Object-in-Place Memory Predicted by Anterolateral Entorhinal Cortex and Parahippocampal Cortex Volume in Older Adults

Abstract

The lateral portion of the entorhinal cortex is one of the first brain regions affected by tau pathology, an important biomarker for Alzheimer's disease (AD). Improving our understanding of this region's cognitive role may help identify better cognitive tests for early detection of AD. Based on its functional connections, we tested the idea that the human anterolateral entorhinal cortex (alERC) may play a role in integrating spatial information into object representations. We recently demonstrated that the volume of the alERC was related to processing the spatial relationships of the features within an object . In the present study, we investigated whether the human alERC might also play a role in processing the spatial relationships between an object and its environment using an eyetracking task that assessed visual fixations to a critical object within a scene. Guided by rodent work, we measured both object-in-place memory, the association of an object with a given context (Wilson et al., 2013), and object-trace memory, the memory for the former location of objects (Tsao, Moser, & Moser, 2013). In a group of older adults with varying stages of brain atrophy and cognitive decline, we found that the volume of the alERC and the volume of the parahippocampal cortex (PHC) selectively predicted object-in-place memory, but not objecttrace memory. These results provide support for the notion that the alERC may integrate spatial information into object representations.

The intersection between the oculomotor and hippocampal memory systems: empirical developments and clinical implications

“…Again, neither study required viewers to comment on the contents of their memory, as no explicit memory task was provided; thus, the eye movements provided an indirect index of mnemonic function in aging. When considered in conjunction with the findings from amnesic cases with hippocampal compromise, the findings suggest that the ERC may provide a rate‐limiting step for the binding functions of the hippocampus: information regarding spatial configurations within and across items from the ERC may be subsequently used by the hippocampus to create lasting representations regarding the broader relations among items. With ERC dysfunction, the binding functions of the hippocampus may not be fully realized.…”

“…Although the field has largely focused on adaptations of the preferential viewing task to screen for neurodegeneration, this task provides a gross measure of memory function that, to date, has been associated broadly with hippocampal and MTL dysfunction. As noted earlier, on tasks that require processing and retention of intra‐ and inter‐item feature configurations, viewing behavior is related to volumes of the alERC, which is one of the first regions to show volumetric changes in MCI and Alzheimer's disease . It is not clear whether the preferential viewing task would be a more effective screen for neurodegenerative conditions like MCI or Alzheimer's disease, compared with tasks that specifically tap into the functions of the alERC.…”

“…Comprehensive eye tracking and computational modeling investigations that examine whether dissociations in patterns of visual exploration and the nature of signal propagation exist depending on the location of lesion or dysfunction remain to be done. In particular, cross‐sectional and longitudinal studies of aging may provide a useful model to explore the cascade of changes in visual exploration and signal propagation that emerge with spreading dysfunction and/or structural compromise across the MTL and hippocampus …”

“…(A) Modified version of the Olsen–Amaral–Palombo segmentation protocol used in Olsen et al . and Yeung et al . Inset images depict coronal slices of the MTL taken at various points along the long axis of the hippocampus (as shown in the sagittal view at bottom left).…”

“…(C) Left : The relationship is plotted between alERC volume residuals (sole contribution of alERC volumes as predictors) and a viewing of the critical region of a previously presented scene that contains a manipulation from a prior viewing. Larger alERC volumes were associated with greater viewing to the manipulated region of a scene that newly contains an object ( object‐in‐place manipulation) . Right : Example scene stimulus is shown; manipulated regions are outlined in green (previous location of an object) and yellow (new location of an object).…”