Parietal thalamocortical circuitry in global dream cessation

Until relatively recently, the overarching agreement in the clinical literature was that total cessation of dreaming is related to posterior parietal lesions. Two recent case reports (Bischof and Bassetti, 2004; Poza and Martí-Massó, 2006), in which patients with medial occipital lesions demonstrated total cessation of dreaming, cast doubt on this clinic-anatomical correlation, and the neuropsychological theory of dreaming associated with it (Solms, 1997). In the current study, seven patients with medial occipital lesions (with posterior cerebral artery ischemic lesions) were recruited. Three patients had total dream cessation and four had intact dreaming (confirmed on REM awakening). Acute phase clinical neuroimaging was reviewed and the extent of the lesions in both groups was meticulously analysed by a neuroanatomist, who was blind to the dreaming status of each patient. The three patients with total cessation of dreaming all demonstrated posterior thalamic infarctions involving the pulvinar nucleus. All four of the patients with intact dreaming demonstrated medial temporo-occipital lesions, and none had thalamic lesions. Upon review of the source images of one of the two case studies with medial occipital damage and total dream cessation (Bischof and Bassetti, 2004), it was noted that the patient also demonstrated infarction of the pulvinar of the thalamus. The pulvinar of the thalamus has discrete thalamo-cortical connections to the parietal lobe, which it innervates. Disruption in the pulvinar of the thalamus can, therefore, reasonably be expected to result in parietal dysfunction. This study represents the largest case-report comparison in patients with REM-confirmed dream cessation with suitably circumscribed pathology. These findings cast doubt on claims of medial occipital mechanisms of dream cessation and suggest that posterior parietal circuitry remains involved

Exploring the neural correlates of dream phenomenology and altered states of consciousness during sleep

Do people routinely pre-activate the meaning and even the phonological form of upcoming words? The most acclaimed evidence for phonological prediction comes from a 2005 Nature Neuroscience publication by DeLong, Urbach and Kutas, who observed a graded modulation of electrical brain potentials (N400) to nouns and preceding articles by the probability that people use a word to continue the sentence fragment (‘cloze’). In our direct replication study spanning 9 laboratories (N=334), pre-registered replication-analyses and exploratory Bayes factor analyses successfully replicated the noun-results but, crucially, not the article-results. Pre-registered single-trial analyses also yielded a statistically significant effect for the nouns but not the articles. Exploratory Bayesian single-trial analyses showed that the article-effect may be non-zero but is likely far smaller than originally reported and too small to observe without very large sample sizes. Our results do not support the view that readers routinely pre-activate the phonological form of predictable words

Chapter Sleep Spindles – As a Biomarker of Brain Function and Plasticity

Alternative & renewable energy sources & technolog

Sleep Spindles – As a Biomarker of Brain Function and Plasticity

Alternative & renewable energy sources & technolog

MEG identifies dorsal medial brain activations during sleep

All sleep stages contain epochs with high-amplitude electrophysiological phasic events, alternating with quieter “core periods.” High-amplitude and core state properties cannot be disentangled with PET and fMRI. Here from high temporal resolution magnetoencephalography data, regional changes in neuronal activity were extracted during core periods in different frequency bands for each sleep stage and waking. We found that gamma-band activity increases in precuneus during light sleep (stages 1/2) and in the left dorso–medial prefrontal cortex (L-DMPFC) during deep sleep (stages 3/4). The L-DMPFC activated area expands laterally during rapid eye movement (REM) sleep, into a volume of about 5 cm3 bounded by regions attributed to Theory of Mind (ToM) and default systems, both involved in introspection. Gamma band activity in this area was higher during REM sleep than other sleep stages and active wakefulness. There is a tantalizing correspondence between increased wide-band activity (dominated by low frequencies) in early non-REM (NREM) sleep stages and increases in gamma-band activity in late NREM and REM periods that we attribute to a lateral disinhibition mechanism. The results provide a description of regional electrophysiological changes in awake state, light and deep sleep, and REM sleep. These changes are most pronounced in the L-DMPFC and the other areas around the dorsal midline that are close to, but do not overlap with areas of the default and ToM systems, suggesting that the DMPFC, particularly in the left hemisphere, plays an important role in late NREM stages, in REM and possibly in dreaming.<br/

