Dissociable contributions within the medial temporal lobe to encoding of object-location associations

Abstract

The crucial role of the medial temporal lobe (MTL) in episodic memory is well established. Although there is little doubt that its anatomical subregions-the hippocampus, peri-, entorhinal and parahippocampal cortex (PHC)-contribute differentially to mnemonic processes, their specific functions in episodic memory are under debate. Data from animal, human lesion, and neuroimaging studies suggest somewhat contradictory perspectives on this functional specialization: a general participation in declarative memory, an exclusive involvement in associative mnemonic processes, and a specific contribution to spatial memory are reported for the hippocampus, adjacent cortices, and the PHC. A functional lateralization in humans dependent on the verbalizability of the material is also discussed herein. To further elucidate the differential contributions of the various MTL subregions to encoding, we employed an object-location association memory paradigm. The memory for each of the studied associations was tested twice: by the object, and by the location serving as retrieval cue. The memory accuracy in response to both cue types was also assessed parametrically. Brain activity during encoding which leads to different degrees of subsequent memory accuracy under the two retrieval conditions was compared. We found the bilateral posterior PHC to participate in encoding of both the object associated with a location and the location associated with an object. In contrast, activity in an area in the left anterior PHC and the right anterior MTL was only correlated with the memory for the location associated with an object.

Healthy aging attenuates task-related specialization in the human medial temporal lobe

“…This is consistent with a general role for the parahippocampal region in spatial memory processing (Dü-zel et al, 2003;Ekstrom and Bookheimer, 2007;Ramsøy et al, 2009;Sommer et al, 2005), and consistent with previous research linking spatial recognition success and the parahippocampal region (Ekstrom and Bookheimer, 2007;Kircher et al, 2008; see also Wais, 2008). Together, our results suggest that, across the life span, patterns of content modulation of activity within distinct MTL regions are linked to variability in encoding and retrieval success for this content.…”

Neural changes when actions change: Adaptation of strong and weak expectations

“…Hence, we take it to reflect continuing mismatch between the internal motor model's expectations and perception, which is increased if the original internal model was highly habituated. The parahippocampal cortex has been associated with topographical learning (Aguirre, Detre, Alsop, & D'Esposito, 1996), scene processing (Epstein & Kanwisher, 1998) and the association of scenes and locations with objects (Bar, Aminoff, & Schacter, 2008;Sommer, Rose, Gläscher, Wolbers, & Büchel, 2005).…”

Distinct roles for medial temporal lobe structures in memory for objects and their locations

“…In a recent study, Sommer et al (2005) reported an area of activation in the right anterior medial temporal lobe that was correlated with memory for the location associated with an object. Using an event-related design, these authors correlated activity during encoding an object-location association with retrieval success when presented with either an object cue or a location cue.…”

“…To date, very few functional imaging studies of recognition memory have examined possible distinctions between medial temporal lobe structures (Davachi et al 2003;Duzel et al 2003;Pihlajamaki et al 2003Pihlajamaki et al , 2004Kohler et al 2005;Sommer et al 2005), and no direct comparisons have been made between the anatomically defined perirhinal and parahippocampal cortices while subjects explicitly perform a memory task across modalities. Here, we compared the activation patterns of the perirhinal cortex and the parahippocampal cortex while subjects performed tasks of visual object and spatial recognition memory.…”