Spatiotemporal Analysis of Multichannel EEG: CARTOOL

TLDR

Topographic analyses of EEG are reference‑independent and yield statistically unambiguous results, with topographic differences directly reflecting changes in active neuronal source configurations. The study presents methods for analyzing multichannel EEG electric fields, focusing on spatial properties and quantitative assessment of topographic changes across time, conditions, or populations, and demonstrates their implementation in CARTOOL. The authors implement global field strength and similarity measures, temporal segmentation, frequency‑domain topographic analysis, statistical topographic analysis, and distributed inverse‑solution source imaging in CARTOOL, a freely available academic software that also offers 3‑D visualization and animation of data and results. CARTOOL therefore is a helpful tool for researchers and clinicians to interpret multichannel EEG and evoked potentials in a global, comprehensive, and unambiguous way.

Abstract

This paper describes methods to analyze the brain's electric fields recorded with multichannel Electroencephalogram (EEG) and demonstrates their implementation in the software CARTOOL. It focuses on the analysis of the spatial properties of these fields and on quantitative assessment of changes of field topographies across time, experimental conditions, or populations. Topographic analyses are advantageous because they are reference independents and thus render statistically unambiguous results. Neurophysiologically, differences in topography directly indicate changes in the configuration of the active neuronal sources in the brain. We describe global measures of field strength and field similarities, temporal segmentation based on topographic variations, topographic analysis in the frequency domain, topographic statistical analysis, and source imaging based on distributed inverse solutions. All analysis methods are implemented in a freely available academic software package called CARTOOL. Besides providing these analysis tools, CARTOOL is particularly designed to visualize the data and the analysis results using 3-dimensional display routines that allow rapid manipulation and animation of 3D images. CARTOOL therefore is a helpful tool for researchers as well as for clinicians to interpret multichannel EEG and evoked potentials in a global, comprehensive, and unambiguous way.