A psychophysiological inquiry into the nature of the Sokolovian orienting response comparator model

73 Ss performed visual discriminations of stimuli within a
warning-stimulus paradigm. The physical complexity of stimuli and their
task relevance were manipulated within Ss, while the nonspecific effects
of workload were controlled with a group factor. Skin conductance
orienting responses (ORs) were measured concurrently with 1-sec epochs
of EEG α and θ power from Fz, Cz, Pz, and Oz. Neither index was reliably
affected by the physical complexity of stimulation alone. However, both
higher task relevance and higher workload significantly increased the
magnitude of EEG ORs and skin conductance ORs. Task averages of central
and autonomic activity showed an overall pattern of covariation, but a
second-by-second breakdown of EEG spectra suggests that the skin
conductance OR may be an aggregate of the activation of diverse brain
mechanisms responsible for physiological orienting. Implications for the
classical OR Sokolovian model are discussed