NEUROANATOMICAL CORRELATES OF RETRIEVAL IN EPISODIC MEMORY - AUDITORYSENTENCE RECOGNITION

This study used positron emission tomography (PET) to investigate the neuroanatomical correlates of remembering previously experienced event s. Twelve young healthy adults listened to ''old'' meaningful sentence s which they had studied 24 hr previously. As a control task the subje cts listened to comparable ''new'' sentences that they had never heard before. Regional cerebral blood flow associated with each task was me asured by PET scans using O-15-labeled water. Comparison (old-sentence task minus new-sentence task) of the PET images revealed an extended strip of increased blood flow in the right dorsolateral prefrontal cor tex (Brodmann's areas 10, 46, and 9) and the anterior portion of area 6. Other principal regions of increased blood flow were situated aroun d the left anterior cingulate sulcus and bilaterally in the parietal l obes (areas 7 and 40). Major decreases in blood flow were situated bil aterally in the temporal lobes (areas 21, 22, 41, and 42). A high prop ortion of activity changes seemed to be located in the depths of corti cal sulci. Increases in blood flow are seen as reflecting the operatio ns of a widely distributed neuronal network involving prefrontal and p arietal cortical regions that subserves the conscious recollection of previously experienced events. Decreases in blood flow in the temporal auditory areas are interpreted as reflecting auditory priming. The pr evalence of sulcal blood-flow changes may reflect extensive cortical g yrification; it may also indicate that memory-related processes rely o n the densely packed neuropil of sulcal regions.