FRONTAL AND INFERIOR TEMPORAL CORTICAL ACTIVITY IN VISUAL TARGET DETECTION - EVIDENCE FROM HIGH SPATIALLY SAMPLED EVENT-RELATED POTENTIALS

Visual event-related potential(ERP) studies show effects due to target detection in the P3 and in earlier negativities over posterior record ing sites. The topography of these earlier components suggests contrib utions from both anterior and posterior neural generators, however the se studies were performed with sparse recording arrays and may not hav e provided a full description of the scalp topography of the visual ER P. The current study employed a high-density recording array (64 chann els) and spherical spline interpolated topographic voltage and current density maps to describe the scalp distribution of the major deflecti ons in the visual ERP from a visual oddball paradigm: the P1, N1, N2/P 2a (a temporally coincident posterior negativity and anterior positivi ty) and P3. A modified difference wave analysis was also performed to track the time-course of target detection effects in the ERP. Target d etection effects were found in the N2/P2a and P3 components. The scalp distribution of the N2/P2a was consistent with separate frontal and p osterior neural generators and this is discussed in reference to human hemodynamic and nonhuman primate studies of neural activity in the in ferior temporal visual object recognition system and in frontal system s of selective attention and working memory in visual target detection tasks.