In this paper, we present an argument strengthening the view of Norman Daniels, Bruce Kennedy and Ichiro Kawachi that justice is good for one's health. We argue that the pathways through which social factors produce inequalities in sleep more strongly imply a unidirectional and non-voluntary causality than with most other public health issues. Specifically, we argue against the 'voluntarism objection' – an objection that suggests that adverse public health outcomes can be traced back to the free and voluntary choices (...) of individual actors. Our argument proceeds along two lines: an empirical line and a conceptual line. We first show that much of the empirical research on sleep supports the view that those with fewer opportunities are those who have poorer sleep habits. We then argue that sleep-related decisions are not of the same nature as most other lifestyle choices, and therefore are not as easily susceptible to the voluntarism objection. (shrink)
In this paper we claim that individual subjects do not have so much control over sleep that it is aptly characterized as a personal choice; and that normative implications related to public health and sleep hygiene do not necessarily follow from current findings. It should be true of any empirical study that normative implications do not necessarily follow, but we think that many public health sleep recommendations falsely infer these implications from a flawed explanatory account of the (...) decision to sleep: the consumer choice view. This view, which we criticize here, proposes that sleepduration and sleep quality be understood as one choice among many. (shrink)
The phylogenetic data are inconsistent with the hypothesis that REM sleepduration is correlated with learning or learning ability. Humans do not have uniquely high amounts of REM sleep. The platypus, marsupials, and other mammals not generally thought to have extraordinary learning abilities have the largest amounts of REM sleep. The whales and dolphins (cetaceans) have the lowest amounts of REM sleep and may go without REM sleep for extended periods of time, despite their (...) prodigious learning abilities. Vertes & Eastman]. (shrink)
The paradigmatic assumption that REM sleep is the physiological equivalent of dreaming is in need of fundamental revision. A mounting body of evidence suggests that dreaming and REM sleep are dissociable states, and that dreaming is controlled by forebrain mechanisms. Recent neuropsychological, radiological, and pharmacological findings suggest that the cholinergic brain stem mechanisms that control the REM state can only generate the psychological phenomena of dreaming through the mediation of a second, probably dopaminergic, forebrain mechanism. The latter mechanism (...) (and thus dreaming itself) can also be activated by a variety of nonREM triggers. Dreaming can be manipulated by dopamine agonists and antagonists with no concomitant change in REM frequency, duration, and density. Dreaming can also be induced by focal forebrain stimulation and by complex partial (forebrain) seizures during nonREM sleep, when the involvement of brainstem REM mechanisms is precluded. Likewise, dreaming is obliterated by focal lesions along a specific (probably dopaminergic) forebrain pathway, and these lesions do not have any appreciable effects on REM frequency, duration, and density. These findings suggest that the forebrain mechanism in question is the final common path to dreaming and that the brainstem oscillator that controls the REM state is just one of the many arousal triggers that can activate this forebrain mechanism. The “REM-on” mechanism (like its various NREM equivalents) therefore stands outside the dream process itself, which is mediated by an independent, forebrain “dream-on” mechanism. Key Words: acetylcholine; brainstem; dopamine; dreaming; forebrain; NREM; REM; sleep. (shrink)
Whereas many researchers see a heuristic potential in the covert REM sleep model for explaining NREM sleep mentation and associated phenomena, many others are unconvinced of its value. At present, there is much circumstantial support for the model, but validation is lacking on many points. Supportive findings from several additional studies are summarized with results from two new studies showing (1) NREM mentation is correlated with duration of prior REM sleep, and (2) REM sleep signs (...) (eye movements, phasic EMG) occur frequently in NREM sleep. The covert REM sleep model represents one class of explanatory models that combines the two assumptions of mind-body isomorphism and a 1-gen mentation generator; its future development will depend largely upon a more detailed understanding of sleep state interactions and their contribution to mind-body isomorphisms. (shrink)
