Neural mechanisms of detecting and orienting attention toward unattended threatening somatosensory target stimuli. II. Intensity effects.

Negative potentials evoked by painful electrical stimulation of the sural nerve that occur at 100-180 ms poststimulus over the contralateral temporal scalp (CTN100-180) and at 130-200 ms over the fronto-central scalp (FCN130-200) exhibit unusual attention effects. That is, their amplitudes are larger when the painful evoking stimulus is unattended than when it is attended. In this experiment, I show that attention has no effect on the CTN100-180 evoked by a weak, nonthreatening sural nerve electrical stimulus. These data suggest that the generators of the CTN100-180, which include the somatosensory association areas in the parietal operculum, are specifically involved in detecting threatening somatosensory stimuli. The FCN130-200 showed a small increase in the unattended condition, which is consistent with the role of its medial prefrontal cortex generators in monitoring any situation that might require a change in attentional control.