Knowledge Bank

There are multiple physiological measurements that can predict successful encoding of a stimulus that can be retrieved from memory later, often referred to as a subsequent memory effects (SMEs). An event related potential (ERP) is a change in EEG signal, positive or negative, that is temporally related to an event. A late positive component (LPC), a positive signal in the parietal region, is predictive of successful memory formation (Mangels et al., 2001). A pupil response (PR) during encoding, measured as the maximum deflection in pupil size after stimulus onset, is an analogue to activity of the locus coeruleus (LC) -- a subcortical brain structure that controls the release of the neurotransmitter norepinephrine (NE)-- and also predicts successful episodic memory formation. To measure the extent to which these two potential correlates of successful memory formation overlap, we examined data from both of these sources while participants were auditorily presented with lists of common nouns, as well as when they were later tested on their recognition of those items. For ERP we found a trend towards a late positive component (LPC) in the parietal region, but it did not achieve significance. PR during encoding showed the beginning of an increase in positive response for stimuli that were later remembered, but the signal recorded did not extend the entire duration of the time period predicted for the effect and also failed to achieve significance.