| Frequency Analysis of EEG |
| eemagine EEG offers a couple of options to perform analysis of spectral properties of EEG data. Frequency analysis results are displayed either in a CDSA (Compressed Density Spectral Array) view showing the time course of the development of the frequency content of EEG signals or in 3D frequency mapping view showing the topographic distribution of EEG frequency content. This application case shows how the 3D frequency mapping of a psychiatric patient performing a mental attention task can be compared to spectral data obtained from a normative group of normal subjects. | ||
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Preparation The first steps guide the user to the loading of the necessary data to perform the 3D frequency analysis: EEG, electrodes and head model. The EEG view provides a couple of options to review the EEG data in an effective way. Marking of artefacts excludes artefact contaminated EEG epochs from subsequent analysis. |  | ||
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Epoch Generation The FFT-analysis starts with the generation of EEG epochs, corresponding to the blocks used during the following FFT computation. |  | ||
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Epoch Review To ensure a good quality of the data used for FFT analysis the single epochs can be fast reviewed using the linked event list view and EEG view. Epochs containing artefacts are disabled and excluded from further analysis. |  | ||
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Result Review FFT values are computed on the basis of the reviewed epochs. To get results, which are better comparable an option can be used, which normalizes the data with respect to the channel with the highest power over all frequency bands. The 3D maps show the spectral mapping for the 4 standard frequency bands. But further options allow to display mappings for a couple of more predefined or user defined frequency bands. |  | ||
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Reading of Reference Data To compare the data with the frequency mapping of a baseline condition or to a pooled set of frequency mapping results of a normative group an ASCII file containing reference FFT data can be loaded. |  | ||
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Comparison to Reference Data The FFT mapping of the actual EEG data can be inspected in one view together with the reference data, the difference between actual and reference data and a significance map. The significance map shows the probability, that the frequency content for a frequency band differs from the reference data set. |  | ||
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Comparison to Reference Data The FFT mapping of the actual EEG data can be inspected in one view together with the reference data, the difference between actual and reference data and a significance map. The significance map shows the probability, that the frequency content for a frequency band differs from the reference data set. | | ||
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