What, if anything, do dreams tell us about ourselves? What is the relationship between types of sleep and types of dreams? Does dreaming serve any purpose? Or are dreams simply meaningless mental noise--"unmusical fingers wandering over the piano keys"? With expertise in philosophy, psychology, and neuroscience, Owen Flanagan is uniquely qualified to answer these questions. In this groundbreaking work, he provides both an accessible survey of the latest research on sleep and dreams and a compelling new theory about (...) the nature and function of dreaming. Flanagan argues that while sleep has a clear biological function and adaptive value, dreams are merely side effects, "free riders," irrelevant from an evolutionary point of view. But dreams are hardly unimportant. Flanagan argues that dreams are self-expressive, the result of our need to find or to create meaning, even when we're sleeping. Written with remarkable insight, Dreaming Souls offers a fascinating new way of apprehending one of the oldest mysteries of mental life. (shrink)
In ‘Location and Perdurance’ (2010), I argued that there are no compelling mereological or sortal grounds requiring the perdurantist to distinguish the molecule Abel from the atom Abel in Gilmore’s original case (2007). The remaining issue Gilmore originally raised concerned the ‘mass history’ of Adam and Abel, the distribution of ‘their’ mass over spacetime. My response to this issue was to admit that mass histories needed to be relativised to a way of partitioning the location of Adam/Abel, but that did (...) not amount to relativising any fundamental natural intrinsic properties—the latter are all had unrelativised, and (so most perdurantists would say). (shrink)
Imants Baruss (2003). Sleep. In Imants Baruss (ed.), Alterations of Consciousness: An Empirical Analysis for Social Scientists. American Psychological Association.score: 15.0
Sleep researchers in different disciplines disagree about how fully dreaming can be explained in terms of brain physiology. Debate has focused on whether REM sleep dreaming is qualitatively different from nonREM (NREM) sleep and waking. A review of psychophysiological studies shows clear quantitative differences between REM and NREM mentation and between REM and waking mentation. Recent neuroimaging and neurophysiological studies also differentiate REM, NREM, and waking in features with phenomenological implications. Both evidence and theory suggest that there (...) are isomorphisms between the phenomenology and the physiology of dreams. We present a three-dimensional model with specific examples from normally and abnormally changing conscious states. Key Words: consciousness; dreaming; neuroimaging; neuromodulation; NREM; phenomenology; qualia; REM; sleep. (shrink)
Sleep onset is associated with marked changes in behavioral, physiological, and subjective phenomena. In daily life though subjective experience is the main criterion in terms of which we identify it. But very few studies have focused on these experiences. This study seeks to identify the subjective variables that reflect sleep onset. Twenty young subjects took an afternoon nap in the laboratory while polysomnographic recordings were made. They were awakened four times in order to assess subjective experiences that correlate (...) with the (1) appearance of slow eye movement, (2) initiation of stage 1 sleep, (3) initiation of stage 2 sleep, and (4) 5 min after the start of stage 2 sleep. A logistic regression identified control over and logic of thought as the two variables that predict the perception of having fallen asleep. For sleep perception, these two variables accurately classified 91.7% of the cases; for the waking state, 84.1%. (shrink)
I use Jonathan Bennett’s, Gilles Deleuze’s and Pierre Macherey’s interpretations of Spinoza to extract a theory of time and duration from Spinoza. I argue that although time can be considered a product of the imagination, duration is a real property of existing things and corresponds to their essence, taking essence (as Deleuze does) as a degree of power of existing. The article then explores the relations among time, duration, essence and eternity, arguing against the idea that Spinoza’s (...) essences or Spinoza’s eternity are atemporal. Essences and eternity both involve necessary references to time, but the time involved is not that of the “fortuitous sequence of events” apprehended through sensory experience. Rather, the “time” is that implicit in the necessity of God’s self-determination through God’s differentiation into natura naturans and natura naturata, which is involved in the production and differentiation of eternal essences. (shrink)
The literature on time perception is discussed. This is done with reference both to the ''cognitive-timer'' model for time estimation and to the subjective experience of apparent duration. Three assumptions underlying the model are scrutinized. I stress the strong interplay among attention, arousal, and time perception, which is at the base of the cognitive-timer model. It is suggested that a multiplicative function of two key components (the number of subjective time units and their size) should predict apparent duration. (...) Implications for other cognitive domains are drawn, and in particular an analogy is suggested between apparent duration and apparent movement. (shrink)
The advent of functional imaging has reinforced the attempts to define dreaming as a sleep state-dependent phenomenon. PET scans revealed major differences between nonREM sleep and REM sleep. However, because dreaming occurs throughout sleep, the common features of the two sleep states, rather than the differences, could help define the prerequisite for the occurrence of dreams. [Hobson et al.; Nielsen; Solms; Revonsuo; Vertes & Eastman].
