Sex, estrogen and working memory : the effects of sex-related differences and estrogen suppression on neuropsychological test performance

Abstract

This body of research investigates the effects of sex and estrogen on higher brain functions, in general, and on working memory, in particular. A female advantage for object-location and verbal working memory has been reported, and estrogen supplementation facilitates performance of the same. Less is known about whether the female advantage is due to the verbalizability of the stimuli, and whether estrogen-suppression adversely affects performance on working memory and other neuropsychological domains sensitive to estrogen. Study 1 examined sex-related differences in young adults on an object-location working memory measure that varied in verbalizability of stimuli and task presentation (i.e., manual or computer); as expected, females performed better than males regardless of the verbalizability of the stimuli or task presentation. Study 2 examined sex-related differences in young adults on the n-back working memory task across verbal, spatial, and object conditions. Contrary to the hypotheses, there was no sex effect for the verbal version of the n-back task, and males actually performed better than females on the object version; as expected, males performed better than females on the spatial version. Study 3 investigated the effect of estrogen suppression in middle-aged and older adult females undergoing treatment for estrogenic breast cancer using the experimental working memory measures from Studies 1 and 2, and a comprehensive neuropsychological battery that included measures considered to be either sensitive (e.g., letter fluency) or insensitive (e.g., spatial ability) to the female advantage and the effects of estrogen. The estrogen suppression group performed more poorly than healthy age-matched controls on certain estrogen-sensitive measures (i.e., speeded visuomotor attention, speeded manual dexterity, and letter fluency), but unexpectedly, the groups did not differ on any of the memory measures presumed to be estrogen-sensitive. This body of research suggests that although certain working memory measures are sensitive to sex effects, the direction depends on the domain, and that estrogen suppression does not impact working memory in postmenopausal women but does adversely impact speeded performance measures.