title: Tracking neural correlates of successful learning over repeated sequence observations.
abstract: The neural correlates of memory formation in humans have long been investigated by exposing subjects to diverse material and comparing responses to items later remembered to those forgotten. Tasks requiring memorization of sensory sequences afford unique possibilities for linking neural memorization processes to behavior, because, rather than comparing across different items of varying content, each individual item can be examined across the successive learning states of being initially unknown, newly learned, and eventually, fully known. Sequence learning paradigms have not yet been exploited in this way, however. Here, we analyze the event-related potentials of subjects attempting to memorize sequences of visual locations over several blocks of repeated observation, with respect to pre- and post-block recall tests. Over centro-parietal regions, we observed a rapid P300 component superimposed on a broader positivity, which exhibited distinct modulations across learning states that were replicated in two separate experiments. Consistent with its well-known encoding of surprise, the P300 deflection monotonically decreased over blocks as locations became better learned and hence more expected. In contrast, the broader positivity was especially elevated at the point when a given item was newly learned, i.e., started being successfully recalled. These results implicate the Broad Positivity in endogenously-driven, intentional memory formation, whereas the P300, in processing the current stimulus to the degree that it was previously uncertain, indexes the cumulative knowledge thereby gained. The decreasing surprise/P300 effect significantly predicted learning success both across blocks and across subjects. This presents a new, neural-based means to evaluate learning capabilities independent of verbal reports, which could have considerable value in distinguishing genuine learning disabilities from difficulties to communicate the outcomes of learning, or perceptual impairments, in a range of clinical brain disorders.
authors.affiliation: Biomedical Engineering Department, The City College of The City University of New York, 160 Convent Ave, New York, NY 10031, USA. Electronic address: nsteinemann@ccny.cuny.edu.
authors.forename: Natalie A
authors.initials: NA
authors.lastname: Steinemann
authors.affiliation: Sophie Davis School of Biomedical Education, The City College of The City University of New York, 160 Convent Ave, New York, NY 10031, USA. Electronic address: cmoisello@gmail.com.
authors.forename: Clara
authors.initials: C
authors.lastname: Moisello
authors.affiliation: Sophie Davis School of Biomedical Education, The City College of The City University of New York, 160 Convent Ave, New York, NY 10031, USA. Electronic address: lice.mg79@gmail.com.
authors.forename: M Felice
authors.initials: MF
authors.lastname: Ghilardi
authors.affiliation: Biomedical Engineering Department, The City College of The City University of New York, 160 Convent Ave, New York, NY 10031, USA; School of Electrical and Electronic Engineering, University College Dublin, Belfield, Dublin 4, Ireland. Electronic address: simon.kelly@ucd.ie.
authors.forename: Simon P
authors.initials: SP
authors.lastname: Kelly
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D005260:Female; D006801:Humans; D007858:Learning / Q000502:physiology*; D008297:Male; D011939:Mental Recall / Q000502:physiology*; D060865:Repetition Priming / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D065852:Spatial Memory / Q000502:physiology*; D013647:Task Performance and Analysis; D014796:Visual Perception / Q000502:physiology*
keywords: Event-related potential; Expectancy; Memory; Sequence learning; Surprise