Fluctuations in spatial recognition memory across the menstrual cycle in female rhesus monkeys

Findings are inconsistent regarding whether women's cognitive performance f luctuates across phases of the menstrual cycle, but differences in methodol ogy and the use of reported cycle phase rather than precise hormonal measur es may underlie these disparities. Studies in monkeys may help resolve thes e discrepant findings, since hormonal status can be reliably determined. We tested four young (5-7 years old) female rhesus monkeys daily during one e ntire menstrual cycle on three cognitive tasks displayed on a computerized touch-screen system: a Matching to Sample task with a 30 s delay (MTS-30s), a Matching to Sample task without delay (MTS-no delay) and the spatial con dition of the Delayed Recognition Span Test (spatial-DRST). Blood samples w ere collected at specific time intervals throughout the cycle and assayed f or estradiol and progesterone in order to identify hormonal status. There w as a nonsignificant trend for the MTS-30s scores to be better during the fo llicular and luteal phases, when estradiol levels were low, than during the peri-ovulatory phase, when estradiol levels were at their highest. MTS-no delay performance did not vary as a function of hormonal status. Spatial-DR ST scores were significantly better during the follicular and luteal phases than during the peri-ovulatory phase of the cycle. These data in the femal e rhesus monkey support the hypothesis that spatial memory performance is s ensitive to estradiol variations across the menstrual cycle, with better pe rformance associated with low estradiol levels. (C) 2001 Elsevier Science L td. All rights reserved.