Eva-Maria Reuter

• With age, one's tactile perception declines. But tactile expertise and short-term tactile learning can induce cortical plasticity and improve tactile perception. Thus, tactile learning might contribute to the maintenance of tactile perception. Open questions were how age and expertise influence tactile perception and learning in middle-aged adults and how the respective electrophysiological correlates are shaped by age, expertise, and learning. We investigated tactile discrimination and event-related potentials as markers of somatosensory and cognitive processing. Participants were of different age groups [young (18-25 years), early middle-aged (35-45 years), and late middle-aged adults (55-65 years)] and expertise levels [non-experts (service employees) and experts (precision mechanics)]. Learning was induced by repetitive tactile stimulation. Late middle-aged performed worse than young and early middle-aged adults. Somatosensory excitability increased and processing speed reduced with age. P300 topography suggested attempted compensation and reduced availability of attentional resources in late middle-aged non-experts. Experts outperformed non-experts, revealed greater somatosensory excitability, and needed less attentional resources, as compared to non-experts. This suggested that comparable electrophysiological changes induced by age and expertise have different underlying mechanisms. Experts improved more than non-experts from the intervention, indicating meta-plasticity. Lower baseline performance was associated with higher learning. Intervention-related changes in P300 indicated that younger adults processed tactile stimuli faster, while older adults became better able to cognitively evaluate the stimuli. Experts established more specific brain activation, with a strong parietal-to-frontal gradient, pointing to more automated processing. Results further the understanding of tactile perception in middle-aged adults and opened up new research questions.