Posterior cerebral artery (PCA) infarcts and dreaming : a neuropsychological study

Recent case reports have shown that global loss of dreaming can result from medial occipitotemporal lesions. These findings have cast doubt on Solms's reformulation of Charcot-Wilbrand Syndrome (CWS) into two distinct disorders of dreaming, and caused substantial confusion in dream research as far as the neurological correlates of dreaming are concerned. This study attempted to confirm these case reports and determine whether there were any characteristics unique to the lesions among patients who had lost the ability to dream following damage to medial occipito-temporal cortex. Nine participants (three non-dreamers and six dreamers) who had suffered non-hemorrhagic infarction in the territory of the posterior cerebral artery were recruited in this study. Case histories and neuroradiological data were used to compare the lesion sites of non-dreamers with dreamers. It was confirmed that complete loss of dreaming could result from lesions in medial occipito-temporal cortex. It was found that non-dreamers always suffered bilateral cortical damage as opposed to dreamers who all suffered unilateral damage. The lesions in the non-dreamers tended to be more posterior than the dreamers. It was further speculated that concomitant damage to the thalamus or parietal areas played a role in the causation of heteromodal loss of dreaming. The implications of these findings were discussed in relation to CWS, Solms's dream system, and dream-function research. Finally, future directions were considered

Temporal patterns of memory source incorporations into dreams and their relationships to dreamed locus of control

Les incorporations des mémoires épisodiques dans les rêves apparaissent en formes fragmentées et suivent un modèle temporel distinct qui suit une courbe sinusoïdale. Ce modèle est caractérisé par les incorporations immédiates, qui apparaissent 1-2 jours après l’événement (effet de résidus diurnes), et les incorporations tardives, qui apparaissent 5-7 jours après l’événement (effet de délai). Ces deux effets sont considérés comme des liens entre les processus de consolidation de la mémoire et la formation du rêve. Cette courbe temporelle a été observée pour une variété de stimuli expérimentaux. Cependant, aucune étude à date n’a démontré que le contenu des rêves réagit aux événements diurnes d’une manière plus générale et non-spécifique. Le but de notre étude était d’examiner si deux événements qualitativement distincts, un séjour nocturne au laboratoire (LAB), considéré comme un événement interpersonnel, et une tâche de réalité virtuelle (RV), considérée comme un événement non-interpersonnel, sont intégrés de façon différente dans le contenu onirique. Selon nos hypothèses, 1) les éléments spécifiques liés au LAB et à RV seraient incorporés dans les rêves avec des patrons tendances temporels différents, et 2) les incorporations spécifiques seraient associées à des changements plus généraux dans le locus de contrôle (LoC) du rêve. Vingt-six participants ont passé une nuit dans le laboratoire, ont été exposé à une tâche de RV, et ont rempli un journal de rêve pendant 10 jours. Les rapports de rêve ont été cotés pour les éléments spécifiques portant sur LAB et sur RV, et pour l'évolution générale de LoC du rêve. Nos deux hypothèses ont été confirmées: 1) les incorporations de LAB et RV sont négativement corrélées et apparaissent dans le rêve selon des modèles temporels différents. Les incorporations du LAB ont suivi une courbe sinusoïdale en forme de U, avec un effet de résidu diurne et un effet de délai. Les incorporations de RV ont suivi un patron différent, et ont eu un maximum d’incorporations au jour 4. 2) les scores du LoC du rêve étaient plus externes pour le jour 1 (max incorporations du LAB) et plus internes pour le jour 4 (max incorporations de RV). Ces modèles d'incorporation distincts peuvent refléter des différences dans la façon dont les deux événements ont été traités par les processus de consolidation de la mémoire. Dans ce cas, une expérience interpersonnelle (LAB) était incorporée plus tôt dans le temps. Les résultats suggèrent que LoC du rêve reflète les processus de mémoire plus généraux, qui affectent le contenu du rêve entier, et qui sont partiellement indépendants des incorporations spécifiques.Memories for a daytime event reappear in fragmented form in dream content following a distinct, U-shaped, temporal pattern: immediate incorporations appear on days 1-2 after the event (day-residue effect) and delayed incorporation appear on days 5-7 after the event (dream-lag effect). These two effects are thought to reflect memory consolidation processes linked with dreaming. The U-shaped pattern has been observed for a variety of experimental stimuli, however, no studies have investigated whether dream content also reacts to daytime events in a more general or non-specific way. The aim of this study was to examine whether two qualitatively distinct events, an overnight laboratory (LAB) stay, considered as an interpersonal event, and virtual reality maze task (VR), considered as a non-interpersonal event, are incorporated differently into dream content. We expected that 1) specific elements related to the LAB and VR events would be expressed with different temporal patterns, and 2) these specific incorporations would be associated with more general changes in Dream locus of control (LoC). 26 participants spent one night in the laboratory, underwent a VR maze task, and kept a dream diary for 10 days. Dream reports were scored for specific LAB and VR elements and for general changes in Dream LoC. Two main findings confirmed our expectations: 1) LAB and VR incorporations were inversely related and exhibited distinct temporal patterns. LAB incorporations were U-shaped with both day-residue and dream-lag effects. VR vi incorporations followed a different pattern, with a peak on day 4. 2) Dream LoC scores were more external for day 1 (peak of LAB incorporations) and more internal for day 4 (peak of VR incorporations). These different incorporation patterns may reflect differences in how memory consolidation processes dealt with the two events, with the interpersonal experience being incorporated earlier in time. Dream LoC findings may reflect more general memory processes that are partially independent from the specific incorporations and that affect construction of the whole dream narrative

