THE EFFECTS OF AGING ON INFORMATION-PROCESSING CHANNELS IN THE SENSE OF TOUCH .3. DIFFERENTIAL SENSITIVITY TO CHANGES IN STIMULUS-INTENSITY

Detection thresholds and difference limens were measured for 16 subjec ts ranging from 19 to 91 years of age. The stimuli were 250-Hz bursts of vibration applied through a 3.0-cm(2) contactor to the thenar emine nce of the right hand. Detection thresholds were higher in older than in younger subjects, as were the absolute values of difference limens. When the difference limen was expressed in relative terms as the prop ortion by which two stimuli had to differ in amplitude to be discrimin ated (Delta A/A), discriminative capacities were unaffected by aging e xcept for stimuli slightly above the detection threshold, in which cas e the difference limens of older subjects were significantly higher th an those of younger subjects. The results are consistent with the hypo thesis that elevations in the detection thresholds of older subjects a re the results of reduced afferent input to central brain centers that , with regard to their capacity to detect the presence of threshold-le vel stimuli and to discriminate differences among suprathreshold stimu li, are relatively unaffected by aging.