Glossary

cluster centers

Arithmetic mean of all the points belonging to the cluster. In the context of microstate analysis, it corresponds to the microstates topographies.

GEV

global explained variance

Global explained variance. Total explained variance expressed by a given state. It is computed as the sum of the explained variance multiplied by the Global Field Power (GFP) of each sample assigned to a given state.

GFP

global field power

Global Field Power (GFP) is a measure of the (non-)uniformity of the electromagnetic field at the sensors. It is typically calculated as the standard deviation of the sensor values at each time point. Thus, it is a one-dimensional time series capturing the spatial variability of the signal across sensor locations. Local maxima of the global field power (GFP) are known to represent the portions of EEG data with highest signal-to-noise ratio (Koenig and Brandeis [KB16]).

inter-cluster distance

Distance between two datapoints belonging to two different clusters. Depending on the metric used, it can be computed in different ways, for example (but no limited to) as the average distance between all datapoint belonging to different clusters, the distance between two cluster centers, the minimal distance between two datapoints belonging to different cluster.

intra-cluster distance

Distance between two datapoint belonging to the same cluster. Depending on the metric used, it can be computed in different ways, for example (but no limited to) as the average distance between all datapoint belonging to the same cluster, the average distance between all datapoint at the cluster center or the maximal distance between two datapoints belonging to the same cluster.