The role of sleep and dreaming in the processing of episodic memory

La présente thèse examine les liens entre le sommeil, la mémoire épisodique et les rêves. Dans une première étude, nous utilisons les technologies de la réalité virtuelle (RV) en liaison avec un paradigme de privation de sommeil paradoxal et de collecte de rêve en vue d'examiner l'hypothèse que le sommeil paradoxal et le rêve sont impliqués dans la consolidation de la mémoire épisodique. Le sommeil paradoxal a été associé au rappel des aspects spatiaux des éléments émotionnels de la tâche RV. De la même façon, l'incorporation de la tâche RV dans les rêves a été associée au rappel des aspects spatiaux de la tâche. De plus, le rappel des aspects factuels et perceptuels de la mémoire épisodique, formé lors de la tâche VR, a été associé au sommeil aux ondes lentes. Une deuxième étude examine l'hypothèse selon laquelle une fonction possible du rêve pourrait être de créer de nouvelles associations entre les éléments de divers souvenirs épisodiques. Un participant a été réveillé 43 fois lors de l'endormissement pour fournir des rapports détaillés de rêves. Les résultats suggèrent qu'un seul rêve peut comporter, dans un même contexte spatiotemporel, divers éléments appartenant aux multiples souvenirs épisodiques. Une troisième étude aborde la question de la cognition lors du sommeil paradoxal, notamment comment les aspects bizarres des rêves, qui sont formés grâce aux nouvelles combinaisons d'éléments de la mémoire épisodique, sont perçus par le rêveur. Les résultats démontrent une dissociation dans les capacités cognitives en sommeil paradoxal caractérisée par un déficit sélectif dans l'appréciation des éléments bizarres des rêves. Les résultats des quatre études suggèrent que le sommeil aux ondes lentes et le sommeil paradoxal sont différemment impliqués dans le traitement de la mémoire épisodique. Le sommeil aux ondes lentes pourrait être implique dans la consolidation de la mémoire épisodique, et le sommeil paradoxal, par l'entremise du rêve, pourrais avoir le rôle d'introduire de la flexibilité dans ce système mnémonique.The present dissertation examines relationships between sleep, episodic memory and dreaming. In Articles I and II we use a novel virtual reality (VR) task in conjunction with a rapid eye movement (REM) sleep deprivation (REMD) paradigm and dream sampling to examine the hypothesis that REM sleep and dreaming are involved in the consolidation of episodic memory. REM sleep was associated with the successful recall of the spatial aspects of emotionally charged elements of the VR task. Similarly, dreaming was associated with improved performance on the spatial aspects of the recall task. Recall of the factual and perceptual aspects of episodic memories formed with the VR task was associated with increased slow wave sleep (SWS) during the post-exposure night. Overall, the results suggest that SWS is associated with the perceptual and factual aspects of episodic memories while REM sleep is not, a finding which may relate to observations that REM sleep dreaming is composed of deconstructed fragments of loosely associated episodic memories. Study II examines the hypothesis that a function of dreaming may be to create new associations between previously unrelated memory items. A participant, highly trained in introspection and mentation reporting, was awakened 43 times during theta bursts at sleep onset and provided detailed reports of resulting imagery and associated memory sources. This technique provided evidence that elements of distally related memory sources are brought together in temporal and spatial proximity within a novel context provided by the dream, suggesting a role for dreaming in memory processing. To allow for this possibility, we speculate that dreaming experiences may be functionally equivalent to waking experiences in their ability to induce neural plasticity. Study III addresses an aspect of this functional equivalence by examining if dream bizarreness is incompatible with behavioral and cognitive features associated with waking state experience-driven plasticity, i.e., whether the dreamer can act upon, emote and be motivated towards an element of the dream that is bizarre and that violates basic assumptions of physical reality. The results demonstrate a dissociation in cognitive ability during dreaming characterized by a selective deficiency in appreciating bizarreness in face of a maintained ability for logical thought. This finding thus addresses the problem of the wake-like mind reflecting upon dream bizarreness and suggests that dreaming is a state in which the cognitive aspects associated with synaptic plasticity (attention, emotion and motivation associated with believing a situation to be reality) are present while allowing for the presentation of memory item combinations which may transcend the limits of physical reality. The results of the four studies are discussed in light of how REM and SWS sleep stages are differentially involved in specific aspects of episodic memory (episodic replay vs. episodic novelty) and the possible role that dreaming, as a driver of synaptic plasticity, may have in these relationships

Neurobiologia del ricordo onirico: la ricerca delle basi elettrofisiologiche del richiamo e dell'oblio del sogno

