Negative Subsequent Memory Effect in ERP: Modeling and Data

The subsequent memory effect (SME) is the ubiquitous phenomena that stimulus that are later retrieved show a more negative going ERP wave than stimulus that are not retrieved. Two basic findings in neurophysiology are that cells respond weaker to repeated stimulation (e.g. synaptic depression) and that the response differentiates during familiarization. This paper presents a computational theory of SME based on synaptic depression and cell differentiation. SME occurs because synaptic depression is stronger for stimuli with larger cell differentiation and these stimuli are also easier to retrieve. The model also predicts a negative subsequent memory effect (NSME) so that a stimulus that are not preceded with other stimuli are recovered from synaptic depression, better recalled, and have a more positive ERP. The model is tested on ERP data collected during study of short lists followed by free recall.