POWER SPECTRAL-ANALYSIS OF EEG IN A MULTIPLE-BEDROOM, MULTIPLE-POLYGRAPH SLEEP LABORATORY

Objectives: We describe the methods for power spectral analysis (PSA) of sleep electroencephalogram (EEG) data at a large clinical and resea rch sleep laboratory. The multiple-bedroom multiple-polygraph design o f the sleep laboratory poses unique challenges for the quantitative an alysis of the data. This paper focuses on the steps taken to ensure th at our PSA results are not biased by the particular bedroom or polygra ph from which the data were acquired. Methods: After describing the da ta acquisition system hardware, we present our signal amplitude calibr ation procedure and our methods for performing PSA. We validate the am plitude calibration procedure in several experiments using PSA to esta blish tolerances for data acquisition from multiple bedrooms and polyg raphs. Results: Since it is not possible to acquire identical digitize d versions of an EEG signal using different sets of equipment, the bes t that can be achieved is data acquisition that is polygraph-independe nt within a known tolerance. We are able to demonstrate a tolerance in signal amplitude of +/- 0.25% when digitizing data from different bed rooms. When different data acquisition hardware is used, the power tol erance is approximately +/- 3% for frequencies from 1 to 35 Hz. The po wer tolerance is between +/- 3 and +/- 7% for frequencies below 1 Hz a nd frequencies between 35 and 50 Hz. Additional data demonstrate that variability due to the hardware system is small relative to the inhere nt variability of the sleep EEG. Conclusion: The PSA results obtained in one location can be replicated elsewhere (subject to known toleranc es) only if the data acquisition system and PSA method are adequately specified. (C) 1997 Elsevier Science Ireland Ltd.