Age Differences in the Effect of Epidermal Hydration on Electrodermal Activity

Abstract

The effect of epidermal hydration on skin potential and conductance measurements was investigated in young and old men. The condition of least hydration used a 0.5% KCl glycol electrolyte. Two conditions used a 0.5% aqueous KCl electrolyte differing in that the most hydrated site received a 15‐min pretreatment of soaking in distilled water whereas the intermediate hydration site received no pretreatment. These hydration conditions were used in recording three channels of skin potential and three channels of skin conductance during three tasks: 1) tone presentations after rest, 2) simple reaction time, and 3) choice reaction time. There were no significant age differences in the effect of electrolyte on skin conductance level and response. There were age differences in the effect of electrolyte on skin potential level (SPL) and response (SPR). Young adult SPR was monotonically related to hydration with the largest response magnitude occurring with the least hydration. Electrolyte did not significantly affect SPR magnitude of the aged. For the young subjects, SPL was monotonically related to hydration with the most negative SPL occurring with the least hydration. For the aged subjects, the least negative SPL occurred in the condition of least hydration. We postulate that this reversal in the hydration/SPL relationship in old age reflects a reversal in the relative magnitudes of sweat gland and epidermal potentials: in old subjects the epidermal potential is greater than the sweat gland potential.

Influence of Relative Humidity on Electrodermal Levels and Responses

“…Concerning SP, although in average, SPL showed more negative value (Figure 2), some test subjects exhibit more negative levels and the remaining showed reduction in the negativity of SPL (Table 3) under the influence of high RH. The less negative SPL values were recorded in accordance with earlier reported measurements [12,[21][22][23][24][25]. These measurements confirm that SPL is negatively decreased (positive) when sweat glands are activated by means of skin hydration.…”

“…This can be explained from the point of view of Edelberg's [26] model of EDA. Moreover, a reduction in epidermal resistance will negatively decrease the recorded SPL since the epidermal skin layer acts as a short circuit to the surface of the skin [12,26]. In addition, this might be due to the high humidity attributed to the inactivation of sweat glands.…”

“…It is known that wetting or occlusion of the skin by the recording electrolyte can significantly influence the EDA recording [11][12][13], but it is not known to what extent the ambient humidity influences the measurement. This is important when experimental conditions are considered for planning studies using EDA measurement, and also in comparison between studies.…”

Electrodermal Activity

“…Eisdorfer (1978) summarized several studies performed by his group, reporting more electrodermal reactivity in older individuals if they were emotionally challenged, but not during learning tasks or under relatively nonthreatening conditions. Garwood et al (1979) could also not demonstrate an influence of age on the SCR in various reaction time (RT) tasks in their above-mentioned investigation. 80 78 Recorded with pure silver spiral electrodes that were chlorided electrolytically.…”

“…To investigate the effects of age on corneal hydration, Garwood, Engel, and Quilter (1979) recorded SC and SP in 12 young and 12 old participants (mean ages 30.8 and 75.5 years), applying KCl electrolytes with varying moisture. The induced 77 In their comparison of eight postmenopausal older females (52-62 years) with eight younger females (20-30 years) during exercise under dry heat, Anderson and Kenney (1987) observed a lower sweating rate in the older group, which reflected a diminished output per heat-activated sweat gland rather than a decrease in the number of sweat glands recruited.…”