Thermal Psychophysics and Associated Brain Activation Patterns Along a Continuum of Healthy Aging

Abstract

Abstract Objective To examine psychophysical and brain activation patterns to innocuous and painful thermal stimulation along a continuum of healthy older adults. Design Single center, cross-sectional, within-subjects design. Methods Thermal perceptual psychophysics (warmth, mild, and moderate pain) were tested in 37 healthy older adults (65–97 years, median = 73 years). Percept thresholds (oC) and unpleasantness ratings (0–20 scale) were obtained and then applied during functional magnetic resonance imaging scanning. General linear modeling assessed effects of age on psychophysical results. Multiple linear regressions were used to test the main and interaction effects of brain activation against age and psychophysical reports. Specifically, differential age effects were examined by comparing percent-signal change slopes between those above/below age 73 (a median split). Results Advancing age was associated with greater thresholds for thermal perception (z = 2.09, P = 0.037), which was driven by age and warmth detection correlation (r = 0.33, P = 0.048). Greater warmth detection thresholds were associated with reduced hippocampal activation in “older” vs “younger” individuals (>/<73 years; beta < 0.40, P < 0.01). Advancing age, in general, was correlated with greater activation of the middle cingulate gyrus (beta > 0.44, P < 0.01) during mild pain. Differential age effects were found for prefrontal activation during moderate pain. In “older” individuals, higher moderate pain thresholds and greater degrees of moderate pain unpleasantness correlated with lesser prefrontal activation (anterolateral prefrontal cortex and middle–frontal operculum; beta < –0.39, P < 0.009); the opposite pattern was found in “younger” individuals. Conclusions Advancing age may lead to altered thermal sensation and (in some circumstances) altered pain perception secondary to age-related changes in attention/novelty detection and cognitive functions.