Individual reliability of amplitude distribution in topographical mapping of EEG.

Whilst there is an accumulation of evidence suggesting that many quantitative EEG parameters show good stability and reliability, no previous study has considered whether the spatial distribution of EEG amplitude is reliable over time within a session. This study reports on the spatio-temporal reliability of EEG using data recorded from 24 subjects in a baseline condition with eyes open and also whilst performing a simple motor task. Both the internal stability and test-retest reliability for electrode parameters were comparable to previously published data. For most individuals, amplitude distribution was stable within each recording condition, but the test-retest reliability after 40 min was less good with the poorest reliability in the delta frequency band. Most subjects showed spatio-temporal reliability of less than 0.7 in at least one frequency band. In contrast, spatio-temporal reliability for the group average was good and exceeded 0.88 in all frequency bands. It is argued that the results indicate that reliability is insufficient to allow topographical comparisons for a single individual, but is more than adequate to allow group comparisons.