what extent these dimensions are impaired and how abnormalities in these processes might contribute to AVH. In this review, we consider behavioral, neuroimaging, and electrophysiological data to investigate the speech, identity, and affective dimensions of voice processing in schizophrenia, and we discuss how abnormalities in these processes might help to elucidate the mechanisms underlying specific phenomenological features of AVH. Schizophrenia patients exhibit behavioral and neural disturbances in the three dimensions of voice processing. Evidence suggesting a role of dysfunctional voice processing in AVH seems to be stronger for the identity and speech dimensions than for the affective domain.

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.

Voice identity discrimination and hallucination-proneness in healthy young adults: a further challenge to the continuum model of psychosis?

INTRODUCTION

Auditory hallucinations occur in schizophrenia and also in the general population. However, evidence points to differences in the nature and the mechanisms of clinical and non-clinical hallucinations, challenging the dominant assumption that they represent the same phenomenon. The current study extended this evidence by examining voice identity perception in hallucination-prone individuals. In schizophrenia, deficiencies discriminating between real (external) voices have been linked to basic acoustic cues, but voice discrimination has not yet been investigated in non-clinical hallucinations.

METHODS

Using a task identical to that employed in patients, multidimensional scaling of voice dissimilarity judgements was used to examine how healthy individuals differing in hallucination-proneness (30 high and 30 low hallucination-prone individuals) distinguish pairs of unfamiliar voices. The resulting dimensions were interpreted with reference to acoustic measures relevant to voice identity.

RESULTS

A two-dimensional "voice space", defined by fundamental frequency (F0) and formant dispersion (Df), was derived for high and low hallucination-prone groups. There were no significant differences in speaker discrimination for high versus low hallucination-prone individuals on the basis of either F0 or Df.

CONCLUSIONS

These findings suggest voice identity perception is not impaired in healthy individuals predisposed to hallucinations, adding a further challenge to the continuum model of psychotic symptoms.

Voice recognition and altered connectivity in schizophrenic patients with auditory hallucinations

Auditory verbal hallucination (AVH) is a pathological hallmark of schizophrenia; however, their neural basis is unclear. Voice identity is an important phenomenological feature of AVHs. Certain voice identity recognition deficits are specific to schizophrenic patients with AVHs. We tested our hypothesis that among schizophrenia patients with hallucination, dysfunctional voice identity recognition is associated with poor functional integration in the neural networks involved in the evaluation of voice identity. Using functional magnetic resonance imaging (fMRI) during a voice recognition task, we examined the modulation of neural network connectivity in 26 schizophrenic patients with or without AVHs, and 13 healthy controls. Our results showed that the schizophrenic patients with AVHs had altered frontotemporal connectivity compared to the schizophrenic patients without AVHs and healthy controls. The latter two groups did not show any differences in functional connectivity. In addition, the strength of frontotemporal connectivity was correlated with the accuracy of voice recognition. These findings provide preliminary evidence that impaired functional integration may contribute to the faulty appraisal of voice identity in schizophrenic patients with AVHs.

Voices to reckon with: perceptions of voice identity in clinical and non-clinical voice hearers

The current review focuses on the perception of voice identity in clinical and non-clinical voice hearers. Identity perception in auditory verbal hallucinations (AVH) is grounded in the mechanisms of human (i.e., real, external) voice perception, and shapes the emotional (distress) and behavioral (help-seeking) response to the experience. Yet, the phenomenological assessment of voice identity is often limited, for example to the gender of the voice, and has failed to take advantage of recent models and evidence on human voice perception. In this paper we aim to synthesize the literature on identity in real and hallucinated voices and begin by providing a comprehensive overview of the features used to judge voice identity in healthy individuals and in people with schizophrenia. The findings suggest some subtle, but possibly systematic biases across different levels of voice identity in clinical hallucinators that are associated with higher levels of distress. Next we provide a critical evaluation of voice processing abilities in clinical and non-clinical voice hearers, including recent data collected in our laboratory. Our studies used diverse methods, assessing recognition and binding of words and voices in memory as well as multidimensional scaling of voice dissimilarity judgments. The findings overall point to significant difficulties recognizing familiar speakers and discriminating between unfamiliar speakers in people with schizophrenia, both with and without AVH. In contrast, these voice processing abilities appear to be generally intact in non-clinical hallucinators. The review highlights some important avenues for future research and treatment of AVH associated with a need for care, and suggests some novel insights into other symptoms of psychosis.