The approach of Hobson et al. is limited to the description of global states of consciousness, although more detailed analyses of the specific contents of consciousness would also be required. Furthermore, their account of the mind-brain relationship remains obscure. Nielsen's discussion suffers from conceptual and definitional unclarity. Mentation during sleep could be clarified by reconceptualizing it as an issue about the contents of consciousness. Vertes & Eastman do not consider the types of memory (emotional) and learning (implicit) that are (...) relevant during REM sleep, and therefore dismiss on inadequate grounds the possibility of memory functions associated with REM sleep. [Hobson et al.; Nielsen; Vertes & Eastman]. (shrink)
There are obvious flaws in REM sleep suppression paradigms that do not allow any conclusion to be drawn either pro or contra the REM sleep-memory hypothesis. However, less intrusive investigations of REM sleep suggest that this sleep stage or its adjunct neuroendocrine characteristics exert a facilitating influence on certain aspects of ongoing memory formation during sleep. [Nielsen; Vertes & Eastman].
In this paper, perhaps the first of its kind, an attempt is made to elucidate and examine the Vedantic theory of soul constructed on the basis of the experience of dreamless sleep which, being radically and qualitatively different from waking and dreaming states, is considered by the Vedantins as a state of temporarily purified individual soul (atman), a state of pure substantial consciousness. They take the experience of dreamless sleep as a model experience of the soul's final liberation (...) from the body and its internal as well as external faculties. The ultimate liberation, according to the Vedantins, is a state of total identification of the individual soul with the Universal Soul (Brahman), the summum bonum of every Vedantin. The paper also includes a critique of the Vedantic soul theory by the Buddhists who vehemently deny any autonomous and substantial soul whose essence is unchangingly permanent, pure consciousness and self-illuminating knowledge. The soul is instead interpreted by the Buddhists as a product of the functioning of a person's psycho-physical organism and a mere subject of knowing, thinking, desiring, etc. The analysis further shows that the Vedanta, especially the Advaita Vedanta, metaphysics of soul is inadequate in many respects and mainly based on a priori and scriptural arguments and emotive appeals, whereas the Buddhists deny any kind of autonomous and permanent agent of knowing, thinking and desiring by successfully reducing substantial consciousness to mere acts of knowing. (shrink)
It has been widely demonstrated that dreaming occurs throughout human sleep. However, we once again are facing new variants of the equation “REM sleep = Dreaming.” Nielsen proposes a model that assumes covert REM processes in NREM sleep. I argue against this possibility, because dream research has shown that REM sleep is not a necessary condition for dreaming to occur. [Nielson].
