Biomarkers of auditory processing in schizophrenia: do they reflect symptom severity? An investigation in schizotypy

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Biomarkers of auditory processing are abnormal in schizophrenia, suggesting their potential for identifying individuals who are experiencing schizophrenia-like symptoms before the onset of psychosis. However, for these biomarkers to be effective, they would need to reflect symptom severity. There are some individuals in the general population who exhibit schizophrenia-like traits but do not experience psychosis, commonly known as schizotypy. The majority of the general population is believed to fall along a spectrum of schizotypic behaviors, with some being more symptomatic and who are referred to as having `high schizotypy'. The aim of this project is to test whether auditory biomarkers associated with schizophrenia are also present in individuals with high schizotypy, and how the different biomarkers relate to one another. If the auditory biomarkers are impacted in high schizotypy, then this would support their use for identifying those who are at- risk of developing schizophrenia. If not, then this suggests that individuals with schizophrenia are categorically different in their auditory processing to the general population, and indicates substantial brain-wide changes at the onset of psychosis. In the current study, we focus on biomarkers of early sensory memory (mismatch negativity; MMN) and later auditory working memory (WM) using electroencephalography (EEG) and behavioral psychophysics. We will also explore how sensory memory and WM impact one other, as a potential mechanism of auditory processing in schizotypy. This project is designed to introduce undergraduate researchers to clinical research. They will learn how to collect electrophysiological data, analysis techniques, and will be involved in disseminating the results. The project will be divided into three Aims. Aim 1 will measure MMN in the EEG to investigate early sensory memory to auditory deviants – single tones that differ in pitch. Aim 2 will investigate WM performance in a 3-back task using behavioral and EEG measures (such as N1 during stimulus encoding). We will investigate MMN and WM independently so that the results from Aim 1 do not impact Aim 2. For Aims 1 and 2, we hypothesize that both MMN and WM performance will be impaired in those with high compared to low schizotypy. Aim 3 will then examine the relationship between the two measures of auditory processing. We hypothesize that impaired MMN will predict poorer WM performance (examined using regression analyses), and this relationship will be stronger in high compared to low schizotypy. This will indicate a potential mechanism to target for treatment: improve early auditory memory to impact later auditory-related cognition. If there is no significant relationship between sensory memory and WM, then this will indicate a third variable that impacts auditory processing. Either result will contribute to a model of auditory processing in schizotypy. Undergraduate researchers will develop an understanding of the utility of biomarkers in psychiatry, and how basic science can be used to investigate the mechanisms underlying schizophrenia.