The Menstrual Cycle, Caffeine, and Verbal Working Memory
Mount Saint Vincent University
Verbal working memory is a domain of cognition critical to educational success. It is influenced by caffeine, with moderate doses generally resulting in improvements as measured by behavioural performance, as well as electroencephalographic (EEG) and functional MRI (i.e. neural) measures. Verbal working memory performance is also known to vary with fluctuations in sex hormones (i.e. estrogen and progesterone) such as those seen across the menstrual cycle. Generally, when estrogen levels are higher, so is performance on working memory tasks. To the best of our knowledge, the interaction between the menstrual cycle, caffeine, and verbal working memory has not been examined, despite there being individual relations between these variables. Employing a double-blind, placebo-controlled design, the present study examined EEG-derived event-related potentials (ERPs) to assess the effects of 200mg of caffeine (vs. placebo) across the luteal and menstrual phases of the menstrual cycle. Specifically, 16 participants completed the verbal n-back task and their corresponding P300 waveforms were analyzed. Results showed an overall effect of menstrual phase, due to quicker reaction times in the luteal (vs. menstrual) phase; this was predominantly observed during the 3-back task. Caffeine only improved reaction time during the 3-back task for participants in the menstrual phase. Participants in the menstrual phase had a larger P300 amplitude in response to the 1-back, while participants in the luteal phase displayed a greater P300 latency in response to the 1-back. Collectively, results showed a task dependent relation between caffeine, verbal working memory, and phases of the menstrual cycle.
Verbal working memory, caffeine, menstruation,