Walker's target article proposes a refinement of the well known two-stage model of memory formation to explain the positive effects of sleep on consolidation. After a first stage in which a labile memory representation is formed, a further stabilisation of the memory trace takes place in the second stage, which is dependent on (REM) sleep. Walker has refined the latter stage into a stage in which a consolidation-based enhancement occurs. It is not completely clear what consolidation-based enhancement implies (...) and how it can be dissociated from a stage for memory-stabilisation. A more serious consideration, however, is whether a second stage in memory consolidation that is solely dependent on sleep, is really necessary. The classical, passive, interference theory is able to explain adequately the findings related to the effects of sleep and memory, and can lead perhaps better to an understanding of the highly variable data in this field. (shrink)
Research in the neurosciences continues to provide evidence that sleep plays a role in the processes of learning and memory. There is less of a consensus, however, regarding the precise stages of memory development during which sleep is considered a requirement, simply favorable, or not important. This article begins with an overview of recent studies regarding sleep and learning, predominantly in the procedural memory domain, and is measured against our current understanding of the mechanisms that govern memory (...) formation. Based on these considerations, I offer a new neurocognitive framework of procedural learning, consisting first of acquisition, followed by two specific stages of consolidation, one involving a process of stabilization, the other involving enhancement, whereby delayed learning occurs. Psychophysiological evidence indicates that initial acquisition does not rely fundamentally on sleep. This also appears to be true for the stabilization phase of consolidation, with durable representations, resistant to interference, clearly developing in a successful manner during time awake (or just time, per se). In contrast, the consolidation stage, resulting in additional/enhanced learning in the absence of further rehearsal, does appear to rely on the process of sleep, with evidence for specific sleep-stage dependencies across the procedural domain. Evaluations at a molecular, cellular, and systems level currently offer several sleep specific candidates that could play a role in sleep-dependent learning. These include the upregulation of select plasticity-associated genes, increased protein synthesis, changes in neurotransmitter concentration, and specific electrical events in neuronal networks that modulate synaptic potentiation. Key Words: consolidation; enhancement; learning; memory; plasticity; sleep; stabilization. (shrink)
The validity of dream recall is discussed. What is the relation between the actual dream and its later reflection? Nielsen proposes differential sleep mentation, which is probably determined by dream accessibility. Solms argues that REM sleep and dreaming are double dissociable states. Dreaming occurs outside REM sleep when cerebral activation is high enough. That various active sleep states correlate with vivid dream reports implies that REM sleep and dreaming are single dissociable states. Vertes & Eastman (...) reject that REM sleep is involved in memory consolidation. Considerable evidence for this was obtained by REM deprivation studies with the dubious water tank technique. [Nielsen; Solms; Vertes & Eastman]. (shrink)
There are strong resemblances between the neurobiological characteristics of hallucinations occurring in the particular case of schizophrenia and the hallucinatory activity observed during the rapid-eye-movement (dreaming) sleep stage: the same prefrontal dorsolateral deactivation; forebrain disconnectivity and disinhibition; sensory deprivation; and acetylcholine, monoamine, and glutamate modifications.
The following review summarizes and examines Mark Solms's article Dreaming and REM Sleep are controlled by different brain mechanisms, which argues why the understanding of REM sleep as the physiological equivalent of dreaming needs to be re-analyzed. An analysis of Solms's article demonstrates that he makes a convincing argument against the paradigmatic activation-synthesis model proposed by Hobson and McCarley and provides provocative evidence to support his claim that REM and dreaming are dissociable states. In addition, to situate Solms's (...) findings in concurrent research, other studies are mentioned that are further elucidated by his argument. [Solms]. (shrink)
Sleep disturbances are common for children with attention-deficit/hyperactivity disorder (ADHD) and are of great clinical significance. Brain dopamine plays an important role for both ADHD symptoms and sleep-wake regulation. We therefore suggest that one basic aspect of integrative brain-behavior relationship such as the sleep-wake cycle may certainly be addressed in a dynamic developmental theory of ADHD.
