The modulation of Pavlovian memory

Exposure to stressful experiences as well as sex differences in the brain a re known to influence the acquisition of new memories. This review focuses on acquisition of two types of Pavlovian learning paradigms: hippocampal-in dependent delay conditioning and hippocampal-dependent trace conditioning a nd their modulation by exposure to stressful experience and sex differences in the brain. We concentrate on two sets of findings: the first is that ex posure to an acute stressful experience enhances Pavlovian conditioning in the male rat, while exposure to the very same experience dramatically impai rs conditioning in female rat. The sexually-opposed effects of stress on co nditioning are mediated by differing hormonal substrates (adrenal versus ov arian steroids) and possibly by differing anatomical and biochemical pathwa ys. The second set of findings is that training with hippocampal-dependent trace conditioning enhances the survival of newly generated neurons in the adult hippocampal formation. The same amount of training with hippocampal-i ndependent delay conditioning does not affect their survival. In addition, females acquire the trace task faster than males and generate more new neur ons. As with the stress effects on learning, these sex effects are influenc ed by hormonal status. It is our contention that identifying the hormonal a nd neuronal processes that modulate associative memory formation will provi de insight into the processes of memory formation itself. (C) 2000 Elsevier Science B.V. All rights reserved.