Significance probability mapping: The final touch int-statistic mapping
Significance Probability Mapping (SPM), based on Student'st-statistic, is widely used for comparing mean brain topography maps of two groups. The map resulting from this process represents the distribution oft-values over the entire scalp. However,t-values by themselves cannot reveal whether or not group differences are significant. Significance levels associated with a fewt-values are therefore commonly indicated on map legends to give the reader an idea of the significance levels oft-values. Nevertheless, a precise significance level topography cannot be achieved with these few significance values. We introduce a new kind of map which directly displays significance level topography in order to relieve the reader from converting multiplet-values to their corresponding significance probabilities, and to obtain a good quantification and a better localization of regions with significant differences between groups. As an illustration of this type of map, we present a comparison of EEG activity in Alzheimer's patients and age-matched control subjects for both wakefulness and REM sleep.
Key wordsEEG Brain mapping Student'st-statistic Significance probability mapping Alzheimer's disease
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