Hypnagogic and hypnopompic experiences (HHEs) accompanying sleep paralysis (SP) are often cited as sources of accounts of supernatural nocturnal assaults and paranormal experiences. Descriptions of such experiences are remarkably consistent across time and cultures and consistent also with known mechanisms of REM states. A three-factor structural model of HHEs based on their relations both to cultural narratives and REM neurophysiology is developed and tested with several large samples. One factor, labeled Intruder, consisting of sensed presence, fear, and auditory and (...) visual hallucinations, is conjectured to originate in a hypervigilant state initiated in the midbrain. Another factor, Incubus, comprising pressure on the chest, breathing difficulties, and pain, is attributed to effects of hyperpolarization of motoneurons on perceptions of respiration. These two factors have in common an implied alien ''other'' consistent with occult narratives identified in numerous contemporary and historical cultures. A third factor, labeled Unusual Bodily Experiences, consisting of floating/flying sensations, out-of-body experiences, and feelings of bliss, is related to physically impossible experiences generated by conflicts of endogenous and exogenous activation related to body position, orientation, and movement. Implications of this last factor for understanding of orientational primacy in self-consciousness are considered. Central features of the model developed here are consistent with recent work on hallucinations associated with hypnosis and schizophrenia. (shrink)
This essay represents a reflection on the nature of shufa, the Chinese “art of writing,” and its ontological grounding as a continuous, “durational transcription,” of an inscriptional event, producing a phenomenology of “viewing.” This distinguishes it from ordinary writing (xiezi) in which attention is focused on the lexical meaning of the written characters (i.e., an experience of “reading”). Viewing a calligraphic inscription actually unfolding in time (i.e., as a dynamical structure or “temporal object event”), however, raises an interesting theoretical question (...) concerning the two complementary aspects of temporal consciousness of calligraphy as both duration and unity. This will be addressed in terms of recent discussions of a dynamical approach to Edmund Husserl’s theory of time consciousness. (shrink)
We believe that this has been a constructive debate on the topic of memory consolidation and REM sleep. It was a lively and spirited exchange – the essence of science. A number of issues were discussed including: the pedestal technique, stress, and early REMD work in animals; REM windows; the processing of declarative versus procedural memory in REM in humans; a mnemonic function for theta rhythm in waking but not in REM sleep; the lack of cognitive deficits in (...) patients on antidepressant drugs that suppress or eliminate REM sleep; the disposition of conscious (dreams) and nonconscious material of REM sleep; and finally our theory of REM sleep. Although our position was strongly challenged, we still hold that REM sleep serves no role in the processing and consolidation of memory. (shrink)
This paper explores the meaning of dreamless sleep. First, I consider four reasons why we commonly pass over sleep's ontological significance. Second, I compare and contrast death and sleep to show how each is oriented to questions regarding the possibilities of "being-a-whole." In the third and final part, I explore the meaning and implications of "being-toward-sleep," arguing that human existence emerges atop naturally anonymous corporeality (i.e. living being). In sum, I try to show that we can (...) recover an authentic — if somewhat ambiguous — sense of "being-a-whole" only by recognizing the ontological significance of dreamless sleep. (shrink)
Insights into the role of sleep in the molecular mechanisms of memory consolidation may come from studies of activity-dependent synaptic plasticity, such as long-term potentiation (LTP). This commentary posits a specific contribution of sleep to LTP stabilization, in which mRNA transported to dendrites during wakefulness is translated during sleep. Brain-derived neurotrophic factor may drive the translation of newly transported and resident mRNA.
We argue that by neglecting the fact that procedural memory may also have episodic qualities, and by considering only a systems approach to memory, Walker's account of consolidation of learning during subsequent sleep ignores alternative accounts of how sleep stages may be interdependent. We also question the proposition that sleep-based consolidation largely bypasses hippocampal structures.
Unfortunately, some researchers think a good scientific theory is one that has been repeatedly confirmed, and a bad theory is one that has not received consistent confirmation. However, confirmation of a theory depends on the extent to which a hypothesis exposes itself to disconfirmation. One confirmation of a highly specific, falsifiable experiment can have a far greater impact than the disconfirmation of twenty experiments that are virtually unfalsifiable. This commentary (1) counteracts misleading biases regarding the REM sleep/memory consolidation theory, (...) and (2) demonstrates how chaotic cerebral activation during sleep is an essential component of long-term memory storage processes. [Vertes & Eastman]. (shrink)
During the paradoxical dreaming sleep stage, characterized by hallucinations and delusions, as in schizophrenia, the increased subcortical release of dopamine, the presynaptic inhibition of thalamic relay nuclei, and serotonergic disinhibition are in accordance with the model for the mechanism of hallucination-induction.
