scholarly journals Human spindle variability

2021 ◽  
Author(s):  
Christopher E Gonzalez ◽  
Xi Jiang ◽  
Jorge Gonzalez-Martinez ◽  
Eric Halgren
Keyword(s):  
Synaptic Plasticity ◽  
Memory Consolidation ◽  
Sleep Spindles ◽  
Large Dataset ◽  
Posterior Cortex ◽  
Slow Oscillations ◽  
Mean Frequency ◽  
Multiple Dimensions ◽  
The Difference

In humans, sleep spindles are 10-16 Hz oscillations lasting approximately 0.5-2 s. Spindles, along with cortical slow oscillations, facilitate memory consolidation by enabling synaptic plasticity. Early recordings of spindles at the scalp found anterior channels had overall slower frequency than central-posterior channels. This robust, topographical finding led to dichotomizing spindles as slow versus fast, modeled as two distinct spindle generators in frontal versus posterior cortex. Using a large dataset of intracranial sEEG recordings (n=20, 365 bipolar recordings), we show that the difference in spindle frequency between frontal and parietal channels is comparable to the variability in spindle frequency within the course of individual spindles, across different spindles recorded by a given site, and across sites within a given region. Thus, fast and slow spindles only capture average differences that obscure a much larger underlying overlap in frequency. Furthermore, differences in mean frequency are only one of several ways that spindles differ. For example, compared to parietal, frontal spindles are smaller, tend to occur after parietal when both are engaged, and show a larger decrease in frequency within-spindles. However, frontal and parietal spindles are similar in being longer, less variable, and more widespread than occipital, temporal, and Rolandic spindles. These characteristics are accentuated in spindles which are highly phase-locked to posterior hippocampal spindles. We propose that rather than a strict parietal-fast/frontal-slow dichotomy, spindles differ continuously and quasi-independently in multiple dimensions, with variability due about equally to within-spindle, within-region and between-region factors.

scholarly journals Shining a Light on the Mechanisms of Sleep for Memory Consolidation

2021 ◽  
Author(s):  
Michelle A. Frazer ◽  
Yesenia Cabrera ◽  
Rockelle S. Guthrie ◽  
Gina R. Poe
Keyword(s):  
Rem Sleep ◽  
Neural Activity ◽  
Memory Consolidation ◽  
Strong Support ◽  
Nrem Sleep ◽  
Future Research ◽  
Sleep Spindles ◽  
Slow Oscillations ◽  
Theta Waves ◽  
Learning Tasks

Abstract Purpose of review This paper reviews all optogenetic studies that directly test various sleep states, traits, and circuit-level activity profiles for the consolidation of different learning tasks. Recent findings Inhibiting or exciting neurons involved either in the production of sleep states or in the encoding and consolidation of memories reveals sleep states and traits that are essential for memory. REM sleep, NREM sleep, and the N2 transition to REM (characterized by sleep spindles) are integral to memory consolidation. Neural activity during sharp-wave ripples, slow oscillations, theta waves, and spindles are the mediators of this process. Summary These studies lend strong support to the hypothesis that sleep is essential to the consolidation of memories from the hippocampus and the consolidation of motor learning which does not necessarily involve the hippocampus. Future research can further probe the types of memory dependent on sleep-related traits and on the neurotransmitters and neuromodulators required.

scholarly journals Selection of stimulus parameters for enhancing slow wave sleep events with a Neural-field theory thalamocortical computational model

2021 ◽  
Author(s):  
Felipe A. Torres ◽  
Patricio Orio ◽  
María-José Escobar
Keyword(s):  
Computational Model ◽  
Slow Wave ◽  
Memory Consolidation ◽  
Closed Loop ◽  
Slow Wave Sleep ◽  
Brain Activity ◽  
Sensory Stimulation ◽  
Sleep Spindles ◽  
Slow Oscillations ◽  
Closed Loop Stimulation

