FUNCTIONAL NEUROANATOMY OF RECALL AND RECOGNITION - A PET STUDY OF EPISODIC MEMORY

The purpose of this study was to directly compare the brain regions in volved in episodic-memory recall and recognition. Changes in regional cerebral blood flow were measured by positron emission tomography whil e young healthy test persons were either recognizing or recalling prev iously studied word pairs. Reading of previously nonstudied pairs serv ed as a reference task for subtractive comparisons. Compared to readin g, both recall and recognition were associated with higher blood flow (activation) at identical sites in the right prefrontal cortex (areas 47, 45, and 10) and the anterior cingulate. Compared to recognition, r ecall was associated with higher activation in the anterior cingulate, globus pallidus, thalamus, and cerebellum, suggesting that these comp onents of the cerebellofrontal pathway play a role in recall processes that they do not in recognition. Compared to recall, recognition was associated with higher activation in the right inferior parietal corte x (areas 39, 40, and 19), suggesting a larger perceptual component in recognition than in recall. Contrary to the expectations based on lesi on data, the activations of the frontal regions were indistinguishable in recall and recognition. This finding is consistent with the notion that frontal activations in explicit memory tasks are related to the general episodic retrieval mode or retrieval attempt, rather than to s pecific mechanisms of ecphory (recovery of stored information).