Wavelet coherence analysis of spontaneous oscillations in cerebral tissue oxyhemoglobin concentrations and arterial blood pressure in elderly subjects

Cerebral autoregulation in response to posture change in elderly subjects-assessment by wavelet phase coherence analysis of cerebral tissue oxyhemoglobin concentrations and arterial blood pressure signals

“…In generally, CA is caused by the cooperative action of both sympathetically mediated and local myogenic or metabolic mechanisms [2]. The WPCO in the low frequency (0.02-0.05 Hz) has been found to be higher in elderly subjects than in young subjects at rest [32]. Changes in CBFV recover faster than the changes in BP, which causes a displacement of CBFV relative to BP in such a manner that CBFV oscillations appear to lead BP oscillations.…”

Predominant endothelial vasomotor activity during human sleep: a near‐infrared spectroscopy study

“…Signal powers of HbO 2 during different sleep stages were estimated with Welch's power spectral density (PSD) method, with a segment length of 1024 samples, and 50% segment overlap. The PSD of a specific component of vasomotion was defined as the mean value of PSDs over the frequency bands of this component [the endothelial component was 3–20 mHz, the neurogenic component was 20–40 mHz, and the myogenic component was 40–150 mHz, according to the literature (Kvernmo et al ., ; Kvandal et al ., ; Nasi et al ., ; Cui et al ., )]. These data‐processing procedures were conducted on both cerebral and muscular NIRS measurements and on systemic SpO 2 data.…”

“…The rhythmic oscillation in tone of blood vessels is referred to as vasomotion. Vasomotion can be evaluated indirectly by measuring the corresponding hemodynamic oscillations in hemodynamic parameters such as blood flow (BF), oxygenated hemoglobin (HbO 2 ), and deoxygenated hemoglobin (HHb) (Aalkjaer et al ., ; Rivadulla et al ., ; Cui et al ., ). Vasomotion‐induced hemodynamic oscillations can be classified into two groups: low‐frequency oscillations (LFOs) (0.04–0.15 Hz) and very low‐frequency oscillations (VLFOs) (0.003–0.04 Hz).…”

“…Transcranial Doppler ultrasonography is hindered by its restricted measurement area (only large arteries) in the brain and the technical challenge in obtaining clean Doppler signals during sleep (Netzer, ). A novel technique used in assessing hemodynamic oscillations is near‐infrared spectroscopy (NIRS) (Obrig et al ., ; Cui et al ., ). NIRS can measure HbO 2 , HHb and oxygenation changes in intracranial small vessels with less motion restriction locally and non‐invasively (Wolf et al ., ).…”

Phase synchronization analysis of prefrontal tissue oxyhemoglobin oscillations in elderly subjects with cerebral infarction

“…33,34 WPCO has been successfully used to analyze the relationships between oscillations in skin blood flow, temperature and oxygen saturation, and intracranial pressure and arterial blood pressure (ABP) signals within certain frequency ranges. [34][35][36][37] In this study, we used the wavelet transform, rather than the Fourier transform or Hilbert transform, approach to the phase coherence as this offers a more intuitive visualization of time-frequency behavior. We hypothesize that the phase synchronization in the left and right prefrontal regions would be altered due to CI.…”