AbstractSlow-wave sleep cortical brain activity, conformed by slow-oscillations and sleep spindles, plays a key role in memory consolidation. The increase of the power of the slow-wave events, obtained by auditory sensory stimulation, positively correlates to memory consolidation performance. However, little is known about the experimental protocol maximizing this effect, which could be induced by the power of slow-oscillation, the number of sleep spindles, or the timing of both events’ co-occurrence. Using a mean-field model of thalamocortical activity, we studied the effect of several stimulation protocols, varying the pulse shape, duration, amplitude, and frequency, as well as a target-phase using a closed-loop approach. We evaluated the effect of these parameters on slow-oscillations (SO) and sleep-spindles (SP), considering: (i) the power at the frequency bands of interest, (ii) the number of SO and SP, (iii) co-occurrences between SO and SP, and (iv) synchronization of SP with the up-peak of the SO. The first three targets are maximized using a decreasing ramp pulse with a pulse duration of 50 ms. Also, we observed a reduction in the number of SO when increasing the stimulus energy by rising its amplitude. To assess the target-phase parameter, we applied closed-loop stimulation at 0º, 45º, and 90º of the phase of the narrow-band filtered ongoing activity, at 0.85 Hz as central frequency. The 0º stimulation produces better results in the power and number of SO and SP than the rhythmic or aleatory stimulation. On the other hand, stimulating at 45º or 90º change the timing distribution of spindles centers but with fewer co-occurrences than rhythmic and 0º phase. Finally, we propose the application of closed-loop stimulation at the rising zero-cross point using pulses with a decreasing ramp shape and 50 ms of duration for future experimental work.Author summaryDuring the non-REM (NREM) phase of sleep, events that are known as slow oscillations (SO) and spindles (SP) can be detected by EEG. These events have been associated with the consolidation of declarative memories and learning. Thus, there is an ongoing interest in promoting them during sleep by non-invasive manipulations such as sensory stimulation. In this paper, we used a computational model of brain activity that generates SO and SP, to investigate which type of sensory stimulus –shape, amplitude, duration, periodicity– would be optimal for increasing the events’ frequency and their co-occurrence. We found that a decreasing ramp of 50 ms duration is the most effective. The effectiveness increases when the stimulus pulse is delivered in a closed-loop configuration triggering the pulse at a target phase of the ongoing SO activity. A desirable secondary effect is to promote SPs at the rising phase of the SO oscillation.

scholarly journals Susceptibility to auditory closed-loop stimulation of sleep slow oscillations changes with age

SLEEP ◽  
2020 ◽  
Vol 43 (12) ◽  
Author(s):  
Jules Schneider ◽  
Penelope A Lewis ◽  
Dominik Koester ◽  
Jan Born ◽  
Hong-Viet V Ngo
Keyword(s):  
Memory Consolidation ◽  
Closed Loop ◽  
Temporal Dynamics ◽  
Age Groups ◽  
Recognition Task ◽  
Auditory Stimulation ◽  
Sleep Spindles ◽  
Slow Oscillations ◽  
Up States ◽  
Closed Loop Stimulation

Abstract Study Objectives Cortical slow oscillations (SOs) and thalamocortical sleep spindles hallmark slow wave sleep and facilitate memory consolidation, both of which are reduced with age. Experiments utilizing auditory closed-loop stimulation to enhance these oscillations showed great potential in young and older subjects. However, the magnitude of responses has yet to be compared between these age groups. We examined the possibility of enhancing SOs and performance on different memory tasks in a healthy middle-aged population using this stimulation and contrast effects to younger adults. Methods In a within-subject design, 17 subjects (55.7 ± 1.0 years) received auditory stimulation in synchrony with SO up-states, which was compared to a no-stimulation sham condition. Overnight memory consolidation was assessed for declarative word-pairs and procedural finger-tapping skill. Post-sleep encoding capabilities were tested with a picture recognition task. Electrophysiological effects of stimulation were compared to a previous younger cohort (n = 11, 24.2 ± 0.9 years). Results Overnight retention and post-sleep encoding performance of the older cohort revealed no beneficial effect of stimulation, which contrasts with the enhancing effect the same stimulation protocol had in our younger cohort. Auditory stimulation prolonged endogenous SO trains and induced sleep spindles phase-locked to SO up-states in the older population. However, responses were markedly reduced compared to younger subjects. Additionally, the temporal dynamics of stimulation effects on SOs and spindles differed between age groups. Conclusions Our findings suggest that the susceptibility to auditory stimulation during sleep drastically changes with age and reveal the difficulties of translating a functional protocol from younger to older populations.

scholarly journals Susceptibility to auditory closed-loop stimulation of sleep slow oscillations changes with age

