Selective spatial memory impairment after right unilateral temporal lobectomy

Nunn, Julia A.; Polkey, C E; Morris, Robin G.

doi:10.1016/s0028-3932(98)00030-x

Cited by 55 publications

(47 citation statements)

References 62 publications

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“…One of the important dimensions of episodic memory is to process objects in association with their locations (Smith and Milner 1989;Abrahams et al 1997;Vargha-Khadem et al 1997;Nunn et al 1998). This component of episodic memory has been studied also in animal models (Gaffan 1994;Gilbert and Kesner 2002;Rolls et al 2005;Bachevalier and Nemanic 2008;Lee and Solivan 2008).…”

Section: Discussionmentioning

confidence: 99%

Dentate gyrus is necessary for disambiguating similar object-place representations

Lee¹,

Solivan²

2010

Learn. Mem.

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Objects are often remembered with their locations, which is an important aspect of event memory. Despite the well-known involvement of the hippocampus in event memory, detailed intrahippocampal mechanisms are poorly understood. In particular, no experimental evidence has been provided in support of the role of the dentate gyrus (DG) in disambiguating such events, even though computational models suggest otherwise. In the current study, rats encountered multiple objects in different locations and were required to discriminate the object-place paired associates for reward. Specifically, two different objects appeared in one of two locations (arms in a radial maze) that were relatively close to each other. Different objects were rewarded depending on the arm in which the objects appeared. The rats with colchicine-based, dorsal DG (dDG) lesions showed severe and sustained impairment in disambiguating the objects compared with controls (Experiment 1). The dDG-lesioned rats were normal, however, in discriminating four different objects presented (Experiment 2) in the same locations as in Experiment 1. Finally, when the two different objects used in Experiment 1 were presented at two remote locations (Experiment 3) involving less overlap between arm-associated contextual cues, the dDG-lesioned animals showed initial deficits in discriminating the objects, but gradually relearned the task, in contrast to the sustained deficits observed in Experiment 1. These results collectively suggest that the DG is necessary when the similarity is maximal between object-place paired associates due to overlapping object and/or spatial information, whereas its role becomes minimal as the overlap in either object or spatial information decreases.The hippocampus and its associated regions are important in remembering spatial contexts and their associated events as discrete memories (O'Keefe and Nadel 1978;Kim and Fanselow 1992). One of the computational problems involved in this process is to disambiguate altered neural representations from the original memory representations formed at the time of encoding the events (Marr 1971;McNaughton and Morris 1987;O'Reilly and McClelland 1994). It is not uncommon that one needs to retrieve a specific memory representation of a particular person seen at a specific place, separately from many paired-associate representations previously formed between that person and other locations. It is largely unknown how the hippocampal networks form specific memory representations for multiple events that share common components and disambiguate those representations from each other when retrieving a specific target memory representation.Among hippocampal subfields, computational models have highlighted the essential role of the dentate gyrus (DG) for disambiguating similar events. This so-called pattern separation refers to the computational process for making representations for similar input patterns more orthogonal to each other for better discrimination (Marr 1971;McNaughton and Morris 1987;O'Reilly and Mc...

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Section: Discussionmentioning

confidence: 99%

Dentate gyrus is necessary for disambiguating similar object-place representations

Lee¹,

Solivan²

2010

Learn. Mem.

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“…It has since been established that this limbic structure has a critical role in episodic memory for spatial, contextual, and relational information (152). Hippocampal lesions produce spatial reference memory deficits in humans (427,458) and rodents (326,660). Lesions to the dorsal but not ventral hippocampus impair spatial reference acquisition in rodents (499), suggesting that the dorsal hippocampus in rodents may play the greater role in reference memory.…”

Section: Hippocampal Functionmentioning

confidence: 99%

Sex Hormones and Cognition: Neuroendocrine Influences on Memory and Learning

Hamson

Roes

Galea

2016

Comprehensive Physiology

171

110

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Sex differences in neurological disease exist in incidence, severity, progression, and symptoms and may ultimately influence treatment. Cognitive disturbances are frequent in neuropsychiatric disease with men showing greater cognitive impairment in schizophrenia, but women showing more severe dementia and cognitive decline with Alzheimer's disease. Although there are no overall differences in intelligence between the sexes, men, and women demonstrate slight but consistent differences in a number of cognitive domains. These include a male advantage, on average, in some types of spatial abilities and a female advantage on some measures of verbal fluency and memory. Sex differences in traits or behaviors generally indicate the involvement of sex hormones, such as androgens and estrogens. We review the literature on whether adult levels of testosterone and estradiol influence spatial ability in both males and females from rodent models to humans. We also include information on estrogens and their ability to modulate verbal memory in men and women. Estrone and progestins are common components of hormone therapies, and we also review the existing literature concerning their effects on cognition. We also review the sex differences in the hippocampus and prefrontal cortex as they relate to cognitive performance in both rodents and humans. There has been greater recognition in the scientific literature that it is important to study both sexes and also to analyze study findings with sex as a variable. Only by examining these sex differences can we progress to finding treatments that will improve the cognitive health of both men and women. © 2016 American Physiological Society. Compr Physiol 6:1295-1337, 2016.

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“…For example, judging objects in terms of a semantic attribute promotes performance on recognition memory tests for object identity and on relocation measures even when no naming response is required at encoding (Carroll et al, 1985;. There is also evidence showing that people are able to remember the identity and absolute location of pictures of meaningless, abstract objects that cannot easily be named (e.g., Nunn, Polkey, & Morris, 1998). Thus, it is possible that encoding processes involved in establishing a perceptual representation of the structural description of an object (Riddoch & Humphreys, 1987) are sufficient to allow for subsequent recovery of its identity and absolute location from episodic memory.…”

Section: Evidence For Common Encoding Processesmentioning

confidence: 99%