Auditory processing and 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.

A detailed examination of pitch discrimination deficits associated with auditory verbal hallucinations in schizophrenia

Individuals with schizophrenia spectrum disorders (SSD) and a history of experiencing auditory verbal hallucinations (AVH) exhibit poor pitch discrimination relative to those with an SSD but no AVH history. The present study extended this research, asking if a lifetime history, and the current presence, of AVH exacerbated the pitch discrimination challenges that are seen in SSD. Participants completed a pitch discrimination task, where the tones presented differed in pitch by either 2 %, 5 %, 10 %, 25 % or 50 %. Pitch discrimination accuracy, sensitivity, reaction time (RT) and intra-individual RT variability (IIV) were examined in individuals with SSD and AVHs (AVH+; n = 46), or without AVHs (AVH-; n = 31), and healthy controls (HC; n = 131). Secondary analyses split the AVH+ group into state (i.e., actively experiencing AVH; n = 32) and trait hallucinators (i.e., a history of, but not actively experiencing, AVH; n = 16). Relative to HC, significantly poorer accuracy and sensitivity was detected in individuals with SSD at 2 % and 5 % pitch deviants, and in hallucinators at 10 %; however, no significant differences in accuracy, sensitivity, RT nor IIV were found between AVH+ and AVH- groups. No differences between state and trait hallucinators were observed. A general SSD deficit drove the current findings. The findings may inform future research into the auditory processing capabilities of AVH+ individuals.

Feasibility and clinical utility of using the tone matching test for assessment of early auditory processing in schizophrenia

Early auditory processing (EAP) deficits are prevalent in schizophrenia and linked to disturbances in higher order cognition and daily functioning. Treatments that target EAP have the potential to drive downstream cognitive and functional improvements, but clinically feasible means to detect EAP impairment are lacking. This report describes the clinical feasibility and utility of using the Tone Matching (TM) Test to assess EAP in adults with schizophrenia. Clinicians were trained to administer the TM Test as part of a baseline cognitive battery to inform choice of cognitive remediation (CR) exercises. Only if the TM Test indicated EAP impairment, were the recommended CR exercises to include EAP training. Results indicated clinicians included the TM Test in all baseline assessments and identified 51.72% as EAP impaired. There were significant positive relationships between TM Test performance and cognitive summary scores, confirming instrumental validity. All clinicians found the TM Test useful for CR treatment planning. CR participants with impaired EAP spent significantly more training time on EAP exercises compared to CR participants with intact EAP (20.11% vs 3.32%). This study found that it is feasible to use the TM Test in community clinics and the test was perceived as clinically useful for personalizing treatment.

Working memory and sensory memory in subclinical high schizotypy: An avenue for understanding schizophrenia?

The search for robust, reliable biomarkers of schizophrenia remains a high priority in psychiatry. Biomarkers are valuable because they can reveal the underlying mechanisms of symptoms and monitor treatment progress and may predict future risk of developing schizophrenia. Despite the existence of various promising biomarkers that relate to symptoms across the schizophrenia spectrum, and despite published recommendations encouraging multivariate metrics, they are rarely investigated simultaneously within the same individuals. In those with schizophrenia, the magnitude of purported biomarkers is complicated by comorbid diagnoses, medications and other treatments. Here, we argue three points. First, we reiterate the importance of assessing multiple biomarkers simultaneously. Second, we argue that investigating biomarkers in those with schizophrenia-related traits (schizotypy) in the general population can accelerate progress in understanding the mechanisms of schizophrenia. We focus on biomarkers of sensory and working memory in schizophrenia and their smaller effects in individuals with nonclinical schizotypy. Third, we note irregularities across research domains leading to the current situation in which there is a preponderance of data on auditory sensory memory and visual working memory, but markedly less in visual (iconic) memory and auditory working memory, particularly when focusing on schizotypy where data are either scarce or inconsistent. Together, this review highlights opportunities for researchers without access to clinical populations to address gaps in knowledge. We conclude by highlighting the theory that early sensory memory deficits contribute negatively to working memory and vice versa. This presents a mechanistic perspective where biomarkers may interact with one another and impact schizophrenia-related symptoms.

