Individual differences and brain structure: correlates with magnetoencephalography

The work presented in this thesis aims to increase clinical capacity for magnetoencephalography (MEG) by developing an understanding of how, in healthy participants, individual differences in brain structure, personality, and demographics influence measurements of neural oscillatory responses and functional connectivity. To this end, a large cohort of normative data was acquired using MEG with additional data acquisition using high-field MRI and supplementary individual difference data collected via a psychometric battery and screening questionnaire. MEG data were analysed to elucidate both primary sensory responses to stimulation and functional connectivity within task and task-free acquisitions. Chapters two and three introduce the physiological origins of the MEG signal and the instrumentation required to record it. Chapter four describes data acquisition and preprocessing, from the methods used in the recruitment of participants to the scanning parameters employed for our MEG and MRI acquisitions. Chapters five to seven present three empirical studies. The first investigates the relationship between MEG derived measurements of functional connectivity and cortical myeloarchitecture. We demonstrate that covariation of cortical myelin is significantly predicted by MEG-derived measurements of functional connectivity both within individual frequency bands and by their linear and non-linear combination. Chapter six presents an exploratory analysis into the impact of aging and sex-differences on MEG derived measurements of sensorimotor responses and whole-brain functional connectivity. We find trends indicating increased oscillatory responses with age. Further, we find female volunteers to exhibit greater induced responses than males. Analysis of whole-brain functional connectivity revealed a near-global increase in connectivity in female participants as compared to males. The final empirical chapter assesses the shared neuronal representations between patients diagnosed with schizophrenia and healthy individuals scoring highly on a personality questionnaire measuring schizotypy. We found highly schizotypal individuals to exhibit attenuated sensorimotor responses akin to those previously observed in schizophrenia. Patients displayed reduced functional connectivity within an occipital network, identified in task and task free data. We found this aberrant network connectivity to also be present in healthy subjects scoring highly on a questionnaire assessing schizotypy. The thesis, in sum, presents work demonstrating the significant modulatory effects of individual differences ranging from sex differences to schizotypy. This work highlights the need for consideration of participant demographics and individual differences in both clinical and basic science studies. Further, the thesis presents a newly identified relationship between MEG-derived measurements of functional connectivity and cortical myeloarchitecture. Future work assessing the role of other sources of individual difference in modulating MEG measurements is required. Moreover, the framework for assessing the relationship between functional connectivity and cortical myeloarchitecture is well suited to application in clinical populations where this relationship is hypothesised to break down