An EEG investigation of the trial-by-trial updating of complex knowledge structures

Memory schemas are higher-level knowledge structures that store an abstraction of multiple previous experiences. They allow us to retain a multitude of information without the cost of storing every detail. Schemas are believed to be relatively stable, but occasionally have to be updated to remain useful in the face of changing environmental conditions. Once a schema is consolidated, schema updating has been proposed to be the result of a prediction-error (PE) based learning mechanism, similar to the updating of less complex knowledge. However, for schema memory this hypothesis has been difficult to test because no sufficiently sensitive tools to track modifications to complex memory schemas existed so far. Current research on the updating of less complex beliefs and at much shorter time scales has identified the P3 as an electrophysiological correlate of PE-induced updating of beliefs. In this study, I recorded electroencephalography and continuous memory measures during the encoding of schema consistent vs. inconsistent material to test the behavioural and neural correlates of schema updating. I observed that PEs predicted the updating of a schema after a 24-hour delay, especially when participants were faced with inconsistent compared to consistent material. Moreover, the P3 amplitude tracked both the PE at the time of learning as well as the updating of the memory schema in the inconsistent condition. These results demonstrate that schema updating in the face of inconsistent information is driven by PE-based learning, and that similar neural mechanisms underlie the updating of consolidated long-term memory schemas and short-term belief structures.