Schizophrenia is described as an incapacitating, chronic and severe mental illness which affects about 1% of the population. Among the most frequently prominent of the cognitive symptoms in schizophrenia are deficits in working memory. More recently, individuals at ultra-high risk (UHR) of psychosis have been proposed to help provide awareness on the nature of prodromal stages and further acknowledge the initial stages to offer possibilities for early and more distinct interventions. It is particularly critical to perform studies on UHR of psychosis subjects as around 30% of UHR people experience progression into psychosis within two years.
A pilot study was conducted (8 females, 4 males) to examine visual P300 amplitude and detect hippocampal activity through scalp EEG, using the ICA analysis methodology. A smaller separate study was also conducted amongst UHR subjects (3 males, 1 female) and controls (2 males, 1 female).
Findings revealed a pattern of high amplitude positivity across the ipsilateral anterior basal temporal, and mid parietal electrodes, alongside a low amplitude positivity, distributed around the cheekbones; similar patterns were identified in UHR subjects. UHR subjects displayed a higher P300 amplitude compared to controls, contrary to previous findings.
The results of the present study provide a stepping stone for future studies to conduct further research incorporating additional source localisation analysis such as sLORETA. Understanding the location of the source of the P300 could allow prospective studies to determine and predict conversion to psychosis and act as possible biomarkers of psychosis amongst individuals with UHR, allowing a platform to provide early interventions for these at-risk individuals.
Table of Contents
Abstract
Introduction
Schizophrenia and Visual Working Memory
Ultra-High-Risk of psychosis
Ultra-High-Risk of psychosis and Visual Working Memory
Hippocampus and Visual Working Memory
Hippocampal Impairments in Schizophrenia
The P300 event related potential
P300 Impairments in Schizophrenia
The P300 as a putative biomarker of psychosis risk
Detecting hippocampal activity through scalp EEG
Rationale, Aims and Hypotheses
Methods
Participants
Pilot study sample
PSYSCAN study sample
Inclusion and exclusion criteria
Ethical considerations
Visual Working Memory Task (based on Hannula, 2015)
Design and Procedure
EEG Data Acquisition and analysis
ERP Processing
Statistical Analysis
Results
Pilot Study Analysis
Demographics
ERPs
Visual Analysis of EEG 3D Amplitude Maps
Power Analysis
PSYSCAN Study Analysis
Demographics
ERPs
Independent samples t-test
Visual Analysis of EEG 3D Amplitude Maps
Discussion
P300 ERP components in a visual working memory task
Mesial sources contribution to scalp EEG
Hippocampus activation and Visual Working Memory
P300 ERP in UHR subjects
Hippocampal activity detection in UHR subjects
Strengths of the current study
Limitations of the current study
Future directions
Conclusion
References
Appendices
APPENDIX A: Demographic information for all samples from pilot study and PSYSCAN study
APPENDIX B: P300 ERP-Waveform Amplitude and Latencies for Each Participant at channels PZ and FZ
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