page_title: EEG microstates
section_title: Creating and assigning classes
hierarchical_section_title: EEG microstates / Identifying and analyzing microstates / From EEG to microstate / Creating and assigning classes
caption_attribution_description: English: Representation of a typical 4-class EEG Microstate topography sequence. Opposing polarity is represented by the arbitrarily designated colors.
context_page_description: EEG microstates are transient, patterned, quasi-stable states or patterns of an electroencephalogram. These tend to last anywhere from milliseconds to seconds and are hypothesized to be the most basic instantiations of human neurological tasks, and are thus nicknamed "the atoms of thought". Microstate estimation and analysis was originally done using alpha band activity, though broader bandwidth EEG bands are now typically used. The quasi-stability of microstates means that the "global [EEG] topography is fixed, but strength might vary and polarity invert."
context_section_description: Most studies reveal the same 4 classes of microstate topography:
  A: right-frontal to left-posterior
  B: left-frontal to right-posterior
  C: frontal to occipital
  D: mostly frontal and medial to slightly less occipital activity than class C
  However, many studies have also found other EEG microstate template maps that are likely to be meaningful. converged on 16 maps to explain a high proportion of the observed variance. found 13 maps using an ICA approach. The number of microstates 'found' and used is partly a function of the cognitive state of the person, but also partly the method used to cluster and assign microstates. Though microstates have historically always been assigned deterministically, recent work has also suggested that there are computational, analytical and conceptual issues that may be addressed through a probabilistic analysis of microstates.
caption: Typical 4-class microstate topography sequence. From left to right: Classes A, B, C, and D
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