Spatio-temporal dynamics of attention to color: Evidence from human electrophysiology

Abstract

This study characterized patterns of brain electrical activity associated with selective attention to the color of a stimulus. Multichannel recordings of event-related potentials (ERPs) were obtained while subjects viewed randomized sequences of checkerboards consisting of isoluminant red or blue checks superimposed on a grey background. Stimuli were presented foveally at a rapid rate, and subjects were required to attend to the red or blue checks in separate blocks of trials and to press a button each time they detected a dimmer target stimulus of the attended color. An early negative ERP component with an onset latency of 50 ms was sensitive to stimulus color but was unaffected by the attentional 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 latency of 100 ms had a source in lateral occipital cortex, while a subsequent negative deflection with an onset at 160 ms had a source in inferior occipito-temporal cortex. Longer-latency attention-sensitive components were localized to premotor frontal areas (onset at 190 ms) and to more anterior regions of the fusiform gyrus (onset at 240 ms). These source localizations correspond closely with cortical areas that were identified in previous neuroimaging studies as being involved in color-selective processing. The present ERP data thus provide information about the time course of stimulus selection processes in cortical areas that subserve attention to color.

Behavioral performance follows the time course of neural facilitation and suppression during cued shifts of feature-selective attention

“…Previous ERP studies on feature selection have typically found the earliest modulations of stimulus processing in the form of a selection negativity beginning around 170 ms post stimulus onset (cf 26,27). In these cases, the tobe-attended color was known before stimulus onset; i.e., these times supposedly do not involve the time required to interpret the cue and to shift attention.…”

Parietal Stimulation Decouples Spatial and Feature-Based Attention

“…A repetitive pulse-train of TMS was delivered on each trial, from 100 to 500 ms after cue onset (five pulses at 10 Hz). The timing of this pulse train was selected to encompass the most likely period during which the parietal cortex would be necessary for controlling spatial and feature-based attention (Anllo-Vento et al, 1998;Slagter et al, 2005a,b). The intensity of stimulation was delivered randomly on a trial-by-trial basis at 40% (low) or 120% (high) of individual resting motor threshold.…”

Attention Modulates Initial Stages of Visual Word Processing

“…It has been shown extensively that selective attention can be deployed to spatial locations (Posner, 1980), objects or their features (Anllo-Vento, Luck, & Hillyard, 1998;Duncan, 1984), motor action (Rushworth, Krams, & Passingham, 2001), temporal intervals (Coull & Nobre, 1998), or information held in working memory (Griffin & Nobre, 2003). One of the most interesting aspects of attentional selection is its temporal profile, as it is informative about the stages of information processing (early vs. late) that are affected by the deployment of attention.…”