• P300;
  • Late Positive Component;
  • Menstrual cycle;
  • Sex hormones;
  • Event-related potential repetition effect;
  • Recognition memory


Event-related potentials (ERPs) were compared between the menses and ovulatory phase of the menstrual cycle in response to visually presented words, some of which were repeated as part of direct and indirect memory tasks. Twelve spontaneously cycling women were tested during the menses and ovulatory phases. For the direct task, participants had to discriminate between new words and those repeated after a mean of six trials. In the indirect task, subjects were required to discriminate between target and nontarget words. Some of the nontarget words were repeated after a mean of six trials. The ERP repetition effect mean amplitude was significantly greater in response to repeated words at both cycle phases but did not differ across the cycle. P300 amplitude was significantly greater during menses than the ovulatory phase. We conclude that context updating mechanisms as indexed by the P300 are sensitive to cyclic hormonal fluctuations.