The capacity and resolution of spatial working memory and its role in the storage of non-spatial features.

The question whether the storage of spatial locations and other non-spatial features in visual working memory (WM) is based on shared or separate processes remains unresolved. We recorded contralateral delay activity (CDA) components as on-line electrophysiological markers of WM maintenance in two tasks where observers had to retain either the colors or locations of sample stimuli. CDA components were elicited both in the Color and in the Location task, and increasing WM load had identical effects on CDA amplitudes, suggesting shared underlying mechanisms. However, CDA amplitudes were generally larger in the Location Task. Experiment 2 demonstrated that the CDA is sensitive to the resolution demands of spatial WM tasks. CDA amplitudes elicited during the storage of object locations in WM were larger when these locations had to be retained with higher precision. These findings support the hypothesis that spatial and non-spatial features of visual objects are represented in an integrated fashion in WM. The activation of these representations is controlled by space-based attentional control processes, and their spatial resolution can be regulated in line with current task demands.