Test-retest reliability of cognitive EEG

Objective: Task-related EEG is sensitive to changes in cognitive state prod uced by increased task difficulty and by transient impairment. If task-rela ted EEG has high test-retest reliability, it could be used as part of a cli nical test to assess changes in cognitive function. The aim of this study w as to determine the reliability of the EEG recorded during the performance of a working memory (WM) task and a psychomotor vigilance task (PVT). Methods: EEG was recorded while subjects rested quietly and while they perf ormed the tasks. Within session (test-retest interval of similar to 1 h) an d between session (test-retest interval of similar to 7 days) reliability w as calculated for four EEC components: frontal midline theta at Fz, posteri or theta at Pt, and slow and fast alpha at Pt. Results: Task-related EEG was highly reliable within and between sessions ( r > 0.9 for all components in WM task, and r > 0.8 for all components in th e PVT). Resting EEG also showed high reliability, although the magnitude of the correlation was somewhat smaller than that of the task-related EEG (r > 0.7 for all 4 components). Conclusions: These results suggest that under appropriate conditions, task- related EEG has sufficient retest reliability for use in assessing clinical changes in cognitive status. (C) 2000 Elsevier Science Ireland Ltd. All ri ghts reserved.