Central conduction time in auditory brainstem response and ear advantage in dichotic listening across menstrual cycle

Abstract

The ovarian hormones fluctuate during the menstrual cycle in women. Such fluctuation of sex hormones, in particular estrogen, is believed to affect the central conduction time in auditory function as well as the language lateralization in cognitive function. However, findings are inconsistent. The underlying mechanisms are also unclear. This paper examined if there was any relation between the central conduction time and the language lateralization at different times during the menstrual cycle. Twenty young women with normal menstrual cycle were tested four times (5 to 7 days apart) across the menstrual cycle. The test battery included the electrophysiological measurement of auditory evoked response in brainstem and the speech performance in dichotic listening with monosyllables as stimulus pairs. The dichotic listening task was conducted under the non-forced, forced-right and forced-left attention. The central conduction time was defined by the time elapsed between two auditory elicited responses along the auditory pathway. The language lateralization in dichotic listening was expressed in ear advantage, which was the right-ear score minus the left-ear score. The results showed that the effects of test time were significant on both the central conduction time and the ear advantage under the forced-left attention. Overall, the interaural difference in the central conduction time correlates with the ear advantage (non-forced attention) at the beginning of the menstrual cycle. The change in central conduction time between two test times correlates significantly with the change in ear advantage under the non-forced and forced-left attention. Conclusively, the central conduction time depends on the time during the menstrual cycle, which in turn may affect the performance in dichotic listening.

The effect of the menstrual cycle on dichotic listening

“…For example, Batta et al [18] reported significantly shorter latencies of auditory brainstem evoked responses when their participants were tested during the days of their menstrual cycles after ovulation. In contrast, Hu and Lau [14] reported longer latency times when their participants were tested during this same portion of the menstrual cycle.…”

“…They found a lower REA in dichotic listening responses for the forced left ear condition measured during the pre-ovulation portion of the menstrual cycle. This increase in lateralization toward the left side coincided with longer brainstem response latencies for peak V of the auditory signals [14]. In contrast, other researchers reported that higher levels of estradiol were associated with lower lateralization scores across all dichotic listening conditions [11, 13].…”

“…The cognitive control in the forced left ear condition has been stated as the participant providing an instruction-based rather than a stimulus-based response. In addition, researchers have used dichotic listening tasks to assess variations in the strength of REA across the hormonal changes that occur in the menstrual cycle [9, 11,12, 13, 14, 15].…”

“…The women in their studies exhibited lower REA scores during the days of menstrual flow and over the following week when ovarian hormones were at their lowest levels compared to scores collected during the days just preceding and just following ovulation. However, other researchers found that their participants exhibited no hormonally based changes across the menstrual cycle to open and forced right ear response dichotic listening tasks, but reductions in REA for a forced left ear response condition during the week before ovulation [9, 14]. The authors of these studies concluded that increased levels of ovarian hormones increased cognitive control, but did not affect selective attention or an open response condition.…”

“…Hu and Lau [14] recorded auditory brainstem responses at four times in the menstrual cycle and for the three dichotic listening conditions, open forced left ear response, and forced right ear response. They found a lower REA in dichotic listening responses for the forced left ear condition measured during the pre-ovulation portion of the menstrual cycle.…”