Academic journal article Memory & Cognition

Two-Category Place Representations Persist over Body Rotations

Academic journal article Memory & Cognition

Two-Category Place Representations Persist over Body Rotations

Article excerpt

Published online: 18 June 2013

© The Author(s) 2013. This article is published with open access at Springerlink.com

Abstract We explored a system that constructs environment-centered frames of reference and coordinates memory for the azimuth of an object in an enclosed space. For one group, we provided two environmental cues (doors): one in the front, and one in the rear. For a second group, we provided two object cues', a front and a rear cue. For a third group, we provided no external cues; we assumed that for this group, their reference frames would be determined by the orthogonal geometry of the floor-and-wall junction that divides a space in half or into multiple territories along the horizontal continuum. Using Huttenlocher, Hedges, and Duncan's (Psychological Review 98: 352-376, 1991) category-adjustment model (cue-based frizzy boundary version) to fit the data, we observed different reference frames than have been seen in prior studies involving two-dimensional domains. The geometry of the environment affected all three conditions and biased the remembered object locations within a two-category (left vs. right) environmental frame. The influence of the environmental geometry remained observable even after the participants' heading within the environment changed due to a body rotation, attenuating the effect of the front but not of the rear cue. The door and object cues both appeared to define boundaries of spatial categories when they were used for reorientation. This supports the idea that both types of cues can assist in environment-centered memory formation.

Keywords Place memory * Coarse-grain representation * Environmental geometry * Landmark * Category * Bias

(ProQuest: ... denotes formulae omitted.)

When people encode where they are placing an object (e.g., a key), they encode the direction and distance of the object relative both to themselves (egocentric coding; Wang et al., 2006; Wang & Spelke, 2000, 2002) and to nearby objects and other features of the environment (allocentric coding; Gallistel, 1990; O'Keefe & Burgess, 1996). The environmental features used for allocentric coding can be subcategorized into environ- mental landmarks and object landmarks. Environmental land- marks include architectural structures such as corners, doorways, and the boundaries or geometric shape of the envi- ronment. Object landmarks refer to salient nontarget objects (e.g., a color patch, a floor lamp) situated among the environ- mental landmarks. Environmental landmarks play a role in constructing environment-centered frames of reference, define possible paths for navigation, and specify reference directions that can be used for reorientation (Carr & Watson, 1908). In addition, environmental landmarks are thought to be more stable cues than object landmarks (Lew, 2011). Location sta- bility can be conceptualized as being proportional to the geo- metric salience of a given location or to the inverse variance of the location representation. Environmental landmarks indicate the most stable framing locations, whereas the stability of object landmarks declines as their distance from a stable fram- ing element increases. Evidence from the animal literature has indicated that environmental and object landmarks have distinct roles in orientation processes and engage different neural sub- strates (see Lew, 2011, for a review); in this literature, however, the stability of the landmark locations is thought to be a more crucial factor than landmark type for determining which brain structures are recruited. The striatum has been reported to support the learning of unstable cue-based localization, whereas the hippocampus is thought to mediate the learning of stable cue-environment associations, and thus to mediate place recognition more generally (e.g., McDonald & White, 1994). The extent to which these types of landmarks might be processed differently in human visual and memory systems remains unclear. …

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