Abstract
Pain perception is a subjective experience and highly variable across time. Brain responses evoked by nociceptive stimuli are highly associated with pain perception and also showed considerable variability. To date, the test–retest reliability of laser-evoked pain perception and its associated brain responses across sessions remain unclear. Here, an experiment with a within-subject repeated-measures design was performed in 22 healthy volunteers. Radiant-heat laser stimuli were delivered on subjects’ left-hand dorsum in two sessions separated by 1–5 days. We observed that laser-evoked pain perception was significantly declined across sessions, coupled with decreased brain responses in the bilateral primary somatosensory cortex (S1), right primary motor cortex, supplementary motor area, and middle cingulate cortex. Intraclass correlation coefficients between the two sessions showed “fair” to “moderate” test–retest reliability for pain perception and brain responses. Additionally, we observed lower resting-state brain activity in the right S1 and lower resting-state functional connectivity between right S1 and dorsolateral prefrontal cortex in the second session than the first session. Altogether, being possibly influenced by changes of baseline mental state, laser-evoked pain perception and brain responses showed considerable across-session variability. This phenomenon should be considered when designing experiments for laboratory studies and evaluating pain abnormalities in clinical practice.
Highlights
Blood oxygenation level-dependent functional magnetic resonance imaging (BOLD fMRI) can measure human brain activity objectively and enable a deep understanding of neural processing mechanisms
Few studies have examined whether the pain perception evoked by radiant-heat laser stimuli and the associated BOLD responses remain stable over time
The paired-sample t-test revealed that the magnitudes of brain activations were significantly smaller in bilateral S1, primary motor cortex (M1), supplementary motor area (SMA), and middle cingulate cortex (MCC) in T2 session than in T1 session. These results showed that the decrease in pain ratings was accompanied by a reduced BOLD response in brain regions responsible for nociceptive information processing
Summary
Blood oxygenation level-dependent functional magnetic resonance imaging (BOLD fMRI) can measure human brain activity objectively and enable a deep understanding of neural processing mechanisms With this technique, the function of pain pathway structures within the central nervous system in states of acute or chronic pain[1,2,3,4,5,6], during therapeutic and psychological pain interventions[3,7,8,9] has been extensively investigated. Radiant-heat laser stimuli were delivered on the dorsum of subjects’ left hand to evoke pain perception and BOLD responses in two different sessions, which were separated by 1–5 days With both behavioral and BOLD fMRI data (task fMRI and resting-state fMRI), we assessed (1) whether laser-evoked pain perception (i.e., pain threshold and pain ratings) and BOLD responses were significantly different between the Scientific Reports | (2021) 11:1322. Mean SD Mean SD p value two sessions; (2) the test–retest reliability of laser-evoked pain perception and BOLD responses in healthy subjects; (3) the possible influence of the changes of resting-state brain activity on the modulation of laser-evoked pain perception and BOLD responses
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