Thesis - Instituto de Telecomunicações

3.3. PHYSIOLOGICAL SIGNALS 45Figure 3.5: Example of electrodermal activity signal over a period of 2 minutes.the skin conductance level. The SCR is composed by two 2 zones: a rise zone and adecay zone. In figure 3.6 a synthetic SCR example is presented with the relevant instantsand amplitudes identified. The initial instant, t 0 , is the moment when the sudomotorsystem reacts to the Autonomous Nervous System (ANS). In case of a controlled stimulipresentation, the instant of presentation of the stimulus is annotated. This initial instantretrieved corresponds to the delay time of the response. Two other instants in time areindicated: the maximum instant, t max , (measured relatively to the value in the initialinstant, sometimes referred as the rise time) and the half recovery time, t half .In table 3.4 we synthesize terminology and the parameters typically used in electrodermalactivity analysis [50]. The EDA signal is measured in Siemens (S).ApplicationsThe measure of the electrical activity of the skin has been used extensively in psychological[35] and clinical studies [134]. An overview of more general application of EDA and otherpsycophysiological signals can be found in a review from Cacioppo et al. [36].A multitude of applications exist based on the EDA signal, here we present some of themore relevant ones, that motivated the creation of a new sound EDA processing model.