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This Article Full Text Full Text (PDF) All Versions of this Article: 559/3/965    most recent jphysiol.2004.066969v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hamner, J. W. Articles by Taylor, J. A. Search for Related Content PubMed PubMed Citation Articles by Hamner, J. W. Articles by Taylor, J. A.

¹ Laboratories for Cardiovascular Research, Research and Training Institute, Hebrew Rehabilitation Center for Aged, Boston, MA 02131, USA
² Gerontology Division, Beth Israel Deaconess Medical Center, and Division on Aging, Harvard Medical School, Boston, MA 02134, USA
³ Department of Cognitive and Neural Systems, Boston University, Boston, MA 02215, USA

We set out to fully examine the frequency domain relationship between arterial pressure and cerebral blood flow. Oscillatory lower body negative pressure (OLBNP) was used to create consistent blood pressure oscillations of varying frequency and amplitude to rigorously test for a frequency- and/or amplitude-dependent relationship between arterial pressure and cerebral flow. We also examined the predictions from OLBNP data for the cerebral flow response to the stepwise drop in pressure subsequent to deflation of ischaemic thigh cuffs. We measured spectral powers, cross-spectral coherence, and transfer function gains and phases in arterial pressure and cerebral flow during three amplitudes (0, 20, and 40 mmHg) and three frequencies (0.10, 0.05, and 0.03 Hz) of OLBNP in nine healthy young volunteers. Pressure fluctuations were directly related to OLBNP amplitude and inversely to OLBNP frequency. Although cerebral flow oscillations were increased, they did not demonstrate the same frequency dependence seen in pressure oscillations. The overall pattern of the pressure–flow relation was of decreasing coherence and gain and increasing phase with decreasing frequency, characteristic of a high-pass filter. Coherence between pressure and flow was increased at all frequencies by OLBNP, but was still significantly lower at frequencies below 0.07 Hz despite the augmented pressure input. In addition, predictions of thigh cuff data from spectral estimates were extremely inconsistent and highly variable, suggesting that cerebral autoregulation is a frequency-dependent mechanism that may not be fully characterized by linear methods.

(Received 21 April 2004; accepted after revision 13 July 2004; first published online 22 July 2004)
Corresponding author J. A. Taylor: Cardiovascular Research Laboratory, Spaulding Rehabilitation Hospital, 125 Nashua Street, Boston, MA 02114, USA. Email: jandrew_taylor{at}hms.harvard.edu

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