Visual event-related potentials to colored patterns and color names: attention to features and dimension.

Four right-handed males and 4 right-handed females were instructed to match pairs of stimuli (colored flashes with either colored patterns or color names) presented sequentially to the central retina. Subjects were to respond to the second stimulus of a pair when it matched the first stimulus in terms of sensory color or word meaning. ERPs recorded from the second stimulus of a pair over occipital and frontal cortical regions indicate the following: Interdimension effects reflect an early and more global discrimination process between colored patterns and word patterns per se. The source of this effect appears to be localized in occipital cortical regions. Intradimension effects were evident later in time and reflect a more refined discrimination process between particular features within a dimension rather than between dimensions. The intradimension color effect began earlier in time than the word effect (229 msec versus 318 msec in the occipital data) and appears to be localized in posterior temporal regions. The onset of the word effect appears to have two neural generators: an early effect localized in frontal regions (274 msec) and a later effect localized in occipital regions (318 msec). The hierarchical model of language processing seems to hold true predominantly in posterior cortical regions. Effects associated with linguistic processing were evident in frontal regions before effects were noted in the occipital regions. This result suggests that either: word information is processed simultaneously and independently in the different regions, or anterior regions feedback onto posterior regions and, therefore, influence the processing in this region.