LOCALIZATION OF AUDITORY-EVOKED POTENTIALS RELATED TO SELECTIVE INTERMODAL ATTENTION

A long-standing question in attention research is the extent to which selection involves gates in the sensory stream and the extent to which they involve added secondary processes. Intermodal attention paradigm s are useful for examining this issue since different modalities invol ve readily distinguished cortical regions. Evoked potential studies ha ve identified an attention-related frontal negativity labeled the Nd i n auditory attention studies. It has been suggested that it arises fro m modulation of the auditory cortex (compatible with gating mechanisms ) or of the frontal cortex (compatible with secondary processes such a s short-term memory buffers). Efforts to localize the Nd have been imp aired by the finding that the Nd comprises multiple components. Some n ovel procedures utilizing principal components analysis, in conjunctio n with high-density 64-channel recordings, were used to address this i ssue. Results suggest that the major source of the early Nd (the porti on of most interest) resides in the frontal cortex, supporting the sec ondary process view for this particular mechanism.