SPATIOTEMPORAL DYNAMICS OF ATTENTION TO COLOR - EVIDENCE FROM HUMAN ELECTROPHYSIOLOGY

This study characterized patterns of brain electrical activity associa ted with selective attention to the color of a stimulus. Multichannel recordings of event-related potentials (ERPs) were obtained while subj ects viewed randomized sequences of checkerboards consisting of isolum inant red or blue checks superimposed on a grey background. Stimuli we re presented foveally at a rapid rate, and subjects were required to a ttend to the red or blue checks in separate blocks of trials and to pr ess a button each time they detected a dimmer target stimulus of the a ttended color. An early negative ERP component with an onset latency o f 50 ms was sensitive to stimulus color but was unaffected by the atte ntional manipulation. ERPs elicited by attended and unattended stimuli began to diverge after approximately 100 ms following stimulus onset. Inverse dipole modelling of the attended-minus-unattended difference waveform indicated that an initial positive deflection with an onset l atency of 100 ms had a source in lateral occipital cortex, while a sub sequent negative deflection with an onset at 160 ms had a source in in ferior occipito-temporal cortex. Longer-latency attention-sensitive co mponents were localized to premotor frontal areas (onset at 190 ms) an d to more anterior regions of the fusiform gyrus (onset at 240 ms). Th ese source localizations correspond closely with cortical areas that w ere identified in previous neuroimaging studies as being involved in c olor-selective processing. The present ERP data thus provide informati on about the time course of stimulus selection processes in cortical a reas that subserve attention to color. Hunt. Brain Mapping ti:216-238, 1998. (C) 1998 Wiley-Liss, Inc.