From encoding to conscious report: Electrophysiological signatures of iconic memory revealed by a partial report task

Despite numerous investigations, a comprehensive electrophysiological characterization of iconic memory remains lacking. Through a partial report paradigm, we aimed to shed light on this topic by disentangling electrophysiological activity related to stimulus perception from that linked with the specific task. We collected EEG data from 26 participants while they performed a partial report task. They were shown circular arrays of six letters lasting 100 ms. After the stimulus, an acoustic cue instructed the participant to report on which side of the array. Differences between reporting conditions were primarily evident in the time window 850-1100 ms, characterized by a positive component predominantly over parieto-occipital electrodes ipsilateral to the reporting side. Through linear regression, we also found a positive relationship between P1 and participants accuracy, as well as negative relationships between P3, VCR, TIF, and accuracy. Our results provide an overview of the different processes involved in iconic memory, corroborating the distinction between a series of neural mechanisms responsible for encoding and maintaining the entire stimulus and higher-order processes in charge of selecting an information subset for conscious report. The TIF component, in particular, could act as a key filtering mechanism to prevent irrelevant information from being selected for further processing. Our results provide, for the first time, a thorough characterization of the electrophysiological dynamics behind iconic memory. Moreover, implications for the consciousness debate are discussed, particularly regarding the overflow argument and how our results could be read through its lens.