Electroencephalography

Electroencephalography
Name	Electroencephalography
Caption	Scalp electroencephalogram recording
Invented by	Hans Berger
Introduced	1929
Modalities	Scalp EEG, Intracranial EEG, Ambulatory EEG, Mobile EEG

Electroencephalography is a noninvasive neurophysiological technique for recording electrical activity of the brain via electrodes placed on the scalp. It provides high temporal resolution measurements used in clinical neurology, cognitive neuroscience, and brain–computer interface development, informing diagnosis and research across neurology, psychiatry, and neurosurgery. Major institutions, clinicians, and investigators worldwide have adopted electroencephalography for work in epilepsy, sleep medicine, cognitive mapping, and intraoperative monitoring.

History

Early human electrophysiology traces through Luigi Galvani, Alessandro Volta, Hermann von Helmholtz, and Richard Caton; the first human scalp recordings were reported by Hans Berger in 1929, who published findings while associated with Jena University and corresponded with contemporaries at University of Freiburg and University of Leipzig. Berger’s first demonstrations influenced laboratories at Boston City Hospital, University College London, and Harvard Medical School, and led to clinical adoption in centers such as Mayo Clinic and Johns Hopkins Hospital. During the mid-20th century, technological advances at institutions including Massachusetts General Hospital, Karolinska Institutet, and Montreal Neurological Institute integrated electroencephalography with surgical practice pioneered by neurosurgeons at The Hospital for Sick Children and research groups at Max Planck Society. The development of digital acquisition systems in the 1970s and 1980s, driven by companies like Siemens, Natus Medical Incorporated, and research at MIT, accelerated applications in intensive care at Cleveland Clinic and sleep labs associated with Stanford University. Modern expansions into mobile and invasive recordings parallel innovations from University of California, San Francisco, Johns Hopkins University, and collaborative projects funded by agencies such as the National Institutes of Health and European Research Council.

Principles and Technology

Electroencephalography records summed postsynaptic potentials primarily from cortical pyramidal neurons; foundational biophysical concepts were formalized by researchers affiliated with University of Pennsylvania, Columbia University, and University of Oxford. Typical systems follow international standards like the 10–20 system developed by groups at International Federation of Clinical Neurophysiology and incorporate amplification, filtering, and analog-to-digital conversion technologies advanced at Bell Labs, Texas Instruments, and STMicroelectronics. Electrode designs range from wet silver/silver chloride electrodes used in early studies at University of Chicago to dry and active electrodes developed by teams at Imperial College London and University of Tokyo, with intracranial grids and depth electrodes employed in centers such as Yale School of Medicine and University of Pennsylvania Health System. Recording modalities include continuous scalp recordings used in sleep units at Rush University Medical Center, intraoperative monitoring popularized at Cleveland Clinic and University College Hospital, and ambulatory systems commercialized by firms like Philips and GE Healthcare.

Clinical Applications

Electroencephalography is essential in epilepsy diagnosis and presurgical evaluation conducted at tertiary centers including Cleveland Clinic, Mayo Clinic, and Mount Sinai Hospital. It supports comatose patient assessment in neurocritical care units at Massachusetts General Hospital, seizure classification work in pediatric centers like Great Ormond Street Hospital, and monitoring during anesthesia in operating rooms at Johns Hopkins Hospital and Karolinska Universitetssjukhuset. Sleep disorder diagnosis in clinics associated with Stanford Sleep Medicine Center and Brigham and Women's Hospital relies on polysomnography with EEG channels, while neurodegenerative disease research at Columbia University Irving Medical Center and UCL Queen Square Institute of Neurology uses EEG biomarkers. Intraoperative neurophysiological monitoring during procedures at Mayo Clinic and Cleveland Clinic employs EEG alongside mapping techniques developed at University of Pennsylvania.

Research Uses and Neurophysiology

Research applications span cognitive neuroscience labs at MIT, Princeton University, University of Cambridge, and University of California, Berkeley investigating event-related potentials first characterized by groups at University of Illinois Urbana-Champaign and Donders Institute. Brain–computer interface research at Carnegie Mellon University, Brown University, and University of Tübingen utilizes EEG for communication and control, while developmental studies at University of Oxford and University of Melbourne probe maturational changes. Large-scale initiatives funded by Human Brain Project, BRAIN Initiative, and consortia involving National Institute of Mental Health integrate EEG with neuroimaging from Stanford University, University College London, and Max Planck Institute for Human Cognitive and Brain Sciences to study network dynamics, oscillatory phenomena described by investigators at McGill University, and cross-species comparisons led by teams at Salk Institute.

Signal Analysis and Interpretation

Signal processing methods developed at EPFL, Technical University of Munich, and ETH Zurich include time-domain averaging for event-related potentials, frequency-domain analyses originating in work at University of Birmingham and University of Glasgow, and source localization algorithms from groups at University of Minnesota and McConnell Brain Imaging Centre. Advanced machine learning applications for pattern detection have been driven by researchers at Google DeepMind, OpenAI, and universities such as Stanford University and University of Toronto. Clinical interpretation follows guidelines promulgated by American Clinical Neurophysiology Society, International League Against Epilepsy, and professional bodies at Royal College of Physicians and European Society of Clinical Neurophysiology, with scoring conventions used widely in sleep labs at Johns Hopkins and University of Pennsylvania.

Safety and Limitations

EEG is considered low risk when performed in controlled settings at hospitals like Mayo Clinic and research facilities including Massachusetts Institute of Technology, yet limitations include low spatial resolution relative to modalities developed at Max Planck Institute for Biological Cybernetics and susceptibility to artifacts studied at University of California, San Diego and University of Arizona. Interpretation requires expertise from clinicians certified by bodies such as American Board of Psychiatry and Neurology and UK’s General Medical Council, and ethical oversight in invasive studies at University Hospital Zurich and Charité – Universitätsmedizin Berlin. Technological and physiological constraints continue to motivate work at device manufacturers like Medtronic and research centers such as Johns Hopkins University.

Category:Neurophysiology