Abstract
Our ability to encode information into our visual long-term memory (VLTM) fluctuates due to many factors. These factors include individual specific fluctuations in cognitive states that contribute to the likelihood of encoding success (e.g., sustained attention; deBettencourt et al., 2018) and stimulus-intrinsic properties that determine the ease of encoding across individuals (e.g., memorability; Bainbridge et al., 2017). We seek to define how these distinct encoding success factors relate to the several existing dissociable electrophysiological markers (frontal positivity, occipital alpha power, and frontal theta power) sensitive to memory encoding success (e.g., Fukuda & Woodman, 2015; Zhao & Woodman, 2020). Thus, we measured participants' EEG while they encoded the same set of 600 pictures of real-world objects (Brady et al., 2008) into their VLTM. Here we first replicated that some pictures were consistently better remembered than other pictures across participants, thus verifying their memorability. Next, we split the pictures into "memorable" and "forgettable" pictures via median split based on collective memory performance and examined the sensitivity of each electrophysiological marker to individual-specific memory encoding success (i.e., correctly recognized vs. missed) in each picture group. For frontal positivity, a repeated-measures ANOVA revealed significant main effects of memorability and encoding success. For occipital alpha power, we found a significant main effect of encoding success as well as a significant interaction between memorability and encoding success. These results demonstrate that frontal positivity and occipital alpha power are sensitive to both stimulus-intrinsic memorability and individual-specific encoding success with dissociable patterns. For frontal theta power, we only found a significant main effect of encoding success, thus revealing frontal theta power's selective sensitivity to individual-specific encoding success. Together, our results support the idea that memory encoding is a multifaceted process by linking distinct encoding success factors to putative neural markers.