Sleep spindles are waxing and waning thalamocortical oscillations with accepted frequencies of be... more Sleep spindles are waxing and waning thalamocortical oscillations with accepted frequencies of between 11 and 16 Hz and a minimum duration of 0.5 s. Our research has suggested that there is spindle activity in all of the sleep stages, and thus for the present analysis we examined the link between spindle activity (Stage 2, rapid eye movement (REM) and slow wave sleep (SWS)) and waking cognitive abilities in 32 healthy adolescents. After software was used to filter frequencies outside the desired range, slow spindles (11.00-13.50 Hz), fast spindles (13.51-16.00 Hz) and spindle-like activity (16.01-18.50 Hz) were observed in Stage 2, SWS and REM sleep. Our analysis suggests that these specific EEG frequencies were significantly related to processing speed, which is one of the subscales of the intelligence score, in adolescents. The relationship was prominent in SWS and REM sleep. Further, the spindle-like activity (16.01-18.50 Hz) that occurred during SWS was strongly related to proce...
The purpose of this study was to compare the changes that occur in sleep architecture following t... more The purpose of this study was to compare the changes that occur in sleep architecture following the acquisition of a simple motor learning task in young and older adults. Subjects included 14 young (range = 17–24 years) and 14 older (range = 62–79 years) adults, all of whom were in good health. Using in-home recording systems, sleep architecture (sleep stages and the density of Stage 2 sleep spindles) was examined before and after learning the pursuit rotor. To control for possible age differences in baseline motor performance and spindle density, both absolute and relative (percent change) measures were examined. Both groups improved significantly on the pursuit rotor task at Retest (1 week later); however, the magnitude of absolute improvement was larger in the young group than in the older group. There was no group difference when a relative measure of improvement (percent increase across sessions) was used. The density of Stage 2 sleep spindles increased significantly following task Acquisition in the young group but not in the older group. These age differences failed to reach significance when change was measured as a percentage of baseline level of spindle density. The increase in spindle density was correlated with performance level during acquisition in the young group but not the older group. The results of the present study are largely consistent with previous studies on sleep and memory in young adults and suggest that more detailed examination of this relationship in older adults is warranted.
Previous research has linked both rapid eye movement (REM) sleep and Stage 2 sleep to procedural ... more Previous research has linked both rapid eye movement (REM) sleep and Stage 2 sleep to procedural memory consolidation. The present study sought to clarify the relationship between sleep stages and procedural memory consolidation by examining the effect of initial skill level in this relationship in young adults. In-home sleep recordings were performed on participants before and after learning the pursuit rotor task. We divided the participants into low- and high-skill groups based on their initial performance of the pursuit rotor task. In high-skill participants, there was a significant increase in Stage 2 spindle density after learning, and there was a significant correlation between the spindle density that occurred after learning and pursuit rotor performance at retest 1 week later. In contrast, there was a significant correlation between changes in REM density and performance on the pursuit rotor task during retest 1 week later in low-skill participants, although the actual increase in REM density failed to reach significance in this group. The results of the present study suggest the presence of a double dissociation in the sleep-related processes that are involved in procedural memory consolidation in low- and high-skill individuals. These results indicate that the changes in sleep microarchitecture that take place after learning depend on the initial skill level of the individual and therefore provide validation for the model proposed by Smith et al. [Smith, C. T., Aubrey, J. B., & Peters, K. R. Different roles for REM and Stage 2 sleep in motor learning. Psychologica Belgica, 44, 79-102, 2004]. Accordingly, skill level is an important variable that needs to be considered in future research on sleep and memory consolidation.
... Despite my efforts to design ex-periments in a way that training and retention testing were n... more ... Despite my efforts to design ex-periments in a way that training and retention testing were not confounded by the pedestal procedure, it became clear that no matter what control experiment I did, I was never going to con-vince everyone. ... 1971; Shiromani et al. ...
The role of posttraining paradoxical sleep (PS) in spatial or nonspatial learning in the Morris w... more The role of posttraining paradoxical sleep (PS) in spatial or nonspatial learning in the Morris water maze was evaluated. Sprague-Dawley rats were given a 12-trial training session in either the hidden or the visible platform versions of the task. Subgroups then underwent paradoxical sleep deprivation (PSD) beginning at different times after training. Rats with PSD imposed from 1-4 hr after spatial training had poorer retest scores than any other group. Other rats, implanted with electrodes to permit continuous recording of sleep electroencephalography, were found to undergo a prolonged period of elevated PS after spatial training. By contrast, rats trained in the nonspatial version of the water maze task did not show retention deficits after PSD or elevated PS after training. These results support a role for PS in spatial, but not nonspatial, learning in the Morris water maze.
