Coupling of Low Frequency Hemodynamic Oscillations between the Brain and Spinal Cord
Poster No:
2110
Submission Type:
Abstract Submission
Authors:
Andrew Frels1, Vidhya Nair2, Brianna Kish1, Amy Schwichtenberg1, Yunjie Tong1
Institutions:
1Purdue University, West Lafayette, IN, 2Indiana University School of Medicine, indianapolis, IN
First Author:
Co-Author(s):
Introduction:
In Functional Magnetic Resonance Imaging (fMRI), the primary contrast is Blood Oxygen Level Dependent (BOLD) signal. Systemic Low Frequency Oscillations (sLFO) are BOLD signals between 0.01 Hz and 0.1 Hz originating from systemic physiological processes [1]. While sLFO signals in the brain have been shown to travel with blood in numerous studies, their behavior in the spinal cord (SC) remains unexplored. This study characterizes the coupling between brain-sLFO and SC-sLFO signals. Understanding brain-SC-coupling is pivotal for unraveling the vascular continuity of the central nervous system, which plays a crucial role in SC-injury pathophysiology, a known cause of early-onset Alzheimer's-like dementia.
Methods:
Data was preprocessed and then the BOLD signal was extracted from each region. This involved registering structural masks (including large blood vessels as reference) to fMRI space to obtain average time series from the brain and the superior sagittal sinus (SSS). The SC region in the fMRI had a well-known bow shape to it (warping artifacts at the bottom of the neck), rendering traditional registration impossible. Therefore, an in-house semi-automatic method was developed to mask the SC in the fMRI space. The sLFOs of the time series were cross-correlated to determine vascular delays and analyzed for band power.
Results:
It was found via cross-correlation analysis that the SC-sLFO signal comprises two components relative to the brain. The first signal is early (4 sec) relative to the global mean (GMean) signal of the brain and is anti-correlated with it. The second, dominant, signal is delayed ( 5.5 sec) relative to the GMean with a positive correlation. It was also observed that the brain-SC sLFO relationship is primarily captured by the outer layer of the SC, likely involving the white matter and surface blood vessels, with this region being dominated by the LFO frequency band. These findings suggest that 1) highly oxygenated blood arrives at the spinal cord before arriving at the brain, and 2) some component of the brain's venous output circulates to or near the spinal cord later. The former pathway is postulated to be the vertebral arteries, which first bring blood to the SC and then to the brain [2]. The latter is the cerebrospinal vascular system, which describes the venous continuity between the brain and SC [3], [4].
Conclusions:
This study is the first to investigate physiological sLFOs in the SC, examining their characteristics and relationships with those in the brain. We identify a significant vascular coupling between the sLFO signal of the brain and that of the SC. These signals may reflect different blood flow pathways to and from the brain and SC. Based on this study, we propose a model with several novel biomarkers that could be used to evaluate the continuity and consistency across the entire CNS. These biomarkers may have a significant impact on the assessment, monitoring, and prognosis of spinal cord injuries.
Modeling and Analysis Methods:
fMRI Connectivity and Network Modeling 2
Methods Development
Neuroanatomy, Physiology, Metabolism and Neurotransmission:
Anatomy and Functional Systems
Physiology, Metabolism and Neurotransmission:
Cerebral Metabolism and Hemodynamics 1
Neurophysiology of Imaging Signals
Keywords:
FUNCTIONAL MRI
Spinal Cord
1|2Indicates the priority used for review
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