Negli ultimi anni numerosi studi hanno tentato di indagare i correlati EEG alla base del richiamo del sogno, partendo dall’assunzione che il ricordo onirico sia l’unico e possibile oggetto di indagine scientifica. Marzano et al. (2011) hanno osservato che specifici pattern EEG presenti negli ultimi 5 minuti di sonno erano in grado di predire il successivo recupero del sogno. Nello specifico, il decremento dell’alpha temporo-parietale durante lo stadio 2 NREM e l’incremento del theta frontale durante il REM erano associati al ricordo onirico. Dal momento che tali pattern EEG erano già stati riscontrati in veglia in relazione a buone prestazioni in compiti di memoria episodica (Klimesch, 1996; 1999), fu possibile ipotizzare una sovrapponibilità tra i meccanismi di codifica e recupero delle memorie episodiche tra diversi stati di coscienza. Nonostante la ricerca delle basi EEG del richiamo del sogno abbia fatto notevoli passi in avanti negli ultimi decenni, rimangono ancora irrisolte alcune questioni. Da una parte, si deve considerare che la maggior parte delle indagini sono state condotte mediante disegni between-subjects, non consentendo di comprendere se i pattern EEG relati al ricordo onirico fossero ascrivibili a fattori di stato o di tratto. Dall’altra parte, si vuole sottolineare che gli studi sono stati realizzati quasi esclusivamente su soggetti giovani e la relazione tra invecchiamento e dreaming è stata scarsamente indagata. L’obiettivo del primo lavoro è stato proprio quello di chiarire la questione “stato-tratto” mediante un disegno within-subjects, tentando, dunque, di comprendere se i correlati EEG del ricordo onirico fossero dipendenti da fattori contingenti il background fisiologico di riferimento da cui i soggetti venivano risvegliati (ipotesi di stato), oppure se fossero dipendenti da fattori interindividuali stabili dei soggetti registrati (ipotesi di tratto). 24 soggetti giovani sono stati registrati mediante polisonnografia (PSG) per almeno 2 sessioni sperimentali, al fine di ottenere entrambe le condizioni di ricordo (REC) e non-ricordo (NREC) del sogno al risveglio da uno stesso stadio di sonno (2NREM o REM). I dati quantitativi dell’EEG sono stati analizzati con la Fast Fourier Transform. I confronti statistici tra REC e NREC hanno mostrato che: a) il ricordo onirico al risveglio da NREM è predetto da un decremento del delta fronto-temporale sinistro (p≤0.0034).; b) il ricordo onirico al risveglio da REM è associato all’incremento dell’alpha parietale (p≤0.008) e da un trend che va nella direzione di un incremento del theta frontale. Date le numerose evidenze di una relazione tra theta frontale e memoria, si è scelto di applicare un’analisi specifica per l’attività oscillatoria (algoritmo BOSC-Better OSCillation, Caplan et al., 2001) del range del theta, che ha confermato la presenza di una robusta associazione tra il theta delle regioni frontopolari e il ricordo onirico. Tale pattern EEG è risultato, peraltro, relato al carico emotivo soggettivamente stimato del ricordo del sogno. Tali risultati sono da un lato in linea con i Modelli di Attivazione (Antrobus, 1991), vale a dire con l’idea che un background EEG caratterizzato da una maggiore desincronizzazione possa favorire il successivo recupero dell’attività mentale (Antrobus, 1991). Dall’altro, la relazione tra il theta frontale e il ricordo onirico nel REM replica i riscontri di Marzano et al. (2011), fornendo ulteriore supporto all’ipotesi di continuità. Inoltre, i risultati sono coerenti con una ipotesi di “stato”: non sono caratteristiche stabili dei soggetti registrati a predire il ricordo onirico al risveglio, ma è una particolare attività corticale durante uno specifico stadio di sonno a determinare il successivo richiamo del sogno. Il secondo studio aveva lo scopo di indagare gli specifici pattern EEG relati al ricordo onirico nell’anziano. 