Figure 2.

Baseline sensitivity across the study. Baseline thermal sensitivity was assessed in adult (12–16 months old) and aged (27–31 months old) rats throughout the experiment. Following testing of initial sensitivity, baseline sessions were composed of three temperature comparisons: hot vs neutral, cold vs neutral, or hot vs cold. The figure shows data from the eight sessions at each comparison. Adult and aged rats showed an aversion to both the hot and cold thermal stimulation (left and center panels) that remained stable and did not differ across ages. During the hot vs cold assessment, there were differences between the age-groups during sessions 3, 4, and 5, with the aged animals showing a marked preference for the hot side relative to the adult rats. Brackets indicate an overall significant main effect of age; * indicates a significant difference from adult rats.