Methodology electroencephalography

For registration of bioelectric activity use electroencephalograph (Fig. 1)containing electronic amplifiers with high gain, low noise level and the frequency band from 1 to 100 Hz or higher. In addition, the EEG is the registration portion representing oscillographic system with access to ink pen, or electron beam Slavny oscilloscopes. Recently in some samples of electroencephalographs found use less inertia than ink, inkjet and thermal record. The discharge electrodes, connecting the investigated object to the input of the amplifier can be placed on the surface of the head, or implanted in the long term in the study of the brain. Currently beginning to develop alelectronic.italy which records the electrical activity of the brain at a distance from the object. In this case bioelectric activity modulates the transmitter frequency of ultrashort waves, located on the head of a man or animal, and the input device electroencephalograph receives these signals. Record the bioelectrical activity of the brain called the electroencephalogram (EEG), if it is registered from intact skull, and electrocorticogram (ECOG) registration directly from the brain-cortex. In the latter case, the method of registration of the currents of the brain called electrocorticography. EEG represent the cumulative curves of changes over time-difference of potentials arising under the electrodes. To assess EEG developed devices analyzers, automatically corrupting these complex curves on the components of their frequency. Most analyzers contains a number of narrow-band filters that are configured on a certain frequency. These filters from the output of the electroencephalograph served bioelectric activity. The results of frequency analysis are submitted to the registering device usually parallel to the course of the experiment (analyzers Walter Kozhevnikov). For EEG analysis, ACOG also use integrators, giving a summary assessment of the intensity of oscillations for some period of time. Their action is based on measurement of potentials capacitor that charges a current proportional to the instantaneous values of the investigated process.

Fig. 1. Shestnadtsatiletnij electroencephalograph EEG-01.

Modern digital EEG systems provide the ability to simultaneously record the electrical activity of not more than 20-40 points CNS Further increase the number of channels of diversion would lead to a significant increase in the size of the EEG, but also strain would use it.
Devices for registration of bioelectric activity, based on the principle of electronic commutation (M. N. Livanov and C. M. Ananiev), give an opportunity to increase the number of check-bioelectric activity to 50-100. In these devices, called electroencephalography (the method is called electroencephalography), bioelectric signals separate parts of the brain in a strict sequence enter the switching system of the instrument and modulate the amount of bearing pulses (Fig. 2). After a corresponding strengthening these signals modulate the brightness of cathode ray oscilloscope. The growth of negativity under the electrode causes a proportional amplification of the brightness of the screen. Since a raster scan certain paragraphs of the screen correspond to the location of the electrodes, the opportunity to observe directly the spatial distribution of changes biopotential of investigated areas of the brain. The second cathode ray oscilloscope with linear scan allows you to accurately measure changes in amplitudes of all exhaust biopotentials, because it reflects them on the screen in the form of columns. The resulting pictures can be captured by the cameras. Investigation of spatial changes of bioelectric activity using electroencephalograph led to the development of a new section of electroencephalography - electroencephalography.
A large amount of information obtained during these studies, requires for its analysis of electronic computers.

Fig. 2. The block diagram of electroencephalograph: M - multivibrator; CP - synchronizer reamers; BSR - block horizontal; BLR - block streak; Hungary - block frame scanning; PU - pre-amplifier; - switching lamp; FB - forming unit; SAT - shift block. In the circle: the location of the relevant discharge electrodes points (1) and pulses (2) on the screen of oscilloscope. Points plotted in the path of the right hemisphere of the rabbit brain.