40 anziani sani sono stati registrati con PSG notturna. 20 soggetti sono stati risvegliati da fase REM e 20 da stadio 2 NREM, raccogliendo al mattino l’eventuale ricordo onirico. I dati quantitativi dell’EEG sono stati analizzati con la Fast Fourier Transform. Per gli ultimi 5 min di sonno è stata effettuata la detezione dell’attività oscillatoria con il metodo BOSC. I confronti statistici tra i REC e i NREC hanno evidenziato che: a) Il ricordo onirico al risveglio da stadio 2 è associato ad una trend che va nella direzione di un incremento dell’attività beta nelle aree temporali durante l’intera notte; b) Il ricordo onirico al risveglio da REM è associato ad un trend che va nella direzione di un incremento dell’attività alpha durante l’intera notte. La BOSC ha rilevato che le oscillazioni alpha a 8.5 Hz negli ultimi minuti di sonno REM predicono il successivo ricordo onirico (p≤0.025). E’ emersa inoltre una relazione robusta tra alcuni parametri macrostrutturali, indicativi della frammentarietà del sonno, e le variabili oniriche. In particolare, per i soggetti risvegliati da sonno NREM: a) la vividezza del ricordo onirico è correlata positivamente alla durata della veglia intrasonno; b) l’indice di efficienza del sonno è correlato negativamente alla lunghezza soggettivamente stimata del sogno; c) il numero totale di parole del report è correlato negativamente al numero di arousal. Per i soggetti risvegliati da sonno REM la bizzarria è correlata positivamente con il numero di arousal. Presi assieme, tali risultati appaiano compatibili con quanto rilevato nello studio precedente, e, dunque, ancora una volta in linea con i Modelli di Attivazione (Antrobus, 1991), dal momento che l’elevata attività beta in NREM e l'attività alpha in REM possono ritenersi espressione di un relativo arousal corticale. E’ opportuno evidenziare alcuni limiti presenti nei due studi condotti. Nel primo esperimento, sebbene i nap pomeridiani abbiano consentito di reiterare più agevolmente le sessioni sperimentali, è possibile che il sonno dei soggetti registrati possa essere meno stabile in questa fascia oraria. Nel secondo lavoro emerge, invece, l’assenza di una notte di adattamento. Tale scelta è stata motivata da una difficoltà di reclutamento e disponibilità, entro la popolazione anziana, di modificare le proprie abitudini di sonno per più di una notte consecutiva. Sarebbe opportuno per il futuro realizzare un’indagine volta a confrontare i correlati EEG del ricordo onirico tra giovani ed anziani entro un unico protocollo notturno. Inoltre, sarà utile considerare anche la condizione del “white dream”, corrispondente alla sensazione del soggetto di aver sognato senza però essere in grado di riportare alcun contenuto onirico. E’, infatti, possibile ipotizzare che a un livello “intermedio” di ricordo onirico, possa corrispondere anche un livello medio di attivazione corticale. Infine, si prevede di tenere sotto controllo, con ulteriori indagini, il contributo della variabile omeostatica e circadiana, implementando un protocollo notturno che preveda risvegli multipli per ciascuno stadio e ciclo di sonno, con la relativa raccolta di report onirici

