Contralateral Delay Activity Tracks Storage Load in Visual Working Memory: Evidence from the Multiple Object Tracking Task

Contralateral delay activity (CDA) is a measure used to assess the amount of information being stored in visual working memory (VWM). However, it has also been suggested that CDA reflects the current focus of spatial attention, as seen in the multiple object tracking task. This study aimed to determine whether the CDA observed in the multiple object tracking task is driven by VWM storage demands, potentially stemming from the feature (cue) masking of target features. To test this, we manipulated whether participants needed to remember the tracked items under masked or unmasked conditions during the tracking phase. Our experiment revealed that CDA occurred in both conditions; the amplitude of CDA was sensitive to the tracking load only in the masked condition. These findings suggest that CDA reflects both sustained attentional activation and representational storage, with the tracking load influencing CDA only when storage in VWM is required. These results support the conclusion that CDA is primarily sensitive to VWM storage rather than the current focus of spatial attention.