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Humans can learn new information during sleep.
Nat Neurosci. 2012 Aug 26
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28 Sep 2012
Mike Crowder
F1000 Anesthesiology & Pain Management
Washington University in St Louis,
St Louis, MO, USA.
F1000 Anesthesiology & Pain Management
Washington University in St Louis,
St Louis, MO, USA.
New Finding
DOI: 10.3410/f.717957232.793461808
This article shows that humans can learn during sleep. The study paired odors with tones during sleep and found that the tones could elicit sniffing behavior upon wakening or even during subsequent sleep. Similar studies during anesthesia may reveal that humans may learn during anesthesia or, altern that...Continue reading
This article shows that humans can learn during sleep. The study paired odors with tones during sleep and found that the tones could elicit sniffing behavior upon wakening or even during subsequent sleep. Similar studies during anesthesia may reveal that humans may learn during anesthesia or, alternatively, that sleep and anesthesia are distinct in this regard.
Disclosures
None declared
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Crowder M: F1000Prime Recommendation of [Arzi A et al., Nat Neurosci 2012]. In F1000Prime, 28 Sep 2012; DOI: 10.3410/f.717957232.793461808. F1000Prime.com/717957232#eval793461808
10 Dec 2012
Jitendra Sharma
F1000 Neurological Disorders
Massachusetts Institute of Technology,
Cambridge, MA, USA.
F1000 Neurological Disorders
Massachusetts Institute of Technology,
Cambridge, MA, USA.
Good for Teaching, New Finding
DOI: 10.3410/f.717957232.793466140
The paper from Arzi and colleagues breaks new ground in our quest for understanding what the sleeping brain can learn and how associations newly formed during sleep impact waking behavior when exposed to a similar set of conditions. Over the past two decades, a number of studies have shown that sleep...Continue reading
The paper from Arzi and colleagues breaks new ground in our quest for understanding what the sleeping brain can learn and how associations newly formed during sleep impact waking behavior when exposed to a similar set of conditions. Over the past two decades, a number of studies have shown that sleep can encode and consolidate memories and improve task-relevant performance. There is some evidence that sleep can also integrate snippets of new memories into those formed earlier. Different phases of sleep, e.g. rapid eye movement (REM) and non-rapid eye movement (NREM), have also been tied to different aspects of memory formation.
Arzi and associates use a clever experimental manipulation of an earlier established protocol of learning association between odors and different sounds. In a partial-reinforcement learning paradigm, healthy volunteers learned to associate specific tones with odors: each odor type, pleasant or unpleasant, was associated with an unambiguous tone. To confirm whether human volunteers selectively perceived different odorants and reliably categorized them into pleasant and unpleasant odors, they used a visual analog scale for subjects to rank odorants according to their pleasantness. Thus establishing a psychophysical framework, they went on to confirm the hypothesis if sleep induces learning new associations and if they were retained and influenced waking behavior. The volunteers were exposed to a tone (400Hz or 1200Hz) played for a fixed period and paired it with an odor which they had earlier perceived as pleasant (e.g. perfume) or aversive (e.g. carrion). There were two schedules used: reinforced trials when there was tone-odor pairing, and non-reinforced trials, when only tone was played without the accompanying odor. An electroencephalogram (EEG) spectral analysis was done to verify sleep during periods of exposure to learning schedules.
After repeating this schedule multiple times, the experimenters evaluated if subjects learnt the association between specific tones and odors. The key to measure learning was subjects’ sniff response, which is an implicit measure, largely uncontaminated by sleep or wakeful state. They measured the volume of sniff during exposure to pleasant or aversive odor and found that the sniff volumes were significantly larger when pleasant odors were presented. The same happened when only the tones were played, that is tones paired with pleasant odors during learning produced significantly larger sniff volumes compared to those paired with unpleasant ones. Interestingly, the difference between sniff volumes increased progressively with repeated presentation of the same tone, aversive or pleasant. The learned associations were formed both during early, short-wave sleep and the later REM phase. The critical test occurred when the subjects were tested soon after waking up; the learned associations persisted, producing larger sniffs during presentation of tones previously paired with pleasant odors than the unpleasant ones.
