Abstract
Analytic tools for psychophysiological signals often make implicit assumptions that are unspecified. In developing a mathematical framework for analysis of skin conductance responses [SCRs], we formalise our assumptions by positing that SCRs can be regarded as the output of a linear time-invariant filter. Here, we provide an empirical test of these assumptions. Our findings indicate that a large component of the variance in SCRs can be explained by one response function per individual. We note that baseline variance (i.e. variance in the absence of evoked responses) is higher than variance that could not be explained by a linear time-invariant model of evoked responses. Furthermore, there was no evidence for nonlinear interactions among evoked responses that depended on their temporal overlap. We develop a canonical response function and show that it can be used for signals from different recording sites. We discuss the implications of these observations for model-based analysis of SCRs.
Highlights
The essence of psychophysiology is to infer psychological processes from measured physiological signals
We have shown that (a) under the linearity assumption, SCRs can be deconvolved even at inter stimulus intervals [ISIs] as short as 3 s, and (b) that in non-overlapping responses, about 75% of the total signal variance can be explained by one impulse response function, where the residual variance incorporates noise and spontaneous fluctuations
In experiment 5, additional recordings were made from the volar middle phalanx of the dominant 2nd/3rd finger, and the medial plantar surface of the non-dominant foot as described in Boucsein (1992, p.99) Recordings were conducted in a magnetically shielded room (MSR), using a custom-built constant voltage coupler (2.5 V), based on a differential amplifier and DC-powered by a 12 V battery to minimise electromagnetic noise
Summary
The essence of psychophysiology is to infer psychological processes from measured physiological signals. The amplitude of event-related skin conductance responses [SCRs] is used to infer sympathetic arousal, where we know that SCRs are generated by sweat secretion initiated by distinct bursts of sudomotor nerve activity (Boucsein, 1992). These sudomotor firing bursts directly relate to autonomic arousal, but the amplitude of the ensuing SCRs is only informative if there is a (linear) mapping from sudomotor firing (and arousal) to SCR amplitude. This amounts to assuming that the compound response is the sum of two single responses
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