Processing Depth and Episodic Retrieval: an fMRI study

Abstract

Background. According to the reinstatement theory that stems from the transfer appropriate processing (TAP) and the encoding specificity principles, episodic retrieval involves reactivation of processes and, therefore, of brain regions that were active during encoding. Hence, if two encoding conditions engage different cognitive operations, qualitative differences are expected also to be present at the retrieval phase. Functional neuroimaging applications have detected qualitative differences on the neural correlates of episodic encoding as a result of deep (semantic) and shallow (phonological) processing conditions. Aims. To explore if there is a qualitative impact on the neural correlates of retrieval orientation and retrieval success when processing depth is manipulated (deep vs. shallow) during encoding. Methods. Sixteen young adults participated in the study (12 analysed). An event-related fMRI design was applied while the participants performed the recognition phase of a memory task. Two retrieval conditions were included. This allowed to explore for processing depth effects after controlling for factors associated with the level of memory performance. Regions of interest and exploratory whole brain analyses were applied. Results. Common retrieval success effects were detected in regions localised in the inferior parietal lobule and the middle temporal gyrus. Greater shallow retrieval success effects were detected in a region localised in the precuneus. Also, greater shallow retrieval orientation effects were observed in regions localised in the fusiform gyrus and the superior temporal gyrus. No regions with the reverse activation pattern (deep > shallow) where detected either for retrieval success or retrieval orientation. Conclusions. The findings suggest that processing depth manipulation during encoding has a qualitative impact on the neural correlates of retrieval orientation and retrieval success that is in accordance with the predictions of the TAP and the encoding specificity principles.