Study-Phase Reinstatement: Encoding Spontaneous Thoughts as Memories

Abstract

AbstractCan the brain improve the retrievability of an experience after it has occurred? Systems consolidation theory proposes that cortical reactivation during extended post-encoding rest periods facilitates the formation of stable memory representations, a prediction supported by neural evidence in humans [1, 2] and animals [3, 4]. Such reactivation may also occur on short time scales as spontaneous thoughts come to mind during encoding, offering a potential account of classic list memory phenomena [5–9] but lacking in support from neural data. Leveraging the high-temporal specificity of intracranial electroencephalography (iEEG), we investigate spontaneous reactivation of previously experienced items during brief sub-second intervals between individual encoding events. Across two large-scale free recall experiments, we show that reactivation, as measured by spectral iEEG similarity, during these periods predicts subsequent recall. In a third experiment, we show that the same methodology can identify post-encoding reactivation that correlates with subsequent memory, consistent with previous results. Thus, spontaneous study-phase reinstatement reliably predicts memory behavior, linking psychological accounts to neural mechanisms and providing the first such evidence for rapid consolidation processes during encoding.