Physicist J. Richard Gott has given an argument that, if good, allows one to make accurate predictions for the future longevity of a process, based solely on its present age. We show that there are problems with some of the details of Gott’s argument, but we defend the crucial insight: in many circumstances, the greater the present age of a process, the more likely a longer future duration.
The Walker model raises a number of questions, particularly about the nature of the sleep states involved in consolidation enhancement. While REM sleep, Stage 2 sleep, and Stage 3/4 sleep have been implicated in procedural learning, we still do not understand which types of learning are involved with specific sleep states. Several possible ideas for future research are suggested.
We propose that sleep is linked to synaptic homeostasis. Specifically, we propose that: (1) Wakefulness is associated with synaptic potentiation in cortical circuits; (2) synaptic potentiation is tied to the homeostatic regulation of slow wave activity; (3) slow wave activity is associated with synaptic downscaling; and (4) synaptic downscaling is tied to several beneficial effects of sleep, including performance enhancement.
Following on from the target article, which presented a new model of procedural skill memory development, in this response I will reflect on issues raised by invited commentators and further expound attributes of the model. Discussion will focus on: evidence against sleep-dependent memory processing, definitions of memory stages and memory systems, and relationships between memory enhancement, sleep-stages, dreaming, circadian time, and sleep-disorders.
Summary. It is proposed to translate the mind-matter distinction into terms of mental and physical time. In the spirit of this idea, we hypothesize a relation between the intensity of mental presence and a crucial time scale (some seconds) often referred to as a measure for the duration of nowness. This duration is experimentally accessible and might, thus, offer a suitable way to characterize the intensity of mental presence. Interesting consequences with respect to the idea of a generalized (...) notion of mental presence, with human consciousness as a special case, are outlined. Our approach includes some features consistent with other, related ideas which are indicated. (shrink)
Nielsen's covert REM process model explains much of the mentation found in REM and NREM sleep, but stops short of postulating an interaction of waking cognitive processes with the dream mechanisms of REM sleep. It ranks with the Hobson et al. paper as a major theoretical advance. The Solms article does not surmount the ever-present problem of defining dreams in a manner conducive to advancing dream theory. Vertes & Eastman review the REM sleep and learning literature, but (...) make questionable assumptions in doing so. [Hobson et al.; Nielsen; Solms; Vertes & Eastman]. (shrink)
The phenomenon of dreamless sleep and its philosophical consequences, particularly deep sleep's relevance to such issues as Self, Consciousness, Personal Identity, Unity of Subject, and Disembodied Life, are explored through a discussion, in varying detail, of certain noted doctrines and views--for example of Advaita Vedānta, Hegel, and H. D. Lewis. Finally, with a cue from Leibniz and McTaggart, the suggestion is made that at no stage during sleep is the self without some perceptions, however indeterminate. Support for (...) this hypothesis is claimed from the current psychoanalytic opinion that mental activity does not cease during any part of sleep and that human beings continue to dream even in the so-called dreamless state. (shrink)
Although considerable attention has been paid to the possible involvement of sleep in memory processing, there is no substantial evidence for it. Walker describes a phenomenon of consolidation-based enhancement (CBE), whereby performance on select procedural tasks improves with overnight sleep; that is, without additional practice on the tasks. CBE, however, appears restricted to a few tasks, and even with these tasks CBE is not confined to sleep but also occurs during wakefulness. Sleep serves no unique role (...) in this process. At best, CBE is a slow, time-dependent process of consolidation that begins with task acquisition in waking and can under some circumstances extend to sleep. (shrink)
The crying curve across early infancy may reflect the developing interaction between circadian and homeostatic processes of sleep-wake regulation. Excessive crying may be interpreted as a misalignment of the two processes. On the basis of the proposed mechanism, excessive crying may be an honest signal of need, namely, to elicit parental resources to modulate the behavioral state.
