Influence of eye orientation on pain as a function of anxiety.

The effect of eye orientation on pain was investigated as a function of the stimulus intensity and the subjects' anxiety. Right-handed female subjects received sequences of electric shocks gradually increasing in intensity. Unpleasantness threshold, pain threshold, tolerance threshold and pain range were obtained when eyes were directed towards a target LED situated in the direction of, or away from, the source of stimulation, in the ipsi- or contralateral hemispace. Directing the eyes ipsilaterally to the stimulated hand yielded a lower unpleasantness threshold when the right hand was stimulated. No significant effect was observed in high trait anxiety subjects. These results are interpreted in terms of hemispatial attention bias. Moreover, an ipsilateral eye orientation increased pain range but this effect reversed in the highest state anxiety subjects. These latter observations could reflect the interacting influences of both spatial attention and state anxiety in selecting the processing mode of painful stimuli.