Memory performance in tree shrews. effects of stressful experiences

Male tree shrews were exposed to alternating non-stressful and stressful co nditions, and their memory performance was tested during three different st ress periods and after rest periods of various lengths using a modified hol eboard. This paradigm circumvents confounding factors, e.g. food or water d eprivation, transport to a special testing arena, and excludes the developm ent of automatic cognitive processes by complex memory tasks. In experiment al tree shrews, psychosocial conflict caused elevated cortisol levels durin g the stress phases. While this resulted in an impairment of the stress-sen sitive declarative memory during the second stress phase, no memory deficit was found during the first and third stress phase. Despite normalized cort isol levels, significant memory deficits in experimental animals were obser ved even 10 weeks after the last stressful experience. The alternating orde r of stressful events revealed that the negative correlation between the le vel of adrenal steroid hormones and memory performance does not account for the long-lasting effects of psychosocial stress in tree shrews. (C) 1998 E lsevier Science Ltd. All rights reserved.