Electrophysiology summarizes the measurement of electrical properties generated by specific biological cells or tissues. For example, electroencephalography (EEG) captures ionic electrical current fluctuations, mainly due to oscillating polarizations between superficial and deeper grey matter layers, which are generated within brain regions containing large clusters of parallel neurons that are activated simultaneously. The EEG reflects rapid as well as slow changes in electrical activity across the scalp and has a high temporal resolution in the range of milliseconds. It is measured non-invasively from standardized positions on the scalp, commonly using EEG caps accommodating different head sizes.
At the CIMH, the CIPP allows EEG acquisition in three EEG cabins offering 64 or more channels, plus mobile recordings and eye tracking. One cabin is specifically equipped to accommodate children and adolescents. Additionally, simultaneous EEG and fMRI recordings are currently possible at one of the 3T scanners (PrismaFit) with EEG preparation in one of the EEG cabins. Two additional rooms with copper wallpaper shielding are readily available for recordings of peripheral physiology. Here, signals such as electrodermal activity (EDA), electromyogram (EMG), electrocardiogram (ECG), pupillometry and eye-movement behavior can be recorded. Additionally visual, auditory, tactile, and electrical stimulation devices are available. The ZIPP further features a separate area specifically designed for children and adolescents, comprising a separate waiting area, an EEG cabin and two rooms with copper wallpaper shielding equipped for Bio- and EEG-Neurofeedback-Trainings.
Advantages / disadvantages compared to other methods
EEG is a cost-effective, non-invasive method that is generally well tolerated by all kinds of study populations due to its ease of administration. In contrast to fMRI, EEG directly measures neuronal activity and has a significantly higher temporal resolution. However, EEG has a lower spatial resolution compared to MRI, which depends considerably on model assumptions and source geometry, and it is less sensitive to neuronal activity in deeper brain regions.
Risks / Limitations
If used properly, there are few risks. The biggest risk conventional EEG and other electrophysiological methods pose is potential skin abrasion during electrode preparation. Simultaneous EEG and fMRI requires a number of precautions, that user group leaders are happy to advise.
Peripheral Psychophysiology: Martin Löffler, Institute of Cognitive and Clinical Neuroscience
Zentralinstitut für Seelische Gesundheit (ZI) - https://www.zi-mannheim.de