Affective modulation of somatosensory-evoked potentials elicited by tactile stimulation.

The present investigation was aimed to evaluate the influence of emotional valence on brain correlates of non-painful somatosensory processing. For this purpose, we examined changes on the somatosensory-evoked potentials (SEP) elicited by frequent and deviant tactile stimuli (probability 14%) when subjects were viewing affective pictures. Twenty healthy volunteers aged between 19 and 47 years old participated in the study. The P50, N80, and P200 components of the SEP, as well as the P200 component of the visual-evoked potentials (VEP) elicited by the affective pictures were analyzed. Overall, a significant P50 amplitude reduction was observed when subjects were viewing unpleasant pictures, in comparison to pleasant pictures. Furthermore, larger SEP amplitudes were obtained in response to the deviant than to the frequent stimuli. In addition, unpleasant pictures elicited larger P200 amplitudes of the VEP than pleasant. Data suggest that affective stimuli may modulate the early processing of somatosensory information in the brain, probably reflecting the existence of an adaptive perceptual/attentional mechanism to motivationally relevant stimuli.