Contralateral delay activity tracks information load in visual working memory: Evidence from the multiple object tracking task

Contralateral delay activity (CDA) is a measure used to assess the quantity of information stored in visual working memory (VWM). Nonetheless, it has been suggested that CDA reflects the current focus of spatial attention, as exhibited in the multiple-object tracking (MOT) task. This study aimed to determine whether the CDA observed in the MOT task was due to the storage requirements of VWM. This study employed masks to manipulate the necessity to memorize the tracked items during the tracking phase. In Experiment 1, a VWM-MOT dual task was conducted in both masked and unmasked conditions, and found that an additional memory load from the VWM task only affected the tracking accuracy of the MOT task in the masked condition (as the classic MOT task), indicating a storage requirement due to the memory resource competition occurred. In Experiment 2, the study recorded event-related potentials (ERPs) during target tracking and measured CDA components in both unmasked and masked conditions. The result found that CDA occurred in both masked and unmasked conditions, but was only sensitive to load in the masked condition. This finding further supports the idea that CDA is a neural marker for the storage of memory representations rather than the current focus of spatial attention.