2019 ◽  
Author(s):  
Jules Schneider ◽  
Penelope A. Lewis ◽  
Dominik Koester ◽  
Jan Born ◽  
Hong-Viet V. Ngo
Keyword(s):  
Memory Consolidation ◽  
Closed Loop ◽  
Age Groups ◽  
Auditory Stimulation ◽  
Sleep Spindles ◽  
Older Population ◽  
Slow Oscillations ◽  
Up States ◽  
Older Subjects ◽  
Closed Loop Stimulation

AbstractBackgroundCortical slow oscillations (SOs) and thalamo-cortical sleep spindles hallmark slow wave sleep and facilitate sleep-dependent memory consolidation. Experiments utilising auditory closed-loop stimulation to enhance these oscillations have shown great potential in young and older subjects. However, the magnitude of responses has yet to be compared between these age groups.ObjectiveWe examined the possibility of enhancing SOs and performance on different memory tasks in a healthy older population using auditory closed-loop stimulation and contrast effects to a young adult cohort.MethodsIn a within-subject design, subjects (n = 17, 55.7 ± 1.0 years, 9 female) received auditory click stimulation in synchrony with SO up-states, which was compared to a no-stimulation sham condition. Overnight memory consolidation was assessed for declarative word-pairs and procedural finger-tapping skill. Post-sleep encoding capabilities were tested with a picture recognition task. Electrophysiological effects of stimulation were compared to those reported previously in a younger cohort (n = 11, 24.2 ± 0.9 years, 8 female).ResultsOvernight retention and post-sleep encoding performance of the older cohort revealed no beneficial effect of stimulation, which contrasts with the enhancing effect the same stimulation protocol had in our younger cohort. Auditory stimulation prolonged endogenous SO trains and induced sleep spindles phase-locked to SO up-states in the older population. However, responses were markedly reduced compared to younger subjects. Additionally, the temporal dynamics of stimulation effects on SOs and spindles differed between age groups.ConclusionsOur findings suggest that the susceptibility to auditory stimulation during sleep drastically changes with age and reveal the difficulties of translating a functional protocol from younger to older populations.HighlightsAuditory closed-loop stimulation induced SOs and sleep spindles in older subjectsStimulation effects were reduced and overall susceptibility diminished with ageSlow oscillation and sleep spindle dynamics deviated from those in younger subjectsStimulation shows no evidence for memory effect in older subjects

scholarly journals Visuomotor adaptation modulates the clustering of sleep spindles into trains

2021 ◽  
Author(s):  
Agustin Solano ◽  
Luis A Riquelme ◽  
Daniel Perez-Chada ◽  
Valeria Della-Maggiore
Keyword(s):  
Memory Consolidation ◽  
Visuomotor Adaptation ◽  
Temporal Organization ◽  
Sleep Spindles ◽  
Memory Retention ◽  
Contralateral Hemisphere ◽  
Slow Oscillations ◽  
Organization Of Sleep ◽  
Train Length ◽  
Biological Advantage

Sleep spindles are thought to promote memory consolidation. Recently, we have shown that visuomotor adaptation (VMA) learning increases the density of spindles and promotes the coupling between spindles and slow oscillations, locally, with the level of spindle-SO synchrony predicting overnight memory retention. Yet, growing evidence suggests that the rhythmicity in spindle occurrence may also influence the stabilization of declarative and procedural memories. Here, we examined if VMA learning promotes the temporal organization of sleep spindles into trains. We found that VMA increased the proportion of spindles and spindle-SO couplings in trains. In agreement with our previous work, this modulation was observed over the contralateral hemisphere to the trained hand, and predicted overnight memory retention. Interestingly, spindles grouped in a cluster showed greater amplitude and duration than isolated spindles. The fact that these features increased as a function of train length, provides evidence supporting a biological advantage of this temporal arrangement. Our work opens the possibility that the periodicity of NREM oscillations may be relevant in the stabilization of procedural memories.

scholarly journals Differential roles of sleep spindles and sleep slow oscillations in memory consolidation

2017 ◽  
Author(s):  
Yina Wei ◽  
Giri P Krishnan ◽  
Maxim Komarov ◽  
Maxim Bazhenov
Keyword(s):  
Memory Consolidation ◽  
Testable Hypothesis ◽  
State Transitions ◽  
Sleep Stages ◽  
Sleep Spindles ◽  
Slow Oscillations ◽  
Natural Sleep ◽  
Sleep Rhythms ◽  
Spike Sequence

