Psychophysical and fMRI Temporal Pain Dynamics Assessment of Task-based Variability 公开
Heras, Sofia (Spring 2024)
Published
Abstract
Introduction and Background: In 2019, approximately 20.9% of Americans suffered from chronic pain. The mechanisms underlying the pain experience are critical to understanding this condition and its biomarkers, but this characterization is challenging due to the dynamic nature of pain. Functional magnetic resonance imaging (fMRI), combined with quantitative sensory testing (QST), can unveil the relationship between painful sensations and neurobiological underpinnings of the pain experience. Current pain measurement in fMRI experiments assess perceived pain following each fMRI run, or trial, using a discrete estimate (e.g., 40/100) of pain, and then model the brain activations based on when the stimulus was being delivered. Given the dynamic nature of the pain experience and the delays between stimulus onsets and experiencing pain from a stimulus, we expected fMRI signals to be better visualized when the temporal course of the pain experience is considered.
Materials and Methods: Twenty-seven pain-free individuals (14 females, mean age = 23.2 yrs) underwent 20-second, moderately painful (i.e., 40/100) noxious heat stimuli on each leg interleaved with 20-seconds of no stimulation. In the lab, participants indicated perceived pain of these stimuli continuously for varying intensities to determine the temporal profile of the pain experience. Then, participants were scanned in a Siemens 3T Magnetom Prisma Fit Scanner during the application of identical stimuli to record pain-evoked brain responses.
Results: Results revealed an average delay of 8 seconds between the onset of a thermal stimulus and perceptible pain, suggesting that modeling brain activations using stimulus onsets is not ideal. Incorporating this delay in the significantly enhanced BOLD signals in key pain- processing areas, including the thalamus, insula, anterior cingulate cortex, and somatosensory cortices. This evidence suggests that incorporating the dynamics of the pain experience in the analysis of pain-evoked BOLD could increase the signal in these types of experiments. Different pain intensities unveiled brain changes directly correlating to the level of intensity, with higher intensity stimuli resulting in more significant activations. These results speak to the sensitivity of the pain experience, as subtle changes in stimuli can cause significant enhancement in activations of pain-processing regions.
Conclusion: Distinguishing the onset of stimulus to that of pain can uncover the mechanisms underpinning the pain experience, helping advance the diagnosis and treatment of chronic pain. Understanding how brain responses differ in accordance with noxious stimuli changes is a useful tool in characterizing the temporal dynamics of perceived pain as well.
Table of Contents
Introduction and Background......................................................................................................1
Quantitative Sensory Testing (QST) ............................................................................................2
Functional Magnetic Resonance Imaging (fMRI).......................................................................3
Materials and Methods .................................................................................................................6
Participants .................................................................................................................................7
QST Behavioral Visit ...................................................................................................................7
Imaging Visit................................................................................................................................9
Data preprocessing....................................................................................................................10
Statistical Analysis..................................................................................................................... 11
Results...........................................................................................................................................14
QST Previous Data ....................................................................................................................14
ON vs OFF Block Comparison .................................................................................................16
Increasing vs Decreasing Trials Comparison ...........................................................................19
Increasing vs Constant Trials Comparison ...............................................................................22
Constant vs Decreasing Trials...................................................................................................24
Discussion .....................................................................................................................................25
Bibliography.................................................................................................................................34
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