Changes with the menstrual cycle in psychophysiological and self-report measures of activation.

This study investigated changes in levels of central autonomic nervous system activity, using objective and self-report measures at two hormonally contrasting phases of the menstrual cycle. The subjects were 36 women who were divided into two groups, one tested in the premenstrual phase and one in the intermenstrual phase. The findings, which would need further confirmation, suggest that the levels of activation in both the central nervous system and in the autonomic nervous system are different in the two phases. Also, the two systems appear to vary independently of each other within the cycle. Cortical levels of activation are higher intermenstrually than premenstrually; autonomic levels are higher premenstrually than intermenstrually. The objective and self-report measures were in agreement both as regards the premenstrual/intermenstrual differences in activation levels, and as regards the central/autonomic differentiation. Further clarification of nervous system activity at the different hormonal phases of the cycle may contribute to an understanding of the relationships between endocrine, physical, psychological and behavioural variables through the menstrual cycle.