Basic auditory processing and its relationship with symptoms in patients with schizophrenia: A systematic review

Processing of basic auditory features, one of the earliest stages of auditory perception, has been the focus of considerable investigations in schizophrenia. Although numerous studies have shown abnormalities in pitch perception in schizophrenia, other basic auditory features such as intensity, duration, and sound localization have been less explored. Additionally, the relationship between basic auditory features and symptom severity shows inconsistent results, preventing concrete conclusions. Our aim was to present a comprehensive overview of basic auditory processing in schizophrenia and its relationship with symptoms. We conducted a systematic review according to the PRISMA guidelines. PubMed, Embase, and PsycINFO databases were searched for studies exploring auditory perception in schizophrenia compared to controls, with at least one behavioral task investigating basic auditory processing using pure tones. Forty-one studies were included. The majority investigated pitch processing while the others investigated intensity, duration and sound localization. The results revealed that patients have a significant deficit in the processing of all basic auditory features. Although the search for a relationship with symptoms was limited, auditory hallucinations experience appears to have an impact on basic auditory processing. Further research may examine correlations with clinical symptoms to explore the performance of patient subgroups and possibly implement remediation strategies.

Speech processing in voice-hearers: Bridging the gap between empirical research and clinical implications

Individuals who hear voices (i.e. auditory verbal hallucinations) have been reported to exhibit a range of difficulties when listening to and processing the speech of other people. These speech processing challenges are observed even in the absence of hearing voices; however, some appear to be exacerbated during periods of acute symptomology. In this advisory piece, key findings from pertinent empirical research into external speech processing in voice-hearers are presented with the intention of informing healthcare professionals. It is the view that through a better understanding of the speech processing deficits faced by individuals who hear voices, more effective communication with such patients can be had.

Perceptual pathways to hallucinogenesis

Recent advances in computational psychiatry have provided unique insights into the neural and cognitive underpinnings of psychotic symptoms. In particular, a host of new data has demonstrated the utility of computational frameworks for understanding how hallucinations might arise from alterations in typical perceptual processing. Of particular promise are models based in Bayesian inference that link hallucinatory perceptual experiences to latent states that may drive them. In this piece, we move beyond these findings to ask: how and why do these latent states arise, and how might we take advantage of heterogeneity in that process to develop precision approaches to the treatment of hallucinations? We leverage specific models of Bayesian inference to discuss components that might lead to the development of hallucinations. Using the unifying power of our model, we attempt to place disparate findings in the study of psychotic symptoms within a common framework. Finally, we suggest directions for future elaboration of these models in the service of a more refined psychiatric nosology based on predictable, testable, and ultimately treatable information processing derangements.

Attention to voices is increased in non-clinical auditory verbal hallucinations irrespective of salience

Alterations in the processing of vocal emotions have been associated with both clinical and non-clinical auditory verbal hallucinations (AVH), suggesting that changes in the mechanisms underpinning voice perception contribute to AVH. These alterations seem to be more pronounced in psychotic patients with AVH when attention demands increase. However, it remains to be clarified how attention modulates the processing of vocal emotions in individuals without clinical diagnoses who report hearing voices but no related distress. Using an active auditory oddball task, the current study clarified how emotion and attention interact during voice processing as a function of AVH proneness, and examined the contributions of stimulus valence and intensity. Participants with vs. without non-clinical AVH were presented with target vocalizations differing in valence (neutral; positive; negative) and intensity (55 decibels (dB); 75 dB). The P3b amplitude was larger in response to louder (vs. softer) vocal targets irrespective of valence, and in response to negative (vs. neutral) vocal targets irrespective of intensity. Of note, the P3b amplitude was globally increased in response to vocal targets in participants reporting AVH, and failed to be modulated by valence and intensity in these participants. These findings suggest enhanced voluntary attention to changes in vocal expressions but reduced discrimination of salient and non-salient cues. A decreased sensitivity to salience cues of vocalizations could contribute to increased cognitive control demands, setting the stage for an AVH.

