Attentional templates in visual working memory

Abstract

Most theories of attention propose that we maintain attentional templates in visual working memory to control what information is selected. In the present study, we directly tested this proposal by measuring the contralateral-delay activity (CDA) of human event-related potentials during visual search tasks in which the target is cued on each trial. Here we show that the CDA can be used to measure the maintenance of attentional templates in visual working memory while processing complex visual scenes. In addition, this method allowed us to directly observe the shift from working memory to long-term memory representations controlling attention as learning occurred and experience accrued searching for the same target object. Our findings provide definitive support for several critical proposals made in theories of attention, learning, and automaticity.

Figure 1.

Example of the stimuli used in experiments 1–3. A, The stimulus sequences used in the one-target condition of experiments 1 and 2. The stimuli for experiment 2 were identical to the one-target condition of experiment 1 except that the cued target shape appearing on the left or right was the same on each trial for a given participant. B, Two possible targets were cued on each trial of in the two-target condition of experiment 1. C, The stimuli in experiment 3 were Landolt Cs with eight possible gap locations.

Figure 2.

The ERP results of experiment 1. A, Grand average waveforms from lateral occipital-temporal electrodes contralateral (red) and ipsilateral (black) to the location of the cue on each trial of the one-target condition in experiment 1. The gray region shows the epoch (300–1000 ms postcue onset) in which a significant CDA component was measured. The shading on the timeline (in C, applies to A and C) indicates the duration of the cue (yellow) and the search array (blue). B, The voltage distribution (spherical spline interpolation) of the CDA during the measurement window for right visual field cues minus left visual field cues. C, The grand average waveforms from the two-target condition. D, The relationship between individual subject's CDA amplitude and behavioral RT on target-present (empty circles) and target-absent trials (filled circles).

Figure 3.

A, The grand average ERP results of experiment 2 using the same conventions defined in Figure 2. B, Waveforms averaged across subjects from just the first block of trials.

Figure 4.

A–C, The grand average ERP results from the three trial-wise bins of experiment 3 using the same conventions defined in Figure 2. D, Plot of the CDA amplitude across consecutive trials with the same search target. The gray line shows the power-function fit and the error bars represent ±1 SEM.