Exploring the relationship between mindfulness in waking and lucidity in dreams

The continuity theory of dreaming proposes that waking and dreaming rely on a shared set of brain-mind processes. Research in the fields of lucid dreaming and mindfulness suggest continuity of certain neurocognitive processes. Specifically, the high levels of attention, reflection, self-awareness, volition, and control which are hypothesized to be related to lucidity are presumed here to be continuous with waking mindfulness. This study aimed to investigate relationships between: 1) Mindfulness in waking and lucidity/mindfulness in dreaming; 2) Neuropsychological functions related to mindfulness and lucidity/mindfulness in dreaming; and 3) Neuropsychological functions and subjective mindfulness in waking.N = 44 participants completed measures of general and recent mindfulness skills and a battery of neuropsychological tests. Each morning for seven days following this initial assessment, participants rated their levels of lucidity, cognitive functioning, sensory and emotional intensity from their preceding night’s dream. Relationships between waking mindfulness levels, neuropsychological functions, and dream variables were evaluated using a correlational design.Waking mindfulness did not account for a significant amount of variance in dream lucidity, but did account for a significant amount of variance in dream mindfulness. Correlations between dream lucidity and neuropsychological measures were not significant. However, better performances on two neuropsychological measures (sustained attention and behavioral self-monitoring) were moderately correlated with dream mindfulness. Also, general mindful awareness and recent mindful acceptance were positively associated with sustained attention and behavioral self-monitoring.Significant relationships found between waking mindfulness and dream mindfulness provide support for continuity theory. Mindfulness appears to be expressed in dreams to a degree that is consistent with recent and general levels of mindful awareness. The relationships between neuropsychological functions and dream mindfulness suggest a shared brain bases for attention and behavioral self-monitoring across dreaming and waking. The failure to find a relationship between lucidity and any of the variables assessed in waking in this study may be due to methodological limitations. Alternatively, while high levels of attention, reflection, volition, self-awareness, and control are often observed in lucid dreams, they may not be exclusive to lucid dreams.Ph.D., Clinical Psychology -- Drexel University, 201