MEG

MEG measures the extremely weak magnetic fields generated by post-synaptic potentials in the brain, and can be used to map functional activity across the cortex with millisecond time resolution. One of its key strengths is in studying the role of cortical oscillatory dynamics in underpinning cognitive functions, both in local regions of the cortex and in mediating the dynamics of transiently connected functional networks across the brain. In CUBRIC, we use cortical oscillations as markers of cognitive function in health and diseases such as Epilepsy, Schizophrenia and Alzheimer’s as well as a sensitive probe of the action of pharmacological agents.

Introduction

Fundamentally, to understand how the brain works and what happens in disease, we need to be able to non-invasively image the electrical activity in the human brain at the speed at which the brain works – in the millisecond time range. MEG – the measurement of external magnetic fields associated with neuro-electric activity – is one of the most powerful tools we have for this task. Importantly, MEG is well suited to studying electrical oscillations within the brain, which are thought to fundamentally underpin the dynamic functional architecture of the brain, allowing moment-to-moment co-ordination of activity within and across brain areas. A key focus of MEG research in CUBRIC is to understand the role of cortical oscillations, both in terms of normal brain function, but also developing new markers of disease state, allowing us to probe synaptic dysfunction both locally within the cortex and across extended brain networks. Finally, MEG characterisation of oscillatory dynamics provides a new direct window on to the cortical action of pharmacological agents, providing a new tool for drug discovery and assessment.
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Mapping oscillatory dynamics across the cortex: translatable markers from animal to human

Using simple tasks, such as passive visual stimulation, we are able to robustly induce oscillatory changes in a variety of frequency ranges, including theta, alpha, beta and gamma. These can be source-localised to the cortex using techniques such as beamforming and then a full time-frequency analysis can yield a complete picture of the complex response phenomenology (see picture right). Crucially these response components, such as the sustained visual gamma are also observed in invasive animal recordings, meaning that MEG can provide a non-invasive measure in humans that is tied directly to the underlying synaptic physiology, enabling forward- and backward-translation of research between human and animal domains.
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