Effects of Early Life Adversities upon Memory Processes and Cognition in Rodent Models

Exposure to stressors in early postnatal life induces long-lasting modifications in brain function. This plasticity, an essential characteristic of the brain that enables adaptation to the environment, may also induce impairments in some psychophysiological functions, including learning and memory. Early life stress (ELS) has long-term effects on the hypothalamic-pituitary-adrenal axis response to stressors, and has been reported to lead to neuroinflammation, altered levels of neurotrophic factors, modifications in neurogenesis and synaptic plasticity, with changes in neurotransmitter systems and network functioning. In this review, we focus on early postnatal stress in animal models and their effects on learning and memory. Many studies have reported ELS-induced impairments in different types of memories, including spatial memory, fear memory, recognition (both for objects and social) memory, working memory and reversal learning. Studies are not always in agreement, however, no effects, or sometimes facilitation, being reported, depending on the nature and intensity of the early intervention, as well as the age when the outcome was evaluated and the sex of the animals. When considering processes occurring after consolidation, related with memory maintenance/persistence or transformation, there are a very reduced number of reports. Future studies addressing the mechanisms underlying memory changes for ELS should shed some light on the understanding of the different effects induced by stressors of different types and intensities on cognitive functions.