Authors:

LEE, A.C.H., Robbins, T.W., GRAHAM, K.S. & Owen, A.M

Reference:

Year of publication:

2001

CBU number:

5343

Abstract:

Few neuroimaging studies have attempted to disentangle semantic memory processes associated with episodic memory encoding and retrieval. To address this issue, subjects were PET scanned whilst learning a series of real words (e.g. 'prey'). In a subsequent scan, the subjects were presented with homophone pairs (e.g. 'prey' vs. 'pray') and were required to choose the one that had been shown previously. In two corresponding baseline tasks, the subjects were scanned whilst learning and recognising pronounceable non-words. Thus, whilst these tasks recruited either episodic memory encoding or retrieval processes, only the homophone tasks recruited semantic memory access. A conjunction analysis designed to isolate activation associated with semantic memory access, revealed changes in several left lateral frontal regions (BA 46, 9 and 44) and in the left inferior temporoparietal cortex (BA 37/39). In contrast, a conjunction analysis designed to isolate activation associated with episodic memory encoding, revealed significant changes in the left hippocampus, as well as in the frontopolar cortex (BA 10) bilaterally, the left inferior parietal cortex (BA 40), and the left superior temporal gyrus (BA 22, 28). The present results clarify and extend recent attempts to understand the neural basis of semantic memory retrieval, by actively controlling for the confounding effects of episodic memory encoding and retrieval processes.