Functional magnetic resonance imaging of source versus item memory.

Both the frontal lobes and the medial temporal lobe (particularly the hippocampus) have been implicated in encoding and retrieval of episodic memory information. We report an experiment that manipulates whether source information, item information, or both are required at retrieval. Two sources were used in a factorial design in which the main effect of source and item retrieval, along with their interaction, could be measured by fMRI activations. When source information was required at retrieval the left frontal lobe showed significant activation but not when item retrieval was required. Hippocampal activation showed no difference between source and item retrieval. This pattern of results supports a model proposing a larger role for the frontal lobes in encoding and retrieval of source information.