Axon-glia interactions in the ascending auditory system

The auditory system detects and encodes sound information with high precision to provide a high-fidelity representation of the environment and communication. In mammals, detection occurs in the peripheral sensory organ (the cochlea) containing specialized mechanosensory cells (hair cells) that initiate the conversion of sound-generated vibrations into action potentials in the auditory nerve. Neural activity in the auditory nerve encodes information regarding the intensity and frequency of sound stimuli, which is transmitted to the auditory cortex through the ascending neural pathways. Glial cells are critical for precise control of neural conduction and synaptic transmission throughout the pathway, allowing for the precise detection of the timing, frequency, and intensity of sound signals, including the sub-millisecond temporal fidelity is necessary for tasks such as sound localization, and in humans, for processing complex sounds including speech and music. In this review, we focus on glia and glia-like cells that interact with hair cells and neurons in the ascending auditory pathway and contribute to the development, maintenance, and modulation of neural circuits and transmission in the auditory system. We also discuss the molecular mechanisms of these interactions, their impact on hearing and on auditory dysfunction associated with pathologies of each cell type.

Multisensory Integration of Emotion in Schizophrenic Patients

Multisensory integration (MSI) of emotion has been increasingly recognized as an essential element of schizophrenic patients' impairments, leading to the breakdown of their interpersonal functioning. The present review provides an updated synopsis of schizophrenics' MSI abilities in emotion processing by examining relevant behavioral and neurological research. Existing behavioral studies have adopted well-established experimental paradigms to investigate how participants understand multisensory emotion stimuli, and interpret their reciprocal interactions. Yet it remains controversial with regard to congruence-induced facilitation effects, modality dominance effects, and generalized vs specific impairment hypotheses. Such inconsistencies are likely due to differences and variations in experimental manipulations, participants' clinical symptomatology, and cognitive abilities. Recent electrophysiological and neuroimaging research has revealed aberrant indices in event-related potential (ERP) and brain activation patterns, further suggesting impaired temporal processing and dysfunctional brain regions, connectivity and circuities at different stages of MSI in emotion processing. The limitations of existing studies and implications for future MSI work are discussed in light of research designs and techniques, study samples and stimuli, and clinical applications.

Auditory processing disorder may be present in schizophrenia and it is highly correlated with formal thought disorder

The present study investigates the presence of Auditory Processing Disorder (APD) in schizophrenia and its association with symptomatology, especially Formal Thought Disorder (FTD). 50 patients with schizophrenia and 25 matched healthy controls completed a battery of three auditory processing tests. Positive and Negative Syndrome Scale (PANSS) and Thought, Language and Communication (TLC) scale were used to assess clinical symptoms. The patient group was divided into two subgroups, according to FTD severity. Auditory processing performance of the control group and the patient group was evaluated. Correlations between auditory processing scores and TLC scores, as well as auditory processing scores and PANSS scores were examined. Most of the patients, especially those with FTD, had auditory deficits that can be classified as APD. Patients showed impaired performance compared to controls in all tests. Total severity and specific factors of FTD, as well as other clinical symptoms and symptom categories were correlated with auditory processing performance. We provided evidence that APD may be present in schizophrenia and that FTD, as well as other clinical symptoms are associated with auditory processing deficits. There are important clinical implications for non-pharmacological interventions and early diagnosis of schizophrenia.

