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Acquisition of Resting-State Functional Magnetic Resonance Imaging Data in the Rat
Published on: August 28, 2021
Resting-state functional MRI as a tool for evaluating brain hemodynamic responsiveness to external stimuli in rats
Jaakko Paasonen1, Raimo A Salo1, Joanna K Huttunen1
1A.I.V. Institute for Molecular Sciences, Department of Neurobiology, University of Eastern Finland, Kuopio, Finland.
Purpose:
Anesthesia is a major confounding factor in functional MRI (fMRI) experiments attributed to its effects on brain function. Recent evidence suggests that parameters obtained with resting-state fMRI (rs-fMRI) are coupled with anesthetic depth. Therefore, we investigated whether parameters obtained with rs-fMRI, such as functional connectivity (FC), are also directly related to blood-oxygen-level-dependent (BOLD) responses.
Methods:
A simple rs-fMRI protocol was implemented in a pharmacological fMRI study to evaluate the coupling between hemodynamic responses and FC under five anesthetics (α-chloralose, isoflurane, medetomidine, thiobutabarbital, and urethane). Temporal change in the FC was evaluated at 1-hour interval. Supplementary forepaw stimulation experiments were also conducted.
Results:
Under thiobutabarbital anesthesia, FC was clearly coupled with nicotine-induced BOLD responses. Good correlation values were also obtained under isoflurane and medetomidine anesthesia. The observations in the thiobutabarbital group were supported by forepaw stimulation experiments. Additionally, the rs-fMRI protocol revealed significant temporal changes in the FC in the α-chloralose, thiobutabarbital, and urethane groups.
Conclusion:
Our results suggest that FC can be used to estimate brain hemodynamic responsiveness to stimuli and evaluate the level and temporal changes of anesthesia. Therefore, analysis of the fMRI baseline signal may be highly valuable tool for controlling the outcome of preclinical fMRI experiments. Magn Reson Med 78:1136-1146, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
Insights
Resting-state functional connectivity (rs-fMRI) can estimate brain hemodynamic responses and anesthetic depth. Analyzing fMRI baseline signals helps control preclinical fMRI experiment outcomes.
Area of Science:
- Neuroimaging
- Anesthesiology
- Pharmacology
Background:
- Anesthesia significantly confounds functional magnetic resonance imaging (fMRI) studies by altering brain function.
- Emerging evidence indicates a link between resting-state fMRI (rs-fMRI) parameters and anesthetic depth.
Purpose of the Study:
- To investigate the relationship between rs-fMRI functional connectivity (FC) and blood-oxygen-level-dependent (BOLD) responses under various anesthetic conditions.
- To determine if FC can serve as a reliable indicator of hemodynamic responsiveness and anesthetic level.
Main Methods:
- A simplified rs-fMRI protocol was applied in a pharmacological fMRI study.
- Evaluated FC temporal changes at hourly intervals under five anesthetics: α-chloralose, isoflurane, medetomidine, thiobutabarbital, and urethane.
- Conducted supplementary forepaw stimulation experiments to validate findings.
Main Results:
- Functional connectivity (FC) strongly correlated with nicotine-induced BOLD responses under thiobutabarbital anesthesia.
- Significant correlations were also observed with isoflurane and medetomidine anesthesia.
- rs-fMRI detected significant temporal FC changes in the α-chloralose, thiobutabarbital, and urethane groups.
Conclusions:
- FC derived from rs-fMRI can effectively estimate brain hemodynamic responsiveness to stimuli.
- rs-fMRI analysis provides a valuable tool for assessing anesthetic level and temporal dynamics.
- Baseline fMRI signal analysis is crucial for controlling outcomes in preclinical fMRI research.
