In this tutorial review, we detail both the rationale for as well as the implementation of a set of analyses of surface-recorded
event-related potentials (ERPs) that uses the reference-free spatial (i.e. topographic) information available from high-density
electrode montages to render statistical information concerning modulations in response strength, latency, and topography
both between and within experimental conditions. In these and other ways these topographic analysis methods allow the experimenter
to glean additional information and neurophysiologic interpretability beyond what is available from canonical waveform analyses.
In this tutorial we present the example of somatosensory evoked potentials (SEPs) in response to stimulation of each hand
to illustrate these points. For each step of these analyses, we provide the reader with both a conceptual and mathematical
description of how the analysis is carried out, what it yields, and how to interpret its statistical outcome. We show that
these topographic analysis methods are intuitive and easy-to-use approaches that can remove much of the guesswork often confronting
ERP researchers and also assist in identifying the information contained within high-density ERP datasets.
Keywords Electroencephalography (EEG) - Event-related potentials (ERPs) - Topography - Spatial - Reference electrode - Global field power - Global dissimilarity - Microstate segmentation