Anterolateral Entorhinal Cortex Volume Predicted by Altered Intra-Item Configural Processing

Abstract

Recent functional imaging studies have proposed that the human entorhinal cortex (ERC) is subdivided into functionally distinct anterolateral (alERC) and posteromedial (pmERC) subregions. The alERC overlaps with regions that are affected earliest by Alzheimer's disease pathology, yet its cognitive function remains poorly understood. Previous human fMRI studies have focused on its role in object memory, but rodent studies on the putatively homologous lateral entorhinal cortex suggest that it also plays an important role in representing spatial properties of objects. To investigate the cognitive effects of human alERC volume differences, we developed an eye-tracking-based task to evaluate intra-item configural processing (i.e., processing the arrangement of an object's features) and used manual segmentation based on a recently developed protocol to delineate the alERC/pmERC and other medial temporal lobe (MTL) subregions. In a group of older adult men and women at varying stages of brain atrophy and cognitive decline, we found that intra-item configural processing, regardless of an object's novelty, was strongly predicted by alERC volume, but not by the volume of any other MTL subregion. These results provide the first evidence that the human alERC plays a role in supporting a distinct aspect of object processing, namely attending to the arrangement of an object's component features.

Modelling the influence of the hippocampal memory system on the oculomotor system

“…Amnesic cases who have compromised HC and/or MTL show specific changes in their viewing behavior compared to healthy individuals (Ryan et al, 2000;Warren et al, 2010;Olsen et al, 2015). Similar findings have been observed in older adults who have suspected HC/MTL compromise , and certain viewing patterns have been shown to track with entorhinal cortex (ERC) volumes (Yeung et al, 2017).…”

“…Eyetracking research with older adults shows that volumes within the alERC significantly predicted viewing behavior that reflected processing of the spatial arrangement of an object's component features (Yeung et al, 2017). Such findings suggest that regions within the ERC may provide information regarding the spatial arrangement of features within an object and the relative positioning of objects in space.…”

“…Multiple memory 'signals' are evident within patterns of gaze fixations, including memory for single stimuli (Althoff & Cohen, 1999;Smith & Squire, 2017) memory for the relative spatial relations within objects (Yeung et al, 2017), and memory for the relative spatial positions among objects (Ryan et al, 2000;Smith, Hopkins & Squire, 2006), and interobject associations . Dissociations in these memory signals can be observed within single gaze patterns in neuropsychological cases (Ryan et al, 2000;.…”

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

“…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 …”

“…). Likewise, in a separate study, Yeung and colleagues had participants study a series of objects that were composed of two features. Subsequently, some objects were repeated in their original form, whereas other objects contained a feature swap, such that both features of the object had been previously viewed but not paired together, and other objects were completely novel.…”