A GABA Interneuron Deficit Model of the Art of Vincent van Gogh

Vincent van Gogh was one of the most influential artists of the Western world, having shaped the post-impressionist art movement by shifting its boundaries forward into abstract expressionism. His distinctive style, which was not valued by the art-buying public during his lifetime, is nowadays one of the most sought after. However, despite the great deal of attention from academic and artistic circles, one important question remains open: was van Gogh's original style a visual manifestation distinct from his troubled mind, or was it in fact a by-product of an impairment that resulted from the psychiatric illness that marred his entire life? In this paper, we use a previously published multi-scale model of brain function to piece together a number of disparate observations about van Gogh's life and art. In particular, we first quantitatively analyze the brushwork of his large production of self-portraits using the image autocorrelation and demonstrate a strong association between the contrasts in the paintings, the occurrence of psychiatric symptoms, and his simultaneous use of absinthe-a strong liquor known to affect gamma aminobutyric acid (GABA) alpha receptors. Secondly, we propose that van Gogh suffered from a defective function of parvalbumin interneurons, which seems likely given his family history of schizophrenia and his addiction to substances associated with GABA action. This could explain the need for the artist to increasingly amplify the contrasts in his brushwork as his disease progressed, as well as his tendency to merge esthetic and personal experiences into a new form of abstraction.

Deficits in Auditory and Visual Sensory Discrimination Reflect a Genetic Liability for Psychosis and Predict Disruptions in Global Cognitive Functioning

Sensory discrimination thresholds (i.e., the briefest stimulus that can be accurately perceived) can be measured using tablet-based auditory and visual sweep paradigms. These basic sensory functions have been found to be diminished in patients with psychosis. However, the extent to which worse sensory discrimination characterizes genetic liability for psychosis, and whether it is related to clinical symptomatology and community functioning remains unknown. In the current study we compared patients with psychosis (PSY; N=76), their first-degree biological relatives (REL; N=44), and groups of healthy controls (CON; N=13 auditory and visual/N=275 auditory/N=267 visual) on measures of auditory and visual sensory discrimination, and examined relationships with a battery of symptom, cognitive, and functioning measures. Sound sweep thresholds differed among the PSY, REL, and CON groups, driven by higher thresholds in the PSY compared to CON group, with the REL group showing intermediate thresholds. Visual thresholds also differed among the three groups, driven by higher thresholds in the REL versus CON group, and no significant differences between the REL and PSY groups. Across groups and among patients, higher thresholds (poorer discrimination) for both sound and visual sweeps strongly correlated with lower global cognitive scores. We conclude that low-level auditory and visual sensory discrimination deficits in psychosis may reflect genetic liability for psychotic illness. Critically, these deficits relate to global cognitive disruptions that are a hallmark of psychotic illnesses such as schizophrenia.

Are basic auditory processes involved in source-monitoring deficits in patients with schizophrenia?

Patients with schizophrenia (SZ) display deficits in both basic non-verbal auditory processing and source-monitoring of speech. To date, the contributions of basic auditory deficits to higher-order cognitive impairments, such as source-monitoring, and to clinical symptoms have yet to be elucidated. The aim of this study was to investigate the deficits and relationships between basic auditory functions, source-monitoring performances, and clinical symptom severity in SZ. Auditory processing of 4 psychoacoustic features (pitch, intensity, amplitude, length) and 2 types of source-monitoring (internal and reality monitoring) performances were assessed in 29 SZ and 29 healthy controls. Clinical symptoms were evaluated in patients with the Positive And Negative Syndrome Scale. Compared to the controls, SZ individuals in showed significant reductions in both global basic auditory processing (p < .0005, d = 1.16) and source-monitoring (p < .0005, d = 1.24) abilities. Both deficits correlated significantly in patients and across groups (all p < .05). Pitch processing skills were negatively correlated with positive symptom severity (r = -0.4, p < .05). A step-wise regression analysis showed that pitch discrimination was a significant predictor of source-monitoring performance. These results suggest that cognitive mechanisms associated with the discrimination of basic auditory features are most compromised in patients with source-monitoring disability. Basic auditory processing may index pathophysiological processes that are critical for optimal source-monitoring in schizophrenia and that are involved in positive symptoms.

