"Task-related oscillatory power changes and their relation to the haemodynamic response."
In recent years many studies have used the BOLD response to characterise the cortical response to perceptual or cognitive tasks. The underlying model is that when an area of the brain is differentially activated, increased oxygen consumption in that region leads to a local increase in oxygenated blood, which can be measured using MRI. At the same time, researchers using Electroencephalography (EEG), and its close relative Magnetoencephalography (MEG) have shown that when subjects are performing sensory or cognitive tasks, there are regional increases or decreases in electrical oscillatory power within the cortex, These increases and decreases in power are known as even-related synchronisation (ERS) and event-related desynchronisation (ERD) and occur within set frequency bands. Using MEG, with its enhanced spatial resolution compared to EEG, we can localise these power changes within the cortex. Despite the very different nature of the BOLD and ERS/ERD measures, there is now increasing evidence that regions of the cortex exhibiting task-related haemodynamic changes, as measured with fMRI, also show task-related oscillatory power changes, as measured with MEG. In my talk I will discuss the relationship between BOLD and ERS/ERD, introduce MEG and its application to studies of ERS/ERD and describe some recent experimental results.