Until recently, the electrophysiological mechanisms involved in strengthening new memories into a... more Until recently, the electrophysiological mechanisms involved in strengthening new memories into a more permanent form during sleep have been largely unknown. The sleep spindle is an event in the electroencephalogram (EEG) characterizing Stage 2 sleep. Sleep spindles may reflect, at the electrophysiological level, an ideal mechanism for inducing long-term synaptic changes in the neocortex. Recent evidence suggests the spindle is highly correlated with tests of intellectual ability (e.g.; IQ tests) and may serve as a physiological index of intelligence. Further, spindles increase in number and duration in sleep following new learning and are correlated with performance improvements. Spindle density and sigma (14-16Hz) spectral power have been found to be positively correlated with performance following a daytime nap, and animal studies suggest the spindle is involved in a hippocampal-neocortical dialogue necessary for memory consolidation. The findings reviewed here collectively provide a compelling body of evidence that the function of the sleep spindle is related to intellectual ability and memory consolidation.
What processes are involved in the formation of enduring memory traces? Sleep has been proposed t... more What processes are involved in the formation of enduring memory traces? Sleep has been proposed to play a role in memory consolidation and the present study provides evidence to support 2-stage models of sleep and memory including both non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. Previous research has shown REM sleep increases following avoidance learning and memory is impaired if REM deprivation occurs during these post-training periods indicating that REM sleep may have a role in memory consolidation processes. These discrete post-training periods have been termed REM sleep windows (RSWs). It is not known whether the electroencephalogram has unique characteristics during the RSW. Further investigation of the RSW was one of the primary goals of this study. We investigated the epidural-recorded electrophysiological learning-related changes following avoidance training in rats. Theta power increased in the learning group during the RSW, suggesting that theta is involved in memory consolidation during this period. Sleep spindles subsequently increased in slow wave sleep (SWS). The results suggest that both NREM and REM sleep are involved in sleep-dependent memory consolidation, and provide support for existing 2-stage models. Perhaps first theta increases to organize and consolidate material via hippocampal-neocortical dialogue, followed by subsequent refinement in the cortex by spindles during SWS.
It has become increasingly clear that sleep is necessary for efficient memory consolidation. Rece... more It has become increasingly clear that sleep is necessary for efficient memory consolidation. Recently, it has been found that Stage 2 sleep disruption impairs procedural memory performance, and that memory performance is correlated with the duration of Stage 2 sleep; but the mechanisms involved in synaptic plasticity for procedural memory during sleep have not been identified. The present study examined the learning-dependent changes in sleep, including Stage 2 sleep spindles. Following an intense period of simple motor procedural learning, the duration of Stage 2 sleep and spindle density increased. There were no changes observed in the duration of any other stage of sleep or in the density of rapid eye movements. These findings support the hypothesis that sleep spindles are involved in the off-line reprocessing of simple motor procedural memory during Stage 2 sleep.
Sleep spindles are waxing and waning thalamocortical oscillations with accepted frequencies of be... more Sleep spindles are waxing and waning thalamocortical oscillations with accepted frequencies of between 11 and 16 Hz and a minimum duration of 0.5 s. Our research has suggested that there is spindle activity in all of the sleep stages, and thus for the present analysis we examined the link between spindle activity (Stage 2, rapid eye movement (REM) and slow wave sleep (SWS)) and waking cognitive abilities in 32 healthy adolescents. After software was used to filter frequencies outside the desired range, slow spindles (11.00-13.50 Hz), fast spindles (13.51-16.00 Hz) and spindle-like activity (16.01-18.50 Hz) were observed in Stage 2, SWS and REM sleep. Our analysis suggests that these specific EEG frequencies were significantly related to processing speed, which is one of the subscales of the intelligence score, in adolescents. The relationship was prominent in SWS and REM sleep. Further, the spindle-like activity (16.01-18.50 Hz) that occurred during SWS was strongly related to proce...
The purpose of this study was to compare the changes that occur in sleep architecture following t... more The purpose of this study was to compare the changes that occur in sleep architecture following the acquisition of a simple motor learning task in young and older adults. Subjects included 14 young (range = 17–24 years) and 14 older (range = 62–79 years) adults, all of whom were in good health. Using in-home recording systems, sleep architecture (sleep stages and the density of Stage 2 sleep spindles) was examined before and after learning the pursuit rotor. To control for possible age differences in baseline motor performance and spindle density, both absolute and relative (percent change) measures were examined. Both groups improved significantly on the pursuit rotor task at Retest (1 week later); however, the magnitude of absolute improvement was larger in the young group than in the older group. There was no group difference when a relative measure of improvement (percent increase across sessions) was used. The density of Stage 2 sleep spindles increased significantly following task Acquisition in the young group but not in the older group. These age differences failed to reach significance when change was measured as a percentage of baseline level of spindle density. The increase in spindle density was correlated with performance level during acquisition in the young group but not the older group. The results of the present study are largely consistent with previous studies on sleep and memory in young adults and suggest that more detailed examination of this relationship in older adults is warranted.
