RESUMO
Transcranial electrical stimulation (tES) during sleep has been shown to successfully modulate memory consolidation. Here, we tested the effect of short duration repetitive tES (SDR-tES) during a daytime nap on the consolidation of declarative memory of facts in healthy individuals. We use a previously described approach to deliver the stimulation at regular intervals during non-rapid eye movement (NREM) sleep, specifically stage NREM2 and NREM3. Similar to previous studies using tES, we find enhanced memory performance compared to sham both after sleep and 48 h later. We also observed an increase in the proportion of time spent in NREM3 sleep and SDR-tES boosted the overall rate of slow oscillations (SOs) during NREM2/NREM3 sleep. Retrospective investigation of brain activity immediately preceding stimulation suggests that increases in the SO rate are more likely when stimulation is delivered during quiescent and asynchronous periods of activity in contrast to other closed-loop approaches which target phasic stimulation during ongoing SOs.
RESUMO
Sounds associated with newly learned information that are replayed during non-rapid eye movement (NREM) sleep can improve recall in simple tasks. The mechanism for this improvement is presumed to be reactivation of the newly learned memory during sleep when consolidation takes place. We have developed an EEG-based closed-loop system to precisely deliver sensory stimulation at the time of down-state to up-state transitions during NREM sleep. Here, we demonstrate that applying this technology to participants performing a realistic navigation task in virtual reality results in a significant improvement in navigation efficiency after sleep that is accompanied by increases in the spectral power especially in the fast (12-15 Hz) sleep spindle band. Our results show promise for the application of sleep-based interventions to drive improvement in real-world tasks.
RESUMO
Although the snow leopard (Uncia uncia) is a common endangered felid species in zoos, little is known about the complex endocrine interactions controlling ovarian function and conception in this species. The goal of this work was to characterize ovarian activity throughout the estrous cycle, nonpregnant luteal phase (pseudopregnancy), and gestation in female snow leopards. This goal was accomplished using an enzyme immunoassay to measure fecal concentrations of estrogen metabolites (E) and progesterone metabolites (P). Fecal samples were collected from 12 female snow leopards (ages 18 months to 18 years) during one to three breeding seasons. In each breeding season, the majority of females (78%, 88%, and 100%, respectively) began to exhibit ovarian activity in December or January. The estrous cycle, defined by the first day of estrus (E ≥ 2 × basal concentration) to the first day of the subsequent estrus, was 12.7 ± 0.6 days (n = 145 cycles). Estrus lasted 4.3 ± 0.4 days with mean concentrations of fecal E during the follicular phase (1661 ± 139 ng/g feces) increasing 3.2-fold above basal concentrations (515 ± 32 ng/g feces). No spontaneous ovulations were observed in any of the cycling females. Nonpregnant luteal phases were observed in eight females that bred but did not become pregnant. The length of the nonpregnant luteal phase ranged from 11 to 72 days (45.7 ± 5.7 days; n = 10) with mean concentrations of fecal P during the luteal phase (12.46 ± 1.7 µg/g feces) increasing 6.2-fold above basal concentrations of P (2.01 ± 0.2 µg/g feces). Three of the females in the study became pregnant and gave birth after a gestation of 93 (n = 2) and 95 (n = 1) days. Fecal P concentrations during pregnancy increased to 11.64 ± 1.3 µg/g feces, or 5.8-fold above basal concentrations. The results of this study provide a comprehensive characterization of reproductive endocrinology in snow leopards, and confirm that fecal hormone monitoring is an effective way to monitor female snow leopards throughout the breeding season.
