Highlights d Presenting odors to one nostril in sleep achieves local TMR in one brain hemisphere d Local TMR selectively improves hemisphere-related memories for specific words d Local TMR differentially modulates slow-wave and spindle power across hemispheres

Memory consolidation can be promoted via Targeted Memory Reactivation (TMR)that re-presents training cues or context during sleep. Whether TMR acts locally or globally on cortical sleep oscillations remains unknown. Here we exploit the unique functional neuroanatomy of olfaction with its ipsilateral stimulus processing to perform local TMR in one brain hemisphere. Participants learned associations between words and locations in left or right visual fields with contextual odor throughout. During post-learning naps, odors were presented to one nostril throughout NREM sleep. We found improved memory for specific words processed in the cued hemisphere (ipsilateral to stimulated nostril). Unilateral odor cues locally modulated slow wave activity (SWA) such that regional SWA increase in the cued hemisphere negatively correlated with select memories for cued words.Moreover, local TMR improved slow wave-spindle coupling specifically in the cued hemisphere. Thus, TMR in human sleep transcends global action by selectively promoting specific memories associated with local sleep oscillations.

Introduction Women’s olfactory perception varies across the menstrual cycle. The influence of oral contraceptives on this variability remains unclear. Methods To further estimate this, we assessed discrimination performance for both body odors and ordinary odorants in 36 women, 18 naturally ovulating, and 18 using oral contraceptives. Each participant was tested once a week over the course of a month, and data was then parsed into menstrual phases. Results In naturally ovulating women, at the transition from follicular to luteal phases, there was a decline of 19% ( p = 0.003) in olfactory discrimination of body odors but not ordinary odorants. In turn, in women using oral contraceptives, only at a later time of the month, at a point corresponding to the late luteal phase and shift from post-ovulation to pre-menstruation, was there a decline of 20% ( p = 0.002) in olfactory discrimination performance. Moreover, when we reorganized the data from women using oral contraceptives in order to separately assess the contraceptive withdrawal period (the few days off pills), we observed a 23% reduction ( p = 0.01) in discrimination accuracy of body odors but not ordinary odorants during this time alone. Conclusions Women have reduced ability to discriminate body odors during the withdrawal period of oral contraception. Implications If women indeed consider men’s body odor in their mate selections, then the oral contraception withdrawal period may not be the best time to make such decisions.