Landmark stability is a prerequisite for spatial but not discrimination learning

Abstract

Neurons sensitive to both place and direction from distinct regions of the hippocampal formation, allometric relationships between spatial learning and hippocampal structure and pronounced impairments in spatial learning after lesions in this area, indicate that the hippocampal formation subserves allocentric spatial learning. To learn more about the process of spatial representation, we have developed a task that provides independent control of both landmark and directional cues. On the basis of physiological and behavioural work, this task also makes it possible to investigate the relevance of associative learning principles, such as predictability, to the spatial domain. We report here that although rats learn to discriminate between landmarks on the basis of their proximity to a reliably predicted food reward, they will only learn to use them to represent its location if they maintain stable locations within a geometric frame of reference.

Orientational manoeuvres in the dark: dissociating allocentric and egocentric influences on spatial memory

“…That is, the effect of a visual landmark may depend on being initially experienced as stable relative to updatable egocentric representations and/or uncontrolled representations of the testing room (the cue is equally unstable across both sessions relative to visual snapshot representations). While we are not aware of experiments on landmark stability in humans, our results are consistent with previous experiments on rats in which the influence of landmarks on searching behaviour depends on their perceived stability (Biegler & Morris, 1993, 1996Lenck-Santini et al, 2002).…”

“…Since the cue's stability relative to the subject's updatable egocentric representations may affect its influence on behaviour, the influence of a static visual cue might be reduced if the subject's internal sense of direction varies from trial-to-trial. This would explain the finding that when rats are systematically disoriented by spinning before each trial, their search is constrained only by the geometry of the environment, ignoring the visual cues within it (Cheng, 1986) unlike non-disoriented rats (Biegler & Morris, 1993, 1996Fenton et al, 1994;Lenck-Santini et al, 2002;Maurer & Derivaz, 2000;O'Keefe & Conway, 1980;Suzuki et al, 1980). It might also explain similar findings in the searching patterns of young children (Hermer & Spelke, 1994) and of adults performing verbal shadowing (Hermer-Vazquez et al, 1999), but cannot explain why non-shadowing adults do use visual landmarks despite having been disoriented.…”

“…We are not aware of previous investigations of landmark stability in humans, but it has a noticeable effect in spatial memory tests in rats. Briefly, rats will search for a location defined by visual landmarks (Biegler & Morris, 1993;Biegler & Morris, 1996;Fenton, Arolfo, Nerad, & Bures, 1994;Lenck-Santini, Muller, Save, & Poucet, 2002;Maurer & Derivaz, 2000;O'Keefe & Conway, 1980;Suzuki, Augerinos, & Black, 1980), but will not do so if the landmark's position has varied from trial-to-trial (Biegler & Morris, 1993, 1996Lenck-Santini et al, 2002). We investigated the effect of cue stability by dividing the conditions into two blocks in which the external cue either remains static throughout or in which it moves between presentation and retrieval on every trial.…”

Performance of goldfish trained in allocentric and egocentric maze procedures suggests the presence of a cognitive mapping system in fishes

“…In addition to the hypothesis of allocentric spatial representations (Biegler & Morris, 1993;Nadel, 1991;Worden, 1992), several authors propose that place responses might be explained by mechanisms involving egocentrically referenced representations of landmarks. For example, it has been suggested that animals can be guided by stored information about the retinal size of each of several landmarks in the room, as viewed from the goal (Leonard & McNaughton, 1990;McNaughton, 1987).…”

Path integration in mammals

“…In conditions in which navigation has to be very precise, such as during the final approach to a goal, PI is too error-prone to be wholly relied upon, and so stable (Biegler and Morris, 1993), necessitating the use of external landmarks. During the outward journey to a known food source, foraging hamsters (Etienne, 2003), like ants (Collett and Collett, 2000), need external cues to stop at the goal site.…”