Electroencephalography: basic biophysical and technological aspects important for clinical applications

Abstract

Electroencephalography (EEG) is the most commonly used functional investigative method in epilepsy. The goal of this educational review paper is to summarize the most important aspects related to the biophysical phenomena of EEG signal generation and the technical features that a clinician needs to understand in order to read and interpret EEGs. We explain the EEG electrodes and recording arrays, amplifiers, filters, analogue‐to‐digital conversion and signal display. We describe the advantages and disadvantages of the different montages and the indications for the various types of EEG recordings and provocative maneuvers. We explain how to use topographic maps to estimate the source of the cortical generator.

EEG Essentials

“…Dipoles generating abnormal electrophysiologic potentials have a specific orientation, with the negative end lying in the superficial cortical layers and the positive end closer to the cell body in deeper layers of the cortex. Scalp topographic representation by EEG is determined by the area of the cortex generating the signal and the orientation of the negative and positive ends of the dipole that determine the spatial distribution of the recorded signal 4 …”

“…Interpretation involves the qualitative process of visually extracting a complex series of brain signals 4 . Most clinical EEG interpretations identify frequencies between 1 and 35 Hz (also known as the Berger band ), including a mixture of frequencies involving alpha (8 to 13 Hz), beta (13 to 30 Hz), theta (4 to 8 Hz), and delta (less than 4 Hz).…”

“…Physicians who treat patients with epilepsy need to understand biophysical aspects of signal generation and recording to accurately interpret the results of the clinical EEG. 4 Signals detected and ultimately recorded by EEG are generated by dynamic extracellular currents produced by transmembrane ion flow. These currents are initiated in the apical dendrites of the pyramidal neurons located in layers IV and V of the cerebral cortex.…”

Conductive Polymers for Bidirectional Neural Interfaces: Fundamentals Aspects and in Vivo Applications

“…Cup electrodes Ag/AgCl 10 mm / 314 mm 2/ 3.1 cm 2 EEG Diagnosis of epilepsy and of regional dysfunctions [24] Subcutaneous…”

Electroencephalography and analysis of functional brain activity

“…Тем не менее метод ЭЭГ продолжает применяться как в научных, так и в клинических исследованиях [4] и на сегодняшний день является единственной технологией, позволяющей регистрировать изменения биоэлектрической активности головного мозга напрямую, без использования различных физических и химических посредников, что дает исследователю возможность анализировать и фиксировать быстропротекающие процессы, недоступные для иных методов [7].…”