Stimulating the sleeping brain: Current approaches to modulating memory-related sleep physiology

Background: One of the most audacious proposals throughout the history of psychology was the potential ability to learn while we sleep. The idea penetrated culture via sci-fi movies and inspired the invention of devices that claimed to teach foreign languages, facts, and even quit smoking by simply listening to audiocassettes or other devices during sleep. However, the promises from this endeavor didn't stand up to experimental scrutiny, and the dream was shunned from the scientific community. Despite the historic evidence that the sleeping brain cannot learn new complex information (i.e., words, images, facts), a new wave of current interventions are demonstrating that sleep can be manipulated to strengthen recent memories. New method: Several recent approaches have been developed that play with the sleeping brain in order to modify ongoing memory processing. Here, we provide an overview of the available techniques to non-invasively modulate memory-related sleep physiology, including sensory, vestibular and electrical stimulation, as well as pharmacological approaches. Results: N/A. Comparison with existing methods: N/A. Conclusions: Although the results are encouraging, suggesting that in general the sleeping brain may be optimized for better memory performance, the road to bring these techniques in free-living conditions is paved with unanswered questions and technical challenges that need to be carefully addressed

Quantifying sleep architecture dynamics and individual differences using big data and Bayesian networks

The pattern of sleep stages across a night (sleep architecture) is influenced by biological, behavioral, and clinical variables. However, traditional measures of sleep architecture such as stage proportions, fail to capture sleep dynamics. Here we quantify the impact of individual differences on the dynamics of sleep architecture and determine which factors or set of factors best predict the next sleep stage from current stage information. We investigated the influence of age, sex, body mass index, time of day, and sleep time on static (e.g. minutes in stage, sleep efficiency) and dynamic measures of sleep architecture (e.g. transition probabilities and stage duration distributions) using a large dataset of 3202 nights from a non-clinical population. Multi-level regressions show that sex effects duration of all Non-Rapid Eye Movement (NREM) stages, and age has a curvilinear relationship for Wake After Sleep Onset (WASO) and slow wave sleep (SWS) minutes. Bayesian network modeling reveals sleep architecture depends on time of day, total sleep time, age and sex, but not BMI. Older adults, and particularly males, have shorter bouts (more fragmentation) of Stage 2, SWS, and they transition less frequently to these stages. Additionally, we showed that the next sleep stage and its duration can be optimally predicted by the prior 2 stages and age. Our results demonstrate the potential benefit of big data and Bayesian network approaches in quantifying static and dynamic architecture of normal sleep

Closed-Loop Targeted Memory Reactivation during Sleep Improves Spatial Navigation

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\u201315 Hz) sleep spindle band. Our results show promise for the application of sleep-based interventions to drive improvement in real-world tasks

ET-1 plasma levels, choroidal thickness and multifocal electroretinogram in retinitis pigmentosa

Aim To assess the relationship between both photoreceptor function and choroidal thickness and endothelin-1 (ET-1) plasma levels in patients with early stage retinitis pigmentosa (RP). Main methods We compared 24 RP patients (14 males and 10 females), 25 to 42 years of age (mean age: 34 ± 7 years) with 24 healthy controls (12 males and 12 females) aged between 28 and 45 years (mean 36 ± 6.8 years). All patients underwent visual field test, electroretinogram and multifocal-electroretinogram and choroidal thickness measurement by using spectral domain optical coherence tomography. Key findings RP patients had a visual acuity of 0.95, a mean defect of the visual field of − 7.90 ± 1.75 dB, a pattern standard deviation index of 6.09 ± 4.22 dB and a b-wave ERG amplitude of 45.08 ± 8.24 μV. Notably RP subjects showed significantly increased ET-1 plasma levels and reduced choroidal thickness compared with controls: respectively, 2.143 ± 0.258 pg/ml vs. 1.219 ± 0.236 pg/ml; p < 0.002 and 226.75 ± 76.37 μm vs. 303.9 ± 39.87 μm; p < 0.03. Spearman's correlation test highlighted that the increase of ET-1 plasma levels was related with the decrease of choroidal thickness (r = − 0.702; p < 0.023) and the increase of implicit time in both ring 2 (r = − 0.669; p < 0.034) and ring 3 (r = − 0.883; p < 0.007) of mfERG. Significance Increased ET-1 plasma levels may play a key role in the impairment of retinal and choroidal blood flow due to the vasoconstriction induced by ET-1. This could lead to worsening of the abiotrophic process of the macular photoreceptors

Interest payment on government debt and public spending in Italy: An empirical analysis

This article investigates how the public expenditure structure, and the expenditures in specific fields of the public sector, are affected by the dynamics of interest payment on public debt, in the case of Italy. Italy has the third largest public debt in the world, and interest payments are of considerable size; though not steadily, however, their dynamics has been decreasing over the last two decades. This could have represented an opportunity for restructuring public expenditure. However, our results show that there is no effect of the dynamics of interest payments upon the dynamics of primary public expenditure. The result is based on the analysis of both Granger-causality links and simultaneous relations between interest payments and primary public expenditure. Public expenditure is considered in aggregate terms in current and capital account, and as articulated in a number of specific areas

Interest payment on government debt and public spending in Italy: An empirical analysis

This article investigates how the public expenditure structure, and the expenditures in specific fields of the public sector, are affected by the dynamics of interest payment on public debt, in the case of Italy. Italy has the third largest public debt in the world, and interest payments are of considerable size; though not steadily, however, their dynamics has been decreasing over the last two decades. This could have represented an opportunity for restructuring public expenditure. However, our results show that there is no effect of the dynamics of interest payments upon the dynamics of primary public expenditure. The result is based on the analysis of both Granger-causality links and simultaneous relations between interest payments and primary public expenditure. Public expenditure is considered in aggregate terms in current and capital account, and as articulated in a number of specific areas

Interest payment on government debt and public spending in Italy: An empirical analysis

This article investigates how the public expenditure structure, and the expenditures in specific fields of the public sector, are affected by the dynamics of interest payment on public debt, in the case of Italy. Italy has the third largest public debt in the world, and interest payments are of considerable size; though not steadily, however, their dynamics has been decreasing over the last two decades. This could have represented an opportunity for restructuring public expenditure. However, our results show that there is no effect of the dynamics of interest payments upon the dynamics of primary public expenditure. The result is based on the analysis of both Granger-causality links and simultaneous relations between interest payments and primary public expenditure. Public expenditure is considered in aggregate terms in current and capital account, and as articulated in a number of specific areas