It does not look odd to me: Perceptual impairments and eye movements in amnesic patients with medial temporal lobe damage

Abstract

Studies of people with memory impairments have shown that a specific set of brain structures in the medial temporal lobe (MTL) is vital for memory function. However, whether these structures have a role outside of memory remains contentious. Recent studies of amnesic patients with damage to two structures within the MTL, the hippocampus and the perirhinal cortex, indicated that these patients also performed poorly on perceptual tasks. More specifically, they performed worse than controls when discriminating between objects, faces and scenes with overlapping features. In order to investigate whether these perceptual deficits are reflected in their viewing strategies, we tested a group of amnesic patients with MTL damage that included the hippocampus and perirhinal cortex on a series of oddity discrimination tasks in which they had to select an odd item from a visual array. Participants' eye movements were monitored throughout the experiment. Results revealed that patients were impaired on tasks that required them to discriminate between items that shared many features, and tasks that required processing items from different viewpoints. An analysis of their eye movements revealed that they exhibited a similar viewing pattern as controls: they fixated more on the target item on trials answered correctly, but not on trials answered incorrectly. In addition, their impaired performance was not explained by an abnormal viewing-strategy that assessed their use of working memory. These results suggest that the perceptual deficits in the MTL patients are not a consequence of abnormal viewing patterns of the objects and scenes, but instead, could involve an inability to bind information gathered from several fixations into a cohesive percept. These data also support the view that MTL structures are important not only for long-term memory, but are also involved in perceptual tasks.

Neural microgenesis of personally familiar face recognition

“…However, our findings are also in agreement with more recent evidence suggesting that both structures, which are strongly connected with inferior temporal visual and prefrontal regions (27,(86)(87)(88), play a crucial role in perception (25,29,89) and assessment of "the significance of entities" (90). The perirhinal cortex, which codes feature conjunctions viewpoint-invariantly (91), is involved in complex visual discrimination (92,93) and has been proposed as an extension of the representational hierarchy in the ventral system (94)(95)(96)(97)(98). These characteristics, along with the anatomical location of the perirhinal cortex, render this structure ideally situated to link perception and semantic memory, as required for generation and maintenance of face representations for face individuation (26) and face discrimination across different viewpoints (30,31,99).…”

Memory for items and relationships among items embedded in realistic scenes: Disproportionate relational memory impairments in amnesia.

“…A handful of recent investigations have implicated the hippocampus in online processing and comparison of complex materials like the scenes used here (Voss et al, 2011; Warren, et al, 2011, 2012; Yee et al, 2014b; see Lee et al, 2012 and Olsen et al, 2012 for reviews; but see Erez et al, 2013), and evaluation of our reaction time data indicates that patients were slower to respond than healthy comparison participants when test trials were administered 1 . This outcome may reflect slower detection of differences across scenes (e.g.…”

Impairments in precision, rather than spatial strategy, characterize performance on the virtual Morris Water Maze: A case study

“…One issue, which we explore in detail here, is that the analyses used in previous studies of the human Morris Water Maze analogues do not provide a continuous measure of navigation, but rather coarse assessments of spatial memory based on dividing the arena into discrete quadrants. Recent findings, though, suggest that the hippocampus is involved in perceptual precision (Olson, Moore, Stark & Chatterjee, 2006; see also Erez, Lee, & Barense, 2013; Ryan, Moses, Barense, & Rosenbaum, 2013; Warren, Duff, Jensen, Tranel and Cohen, 2012) and a recently proposed alternative theory (which we refer to here as the Precision and Binding Model [PBM]) argues for a role of the hippocampus in spatial precision rather than spatial strategy per se (Yonelinas, 2013). Thus, a more in depth consideration of the precision of trajectories taken through the arena following hippocampal damage could better characterize navigational impairments following MTL damage and possibly help better understand the role of the hippocampus in perceptual precision and navigation.…”