Chapter 4 27, speed of information processing (Trail Making Test, part A 18; Stroop, card I and II 28; and Symbol Digit Modality Test 24), executive functioning (Trail Making Test, part B: Stroop, card III), and verbal fluency (fluency animals, 60 seconds) 29. CBF ABP Ra Cp Rp Figure 1 Windkessel model consisting of arterial resistance Ra, peripheral resistance Rp and peripheral compliance Cp with pressure ABP representing arterial blood pressure and CBF cerebral blood flow. Data analysis Raw data from the Task Force Monitor were exported to an in-house made acquisition and analysis software package (AFOnew version 2.48, IDEE Maas- tricht®, the Netherlands). An automatic algorithm detected the ECG R-waves and determined the subsequent diastolic, mean and systolic blood pressure and corresponding end diastolic, mean and peak systolic CBFV. Artefacts were removed manually by linear interpolation. The beat-to-beat values of ABP and CBFV were exported to Matlab and resampled at 5 Hz using spline interpolation 16. ABP and CBFV were normalized with respect to the mean. This resulted in zero-mean signals suited for spectral analysis to estimate the transfer function. Estimation of the transfer function was performed as previously described 10. Phase and gain were evaluated for different frequency bands of autoregulation namely Total (0.04-0.11 Hz) , very low frequency VLF (0.04-0.06 Hz), 01 (0.1 Hz) , low frequency LF (0.06-0.11 Hz). In order to compare the results (addition JC in abbreviations) reported by Claassen et al 4 with ours, we also computed the different CA parameters for the frequency bands VLFJC (0.02-0.07 Hz), LFJC (0.07-0.2 Hz) and HFJC (0.2-0.35 Hz). To be strict in acceptance of data, the coherence threshold applied is three times the previously described theoretically derived value 9. With 15 minute recordings this means only recordings with a 64
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