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. 2015 Mar:119:69-76.
doi: 10.1016/j.nlm.2015.01.007. Epub 2015 Jan 28.

Impaired allocentric spatial processing in posttraumatic stress disorder

Kirsten V Smith  1 , Neil Burgess  2 , Chris R Brewin  3 , John A King  4
Affiliations

Impaired allocentric spatial processing in posttraumatic stress disorder

Kirsten V Smith et al. Neurobiol Learn Mem. 2015 Mar.

Abstract

A neurobiological dual representation model of PTSD proposes that reduced hippocampus-dependent contextual processing contributes to intrusive imagery due to a loss of control over hippocampus-independent sensory and affective representations. We investigated whether PTSD sufferers show impaired allocentric spatial processing indicative of reduced hippocampal functioning. Trauma-exposed individuals with (N=29) and without (N=30) a diagnosis of PTSD completed two tests of spatial processing: a topographical recognition task comprising perceptual and memory components, and a test of memory for objects' locations within a virtual environment in which the test is from either the same viewpoint as presentation (solvable with egocentric memory) or a different viewpoint (requiring allocentric memory). Participants in the PTSD group performed significantly worse on allocentric spatial processing than trauma-exposed controls. Groups performed comparably on egocentric memory and non-spatial memory for lists of objects. Exposure to repeated incident trauma was also associated with significantly worse spatial processing in the PTSD group. Results show a selective impairment in allocentric spatial processing, implicating weak hippocampal functioning, as predicted by a neurobiological dual representation model of PTSD. These findings have important clinical implications for cognitive therapy.

Keywords: Allocentric memory; Hippocampus; PTSD; Spatial memory; Trauma.

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Figures

Fig. 1
Fig. 1
The Four Mountains Task. Left panel: a typical example of a stimulus image. Right panel: four forced-choice response items. Each shows a different arrangement of topography, one of which is the stimulus shown from a different position. The correct response is highlighted for clarity in this figure only.
Fig. 2
Fig. 2
The Town Square Task. Left panels show learning items, right panels show the memory test, with one item in the original location and three foil copies in random locations. Upper panels show a shifted-view item at learning and test, lower panels show a same-view item. Colors are used for participants to indicate their chosen response.
Fig. 3
Fig. 3
Performance on the Four Mountains Task. Asterix indicates a significant (P < 0.05) main effect of group (PTSD vs. control), no other comparisons were significant. Error bars represent two standard errors.
Fig. 4
Fig. 4
Performance on egocentric and allocentric spatial memory in the Town Square task, by group (∗P = .01).
See this image and copyright information in PMC

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