Coding of spatio-temporal attributes: the roles of age and enriched environment

IntroductionSpatial behaviour is the ability to orient or perceive one's body in space or to detect or reason about spatial relationship (VandenBos, 2007). Spatial ability about a given environment often leads to development of spatial memory which comes with passage of time. Spatial memory is the capacity to remember the position and location of objects or places which may include orientation, direction and distance (VandenBos, 2007). Spatial attributes have been linked with the concept of cognitive mapping. Dkwns and Stea (1973) defined cognitive mapping as a process composed of a series of psychological transformations by which an individual acquires, codes, stores, recalls and decodes information about the relative locations and attributes of phenomena in his everyday spatial environment. Different schools of thought like the stimulus-Response school and field theorists have explained the bases of spatial behaviour (Tolman, 1973). However evidences pants towards neural system functionary in spatial learning.Spatial and temporal behaviours have been major areas of concern as it relates to neural bases of learning and memory. Certain lesions of the brain have been linked to deficits in spatial learning both in humans and animals (Winocur, 1982; Kesner, 1985; Jarrard, 1993; Astur, Taylor, Mamelak, Philpott & Sutherland, 2002). In particular the hippocampus has been implicated in deficits of spatial and temporal attributes in learning and memory. The discovery by O'keefe and Dostrovsky (1971) confirmed by Olton, Branch and Best (1978) and Ranck (1973) that some hippocampal cells fire according to the animal's position in its environment suggested an important role for the hippocampus in mediating spatially oriented behaviours (Wincour, 1982). Since then many studies in that direction have implicated the hippocampus in spatial learning and forgetting. Piber, Schulterbraucks, Mueller, Deuter, Wingenfeld and Otte (2016) demonstrated the effects of mineralocorticoid receptor (MR) stimulation on spatial memory in healthy young adults using Virtual Morris Water Maze task (VMWM). Although there was no effect of MR stimulation on spatial encoding during the VMWM task, participants who received fludrocortisone exhibited improved hippocampal spatial memory retrieval performance and there was neither a main effect of sex by treatment interaction. This study lends support to the findings by Wang, Lee, Brain and Enck (2016) on the effects of probiotics on spatial and non spatial memory abilities in rats. Although evidence regarding hippocampal lesion on spatial learning abounds in literature (Mc Clelland, Mc Naughton & O' Reilly, 1995; Moser, Moser & Andersen, 1993; Weatherly, Harding & Wright, 1996; Vorhees & Williams, 2006; O'Reilly & Rudy, 2001), limited studies have been done on the roles of demographic variables and cognitive reserve in improving spatial learning abilities. On the other hand, many studies of that nature have not employed complex radial arm maze manipulations that tap working memory and spatio - temporal learnings. Nilssion, Perfilieva, Johansson, Oewar and Ariksoson (1999) studied whether the proliferation of progenitor cells and the subsequent generation of new neurons within the dentate gyrus in adult rats are induced by environmental stimuli and to also assess their performance on spatial learning test. Their results showed that adult rats housed in an enriched environment showed improved performance in a spatial learning test. The results suggest that environmental cues can enhance neurogenesis in adult hippocampal region which is associated with improved spatial memory. Frick, Stearns, Pan and Berger-Sweeney (2003) studied effects of environmental enrichment on spatial memory and neurochemistry in middle aged mice. The results of their study showed that environmental enrichment reduced the age related impairment in spatial acquisition and retention. Relative to adult social controls, middle aged enriched mice were unimpaired where as middle aged mice social controls were impaired. …