Abstract
Recent functional MRI studies have demonstrated that regions of early visual cortex whose receptive fields overlie locations occupied by a cued object show increased activation, providing a possible neural basis for the behavioral facilitation observed for information appearing within these locations (Muller & Kleinschmidt, 2003). However, the timecourse of this effect is obscured by the poor temporal resolution of fMRI. In this set of experiments, we used ERPs to investigate the neural timecourse of object-based attention using a well-established object-based attention paradigm (Egly, Driver, & Rafal, 1994). We found time-specific modulation of the N2 component in parietal, occipital, and temporal electrodes for within- versus between-object trials. We next extended the paradigm to include targets in the surround of the cued object. This allowed us to ascertain the dynamics associated with benefits that accrue not only to the cued object but also to objects in the spatial surround of the cued object (Kravitz & Behrmann, in press). Taken together, these results indicate a close coupling between spatial and object representations, whereby information from both interacts to determine the distribution of attentional facilitation throughout a visual scene. These results are consistent with an account of a general attention mechanism in which information is distributed across multiple levels of representation and in which these representations interact to form an attentional gradient.
This work was supported by a grant from NIH to MB.