Novel vs. well-learned memory for faces: A positron emission tomography study

Previous work has suggested that familiarity/novelty of learned materials a ffects the circuitry involved in memory, primarily in the size of activatio ns rather than the pattern of activation. Although this work has examined b oth recall and recognition, it has been limited to verbal material. In this study, we set out to determine if the same result applies to nonverbal mem ory. We used the same experimental design, but used faces as the memory tas k. Healthy volunteers thoroughly learned a set of 18 faces a week prior to the Positron Emission Tomography (PET) experiment (well-learned memory) and were asked to remember another set of 18 faces, to which they were exposed 1 min before the PET experiment (novel memory). During the PET session, th eir task was to recognize the faces learned a week before and the faces see n a minute before; the "remembered faces" were interspersed among entirely new (distractor) faces. We found that, unlike for verbal material, the rete ntion interval and the familiarity level of the faces affected both the pat tern and the size of activations. Comparing the novel and well-learned reco gnition tasks revealed that novel memory for faces is primarily a frontal-l obe task, while well-learned recognition memory for faces utilizes a more d istributed neural circuit, including visual areas, which appear to serve as memory-storage sites.