Available as an open access download from Nature Scientific Reports
Exposure to severe and prolonged stress has detrimental effects on the hippocampus. However, relatively little is known about the gradual changes in hippocampal structure, and its behavioral consequences, over the course of repeated stress. Behavioral analyses during 10 days of chronic stress pointed to a delayed decline in spatial memory, the full impact of which is evident only after the end of stress. In contrast, concurrent volumetric measurements in the same animals revealed significant reduction in hippocampal volumes in stressed animals relative to their unstressed counterparts, as early as the third day of stress. Notably, animals that were behaviorally the worst affected at the end of chronic stress suffered the most pronounced early loss in hippocampal volume. Together, these findings support the view that not only is smaller hippocampal volume linked to stress-induced memory deficits, but it may also act as an early risk factor for the eventual development of cognitive impairments seen in stress-related psychiatric disorders.
Stress causes a loss in total hippocampal volume as early as day3, which progresses with the 10-day chronic stress. The right hippocampal volume loss is evident only after chronic stress, but the left hippocampal volume loss is evident as early as day3 and progresses with the 10-day chronic stress paradigm. The spatial memory impairment caused by stress also varies over time. A trend of deficit in spatial memory was observed on day5 in Morris water maze task, however the same animals show a strong deficit in spatial memory on day13 observed in object displacement task.