Psychophysical research on the human senses has tended to slight the cutaneous senses (tactile and temperature), when it comes to their capacities to function over the life span. The goal is to examine five fundamental (and largely mutually independent) measures of cutaneous sensitivity, over the whole body surface, and from childhood to old age. The five types, all implicated as age-related by background research and pilot data, are: (1) spatial acuity (alignment threshold), (2) error of point localization, (3) texture discrimination, (4) absolute thresholds to warming and cooling, and (5) absolute thresholds to high-frequency vibration. State-of-the-art, forced-choice, psychophysical procedures will be brought to bear throughout. The somatic profiles of tactile sensitivity therewith constructed will help to elucidate two basic issues: (a) Does aging influence these five types of sensitivity uniformly or differentially? (b) Does aging affect all body regions uniformly or differentially? Preliminary evidence favors the working hypotheses that (1) all five types may suffer impairment but in varying degrees, and that (2) the more peripheral the region, the greater may be the toll taken by aging. Measurement will address primarily the gradual changes characterizing the normal aging process. They may nonetheless have important secondary implications for other age-related human conditions, whose study in turn may also reciprocally help to characterize normal aging. Four of these will come under study: (1) spatial acuity and texture discrimination in blind persons of various ages, and the relation of age-related changes in cutaneous sensitivity to the speed of braille-reading; (2) the effects of chronic cigarette smoking on cutaneous sensitivity and the possible recovery after quitting; (3) the manifestation of long-term occupational exposure to vibration on cutaneous sensitivities of patients with Hand-Arm Vibration Syndrome (and a sub-set of these patients who are also diabetic); and (4) the relation of habitual physical activity and fitness to peripheral circulation and cutaneous sensitivity, especially in older persons.
