Testing a Bayesian model of auditory verbal hallucinations in the adolescent brain

听觉言语幻觉（AVH）是精神分裂症等精神状态的典型症状。青少年特别容易患上AVH和精神分裂症（Dalsgaard et al., 2020）。表征和模拟精神病的发展机制以及开发有效的早期发现和诊断方法以优化干预措施是必不可少的。大脑是如何产生AVH的还不太确定。一些理论认为，AVH是由于未能监控自己的内心语言、言语思想或记忆，因此它们被认为是外来的或外部的（Frith, 2014）。其他人则声称，AVH是大脑无法抑制的侵入性记忆（通常来自童年创伤事件）（Waters et al., 2006）。由于这些模型都将AVH的病理定位于一个症状维度或认知机制，因此没有一个模型可以单独解释AVH的全部复杂性。“贝叶斯推理”已经变得越来越有影响力，因为它有可能在一个广义的理论框架下统一AVH的多种机制。大脑可能使用不同的机制来计算给定先前经验和当前感觉的感知概率。因此，是否能听到言语最终取决于大脑对先前经验（先验）和当前听到的内容的重视程度。当大脑具有非常强烈和不变的先验期望时，AVH可能在没有刺激的情况下发生（Corlett et al., 2019）。目前的项目旨在测试AVH的贝叶斯模型，以表征和模拟青少年AVH的发展机制。我们将招募年龄在15-25岁之间的人，并且：(1)在一系列信号检测任务中，通过模拟实验操纵的先验信念（听到语音）和感官证据（语音是否存在）来证明建模方法的概念（Brookwell等人，2013）；(2)检验贝叶斯模型是否比测量必然放电、源监测或记忆抑制任务更可靠地区分健康组、风险组和临床组；(3)利用脑电图（EEG）将先验信念的变化定位为大脑中的电生理特征（Yao et al., 2021），以确定非侵入性脑刺激治疗的潜在生物标志物。博士将受益于认知神经科学和临床心理学的跨学科专业知识，并接受贝叶斯建模，统计分析和脑电图数据处理以及精神病症状临床评估和研究管理方面的定量技能的全面培训

Auditory verbal hallucinations (AVH) are a characteristic symptom of psychotic states such as schizophrenia. Adolescents are particular vulnerable to developing AVH and schizophrenia (Dalsgaard et al., 2020). It is imperative to characterise and model the developmental mechanisms of psychosis and to develop effective methods for early detection and diagnosis to optimize interventions. Little is certain about how the brain produces AVH. Some theories propose that AVH result from a failure to monitor one's own inner speech, verbal thoughts or memories so that they are perceived to be foreign or external (Frith, 2014). Others claim that AVH are intrusive memories (often from childhood traumatic events) that the brain fails to suppress (Waters et al., 2006). Because each of these models localises the pathology of AVH to one symptom dimension or cognitive mechanism, none can explain the full complexity of AVH alone. 'Bayesian inferencing' has become increasingly influential as it has the potential to unify multiple mechanisms of AVH under a generalised theoretical framework. The brain may use different mechanisms to compute the probability of a perception given prior experience and the current sensations. So whether speech is heard ultimately depends on the weight the brain attaches to previous experience (the priors) and to what is currently being heard. AVH may occur in the absence of a stimulus when the brain has a very strong and unchanging prior expectation (Corlett et al., 2019). The current project aims to test the Bayesian model of AVH to characterise and model the developmental mechanisms of AVH in adolescents. We will recruit people aged 15-25yo and: (1) prove the concept of a modelling approach by modelling experimentally manipulated prior beliefs (of hearing a speech) and sensory evidence (of whether the speech is present) in a series of signal detection tasks (Brookwell et al., 2013); (2) test if Bayesian modelling can separate healthy vs. at-risk and clinical groups more reliably than tasks measuring corollary discharge, source monitoring or memory inhibition; (3) localise the changes of prior beliefs to electrophysiological signatures in the brain using EEG (Yao et al., 2021), to identify potential biomarkers for non-invasive brain stimulation treatments. The PhD will benefit from interdisciplinary expertise in cognitive neuroscience and clinical psychology and receive comprehensive training in quantitative skills in Bayesian modelling, statistical analysis and EEG data processing, as well as in clinical assessment of psychotic symptoms and research governance