Spectral analysis of physiological brain pulsations affecting the BOLD signal

• Main Authors: Helakari, H. (Author), Huotari, N. (Author), Kananen, J. (Author), Kiviniemi, V. (Author), Koivula, A. (Author), Korhonen, V. (Author), Raitamaa, L. (Author)
• Format: Article
• Language: English
• Published: John Wiley and Sons Inc 2021
• Subjects: adult; Adult; amplitude of low-frequency fluctuation; article; blood vessel; BOLD signal; brain; Brain; brain radiography; breathing; cardiorespiratory modulation; cardiovascular function; Cardiovascular Physiological Phenomena; cerebrospinal fluid; diagnostic imaging; fast fMRI; female; Female; functional magnetic resonance imaging; global signal; gray matter; heart; human; Humans; Magnetic Resonance Imaging; male; Male; middle aged; Middle Aged; nervous system function; Nervous System Physiological Phenomena; neuroimaging; Neuroimaging; nuclear magnetic resonance imaging; physiological brain pulsations; physiological process; physiology; procedures; respiratory function; Respiratory Physiological Phenomena; resting state; spectroscopy
• Online Access: View Fulltext in Publisher

 Physiological pulsations have been shown to affect the global blood oxygen level dependent (BOLD) signal in human brain. While these pulsations have previously been regarded as noise, recent studies show their potential as biomarkers of brain pathology. We used the extended 5 Hz spectral range of magnetic resonance encephalography (MREG) data to investigate spatial and frequency distributions of physiological BOLD signal sources. Amplitude spectra of the global image signals revealed cardiorespiratory envelope modulation (CREM) peaks, in addition to the previously known very low frequency (VLF) and cardiorespiratory pulsations. We then proceeded to extend the amplitude of low frequency fluctuations (ALFF) method to each of these pulsations. The respiratory pulsations were spatially dominating over most brain structures. The VLF pulsations overcame the respiratory pulsations in frontal and parietal gray matter, whereas cardiac and CREM pulsations had this effect in central cerebrospinal fluid (CSF) spaces and major blood vessels. A quasi-periodic pattern (QPP) analysis showed that the CREM pulsations propagated as waves, with a spatiotemporal pattern differing from that of respiratory pulsations, indicating them to be distinct intracranial physiological phenomenon. In conclusion, the respiration has a dominant effect on the global BOLD signal and directly modulates cardiovascular brain pulsations. © 2021 The Authors. Human Brain Mapping published by Wiley Periodicals LLC.