The results of this study make an incremental but important advance: simple associations between sensory information, even across different modalities can be learned during sleep and retained at least for a short period during subsequent awake state. It is intriguing that authors did not test (or do not report) how long the information could be retained beyond the first time-point in the waking state. To their credit they do point out some of the limitations of their study, especially their inability to assess the learning in either NREM or REM sleep alone. Further studies using physiological measure will be necessary to investigate the main unresolved questions: what neural circuits are involved in learning during sleep, do these networks overlap with learning networks during wake state, and if so, what are the critical nodes common to the two networks.
Arzi and associates use a clever experimental manipulation of an earlier established protocol of learning association between odors and different sounds. In a partial-reinforcement learning paradigm, healthy volunteers learned to associate specific tones with odors: each odor type, pleasant or unpleasant, was associated with an unambiguous tone. To confirm whether human volunteers selectively perceived different odorants and reliably categorized them into pleasant and unpleasant odors, they used a visual analog scale for subjects to rank odorants according to their pleasantness. Thus establishing a psychophysical framework, they went on to confirm the hypothesis if sleep induces learning new associations and if they were retained and influenced waking behavior. The volunteers were exposed to a tone (400Hz or 1200Hz) played for a fixed period and paired it with an odor which they had earlier perceived as pleasant (e.g. perfume) or aversive (e.g. carrion). There were two schedules used: reinforced trials when there was tone-odor pairing, and non-reinforced trials, when only tone was played without the accompanying odor. An electroencephalogram (EEG) spectral analysis was done to verify sleep during periods of exposure to learning schedules.
After repeating this schedule multiple times, the experimenters evaluated if subjects learnt the association between specific tones and odors. The key to measure learning was subjects’ sniff response, which is an implicit measure, largely uncontaminated by sleep or wakeful state. They measured the volume of sniff during exposure to pleasant or aversive odor and found that the sniff volumes were significantly larger when pleasant odors were presented. The same happened when only the tones were played, that is tones paired with pleasant odors during learning produced significantly larger sniff volumes compared to those paired with unpleasant ones. Interestingly, the difference between sniff volumes increased progressively with repeated presentation of the same tone, aversive or pleasant. The learned associations were formed both during early, short-wave sleep and the later REM phase. The critical test occurred when the subjects were tested soon after waking up; the learned associations persisted, producing larger sniffs during presentation of tones previously paired with pleasant odors than the unpleasant ones.
The results of this study make an incremental but important advance: simple associations between sensory information, even across different modalities can be learned during sleep and retained at least for a short period during subsequent awake state. It is intriguing that authors did not test (or do not report) how long the information could be retained beyond the first time-point in the waking state. To their credit they do point out some of the limitations of their study, especially their inability to assess the learning in either NREM or REM sleep alone. Further studies using physiological measure will be necessary to investigate the main unresolved questions: what neural circuits are involved in learning during sleep, do these networks overlap with learning networks during wake state, and if so, what are the critical nodes common to the two networks.
Disclosures
None declared
Sharma J: F1000Prime Recommendation of [Arzi A et al., Nat Neurosci 2012]. In F1000Prime, 10 Dec 2012; DOI: 10.3410/f.717957232.793466140. F1000Prime.com/717957232#eval793466140
F1000Prime Recommendations, Dissents and Comments for [Arzi A et al., Nat Neurosci 2012]. In F1000Prime, 21 May 2013; F1000Prime.com/717957232
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During sleep, humans can strengthen previously acquired memories, but whether they can acquire entirely new information remains unknown. The nonverbal nature of the olfactory sniff response, in which pleasant odors drive stronger sniffs and unpleasant odors drive weaker sniffs, allowed us to test learning in humans during sleep. Using partial-reinforcement trace conditioning, we paired pleasant and unpleasant odors with different tones during sleep and then measured the sniff response to tones alone during the same nights' sleep and during ensuing wake. We found that sleeping subjects learned novel associations between tones and odors such that they then sniffed in response to tones alone. Moreover, these newly learned tone-induced sniffs differed according to the odor pleasantness that was previously associated with the tone during sleep. This acquired behavior persisted throughout the night and into ensuing wake, without later awareness of the learning process. Thus, humans learned new information during sleep.
DOI: 10.1038/nn.3193
PMID: 22922782
