Steroids, learning and memory

Steroid hormones initiate and coordinate a wide variety of functions vital to the survival and procreation of organisms. Gonadal steroids, such as estrogens, progestins, and androgens, maintain the structures and control the events necessary for successful reproduction. Adrenal steroids, such as corticosterone and cortisol, regulate daily physiological functions and sustain organisms through periods of stress. A common property of hormonal communication is the integration of activities supportive of a specific function by acting at target tissues throughout the body. Access of steroid hormones to almost every cell in the body via the circulation affords these chemical messengers the opportunity to influence a broad range of cellular functions. Evidence now exists that steroid hormones released by the gonads and adrenals contribute to the modulation of processes beyond their traditional roles in reproduction and stress. This chapter examines the hypothesis that steroid hormones influence the neural systems that allow organisms to learn and remember new information. Although a wealth of published findings supports this hypothesis, the effects of steroid hormones on learning and memory have proven to be complex, varying with task, sex, age, and steroid. However, as neuroscientists navigate the labyrinth of steroids and cognition, the therapeutic implications continue to tantalize the biomedical community. The potential of gonadal steroids to preserve cognitive functions challenged by age, disease, or trauma remains controversial but promising. Meanwhile, new treatments to mitigate the debilitating effects of overexposure to adrenal steroids offer hope in the management of various stress disorders. In this chapter, we review the course of contemporary research with special emphasis on the nonhuman models that are allowing neuroscientists to explore the phenomenon of steroid modulation of cognition and decipher the mechanisms underlying steroid action.