A working memory related mechanism of auditory hallucinations

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.

Executive control of language in schizophrenia patients with history of auditory verbal hallucinations: A neuropsychological and resting-state fMRI study

BACKGROUND

As demonstrated by a plethora of studies, compromised executive functions (EF) and language are implicated in mechanisms of auditory verbal hallucinations (AVH), but the contribution of their interaction to AVH remains unclear. We hypothesized that schizophrenia patients with history of AVH (AVHh+) vs. without history of AVH (AVHh-) have a specific deficit of executive control of language and alterations in functional connectivity (FC) between the brain regions involved in EF and language, and these neuropsychological and neurophysiological traits are associated with each other.

METHODS

To explore the executive control of language and its contribution to AVH, we used an integrative approach involving analysis of neuropsychological and resting-state fMRI data of 34 AVHh+, 16 AVHh-, and 40 healthy controls. We identified the neuropsychological and FC measures that differentiated between AVHh+, AVHh-, and HC, and tested the associations between them.

RESULTS

AVHh+ were characterized by decreased category and phonological verbal fluency, utterance length, productivity in the planning tasks, and poorer retelling. AVHh+ had decreased FC between the left inferior frontal gyrus and the anterior cingulate cortex. Productivity in category verbal fluency was associated with the FC between these regions.

CONCLUSIONS

Poor executive control of word retrieval and deficient programming of sentence and narrative related to more general deficits of planning may be the neuropsychological traits specific for AVHh+. A neurophysiological trait specific for AVHh+ may be a decreased FC between regions involved in language production and differentiation between alien- vs. self-generated speech and between language production vs. comprehension.

Identifying the cognitive underpinnings of voice-hearing by comparing never, past and current voice-hearers

OBJECTIVE

The current study aimed to compare specific cognitive profiles corresponding to auditory verbal hallucinations (AVH) status and elucidate which pattern of cognitive deficits may predict voice-hearing status.

METHOD

Clinical participants with schizophrenia spectrum disorders were partitioned into: (i) current voice-hearers (n = 46), (ii) past voice-hearers (n = 37) and (iii) never voice-hearers (n = 40), and compared with 319 non-clinical controls. Cognitive assessment employed the MATRICS Consensus Cognitive Battery (MCCB), supplemented by the Delis-Kaplan Executive Function System (D-KEFS) Colour-Word Interference Test (Stroop) as a robust measure of executive function.

RESULTS

On the Visual Learning domain, current and past voice-hearers had significantly poorer performance relative to never voice-hearers, who in turn had significantly poorer performance than non-clinical controls. Current and never voice-hearers had significantly poorer performance on the Social Cognition domain relative to non-clinical controls. Current voice-hearers also had significantly poorer performance on the Inhibition domain relative to non-clinical controls. Binary logistic regression revealed that Visual Learning was the only significant cognitive predictor of AVH presence.

CONCLUSION

Visual learning, and potentially inhibition, may be viable therapeutic targets when addressing cognitive mechanisms associated with AVHs. Future research should focus on investigating additional cognitive mechanisms, employing diverse voice-hearing populations and embarking on related longitudinal studies.

Brain function differences in drug-naïve first-episode auditory verbal hallucination-schizophrenia patients with versus without insight

Background:

Few studies have reported brain function differences in drug-naïve first-episode schizophrenia patients who had auditory verbal hallucinations (AVH) with insight vs. those without insight. This study aimed to investigate brain function differences between drug-naïve first-episode AVH-schizophrenia patients with and without insight.

Methods:

Forty first-episode drug-naïve AVH-schizophrenia patients with or without insight and 40 healthy controls between December 2016 and December 2018 were recruited in this study. The auditory hallucinations rating scale (AHRS) was used to assess AVH severity, while the insight and treatment attitudes questionnaire was used to distinguish insight. The global functional connectivity density (gFCD) between different groups was compared using a voxel-wise one-way analysis of covariance. The relationship between gFCD and AHRS total scores were analyzed using voxel-wise multiple regression.

Results:

Finally, 13 first-episode drug-naïve AVH-schizophrenia patients with insight, 15 AVH-schizophrenia patients without insight, and 20 healthy controls were included for analysis. Except for global assessment of functioning scores, there were no significant differences in sociodemographic information between the AVH-schizophrenia and healthy groups (P > 0.05). Compared to the healthy controls, AVH-schizophrenia patients with insight demonstrated a decreased gFCD in the supra-marginal gyrus within the primary auditory cortex, while those without insight demonstrated an increased gFCD in the inferior frontal gyrus and superior temporal gyrus and decreased gFCD in the supplemental motor area. Compared to the AVH-schizophrenia patients with insight, those without insight demonstrated an increased gFCD in the supra-marginal gyrus and posterior superior temporal lobule and a decreased gFCD in the frontal lobe. No significant correlation between gFCD and AVH severity (AHRS total score: r = 0.23, P = 0.590; and frequency: r = 0.42, P = 0.820) was found in both AVH-schizophrenia groups.

Conclusions:

The gFCD-aberrant brain regions in the AVH-schizophrenia patients without insight were wider compared to those with insight, although the AHRS scores were not significantly different. The AVH-schizophrenia patients without insight had wide functional impairment in the frontal lobule, which may underlie the lack of insight and the abnormal hyperactivity in the inferior frontal gurus and temporal lobe related to the AVH symptoms.