Medial temporal lobe and topographical memory

Abstract

There has been interest in the idea that medial temporal lobe (MTL) structures might be especially important for spatial processing and spatial memory. We tested the proposal that the MTL has a specific role in topographical memory as assessed in tasks of scene memory where the viewpoint shifts from study to test. Building on materials used previously for such studies, we administered three different tasks in a total of nine conditions. Participants studied a scene depicting four hills of different shapes and sizes and made a choice among four test images. In the Rotation task, the correct choice depicted the study scene from a shifted perspective. MTL patients succeeded when the study and test images were presented together but failed the moment the study scene was removed (even at a 0-s delay). In the No-Rotation task, the correct choice was a duplicate of the study scene. Patients were impaired to the same extent in the No-Rotation and Rotation tasks after matching for difficulty. Thus, an inability to accommodate changes in viewpoint does not account for patient impairment. In the Nonspatial-Perceptual task, the correct choice depicted the same overall coloring as the study scene. Patients were intact at a 2-s delay but failed at longer, distraction-filled delays. The different results for the spatial and nonspatial tasks are discussed in terms of differences in demand on working memory. We suggest that the difficulty of the spatial tasks rests on the neocortex and on the limitations of working memory, not on the MTL.hippocampus | spatial memory | working memory | long-term memory T he capacity to form declarative memory depends on the integrity of the hippocampus and related medial temporal lobe (MTL) structures (1, 2). Declarative memory provides for the representation of relationships and permits comparison among items and contexts (3). There has also been interest in the idea that the MTL, and the hippocampus in particular, might have a special role in spatial processing beyond its established role in memory (4, 5). Several studies have reported that patients with damage to the MTL were impaired in various kinds of spatial tasks, even when the burden on memory appeared quite small and when tasks of nonspatial memory appeared less affected (6-9).In one series of studies, MTL patients were impaired when they needed to appreciate a rotation in viewpoint from one perspective to another (6, 10, 11). For example, participants studied a scene depicting four hills of different shapes and sizes placed at different locations in the scene. They then decided which of four test images depicted the same study scene but now rotated from 15 to 90 degrees (6). MTL patients performed worse than controls even when a brief delay (2 s) intervened between study and test.A question arises as to whether the impairment reflects a specific difficulty in appreciating the rotation of perspective, or whether an equally severe impairment would be found even if no rotation occurred. A second question is whether the impairment reflects...

Preserved capacity for scene construction and shifts in perspective after hippocampal lesions

“…In this example, the scene in the right panel is identical to the scene in the left panel. controls, apparently by using working memory to hold spatial information in mind as they navigated in space (Shrager et al 2007(Shrager et al , 2008Kim et al 2013;Urgolites et al 2017). The current finding, together with these earlier results, counts against the idea that the hippocampus has an essential role in spatial cognition independent of its role in the formation of long-term memory.…”

Spared Perception of the Structure of Scenes after Hippocampal Damage

“…Thus, in these studies, lesions limited to the hippocampus did not affect the ability to judge the structural coherence of objects, objects embedded in scenes, or scenes themselves. This conclusion is in accord with our earlier findings that the hippocampus is also not needed for a variety of other spatial tasks, so long as the tasks do not depend on long-term memory (Rungratsameetaweemana & Squire, 2018;Urgolites et al, 2016Urgolites et al, , 2017Kim et al, 2011Kim et al, , 2015Kim, Borst, et al, 2013;Kim, Sapiurka, et al, 2013;Shrager et al, 2008).…”

“…In these circumstances, patients with hippocampal lesions might have been disadvantaged due to their memory impairment. In our own studies of spatial tasks, where we attempted to minimize the contribution of long-term memory (by limiting the number of stimuli or by using trial-unique stimuli), hippocampal patients performed as well as controls (path integration, Kim, Sapiurka, Clark, & Squire, 2013;Shrager, Kirwan, & Squire, 2008; visual discrimination of scenes, Kim et al, 2011;spatial imagery, Kim, Borst, et al, 2013; scene construction, Kim, Dede, Hopkins, & Squire, 2015; map reading and navigation, Urgolites, Kim, Hopkins, & Squire, 2016; topographical memory with shifts of viewpoint, Urgolites, Hopkins, & Squire, 2017; scene construction with shifts of viewpoint, Rungratsameetaweemana & Squire, 2018). For a report of impaired performance in a task using trial-unique stimuli, see Lee et al (2005).…”

Memory System Neurons Represent Gaze Position and the Visual World

“…Consistent with this idea, patients who have HF damage are particularly impaired at remembering spatial layout of a scene compared with other scene aspects, even immediately after viewing it. 24 Our observation of entorhinal neurons coding gaze position relative to major visual structure may be a neural signature of visual memory—driven by current visual input—that underlies memory-guided looking behavior.…”