Robert Stickgold

Harvard Medical School | HMS · Department of Psychiatry

Over time, memories lose episodic detail and become distorted, a process with serious ramifications for eyewitness identification. What are the processes contributing to such transformations over time? We investigated the roles of post learning sleep and retrieval practice in memory accuracy and distortion, using a naturalistic story recollection t...

Study Objectives Disrupted nighttime sleep (DNS) is common in pediatric Narcolepsy type 1, yet its cognitive impact is unknown. As N2 sleep spindles are necessary for sleep-dependent memory consolidation, we hypothesized that Narcolepsy Type 1 impairs memory consolidation via N2 sleep fragmentation and N2 sleep spindle alterations. Methods We trai...

Multiple facets of sleep neurophysiology, including electroencephalography (EEG) metrics such as non-rapid eye movement (NREM) spindles and slow oscillations, are altered in individuals with schizophrenia (SCZ). However, beyond group-level analyses, the extent to which NREM deficits vary among patients is unclear, as are their relationships to othe...

The Oxford Handbook of Human Memory covers the science of human memory, its application to clinical disorders, and its broader implications for learning and memory in real-world contexts. Written by field leaders, the handbook integrates behavioral, neural, and computational evidence with current theories of how humans learn and remember. Following...

Background Objective and quantifiable markers are crucial for developing novel therapeutics for mental disorders by 1) stratifying clinically similar patients with different underlying neurobiological deficits and 2) objectively tracking disease trajectory and treatment response. Schizophrenia is often confounded with other psychiatric disorders, e...

Although research on the hippocampus has largely focused on its role in active learning, critical aspects of learning and memory happen offline, during both wake and sleep. When healthy young people learn a motor sequence task, most of their performance improvement happens not while typing, but offline, during interleaved rest breaks. Although pati...

Introduction While a brief period of recovery sleep can ameliorate the negative impacts of total sleep deprivation (TSD) on cognitive functioning, the effects of post-TSD recovery sleep on different forms of emotional functioning remain equivocal. Here, we investigated the effects of TSD and post-TSD recovery sleep on emotional memory processing an...

Research on the role of the hippocampus in memory acquisition has generally focused on active learning. But to understand memory, it is at least as important to understand processes that happen offline, during both wake and sleep. In a study of patients with amnesia, we previously demonstrated that although a functional hippocampus is not necessary...

Background: Multiple facets of sleep neurophysiology, including electroencephalography (EEG) metrics such as non-rapid eye movement (NREM) spindles and slow oscillations (SO), are altered in individuals with schizophrenia (SCZ). However, beyond group-level analyses which treat all patients as a unitary set, the extent to which NREM deficits vary am...

Sleep spindles are believed to mediate sleep-dependent memory consolidation, particularly when coupled to neocortical slow oscillations. Schizophrenia is characterized by a deficit in sleep spindles that correlates with reduced overnight memory consolidation. Here, we examined sleep spindle activity, slow oscillation-spindle coupling, and both moto...

Microstate analysis is a promising technique for analyzing high-density electroencephalographic data, but there are multiple questions about methodological best practices. Between and within individuals, microstates can differ both in terms of characteristic topographies and temporal dynamics, which leads to analytic challenges as the measurement o...

The filtering out of apparently extraneous and redundant stimuli is critical for the effective processing of novel and relevant sensory information. But brain mechanisms that evolved to perform this function are necessarily less than perfect, in some cases failing to filter out irrelevant stimuli and in others filtering out important information. W...

Introduction Disrupted nighttime sleep (DNS) is common in narcolepsy type 1 (NT1), yet its impact on cognitive function is unknown. Given known associations between sleep-dependent memory consolidation and N2 sleep spindles, we hypothesized that NT1 impairs memory consolidation, due to fragmented N2 sleep and altered N2 sleep spindles in the NT1 gr...

The link between dreams and creativity has been a topic of intense speculation. Recent scientific findings suggest that sleep onset (known as N1) may be an ideal brain state for creative ideation. However, the specific link between N1 dream content and creativity has remained unclear. To investigate the contribution of N1 dream content to creative...

Sleep supports memory consolidation. However, it is not completely clear how different sleep stages contribute to this process. While rapid eye movement sleep (REM) has been traditionally implicated in the processing of emotionally charged material, recent studies indicate a role for slow wave sleep (SWS) in strengthening the memories of emotional...

