Electrocortical indices of subjectively perceived confidence in episodic memory.

Electrophysiological studies on recognition memory have identified several brain signals that are associated with subjective perceived confidence. However, the extent these brain signals reflect a generic process and are independent of the type of information recognized remains an open question. To address this issue, twenty-seven healthy volunteers performed an episodic memory task while their electro-encephalogram (EEG) was recorded. Participants encoded a set of abstract pictures, and subsequently rated their confidence on recognition decisions. Similar to results reported in previous studies using concrete words, we found retrieval-related theta power, FN400 and late positive component (LPC) effects. In contrast to previous studies using verbal material, a subsequent memory effect for encoding-related evoked theta power, sensitive to subjectively perceived memory confidence, was observed. Our findings suggest that brain signals that are associated with subjectively perceived confidence reflect specific encoding, but generic retrieval processes.