Impact of baseline early auditory processing on response to cognitive remediation for schizophrenia

BACKGROUND

Early auditory processing (EAP) has increasingly become a focus of efforts to identify biomarkers of treatment response in schizophrenia. EAP deficits lead to poor functional outcome via impaired cognition, and treatments that target EAP may drive downstream cognitive improvements. Assessment of baseline need provides an opportunity for cognitive remediation (CR) programs that give EAP training to personalize treatment and optimize its impact. This initial efficacy study examined the differential benefit of EAP training for those with and without baseline EAP deficits as defined by performance on the Tone Matching Test.

METHODS

103 outpatient adults diagnosed with schizophrenia or schizoaffective disorder were classified as having intact (48.5%) or impaired (51.5%) EAP and randomized to a CR program with restorative exercise plans that either included EAP training (N = 49) or did not (N = 54). Cognitive and functional outcomes were measured post-treatment and 3 months later.

RESULTS

Only in EAP impaired participants was there a significant benefit from EAP training on verbal learning. Treatment condition did not significantly impact global cognitive or functional outcomes for either EAP group. Cognitive gains partially mediated the relationship between gains in EAP and functional capacity.

CONCLUSION

These findings support the importance of addressing basic auditory deficits when attempting to remediate higher order auditory impairments such as verbal learning. In addition, they highlight the need for routine assessment of EAP in cognitive remediation participants, as well as the need for more effective programs to reverse these impairments.

Emotional Prosody Processing in Schizophrenic Patients: A Selective Review and Meta-Analysis

Emotional prosody (EP) has been increasingly recognized as an important area of schizophrenic patients’ dysfunctions in their language use and social communication. The present review aims to provide an updated synopsis on emotional prosody processing (EPP) in schizophrenic disorders, with a specific focus on performance characteristics, the influential factors and underlying neural mechanisms. A literature search up to 2018 was conducted with online databases, and final selections were limited to empirical studies which investigated the prosodic processing of at least one of the six basic emotions in patients with a clear diagnosis of schizophrenia without co-morbid diseases. A narrative synthesis was performed, covering the range of research topics, task paradigms, stimulus presentation, study populations and statistical power with a quantitative meta-analytic approach in Comprehensive Meta-Analysis Version 2.0. Study outcomes indicated that schizophrenic patients’ EPP deficits were consistently observed across studies (d = −0.92, 95% CI = −1.06 < δ < −0.78), with identification tasks (d = −0.95, 95% CI = −1.11 < δ < −0.80) being more difficult to process than discrimination tasks (d = −0.74, 95% CI = −1.03 < δ < −0.44) and emotional stimuli being more difficult than neutral stimuli. Patients’ performance was influenced by both participant- and experiment-related factors. Their social cognitive deficits in EP could be further explained by right-lateralized impairments and abnormalities in primary auditory cortex, medial prefrontal cortex and auditory-insula connectivity. The data pointed to impaired pre-attentive and attentive processes, both of which played important roles in the abnormal EPP in the schizophrenic population. The current selective review and meta-analysis support the clinical advocacy of including EP in early diagnosis and rehabilitation in the general framework of social cognition and neurocognition deficits in schizophrenic disorders. Future cross-sectional and longitudinal studies are further suggested to investigate schizophrenic patients’ perception and production of EP in different languages and cultures, modality forms and neuro-cognitive domains.

Auditory feature perception and auditory hallucinatory experiences in schizophrenia spectrum disorder

Schizophrenia spectrum disorder (SZ) is associated with deficits in auditory perception as well as auditory verbal hallucinations (AVH). However, the relationship between auditory feature perception and auditory verbal hallucinations (AVH), one of the most commonly occurring symptoms in psychosis, has not been well characterized. This study evaluated perception of a broad range of auditory features in SZ and determined whether current AVHs relate to auditory feature perception. Auditory perception, including frequency, intensity, duration, pulse-train and temporal order discrimination, as well as an embedded tone task, was assessed in both AVH (n = 20) and non-AVH (n = 24) SZ individuals and in healthy controls (n = 29) with the Test of Basic Auditory Capabilities (TBAC). The Hamilton Program for Schizophrenia Voices Questionnaire (HPSVQ) was used to assess the experience of auditory hallucinations in patients with SZ. Findings suggest that compared to controls, the SZ group had greater deficits on an array of auditory features, with non-AVH SZ individuals showing the most severe degree of abnormality. IQ and measures of cognitive processing were positively associated with performance on the TBAC for all SZ individuals, but not with the HPSVQ scores. These findings indicate that persons with SZ demonstrate impaired auditory perception for a broad range of features. It does not appear that impaired auditory perception is associated with recent auditory verbal hallucinations, but instead associated with the degree of intellectual impairment in SZ.

