EEG analysis

Electroencephalography (EEG) is a non-invasive method of measuring the electrical activity of the brain by recording electrical potentials from the surface of the head using electrodes placed on the scalp. EEG is one of only two techniques currently available (the other being magnetoencephalopgraphy, or MEG) that allow us to measure the activity of the brain in real time, on a millisecond by millisecond basis, in awake people. We are researching a number of state-of-the-art methods of analysing the data from these recordings, to tell us more about when and where these signals are generated within the brain.

Source localisation

EEG involves measuring electrical potentials at a number of electrodes on the scalp. To find out where in the brain these electrical potentials are generated, it is necessary to mathematically model possible sources of the electrical activity. This modelling is known as electric source localisation. In the past, spherical head models were used in this analysis. However, as these models did not accurately reflect the geometry of the head, it was impossible to localise the sources precisely. We have carried out a number of EEG studies in which the source localisation was performed using realistic head models derived from the individual subjects' magnetic resonance imaging (MRI) scans. These studies were carried out in collaboration with Dr Stuart Derbyshire at the University of Pittsburgh Medical Center in the USA, and were some of the first to use realistic head models in source localisation of pain signals.

Anatomical position, in cingulate cortex, of the dipole sources explaining the P2 peak of the laser evoked potentials for one subject. The dipole source has been co-registered with the subject's structural MRI scan.

Key publications:

Bentley DE, Derbyshire SWG, Youell PD, Jones AKP. Caudal cingulate cortex involvement in pain processing: An inter-individual laser evoked potential source localisation study using realistic head models. Pain 2003; 102(3):265-271

Bentley DE, Jones AKP, Youell PD. Anatomical localisation and intra-subject reproducibility of laser evoked potential sources in cingulate cortex, using a realistic head model. Clin Neurophysiol 2002; 113:1351-1356

Bentley DE, Youell PD, Crossman AR, Jones AKP. Source localisation of 62-electrode human laser pain evoked potential data using a realistic head model. Int J Psychophysiol 2001; 41(2):187-193