AbstractSleep plays an important role in consolidation of recent memories. However, the mechanisms of consolidation remain poorly understood. In this study, using a realistic computational model of the thalamocortical network, we demonstrated that sleep spindles (the hallmark of N2 stage sleep) and slow oscillations (the hallmark of N3 stage sleep) both facilitate spike sequence replay as necessary for consolidation. When multiple memories were trained, the local nature of spike sequence replay during spindles allowed replay of the memories independently, while during slow oscillations replay of the weak memory was competing to the strong memory replay. This led to the weak memory extinction unless when sleep spindles (N2 sleep) preceded slow oscillations (N3 sleep), as observed during natural sleep. Our study presents a mechanistic explanation for the role of sleep rhythms in memory consolidation and proposes a testable hypothesis how the natural structure of sleep stages provides an optimal environment to consolidate memories.Significant StatementNumerous studies suggest importance of NREM sleep rhythms – spindles and slow oscillations - in sleep related memory consolidation. However, synaptic mechanisms behind the role of these rhythms in memory and learning are still unknown. Our new study predicts that sleep replay - the neuronal substrate of memory consolidation - is organized within the sleep spindles and coordinated by the Down to Up state transitions of the slow oscillation. For multiple competing memories, slow oscillations facilitated only strongest memory replay, while sleep spindles allowed a consolidation of the multiple competing memories independently. Our study predicts how the basic structure of the natural sleep stages provides an optimal environment for consolidation of multiple memories.

scholarly journals Selection of stimulus parameters for enhancing slow wave sleep events with a neural-field theory thalamocortical model

2021 ◽  
Vol 17 (7) ◽  
pp. e1008758
Author(s):  
Felipe A. Torres ◽  
Patricio Orio ◽  
María-José Escobar
Keyword(s):  
Slow Wave ◽  
Memory Consolidation ◽  
Closed Loop ◽  
Slow Wave Sleep ◽  
Brain Activity ◽  
Sleep Spindles ◽  
Mean Field Model ◽  
Cross Point ◽  
Slow Oscillations ◽  
Closed Loop Stimulation

Slow-wave sleep cortical brain activity, conformed by slow-oscillations and sleep spindles, plays a key role in memory consolidation. The increase of the power of the slow-wave events, obtained by auditory sensory stimulation, positively correlates to memory consolidation performance. However, little is known about the experimental protocol maximizing this effect, which could be induced by the power of slow-oscillation, the number of sleep spindles, or the timing of both events’ co-occurrence. Using a mean-field model of thalamocortical activity, we studied the effect of several stimulation protocols, varying the pulse shape, duration, amplitude, and frequency, as well as a target-phase using a closed-loop approach. We evaluated the effect of these parameters on slow-oscillations (SO) and sleep-spindles (SP), considering: (i) the power at the frequency bands of interest, (ii) the number of SO and SP, (iii) co-occurrences between SO and SP, and (iv) synchronization of SP with the up-peak of the SO. The first three targets are maximized using a decreasing ramp pulse with a pulse duration of 50 ms. Also, we observed a reduction in the number of SO when increasing the stimulus energy by rising its amplitude. To assess the target-phase parameter, we applied closed-loop stimulation at 0°, 45°, and 90° of the phase of the narrow-band filtered ongoing activity, at 0.85 Hz as central frequency. The 0° stimulation produces better results in the power and number of SO and SP than the rhythmic or random stimulation. On the other hand, stimulating at 45° or 90° change the timing distribution of spindles centers but with fewer co-occurrences than rhythmic and 0° phase. Finally, we propose the application of closed-loop stimulation at the rising zero-cross point using pulses with a decreasing ramp shape and 50 ms of duration for future experimental work.

scholarly journals Differential roles of sleep spindles and sleep slow oscillations in memory consolidation

2018 ◽  
Vol 14 (7) ◽  
pp. e1006322 ◽  
Author(s):  
Yina Wei ◽  
Giri P. Krishnan ◽  
Maxim Komarov ◽  
Maxim Bazhenov
Keyword(s):  
Memory Consolidation ◽  
Sleep Spindles ◽  
Slow Oscillations

scholarly journals Sleep spindles facilitate selective memory consolidation

2020 ◽  
Author(s):  
Dan Denis ◽  
Dimitris Mylonas ◽  
Craig Poskanzer ◽  
Verda Bursal ◽  
Jessica D. Payne ◽  
...  
Keyword(s):  
Memory Consolidation ◽  
Slow Wave Sleep ◽  
Sleep Spindles ◽  
Slow Oscillations ◽  
Initial Strength ◽  
Long Term Storage ◽  
Cortical Oscillations ◽  
Memory Traces ◽  
New Evidence ◽  
The Brain

