Functional brain correlates of auditory verbal hallucinations in schizophrenia: a design of an fMRI study testing perceptual and cognitive models

Abstract

Auditory verbal hallucinations (AVHs, or ‘hearing voices’) are a cardinal symptom of schizophrenia, and yet, their biological basis has not been fully determined. As of now, theories that attempt to disentangle the origins of AVHs can be separated into two main types (or models): perceptual versus cognitive. The former has considered AVHs to be due to malfunction in perceptual processing, namely an abnormal activation in the auditory cortex, as well as having a top-down cognitive influence. The latter considers AVHs to be due to one of two cognitive processes: the misinterpretation of intrusive memories (which posit that AVHs are the result of a breakdown in the processes monitoring the source of memories) or to the malfunction of inner speech (which posits that AVHs are due to dysfunction of speech monitoring). The current study aims to propose an adequate experimental design of a prospective fMRI study that will test both the perceptual and cognitive approaches allowing to fill the gaps in the general framework for AVHs. Firstly, to test the perceptual model, an experimental design borrowed from Fuentes-Claramonte and colleagues (2021) will be adapted, with a modification controlling for motor activity. To test one side of the Cognitive Model, the theory of intrusive memory, the experimental paradigm that has been created by Fuentes-Claramonte and colleagues (2019) and validated by Martin-Subero and colleagues (2021) will be adapted to test schizophrenic patients with AVHs, which has not been done before. It will elicit negatively valenced autobiographical memories, which has been shown to activate parts of the default mode network, a circuit thought to be impaired in schizophrenia. Thirdly, to test the other side of the Cognitive Model, namely the theory of inner speech, an experimental paradigm will be proposed called the Rhyming task, a phonological encoding task that is known to activate brain regions involved in subvocal rehearsal and short-term storage of information. However, because the stimuli for this task is lacking for the Spanish population, a pilot study (an online survey) was conducted, presenting healthy participants with pairs of objects (created partly from a personalized corpus), and asked them to do three tasks: to decide whether the names of both objects rhyme; provide the name of each object; and rate the object on a 1 to 5 Likert scale for the purposes of determining emotional valence. The results of the pilot study guided the selection of the appropriate stimuli for the prospective imaging study. The proposed fMRI study tackles the biological basis of AVHs from different perspectives, helping to improve patients' lives that are touched by this cardinal symptom, and thus enabling future research to sculpt appropriate clinical intervention thanks to pinpointing the exact biological basis of hearing voices.