Previous research has linked both rapid eye movement (REM) sleep and Stage 2 sleep to procedural ... more Previous research has linked both rapid eye movement (REM) sleep and Stage 2 sleep to procedural memory consolidation. The present study sought to clarify the relationship between sleep stages and procedural memory consolidation by examining the effect of initial skill level in this relationship in young adults. In-home sleep recordings were performed on participants before and after learning the pursuit rotor task. We divided the participants into low- and high-skill groups based on their initial performance of the pursuit rotor task. In high-skill participants, there was a significant increase in Stage 2 spindle density after learning, and there was a significant correlation between the spindle density that occurred after learning and pursuit rotor performance at retest 1 week later. In contrast, there was a significant correlation between changes in REM density and performance on the pursuit rotor task during retest 1 week later in low-skill participants, although the actual increase in REM density failed to reach significance in this group. The results of the present study suggest the presence of a double dissociation in the sleep-related processes that are involved in procedural memory consolidation in low- and high-skill individuals. These results indicate that the changes in sleep microarchitecture that take place after learning depend on the initial skill level of the individual and therefore provide validation for the model proposed by Smith et al. [Smith, C. T., Aubrey, J. B., & Peters, K. R. Different roles for REM and Stage 2 sleep in motor learning. Psychologica Belgica, 44, 79-102, 2004]. Accordingly, skill level is an important variable that needs to be considered in future research on sleep and memory consolidation.
... Despite my efforts to design ex-periments in a way that training and retention testing were n... more ... Despite my efforts to design ex-periments in a way that training and retention testing were not confounded by the pedestal procedure, it became clear that no matter what control experiment I did, I was never going to con-vince everyone. ... 1971; Shiromani et al. ...
The role of posttraining paradoxical sleep (PS) in spatial or nonspatial learning in the Morris w... more The role of posttraining paradoxical sleep (PS) in spatial or nonspatial learning in the Morris water maze was evaluated. Sprague-Dawley rats were given a 12-trial training session in either the hidden or the visible platform versions of the task. Subgroups then underwent paradoxical sleep deprivation (PSD) beginning at different times after training. Rats with PSD imposed from 1-4 hr after spatial training had poorer retest scores than any other group. Other rats, implanted with electrodes to permit continuous recording of sleep electroencephalography, were found to undergo a prolonged period of elevated PS after spatial training. By contrast, rats trained in the nonspatial version of the water maze task did not show retention deficits after PSD or elevated PS after training. These results support a role for PS in spatial, but not nonspatial, learning in the Morris water maze.
Until recently, the electrophysiological mechanisms involved in strengthening new memories into a... more Until recently, the electrophysiological mechanisms involved in strengthening new memories into a more permanent form during sleep have been largely unknown. The sleep spindle is an event in the electroencephalogram (EEG) characterizing Stage 2 sleep. Sleep spindles may reflect, at the electrophysiological level, an ideal mechanism for inducing long-term synaptic changes in the neocortex. Recent evidence suggests the spindle is highly correlated with tests of intellectual ability (e.g.; IQ tests) and may serve as a physiological index of intelligence. Further, spindles increase in number and duration in sleep following new learning and are correlated with performance improvements. Spindle density and sigma (14-16Hz) spectral power have been found to be positively correlated with performance following a daytime nap, and animal studies suggest the spindle is involved in a hippocampal-neocortical dialogue necessary for memory consolidation. The findings reviewed here collectively provide a compelling body of evidence that the function of the sleep spindle is related to intellectual ability and memory consolidation.
What processes are involved in the formation of enduring memory traces? Sleep has been proposed t... more What processes are involved in the formation of enduring memory traces? Sleep has been proposed to play a role in memory consolidation and the present study provides evidence to support 2-stage models of sleep and memory including both non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. Previous research has shown REM sleep increases following avoidance learning and memory is impaired if REM deprivation occurs during these post-training periods indicating that REM sleep may have a role in memory consolidation processes. These discrete post-training periods have been termed REM sleep windows (RSWs). It is not known whether the electroencephalogram has unique characteristics during the RSW. Further investigation of the RSW was one of the primary goals of this study. We investigated the epidural-recorded electrophysiological learning-related changes following avoidance training in rats. Theta power increased in the learning group during the RSW, suggesting that theta is involved in memory consolidation during this period. Sleep spindles subsequently increased in slow wave sleep (SWS). The results suggest that both NREM and REM sleep are involved in sleep-dependent memory consolidation, and provide support for existing 2-stage models. Perhaps first theta increases to organize and consolidate material via hippocampal-neocortical dialogue, followed by subsequent refinement in the cortex by spindles during SWS.
It has become increasingly clear that sleep is necessary for efficient memory consolidation. Rece... more It has become increasingly clear that sleep is necessary for efficient memory consolidation. Recently, it has been found that Stage 2 sleep disruption impairs procedural memory performance, and that memory performance is correlated with the duration of Stage 2 sleep; but the mechanisms involved in synaptic plasticity for procedural memory during sleep have not been identified. The present study examined the learning-dependent changes in sleep, including Stage 2 sleep spindles. Following an intense period of simple motor procedural learning, the duration of Stage 2 sleep and spindle density increased. There were no changes observed in the duration of any other stage of sleep or in the density of rapid eye movements. These findings support the hypothesis that sleep spindles are involved in the off-line reprocessing of simple motor procedural memory during Stage 2 sleep.
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Papers by Carlyle Smith
Peer-reviewed research papers by Carlyle Smith