Temporal discrimination threshold on various parts of the body.

The temporal discrimination threshold (TDT) of various parts of the body was investigated in 35 healthy volunteers, and the effect of aging on the TDT was studied in 80 subjects (aged 18-82 years). Ascending (ATDT) and descending (DTDT) TDT values were measured in 13 areas using a pair of electrical stimuli. Both ATDT and DTDT differed significantly among the body parts (P < 0.01, one-way repeated ANOVA), and the TDT was shortest on the index finger and longest on the lower leg, where it was approximately 156% of that on the finger. There was no difference of the TDT value with gender or between sides. There was no effect of aging on the TDT in subjects aged 18-64 years, but the value was prolonged in subjects over 65 years. We suggest that the TDT difference among body parts is mainly due to the difference in sensory processes in the central nervous system, and that it may provide information about changes in the system related to aging.