A spatio-temporal comparison of semantic and episodic cued recall and recognition using event-related brain potentials.

The event-related brain potential (ERP) was used to spatially and temporally map the brain areas active as a function of type of recall (semantic vs. episodic) and episodic retrieval mode (recall vs. recognition) while difficulty of episodic recall was manipulated. ERPs were recorded from 32 scalp sites in 12 subjects, along with behavioral accuracy and recall speed. The results revealed that different but overlapping patterns of ERP activity were elicited during semantic and episodic recall. Recall of both types of information was characterized by ERP activity over left inferior frontal, central, bilateral temporal and posterior inferior brain areas. Compared to semantic recall, episodic recall elicited more activity over the frontal poles and right frontal scalp. Different but overlapping patterns of ERP activity were also found as a function of episodic retrieval mode. While episodic recall and recognition showed similar activity over the frontal poles and central scalp, there was no left inferior frontal activity elicited during recognition and no large, topographically widespread, late positive component (LPC) elicited when the same words were recalled. Manipulation of episodic recall difficulty and analysis of trials when recall failed indicated that these task (i.e., episodic vs. semantic) and retrieval mode (recall vs. recognition) differences in ERP activity were not likely to be due to differences in task difficulty. The results are discussed in terms of processes that the ERP activity may reflect and their similarity to results of PET studies of semantic and episodic retrieval.