Functional magnetic resonance imaging of brain activation during pleasant and unpleasant active tactile stimulation in older adults

This study aimed to characterize subjective pleasantness and brain activation during active tactile exploration of preferred and disliked objects in older adults. Functional magnetic resonance imaging was performed on 41 healthy older adults while they actively explored a preferred object, a disliked object, and a control object (tennis ball). These three conditions were evaluated in separate functional runs. Subjective pleasantness ratings differed significantly across the conditions. Whole-brain analyses conducted separately for each condition revealed activation primarily within sensorimotor, parietal, and cerebellar regions. The “Like” and “Dislike” conditions elicited broadly overlapping activation patterns, including within regions previously implicated in active touch and somatosensory processing. Because the whole-brain activation patterns of the “Like” and “Dislike” conditions were not directly compared statistically, differences in regions reaching significance in the separate analyses cannot be interpreted as evidence of valence-specific neural processing. Region of interest analyses of the anterior cingulate cortex, orbitofrontal cortex, insula, and amygdala revealed no significant differences among the conditions. Overall, these findings characterize the neural substrates of active tactile exploration of preferred and disliked objects in older adults but do not establish valence-dependent differences in neural processing.