This chapter focuses on the impact of the stress-related adrenal hormones, epinephrine and corticosterone, and the reproduction-related ovarian hormones, estrogen and progesterone on learning and memory. Epinephrine enhances learning and memory in a wide range of tasks, including avoidance, extinction of avoidance, and spatial memory tasks. Some of the recent works indicate that adrenal steroids, particularly corticosterone, have potent effects on learning and memory. Like injections of epinephrine, injections of corticosterone enhance memory for a wide range of tasks, e.g., inhibitory avoidance, fear conditioning, and object recognition. Estrogen has potent effects on the structure and functioning of the adult brain. The direction of estrogen action on learning and memory depends on several variables: stress levels, type and duration of hormone regimen, and specific task and memory demands. Present literature validates that estradiol, the most potent naturally found estrogen in mammals, modulates memory formation and maintenance; and biases the learning strategy used to solve a task by altering the relative participation of different neural systems during task performance. There are also consistent findings present showing that progesterone has dramatic effects on brain function and behavior, particularly related to anxiety and fear. The effects of progesterone on cognition are dependent on factors such as the timing of treatments and testing paradigms. The chapter also describes evidence that both stress hormones and reproductive hormones have robust and reliable effects on learning and memory. There are several features of this finding: broad cognitive effects, timing, peripheral and central effects, and molecular and cellular bases,.
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