Submitted to: Behavioral Neuroscience
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/12/2001
Publication Date: 10/1/2001
Citation: Shukitt-Hale, B., Casadesus, G., Cantuti-Castelvetri, I., and Joseph, J.A. Effect of age on object exploration, habituation, and response to spatial and non-spatial change. Behav. Neurosci. 2001, 115: 1059-1064. Interpretive Summary: How well do you notice changes in your environment? Does our ability to detect "newness" decline with age? These interesting questions, which ultimately relate to our ability to attend to the wide array of stimuli around us every day, were tested in a study in which we explored the ability of young (6 mo) and aged (22-24 mo) rats to detect changes in their ropen field ( an open-top square box about 4ft/side). We placed 5 differen objects in the field (ball, etc.) and assessed the amount of time that the rat spent exploring each object. We then moved the objects around or we substituted a new object and assessed the time that the rat spent exploring the objects. The results indicated that the old animals spent less time exploring old objects, suggesting that they did not know that the objects had been moved, but there were no age-differences in the time spent exploring the new object. These findings indicate that the aged rat has an ninability to represent a cognitive "map" of where the old objects were in the box and thus, was unable to tell when they had been moved, but did not lose the ability to detect new objects.
Technical Abstract: To measure the ability to detect novel arrangements in a given environment, young (6 month) and senescent (22-24 month) male F344 rats were repeatedly exposed to a given spatial configuration of objects contained in an open field (8 successive 6-minute trials, separated by 3 minutes). After the rats were habituated to the novel environment (1 trial with no objects, followed by 3 trials with 5 salient objects), the spatial arrangement of the objects was modified (2 trials), and object novelty was subsequently tested (2 trials) by substituting a familiar object with a new one at the same location (non-spatial change). The results indicated that the senescent animals had less frequency and duration of contact with old objects than young animals, particularly on trial 2, and old object contact decreased from trial 2 to 8, in both groups. On the first trial with displaced objects (trial 5), the senescent animals had less contact and spent less time with the displaced objects when compared to the young rats. However, when a new object was placed in the field (trials 7-8), there were no age differences seen with respect to frequency or duration of new object exploration, and both groups had more occurrences of contact and spent more time with the new objects on trial 7 than the old. These results suggest that senescent rats have decrements in the ability to build spatial representations of the environment and to utilize this information to detect such changes, even though object recognition is not impaired with age.