ADHD has been associated with cortico-striatal dysfunction that may lead to procedural memory abnormalities. Sleep plays a critical role in consolidating procedural memories, and sleep problems are an integral part of the psychopathology of ADHD. This raises the possibility that altered sleep processes characterizing those with ADHD could contribut...

Rationale: A growing body of evidence suggests that sleep is critical for the adaptive processing and consolidation of emotional information into long-term memory. Previous research has indicated that emotional components of scenes particularly benefit from sleep in healthy groups yet sleep-dependent emotional memory processes remain unexplored in...

Objectives Major sociopolitical events can influence the general public's affective state and other affect-related processes, such as sleep. Here, we investigated the extent that the 2020 US presidential election impacted sleep, public mood, and alcohol consumption. We also explored the relationship between affect and sleep changes during the peak...

Transient oscillatory events in the sleep electroencephalogram represent short-term coordinated network activity. Of particular importance, sleep spindles are transient oscillatory events associated with memory consolidation, which are altered in aging and in several psychiatric and neurodegenerative disorders. Spindle identification, however, curr...

For two decades, sleep has been touted as one of the primary drivers for the encoding, consolidation, retention, and retrieval of episodic emotional memory. Recently, however, sleep’s role in emotional memory processing has received renewed scrutiny as meta-analyses and reviews have indicated that sleep may only contribute a small effect that hinge...

Motivated by the potential of objective neurophysiological markers to index thalamocortical function in patients with severe psychiatric illnesses, we comprehensively characterized key non-rapid eye movement (NREM) sleep parameters across multiple domains, their interdependencies, and their relationship to waking event-related potentials and sympto...

Study Objectives Converging evidence from neuroimaging, sleep, and genetic studies suggests that dysregulation of thalamocortical interactions mediated by the thalamic reticular nucleus (TRN) contribute to autism spectrum disorder (ASD). Sleep spindles assay TRN function, and their coordination with cortical slow oscillations (SOs) indexes thalamoc...

Motivated by the potential of objective neurophysiological markers to index thalamocortical function in patients with severe psychiatric illnesses, we comprehensively characterized key NREM sleep parameters across multiple domains, their interdependencies, and their relationship to waking event-related potentials and symptom severity. In 130 schizo...

Sleep abnormalities are an early feature of schizophrenia (SZ) characterized by reductions in sleep spindles that have been associated with deficits in brain connectivity and cognitive function. This study investigated sleep spindle density (SSD) differences between SZ, first episode psychosis (FEP), and family high-risk (FHR) populations and match...

Second Edition enriched with a Foreword written by Jakub Przybyła Frenis Zero publishing house, 2021, ISBN 978-88-97479-30-7 Presentation: The second edition of the book is foreworded by Jakub Przybyła who criticizes the idea of integrating neurobiology and psychotherapy based mainly on the study of psychoanalysis and neuropsychoanalysis. The autho...

Extracting shared structure across our experiences allows us to generalize our knowledge to novel contexts. How do different brain states influence this ability to generalize? Using a novel category learning paradigm, we assess the effect of both sleep and time of day on generalization that depends on the flexible integration of recent information....

Over time, memories lose episodic detail and become distorted, a process with serious ramifications for topics such as eyewitness identification. What are the processes which contribute to such transformation over time? We investigated the roles of post learning sleep and retrieval practice in memory accuracy, transformation, and distortion, using...

Introduction The Apolipoprotein E (APOE)-ε4 genotype is a marker of susceptibility for late-onset Alzheimer’s disease (AD). Sleep disturbances may accelerate the aging process and increase the risk for future development of cognitive impairment and dementia. Given that the pathophysiological process of AD can predate its clinical manifestations by...

Introduction A growing body of evidence suggests that sleep is critical for the processing and consolidation of emotional information into long-term memory. Previous research has indicated that emotional components of scenes particularly benefit from sleep in healthy groups, yet sleep dependent emotional memory processes remain unexplored in many c...

Study objectives: Sleep spindles are defined based on expert observations of waveform features in the electroencephalogram traces. This is a potentially limiting characterization, as transient oscillatory bursts like spindles are easily obscured in the time-domain by higher amplitude activity at other frequencies or by noise. It is therefore highl...

Sleep has been shown to be critical for memory consolidation, with some research suggesting that certain memories are prioritized for consolidation. Initial strength of a memory appears to be an important boundary condition in determining which memories are consolidated during sleep. However, the role of consolidation-mediating oscillations, such a...