AbstractSleep has been shown to be critical for memory consolidation, and recent research has demonstrated that this consolidation effect is selective, with certain memories being prioritized for strengthening. Initial strength of a memory appears to be one metric the brain uses to prioritize memory traces for sleep-based consolidation, but the role of consolidation-mediating cortical oscillations, such as sleep spindles and slow oscillations, has not been explored. Here, N=54 participants studied pairs of words to three distinct encoding strengths, with recall being tested immediately following learning and again six hours later. N=36 had a two-hour afternoon nap opportunity following learning, whilst the remaining (n=18) remained awake throughout. Results showed a selective benefit of sleep on memory, with sleep preferentially consolidating weakly encoded items (p=.003). The magnitude of this effect (d=0.90, 95% CI=0.29-1.50) was similar when compared to a previous study examining the benefits of a full night of sleep (d=1.36, 95% CI=0.59-2.12). Within the nap group, consolidation of weakly encoded items was associated with sleep spindle density during slow wave sleep (r=.48, p=.003). This association was present when separately examining spindles coupled (r=.41, p=.013), and uncoupled (r=.44, p=.007) with slow oscillations. Memory was significantly better in individuals who showed an amount of slow oscillation-spindle coupling that was greater than what would be expected by chance (p=.006, d=1.15). These relationships were unique to weakly encoded items, with spindles not correlating with memory for intermediate or strong items. This suggests that sleep spindles facilitate selective memory consolidation, guided in part by memory strength.Significance statementGiven the countless pieces of information we encode each day, how does the brain select which memories to commit to long-term storage? Sleep is known to aid in memory consolidation, but less research has examined which memories are prioritized to receive this benefit. Here, we found that compared to staying awake, sleep was associated with better memory for weakly encoded information. This suggests sleep helps to rescue weak memory traces from being forgotten. Sleep spindles, a hallmark oscillation of non-rapid eye movement sleep, mediates consolidation processes. We extended this to show that spindles selectively facilitated consolidation of weakly encoded memories. This provides new evidence for the selective nature of sleep-based consolidation and elucidates a physiological correlate of this preferential benefit.

scholarly journals Electrophysiological Indicators of Sleep-associated Memory Consolidation in 5- to 6-year-old Children

2020 ◽  
Author(s):  
Ann-Kathrin Joechner ◽  
Sarah Wehmeier ◽  
Markus Werkle-Bergner
Keyword(s):  
Young Adults ◽  
School Children ◽  
Memory Consolidation ◽  
Declarative Memory ◽  
Slow Oscillation ◽  
Sleep Spindles ◽  
Sleep Spindle ◽  
Slow Oscillations ◽  
Slow Sleep ◽  
Temporal Coupling

ABSTRACTIn young adults, memory consolidation during sleep is supported by a time-coordinated interplay of sleep spindles and slow oscillations. However, given tremendous developmental changes in sleep spindle and slow oscillation morphology, it remains elusive whether the same mechanisms as identified in young adults are comparably functional across childhood. Here, we characterise slow and fast sleep spindles and their temporal coupling to slow oscillations in 24 pre-school children. Further, we ask whether slow and fast sleep spindles and their modulation during slow oscillations are similarly associated with behavioural indicators of declarative memory consolidation as suggested from adult literature. Employing a development-sensitive, individualised approach, we reliably identify an inherent, development-specific fast sleep spindle type, though nested in the adult-like slow sleep spindle frequency range, along with a dominant slow sleep spindle type. Further, we provide evidence for the modulation of fast sleep spindles during slow oscillations, already in pre-school children. However, the temporal coordination between fast sleep spindles and slow oscillations is weaker and less precise than expected from adult research. While we do not find evidence for a critical contribution of the pattern of fast sleep spindle modulation during slow oscillations for memory consolidation, crucially, both inherent slow and fast sleep spindles separately are differentially related to sleep-associated consolidation of items of varying quality. While a higher number of slow sleep spindles is associated with stronger maintenance of medium-quality memories, more fast sleep spindles are linked to higher gain of low-quality items. Our results provide evidence for two functionally relevant inherent sleep spindle types in pre-school children despite not fully matured sleep spindle – slow oscillation coupling.

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