Abstract
Aging is known to affect nociceptive processing, e.g., the ability to inhibit pain. This study aims to investigate whether pain responses in older individuals are associated with prefrontal characteristics, namely (i) executive functioning performance and (ii) structural brain variations in the prefrontal cortex. Heat and pressure stimuli were applied to assess pressure pain sensitivity and endogenous pain inhibition in 46 healthy older individuals. Executive functioning performance was assessed in three domains (i.e., cognitive inhibition, shifting, and updating) and structural brain variations were assessed in both gray and white matter. Overall pain responses were significantly associated with the executive functioning domains cognitive inhibition and shifting. However, no specific type of pain response showed an especially strong association. Endogenous pain inhibition specifically showed a significant association with gray matter volume in the prefrontal cortex and with variations in white matter structure of tracts connecting the prefrontal cortex with the periaqueductal gray. Hierarchical regression analyses showed that these variations in the prefrontal cortex can explain variance in pain inhibition beyond what can be explained by executive functioning. This might indicate that known deficits in pain inhibition in older individuals are associated with structural variations in prefrontal areas.
Highlights
Acute and chronic pain are more common in older than in younger individuals [1,2], and it has been suggested that this increased pain prevalence is partly due to age-related changes in nociceptive processing
We aimed to investigate whether experimental pain responses in older individuals correlate with fractional anisotropy (FA) of the white matter tracts between the prefrontal cortex and the periaqueductal gray (PAG), located in the brainstem
Stein et al only studied the tracts between the PAG and the dorsolateral prefrontal cortex (dlPFC), but we extended our analysis to the white matter tracts between the PAG and the ventrolateral prefrontal cortex (vlPFC) as well as the ventromedial prefrontal cortex (vmPFC), to mirror our analysis approach for gray matter
Summary
Acute and chronic pain are more common in older than in younger individuals [1,2], and it has been suggested that this increased pain prevalence is partly due to age-related changes in nociceptive processing. Using experimental pain to study age-related changes in pain processing, the majority of evidence point to an increase in pain threshold (indicating decreased nociceptive processing), and an increase in temporal summation of pain as well as a decrease in endogenous pain inhibition (both indicating increased nociceptive processing). Based on these findings, it has been suggested that both ascending excitatory and descending inhibitory pathways are altered during aging. Frontal functioning might be one mechanism underlying increased pain processing in older individuals
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