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Stress
The International Journal on the Biology of Stress
Volume 16, 2013 - Issue 1
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Research Article

Reactivation of an aversive memory modulates learning strategy preference in male rats

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Pages 73-86 | Received 20 Dec 2011, Accepted 04 Apr 2012, Published online: 09 May 2012
 

Abstract

Reminders of an aversive event adversely impact retrieval of hippocampus-dependent memories and exacerbate stress-induced levels of anxiety. Interestingly, stress and anxiety shift control over learning away from the hippocampus and toward the striatum. The aims of the current study were to determine whether spatial memory and learning strategy are impacted by reminders of a stressor. Adult male Long-Evans rats (N = 47) were subjected to an inhibitory avoidance (IA) training trial in which 32 rats were exposed (3 s) to a single inescapable electrical footshock (0.6 mA). Prior to the retention trial of a Y-maze task and the probe trials of two different learning strategy tasks, some of the rats that were exposed to the footshock (n = 17) were reminded of the stressor on an IA retrieval trial. Both groups of rats exposed to the initial stressor exhibited hypoactivity, but no impairment in spatial memory, on the Y-maze task conducted 1 week after exposure to the footshock. One month after exposure to footshock, both groups of rats exposed to the initial stressor tended to prefer a striatum-dependent learning strategy on a water T-maze task. However, 2 months after exposure to footshock, only shocked rats that were reminded of the stressor exhibited a preference for a striatum-dependent learning strategy on a visible-platform water maze task, which corresponded with lower levels of activity in an open field. The results indicate that reminders of a stressor perpetuate the deleterious effects of stress on affective and cognitive processes.

Acknowledgements

This research was supported by the Louisiana Board of Regents, Flowerree Summer Research Fellowship, the Tulane University Department of Psychology and Tulane University Program in Neuroscience. The authors gratefully acknowledge the technical assistance of Paul Tran. The expert supervision of animal care by Kimberly Scamardo is greatly appreciated.

Declaration of interest : The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

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