Getting started, tracing

One or more EEG fragments with characteristic features are selected for staged localization of a source (tracing). The required EEG fragments can be selected in software for EEG studies ("Encephalan-EEGA" or "Encephalan-EEGR") or directly in "Encephalan-3D" Software. EP-studies data can also be downloaded for localization from "Encephalan-EP" software.

It is necessary to choose the localization model (single-, two- or three-dipole) to calculate the localization of the source. For this purpose the topography of potential distribution in several EEG time cuts is preliminarily evaluated, the number of the most typical and stable focuses is computed by EEG amplitude map.

During tracing, the software is alternatively analyzing EEG/EP time samples. Processing is displayed by moving of a special marker. Found dipoles are displayed on head cuts. At the same time, localization is analyzed for conformity so that a user can pause the tracing and adjust the settings in case of a large number of mismatches.

Analysis and specification of the obtained data

At the end of the tracing, the Localization window displays dipole "clouds" (groups) on the head cuts, two amplitude topographic maps based on the native EEG and localization data (for quick visual comparison and evaluation of the result), and a table with coordinates, accuracy and energy values of the selected dipoles.

Any head projection with found dipoles can be viewed enlarged, as well as dipoles distribution over three-dimensional head model, and graphs of temporal and spatial localization dynamics.

An important feature of "Encephalan-3D"» software is the simultaneous displaying of changes in all displayed data: dipoles distribution, topographic maps and localization graphs for a particular moment in time are displayed when moving the marker over the EEG signal. And vice versa, when specifying a particular dipole, the marker on signals moves to EEG cut, where the dipole has the maximum energy, and the table displays its characteristics, etc.

Localization of source is carried out both for one fragment only and several selected ones.

The "Encephalan-3D" application allows numerically estimating the accuracy of scalp voltages restoration by comparing the instantaneous amplitude values of initial and reconstructed signals of the current time cut, as well as visually comparing amplitude topographic maps.

Calculation and display of accuracy and energy changing graphs, and spatial and temporal dipole motion path for all localized fragments are performed to estimate the source dynamics.

These graphs allow identifying dipole switch moments, for example in the presence of mirror foci.

Since the great number of dipoles and their close location to each other on the screen, the Enlargement window is used for a detailed view.

Dipole of maximum accuracy and maximum energy (according to color scale) is of the most interest.

There can be displayed not only dipoles but also coordinating vectors with diagnostically significant dynamics on the enlarged head cut.

Three-dimensional localization of sources can be applied not only to typical EEG graph elements (e.g., spike-wave), but also to evoked potentials (EP) components. Cognitive EP P300 example shows localized regions that are located in the front areas of the brain and characterize the most active areas of the brain in endogenous processes of the relevant stimuli recognition.

Three-dimensional localization for EP data requires their export to UDF format (to "Encephalan-EP" Software) and further import to "Encephalan-3D" Software.

The first two images show the localization for averaged EP CNV responses (complex stimulus – a click, a pause, probabilistic stimulus: significant – 30%, insignificant – 70%) from 3 averagers: "Significant", "Insignificant" "General".

The last image shows localization analysis during the EP P300 study (changing the source location in reaction to significant and insignificant stimulus).