Exploring Electrodermal Activity in Water-Immersed Subjects

In conditions of pressure and temperature associated with immersion in water, humans are more susceptible to severe stress, challenging the human physiological control systems. Reliable tools for the assessment of the stress underwater are needed. Electrodermal activity (EDA) is considered a promising alternative for the assessment of the level of stress in humans. EDA is a measure of the changes in conductance at the skin surface related to sweat production. In normal humidity conditions, EDA changes in response to stress in three main ways: the skin conductance level (SCL) is increased, the occurrence of non-specific skin conductance responses (NS.SCRs) increases, and the normalized spectral power in the band from (EDASympn) 0.045 to 0.25 Hz is elevated. When skin is immersed in water, the humidity blocks the sweat glands, changing the dynamics of EDA. For this reason, we have tested the measures of EDA for subjects immersed in water, as response to cognitive stress. Four subjects were recruited for the experiment. Subjects remained four minutes underwater, prior to performing the Stroop task, a test utilized to induce cognitive stress. The SCL and NS.SCRs, didn't exhibit significant differences due to cognitive stress, compared to baseline measurements. EDASymp exhibited significant differences due to cognitive stress. We conclude that the only measure of EDA sensitive to cognitive stress under water is the EDASymp, and it can be potentially used to assess cognitive stress level in divers.