Long latency auditory evoked responses in ovulatory and anovulatory menstrual cycle

Central nervous system pathways get influenced by the changing hormonal levels across the menstrual cycle. In an effort to see the effects on the conduction in central auditory pathways we recorded long latency auditory evoked potentials (LLAEPs) across the 4 different phases of the menstrual cycle. 20 females having normal ovulatory menstrual cycles were tested 4 times in a single cycle and LLAEPs were recorded from Cz-A1 and Cz-A2 position with alternating 90 dB sound pressure click stimuli. Twenty age matched control females having anovulatory menstrual cycles were also tested on the corresponding days. All control females were taking oral contraceptive (O.C.) pills. The LLAEPs were compared inter-group wise as well as inter-phase wise for each parameter by using hierarchal ANOVA design and Tukey test was applied to find out the significance level. Peak latencies of waves P2 and N2 were found to be delayed during mid-cycle and relatively reduced mid-luteal phase in ovulatory menstrual cycles. No such response was noticed in oral contraceptive using group. This indicates that normal cyclic variations of female sex hormones especially estrogen and progesterone modify the central processing of the auditory information. Estrogen may be responsible for delaying the conduction by influencing GABA release at the level of polysensory association areas of the brain.