ABSTRACT
During Sustained Attention to stimuli across many modalities neural activity often decreases over time on task, while Errors in task performance increase (Vigilance Decrement). Sustained Attention to pain has rarely been investigated experimentally despite its clinical significance. We have employed a Sustained Attention protocol (Continuous Performance Task, CPT) in which the subject counts painful laser stimuli (targets) when they occur randomly in a prolonged train of nonpainful nontargets. We hypothesize that the magnitude of the poststimulus oscillatory power divided by baseline power (Event-Related Spectral Perturbation, ERSP - scalp EEG) over Frontoparietal structures will decrease at all frequencies with time on task, while Beta ERSP (14-30Hz) will be correlated with Error Rates in performance of the CPT. During the CPT with a painful target ERSP was found in four separate Windows, as defined by both their frequency band and the time after the stimulus. A Vigilance Decrement was found which confirms that Sustained Attention to pain was produced by this CPT. In addition, Error Rates was correlated inversely with laser energy, and with ratings of pain unpleasantness and salience. Error Rates also were related directly to the Beta ERSP Window at scalp EEG electrodes over the central sulcus. Over time on task, the ERSP magnitude decreased in Alpha (8-14Hz) Window, was unchanged in early and late Delta/Theta Windows (0-8Hz), and increased in the Beta Window. The increase in Beta ERSP and a decrease in the Alpha ERSP occurred at the same EEG electrode over the parietal lobe to a significant degree across subjects. Overall, Beta activity increases with time on task, and with higher Error Rates as in the case of other modalities. In the case of pain increased Errors correspond to misidentification of painful and nonpainful stimuli and so modulate the sensation of pain under the influence of Sustained Attention.