Evidence suggests that the brain preferentially consolidates memories during “offline” periods, in which an individual is not performing a task and their attention is otherwise undirected, including spans of quiet, resting wakefulness. Moreover, research has demonstrated that factors such as the initial encoding strength of information influence wh...

Childhood epilepsy with centrotemporal spikes (CECTS) is the most common focal epilepsy syndrome, yet the cause of this disease remains unknown. Now recognized as a mild epileptic encephalopathy, children exhibit sleep-activated focal epileptiform discharges and cognitive difficulties during the active phase of the disease. The association between...

Abnormal sleep is a prominent feature of many of the major neuropsychiatric disorders that likely reflects their pathophysiology and contributes to their associated symptoms and cognitive deficits.

What is a dream? During wakefulness, the brain interprets information, stores memories, and uses knowledge to form and execute plans of action. In sleep, the brain continues these information-processing functions of the waking brain. Throughout the night, and even during the deepest phases of slow wave sleep, the sleeping brain replays past experie...

Memory consolidation during sleep does not benefit all memories equally. Initial encoding strength appears to play a role in governing where sleep effects are seen, but it is unclear whether sleep preferentially consolidates weaker or stronger memories. We manipulated encoding strength along two dimensions-the number of item presentations, and succ...

Extracting shared structure across our experiences allows us to generalize our knowledge to novel contexts. How do different brain states influence this ability to generalize? Using a novel category learning paradigm, we assess the effect of both sleep and time of day on generalization that depends on the flexible integration of recent information....

Sleep spindles, defining oscillations of stage 2 non-rapid eye movement sleep (N2), mediate memory consolidation. Schizophrenia is characterized by reduced spindle activity that correlates with impaired sleep-dependent memory consolidation. In a small, randomized, placebo-controlled pilot study of schizophrenia, eszopiclone (Lunesta®), a nonbenzodi...

Information processing during sleep is active, ongoing and accessible to engineering. Protocols such as targeted memory reactivation use sensory stimuli during sleep to reactivate memories and demonstrate subsequent, specific enhancement of their consolidation. These protocols rely on physiological, as opposed to phenomenological, evidence of their...

Introduction Converging evidence supports the hypothesis that reduced sleep spindles and spindle-slow oscillation (SO) coordination contribute to cognitive deficits in schizophrenia. Closed-loop auditory stimulation in healthy adults increases sleep spindles and improves declarative memory consolidation. Here we investigated whether closed-loop aud...

Evidence suggests that the brain preferentially consolidates memories during "offline" periods, in which an individual is not performing a task and their attention is otherwise undirected, including spans of quiet, resting wakefulness. Moreover, research has demonstrated that factors such as the initial encoding strength of information influence wh...

Sleep has been shown to be critical for memory consolidation, with some research suggesting that certain memories are prioritized for consolidation. Initial strength of a memory appears to be an important boundary condition in determining which memories are consolidated during sleep. However, the role of consolidation-mediating oscillations, such a...

Study objectives: The clinical importance of obstructive sleep apnea, which can be prevalent during REM sleep, is unclear. The present study examines the effect of REM-related obstructive sleep apnea on motor memory consolidation as well as on mood states. Methods: We compared performance on the motor sequence task (MST), psychomotor vigilance t...

Sleep spindles, defining oscillations of non‐rapid eye movement stage 2 sleep (N2), mediate memory consolidation. Spindle density (spindles/minute) is a stable, heritable feature of the sleep electroencephalogram. In schizophrenia, reduced spindle density correlates with impaired sleep‐dependent memory consolidation and is a promising treatment tar...

Sleep plays a critical role in the consolidation of memories. But this process is selective, with only some memories benefiting. One component of this selection process is encoding strength. The role that initial encoding strength plays in the prioritization for consolidation during sleep is currently unclear, with some studies suggesting that weak...

Background: Microstates are periods of characteristic electroencephalographic signal topography that are related to activity in brain networks. Previous work has identified abnormal microstate parameters in individuals with psychotic disorders. We combined microstate analysis with sample entropy analysis to study the dynamics of resting-state netw...

During sleep, the hippocampus plays an active role in consolidating memories that depend on it for initial encoding. There are hints in the literature that the hippocampus may have a broader influence, contributing to the consolidation of memories that may not initially require the area. We tested this possibility by evaluating learning and consoli...

