Hemispheric specialization varies with EEG brain resting states and phase of menstrual cycle

Abstract

A growing body of behavioral studies has demonstrated that women's hemispheric specialization varies as a function of their menstrual cycle, with hemispheric specialization enhanced during their menstruation period. Our recent high-density electroencephalogram (EEG) study with lateralized emotional versus neutral words extended these behavioral results by showing that hemispheric specialization in men, but not in women under birth-control, depends upon specific EEG resting brain states at stimulus arrival, suggesting that hemispheric specialization may be pre-determined at the moment of the stimulus onset. To investigate whether EEG brain resting state for hemispheric specialization could vary as a function of the menstrual phase, we tested 12 right-handed healthy women over different phases of their menstrual cycle combining high-density EEG recordings and the same lateralized lexical decision paradigm with emotional versus neutral words. Results showed the presence of specific EEG resting brain states, associated with hemispheric specialization for emotional words, at the moment of the stimulus onset during the menstruation period only. These results suggest that the pre-stimulus EEG pattern influencing hemispheric specialization is modulated by the hormonal state.

Figure 1. Mean emotional word advantage (EWA) index scores for correct lexical decisions after word presentation to the right visual field (RVF) and left visual field (LVF).

Positive values indicate an emotional word advantage and negative values a neutral word (NWA) advantage. Index scores are displayed for two phases of the menstrual cycle (MENSTRUATION; and EARLY LUTEAL PHASE). Asterisks indicate significant group differences and vertical bars indicate standard errors. *p values <.05.

Figure 2. Mean emotional word advantage (EWA) index scores for correct lexical decisions after word presentation to the right visual field (RVF) and left visual field (LVF) across the different phases of the menstrual cycle.

Figure 3. The 13 maps determined from the spatial cluster analysis.

Shown in the upper row are the six functional brain state maps with a left anterior-right posterior (LA-RP) orientation of the extrema and in the lower row those with a right anterior-left posterior (RA-LP) orientation.

Figure 4. Functional brain state classes as a function of the period of the menstrual cycle.

Index scores are displayed for two phases of the menstrual cycle (MENSTRUATION, A; and EARLY LUTEAL PHASE, B) and two classes of FBS (LA-RP, the so-called LA, and RA-LP, the so-called RA) separately. Positive values indicate an emotional word advantage (EWA) and negative values a neutral word (NWA) advantage. Asterisks indicate significant group differences and vertical bars indicate standard errors. *p values <.05, **p values <.01.