Hallucinations, neuroplasticity, and prediction errors in schizophrenia

Auditory hallucinations, a hallmark symptom of psychosis, are experienced by most people with a diagnosis of schizophrenia at some point in their illness. Auditory hallucinations can be understood as a failure in predictive coding, whereby abnormalities in sensory/perceptual processing combine with biased cognitive processes to result in a dampening of normal prediction error signaling. In this paper, we used a roving mismatch negativity (MMN) paradigm to optimize evaluation of prediction error signaling and short-term neuroplasticity in 30 people with schizophrenia (n = 16 with and n = 14 without recent auditory hallucinations) and 20 healthy comparison participants. The recent hallucinations group exhibited an abnormal roving MMN profile [F(2,27) = 3.98, p = 0.03], significantly reduced prediction error signaling [t(28) = -2.25, p = 0.03], and a trend for diminished short-term neuroplasticity [t(28) = 1.80, p = 0.08]. There were no statistically significant differences between the healthy comparison group and the combined schizophrenia group on any of the roving MMN indices. These findings are consistent with a predictive coding account of hallucinations in schizophrenia, which posits reduced prediction error signaling in those who are prone to hallucinations. These results also suggest that plasticity-mediated formation and online updating of predictive coding models may also be disrupted in individuals with recent hallucinations.

Hallucination- and speech-specific hypercoupling in frontotemporal auditory and language networks in schizophrenia using combined task-based fMRI data: An fBIRN study

Hypercoupling of activity in speech-perception-specific brain networks has been proposed to play a role in the generation of auditory-verbal hallucinations (AVHs) in schizophrenia; however, it is unclear whether this hypercoupling extends to nonverbal auditory perception. We investigated this by comparing schizophrenia patients with and without AVHs, and healthy controls, on task-based functional magnetic resonance imaging (fMRI) data combining verbal speech perception (SP), inner verbal thought generation (VTG), and nonverbal auditory oddball detection (AO). Data from two previously published fMRI studies were simultaneously analyzed using group constrained principal component analysis for fMRI (group fMRI-CPCA), which allowed for comparison of task-related functional brain networks across groups and tasks while holding the brain networks under study constant, leading to determination of the degree to which networks are common to verbal and nonverbal perception conditions, and which show coordinated hyperactivity in hallucinations. Three functional brain networks emerged: (a) auditory-motor, (b) language processing, and (c) default-mode (DMN) networks. Combining the AO and sentence tasks allowed the auditory-motor and language networks to separately emerge, whereas they were aggregated when individual tasks were analyzed. AVH patients showed greater coordinated activity (deactivity for DMN regions) than non-AVH patients during SP in all networks, but this did not extend to VTG or AO. This suggests that the hypercoupling in AVH patients in speech-perception-related brain networks is specific to perceived speech, and does not extend to perceived nonspeech or inner verbal thought generation.

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?

Myelin development, plasticity, and pathology in the auditory system

Myelin allows for the rapid and precise timing of action potential propagation along neuronal circuits and is essential for healthy auditory system function. In this article, we discuss what is currently known about myelin in the auditory system with a focus on the timing of myelination during auditory system development, the role of myelin in supporting peripheral and central auditory circuit function, and how various myelin pathologies compromise auditory information processing. Additionally, in keeping with the increasing recognition that myelin is dynamic and is influenced by experience throughout life, we review the growing evidence that auditory sensory deprivation alters myelin along specific segments of the brain's auditory circuit. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 78: 80-92, 2018.