There is overwhelming evidence that sleep is crucial for memory consolidation. Patients with schizophrenia and their unaffected relatives have a specific deficit in sleep spindles, a defining oscillation of non-rapid eye movement (NREM) Stage 2 sleep that, in coordination with other NREM oscillations, mediate memory consolidation. In schizophrenia,...

Background: Converging evidence implicates abnormal thalamocortical interactions in the pathophysiology of schizophrenia. This evidence includes consistent findings of increased resting-state functional connectivity of the thalamus with somatosensory and motor cortex during wake and reduced spindle activity during sleep. We hypothesized that these...

Introduction Patients with schizophrenia have sleep spindle deficits that correlate with impaired sleep-dependent memory consolidation. In a previous study of schizophrenia, eszopiclone, a non-benzodiazepine sedative hypnotic, despite increasing spindles, failed to improve memory. Here, we investigated whether this failure reflected that eszopiclon...

Introduction A large body of evidence has shown that sleep plays a critical role in the consolidation of memories, a process facilitated in part by sleep spindles, a hallmark feature of non-rapid eye movement (NREM) sleep. It is less clear how the brain selects and prioritizes which memories get consolidated during sleep. Here, we used EEG to ident...

Introduction Recent data implicate abnormalities of the thalamic reticular nucleus (TRN) and thalamocortical circuitry in schizophrenia (SZ) risk. Sleep spindles are initiated by the TRN and propagated to the cortex via thalamocortical feedback loops.During wakefulness, TRN modulates sensory processing by gating thalamocortical communication. Patie...

Introduction Prospective memory (PM)—the ability to plan and spontaneously remember to execute activities in the future—has been shown to improve across periods of sleep. While evidence indicates PM benefits most from SWS-rich sleep, the specific components of sleep that benefit PM performance remain undetermined. Methods Participants arrived at 9...

Introduction There is converging evidence that motor-skill learning is consolidated by sleep spindles during non-rapid eye movement stage 2 (N2) sleep, resulting in improved post-sleep performance. We localized learning-related changes in spindle activity with source localization of simultaneous electroencephalogram (EEG) and magnetoencephalography...

Introduction Sleep has been shown to facilitate the consolidation of explicit motor-sequence learning on the finger-tapping motor sequence task (MST). However, whether sleep's contribution constitutes stabilization or enhancement is currently under debate. A transient boost in performance after a short break from practice on the MST has been report...

Introduction Sleep spindles mediate memory consolidation during sleep and are markedly reduced in schizophrenia. While spindle deficits correlate with impaired sleep-dependent memory, pharmacologically increasing spindle density in schizophrenia does not always improve memory. This may be because coupling with other NREM sleep oscillations like hip...

Sleep and emotion are both powerful modulators of the long-term stability of episodic memories, but precisely how these factors interact remains unresolved. We assessed changes in item recognition, contextual memory, and affective tone for negative and neutral memories across a 12 h interval containing sleep or wakefulness in 71 human volunteers. O...

During sleep, the hippocampus plays an active role in consolidating memories that depend on it for initial encoding. There are hints in the literature that the hippocampus may have a broader influence, contributing to the consolidation of memories that may not initially require the area. We tested this possibility by evaluating learning and consoli...

Slow oscillations and sleep spindles, the canonical electrophysiological oscillations of non-rapid eye movement sleep, are thought to gate incoming sensory information, underlie processes of sleep-dependent memory consolidation, and are altered in various neuropsychiatric disorders. Accumulating evidence of the predominantly local expression of the...

Sleep following learning benefits memory. One model attributes this effect to the iterative “reactivation” of memory traces in the sleeping brain, demonstrated in animal models. Although technical limitations prohibit using the same methods to observe memory reactivation in the human brain, the study of mental activity during sleep provides an alte...

Sleep and emotion are both powerful modulators of the long-term stability of episodic memories, but precisely how these factors interact remains unresolved. We assessed changes in item recognition, contextual memory, and affective tone for negative and neutral memories across a 12 h interval containing sleep or wakefulness in 71 human volunteers. O...

Introduction A large body of evidence has shown that sleep plays an important role in the consolidation of declarative memory. More recently, it has been suggested that the brain prioritizes certain memories to be consolidated over others. The mechanisms underlying this remain unclear. This study investigated the role initial encoding strength may...