Weighting Mechanisms Within and Across Modalities: Evidence from Event-related Brain Potentials

In visual search, there is a RT cost for targets on a given trial if the previous target was defined in a different (e.g., orientation color), compared to the same (e.g., color color), visual dimension. According to the ‘dimension-weighting’ account (Müller et al., 1995), limited attentional weight needs to be shifted from the old to the new targetdefining dimension, resulting in prolonged behavioral response times. The present study aimed at identifying brain electrical correlates associated with this weight shifting process. Analyses of ERPs revealed several components to reflect dimension changes whether the task was to detect the target or to identify its defining dimension. N2 amplitudes were more negative whenever the dimension changed. The P3 exhibited latency differences that mirrored RTs in both tasks; but the amplitudes showed no direct relation to stimulusor response-related processing. Finally, slow-wave amplitudes were enhanced for dimension changes. Taken together, the results provide support for relatively early, perceptual-related processes involved in the generation of behavioral dimension change costs. Brain electrical correlates of visual dimension weighting 33