Temporal dynamics and readout latency in perception and iconic memory

Following the offset of complex visual stimuli, rich stimulus information remains briefly available to the observer, reflecting a rapidly decaying iconic memory trace. Traditionally, iconic memory decay is assumed to begin with stimulus offset. Instead, here we found that available information begins decaying already when cues are presented in the final stage of stimulus presentation. Using closely spaced ("micro-timed") readout cues and a theoretical model of information availability, we observed that a cue has to be presented around 10-30 milliseconds before stimulus offset in order to access the full sensory information. We suggest that this does not reflect an early loss in sensory encoding, but instead it is a consequence of a latency in the processing of the cue which postpones the readout of the sensory representation by 10-30 milliseconds. Our analysis also shows that spatial proximity of items in complex arrays impacts sensory representation during both perceptual encoding and initial memory decay. Overall, these results provide a theoretical and empirical characterization of the readout from visual representations, and offer a detailed insight into the transition from perception into iconic memory.