Mismatch negativity to pitch pattern deviants in schizophrenia

Simple mismatch negativity (MMN) to infrequent pitch deviants is impaired in individuals with long-term schizophrenia (Sz). The complex MMN elicited by pattern deviance often manifes is cut from here]->ts later after deviant onset than simple MMN and can ascertain deficits in abstracting relationships between stimuli. Sz exhibit reduced complex MMN, but so far this has only been measured when deviance detection relies on a grouping rule. We measured MMN to deviants in pitch-based rules to see whether MMN is also abnormal in Sz under these conditions. Three experiments were conducted. Twenty-seven Sz and 28 healthy matched controls (HC) participated in Experiments 1 and 2, and 24 Sz and 26 HC participated in Experiment 3. Experiment 1 was a standard pitch MMN task, and Sz showed the expected MMN reduction (~ 115 ms) in the simple pitch deviant compared to HC. Experiment 2 comprised standard groups of six tones that ascended in pitch, and deviant groups where the last tone descended in pitch. Complex MMN was late (~ 510 ms) and significantly blunted in Sz. Experiment 3 comprised standard groups of 12 tones (six tones ascending in pitch followed by six tones descending in pitch, like a scale), and deviant groups containing two repetitions of six ascending tones (the scale restarted midstream). Complex MMN was also late (~ 460 ms) and significantly blunted in Sz. These results identify a late pitch pattern deviance-related MMN that is deficient in schizophrenia. This suggests specific deficits in later more complex deviance detection in schizophrenia for abstract patterns.

Tone-matching ability in patients with schizophrenia: A systematic review and meta-analysis

CONTEXT

Patients with schizophrenia display abnormalities in pitch discrimination of non-verbal tones as revealed by the Tone-Matching Task (TMT). It may lead to deficits in higher-order cognitive functions and clinical symptoms.

OBJECTIVES

We conducted a systematic review and meta-analysis pooling data about TMT score differences between patients with schizophrenia and healthy controls, to evaluate the deficit's effect size, and to develop reliable knowledge about pitch processing impairment and its pejorative impact.

METHOD

Relevant publications were identified by a systematic search of PubMed and EMBASE databases. Then, we excluded non-relevant studies for the meta-analysis. Effect size for percent of correct responses to the TMT was expressed as standardized mean difference (SMD).

RESULTS

Eighteen of 167 identified studies met eligibility criteria for review, of which 10 were included in the meta-analysis. Our meta-analysis showed that the effect size for the percent of correct response to the TMT between patients (N=371) and controls (N=342) was large: SMD=1.17 [95% CI: 0.926-1.418] (z-value=9.338 and p-value<0.001). Meta-analysis showed moderate heterogeneity between studies (Q(9)=17.22, p=0.04, I²=47.74%). The relationship between tone-matching impairment and clinical symptoms of schizophrenia remains heterogeneous across studies. Some authors observed significant correlations between tone-matching performance and a number of higher-order cognitive abilities.

CONCLUSION

This review and meta-analysis highlights a large significant disturbance in tone-matching ability in patients as compared with controls. The study of basic auditory processing opens promising perspectives for pathophysiological modelling of the disorder and therapeutic issues.

Comparing the experience of voices in borderline personality disorder with the experience of voices in a psychotic disorder: A systematic review

OBJECTIVE

In clinical settings, there is substantial evidence both clinically and empirically to suggest that approximately 50% of individuals with borderline personality disorder experience auditory verbal hallucinations. However, there is limited research investigating the phenomenology of these voices. The aim of this study was to review and compare our current understanding of auditory verbal hallucinations in borderline personality disorder with auditory verbal hallucinations in patients with a psychotic disorder, to critically analyse existing studies investigating auditory verbal hallucinations in borderline personality disorder and to identify gaps in current knowledge, which will help direct future research.

