VISUAL EVENT-RELATED POTENTIALS DURING ODOR LABELING

Sixteen subjects judged the accuracy of visual labels which identified previously occurring olfactory or visual stimuli. Labels correctly id entified the previous stimuli on 75 % of the trials (frequent conditio n) and incorrectly identified the previous condition in 25 % of the tr ials (rare condition). Event-related potentials were recorded from run e scalp locations during the administration of the visual labels. As w ould be expected, P300b was significantly larger during the rare non-m atching trials, but was independent of the modality of the previous st imulus. Previously occurring olfactory stimuli did, however, produce a significant increase in negativity recorded over the left frontal lob e during the visual label. The amplitude of this negativity was found to be correlated with subjects' performance on the Connecticut Clinica l Chemosensory Research Center test such that increased left frontal n egativity predicted better olfactory performance. These data suggest t he presence of a left frontal mechanism that is important for judging the accuracy of labels for olfactory, but not necessarily visual, stim uli.