Vol 4 n° 2 - Cerebral aspects of reproductive endocrinology
Past issues Contributors How to publish Contributions and comments Home
 
It has become increasingly clear that males and females differ even more dramatically than we previously thought. Not only do they exhibit differing responses to stress and environmental experience, but they can also respond in opposite directions. In rats, it has been shown that expo- sure to an acute stressful event can enhance subsequent learning in males while dramatically impairing learning in females. These opposite effects of stress on memory for- mation are accompanied by similarly opposite effects on neuroanatomical measures, such as dendritic spines in the hippocampal formation. Moreover, these opposite effects of  stress  are  mediated  by  different  hormonal  systems between the sexes. These unique responses to stressful experience in male versus female rats may be used to model sex differences in mental illness, such as those that exist for depression and posttraumatic stress disorder. Dialogues Clin Neurosci. 2002;4:139-147. t is obvious that there are many differences between the sexes, and our external differences only mask those beneath. However, for various reasons, some cultural,  it  is  often  assumed  that  male  and  female response systems differ only as a matter of degree and not of direction. Indeed, it is often assumed that differ- ences in our experiences or response to external events stem from differences in habits or belief systems that are malleable and could change by adopting a perspective more like the other sex. In this review, I will present data from a series of studies that indicate that males and females not only differ in the degree of their response, but often in direction too.To illustrate this phenomenon, I will focus on behavioral and neuronal responses to stressful experience and learning opportunities. These examples arise from studies conducted in the white albi- no laboratory rat.This approach eliminates some of the cultural  and  sociological  considerations  inherent  to many discussions about sex differences in behavior. In addition to behavioral measures, I will present data indi- cating that anatomical measures of plasticity in the male and female brain can respond in opposite directions to the same environmental event. These behavioral and neuronal differences are dependent on the presence of sex and stress hormones, but differing ones for males versus females. Finally, I will discuss how these sexually dimorphic and diergic responses to life experience may be used to model sex differences in mental disorders, such as depression and posttraumatic stress disorder. Sex differences in learning and memory There are numerous reports of sex differences in basic learning processes.1,2 However, they vary greatly depend- ing on the task used and species involved. In general, men tend to outperform women on tasks that require mental and spatial rotation, whereas women tend to B a s i c   r e s e a r c h 1 3 9 Opposite effects of stressful experience on memory formation in males versus females Tracey J. Shors, PhD I Keywords: stress; memory formation; gender; depression; posttraumatic stress disorder

Author affiliations: Department of Psychology, Center for Collaborative Neuroscience, Rutgers University, Piscataway, NJ, USA

Address for correspondence: Tracey J. Shors, PhD, Department of Psychology, Center for Collaborative Neuroscience, 152 Frelinghuysen Road, Rutgers University, Piscataway, NJ 08854-8020, USA (e-mail: shors@rci.rutgers.edu