METHOD

The literature was searched using the electronic database Scopus, PubMed and MEDLINE. Relevant studies were included if they were written in English, were empirical studies specifically addressing auditory verbal hallucinations and borderline personality disorder, were peer reviewed, used only adult humans and sample comprising borderline personality disorder as the primary diagnosis, and included a comparison group with a primary psychotic disorder such as schizophrenia.

RESULTS

Our search strategy revealed a total of 16 articles investigating the phenomenology of auditory verbal hallucinations in borderline personality disorder. Some studies provided evidence to suggest that the voice experiences in borderline personality disorder are similar to those experienced by people with schizophrenia, for example, occur inside the head, and often involved persecutory voices. Other studies revealed some differences between schizophrenia and borderline personality disorder voice experiences, with the borderline personality disorder voices sounding more derogatory and self-critical in nature and the voice-hearers' response to the voices were more emotionally resistive. Furthermore, in one study, the schizophrenia group's voices resulted in more disruption in daily functioning. These studies are, however, limited in number and do not provide definitive evidence of these differences.

CONCLUSION

The limited research examining auditory verbal hallucinations experiences in borderline personality disorder poses a significant diagnostic and treatment challenge. A deeper understanding of the precise phenomenological characteristics will help us in terms of diagnostic distinction as well as inform treatments.

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.

Auditory processing deficits in bipolar disorder with and without a history of psychotic features

OBJECTIVES

Auditory perception deficits have been identified in schizophrenia (SZ) and linked to dysfunction in the auditory cortex. Given that psychotic symptoms, including auditory hallucinations, are also seen in bipolar disorder (BD), it may be that individuals with BD who also exhibit psychotic symptoms demonstrate a similar impairment in auditory perception.

METHODS

Fifty individuals with SZ, 30 individuals with bipolar I disorder with a history of psychosis (BD+), 28 individuals with bipolar I disorder with no history of psychotic features (BD-), and 29 normal controls (NC) were administered a tone discrimination task and an emotion recognition task.

RESULTS

Mixed-model analyses of covariance with planned comparisons indicated that individuals with BD+ performed at a level that was intermediate between those with BD- and those with SZ on the more difficult condition of the tone discrimination task and on the auditory condition of the emotion recognition task. There were no differences between the BD+ and BD- groups on the visual or auditory-visual affect recognition conditions. Regression analyses indicated that performance on the tone discrimination task predicted performance on all conditions of the emotion recognition task. Auditory hallucinations in BD+ were not related to performance on either task.

CONCLUSIONS

Our findings suggested that, although deficits in frequency discrimination and emotion recognition are more severe in SZ, these impairments extend to BD+. Although our results did not support the idea that auditory hallucinations may be related to these deficits, they indicated that basic auditory deficits may be a marker for psychosis, regardless of SZ or BD diagnosis.

Comparison of two tests of auditory temporal resolution in children with central auditory processing disorder, adults with psychosis, and adult professional musicians

OBJECTIVE

Evaluate auditory temporal resolution threshold outcomes across three different populations.

DESIGN

Two commercially available tests of auditory gap detection (Random gap detection (RGDT) test, and Gaps-in-noise (GIN) test) were administered to all participants.

STUDY SAMPLE

Adult professional musicians (APM) (N = 11, age range 28-61 years); children with central auditory processing disorder (CAPD) (N = 22, age range 7.5-17 years); and first episode psychosis patients (FEP) (N = 17, age range 18-48 years).

RESULTS

It was not possible to calculate a threshold for the RGDT for 13 of 22 children with CAPD and for 7 of 17 adults with FEP due to response inconsistency. Analysis of variance (ANOVA) excluding cases that produced inconsistent RGDT results showed that only RGDT thresholds differed across groups (F = 8.73, p = 0.001). Three t-tests comparing test means within group revealed statistically significant differences between the gap detection thresholds obtained with the RGDT vs. the GIN for each group. No significant correlations were seen between RGDT and GIN.

CONCLUSION

Lower/better gap detection thresholds and smaller standard deviations were obtained using the GIN in all three groups. Lack of correlation between the two tests suggests that they may measure different processes.