Atypical language lateralization in positive schizotypy and modulating effects of the menstrual cycle

Previous studies have shown atypical language asymmetry in male participants with high schizotypy traits, but in female participants the pattern is less clear. Such sex differences could suggest a role of sex hormones, especially since hemispheric asymmetries have been shown to change across the menstrual cycle. By modulating attention in a consonant-vowel dichotic listening test, the current study aimed to investigate language lateralization (ear advantage of non-forced condition) in high vs low positive-schizotypy and the role of the menstrual cycle. In addition, we aimed to replicate menstrual cycle effects on the left attention condition. Thirty-nine female participants were tested in the menstrual (low estradiol) or follicular (high estradiol) cycle phase. Women tested in the follicular phase were found to perform better on the left attention condition, indicating enhanced cognitive control. In the non-forced condition, the high positive-schizotypy group showed increased right hemispheric involvement during the follicular phase relative to the menstrual phase; whereas an increase in left hemispheric dominance was seen in the low positive-schizotypy group during this cycle phase. The results suggest an underlying difference in lateralization between low and high positive-schizotypy that is enhanced by gonadal hormones, perhaps through altered interhemispheric inhibition. Overall, the study suggests that the atypical language lateralization in high schizotypy individuals is highly flexible and dependent on the hormonal milieu, and could potentially be related to neuroprotective effects of estradiol.