Abstract
Visual working memory (VWM) capacity is known to be severely limited, and most individuals can accurately maintain about three items simultaneously. However, it is known that individuals can boost their VWM performance by utilizing a cue presented well after the offset of the memory array (retro-cue effect). The fact that this effect outlives the typical iconic memory duration (~1sec) has led some researchers to propose that VWM can hold more information than typically thought. To better understand the role of VWM in the retro-cue effect, we recorded ERPs while subjects performed a VWM recall task in which a cue was often presented during the retention period. First, by manipulating the type of the cue stimulus (i.e. dot position cue and color patch cue) and its SOA from the memory array, we found that the retro-cue effect is best observed with a dot position cue presented at the shortest SOA, and is the smallest with a color patch cue across all SOAs. This suggests that the representation subserving the retro-cue effect decays over time, and is vulnerable to the masking effect induced by the cue stimulus. Such characteristic is in stark contrast with VWM representations that do not decay, and are resistant against masking. To further demonstrate the contrast, we examined the neural activity during the retention interval using ERP techniques. Here we found that the magnitude of the retro-cue effect was strongly predicted by the amplitude of P3 wave induced by the onset of the retro-cue. Critically, the amplitude of P3 wave and the behavioral retro-cue effect was independent of individuals' VWM capacity and its neural correlate (Contralateral delay activity). Taken together, the retro-cue effect is obtained by accessing a residual representation that is held outside of VWM, and therefore that is vulnerable to masking and decays over time.
Meeting abstract presented at VSS 2012