The “problem” of dreaming in NREM sleep continues to challenge models that propose a causal relationship between REM mechanisms and the psychological features of dreaming. I suggest that, ultimately, efforts to identify correspondences among multiple levels of analysis will be more productive for dream theory than attempts to reduce dreaming to any one level of analysis. [Hobson et al. ; Nielsen].
As reported by Vertes & Eastman, convincing evidence rules out any role for REM sleep in memory consolidation. However, they do not provide convincing evidence for their claim that sleep in generaI – as opposed to REM sleep per se – has no influence on memory consolidation. Recent correlational data suggest that the number of NREM/REM cycles is associated with performance on a verbal recall task. [Vertes & Eastman].
Numerous studies have replicated the finding of mentation in both rapid eye movement (REM) and nonrapid eye movement (NREM) sleep. However, two different theoretical models have been proposed to account for this finding: (1) a one-generator model, in which mentation is generated by a single set of processes regardless of physiological differences between REM and NREM sleep; and (2) a two-generator model, in which qualitatively different generators produce cognitive activity in the two states. First, research is reviewed demonstrating (...) conclusively that mentation can occur in NREM sleep; global estimates show an average mentation recall rate of about 50% from NREM sleep – a value that has increased substantially over the years. Second, nine different types of research on REM and NREM cognitive activity are examined for evidence supporting or refuting the two models. The evidence largely, but not completely, favors the two-generator model. Finally, in a preliminary attempt to reconcile the two models, an alternative model is proposed that assumes the existence of covert REM sleep processes during NREM sleep. Such covert activity may be responsible for much of the dreamlike cognitive activity occurring in NREM sleep. Key Words: cognition in sleep; dreaming; NREM sleep; REM sleep; sleep mentation. (shrink)
The target articles on sleep and dreaming are discussed in terms of the concept of search activity integrating different types of behavior, body resistance, REM sleep/dream functions, and the brain catecholamine system. REM sleep may be functionally sufficient or insufficient, depending on the dream scenario, the latter being more important than the physiological manifestation of REM sleep. REM sleep contributes to memory consolidation in the indirect way. [Nielsen; Revonsuo; Solms; Vertes & Eastman].
We present evidence disputing the hypothesis that memories are processed or consolidated in REM sleep. A review of REM deprivation (REMD) studies in animals shows these reports to be about equally divided in showing that REMD does, or does not, disrupt learning/memory. The studies supporting a relationship between REM sleep and memory have been strongly criticized for the confounding effects of very stressful REM deprivation techniques. The three major classes of antidepressant drugs, monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (...) (TCAs), and selective serotonin reuptake inhibitors (SSRIs), profoundly suppress REM sleep. The MAOIs virtually abolish REM sleep, and the TCAs and SSRIs have been shown to produce immediate (40–85%) and sustained (30–50%) reductions in REM sleep. Despite marked suppression of REM sleep, these classes of antidepressants on the whole do not disrupt learning/memory. There have been a few reports of patients who have survived bilateral lesions of the pons with few lingering complications. Although these lesions essentially abolished REM sleep, the patients reportedly led normal lives. Recent functional imaging studies in humans have revealed patterns of brain activity in REM sleep that are consistent with dream processes but not with memory consolidation. We propose that the primary function of REM sleep is to provide periodic endogenous stimulation to the brain which serves to maintain requisite levels of central nervous system (CNS) activity throughout sleep. REM is the mechanism used by the brain to promote recovery from sleep. We believe that the cumulative evidence indicates that REM sleep serves no role in the processing or consolidation of memory. Key Words: antidepressant drugs; brain stem lesions; dreams; functional imaging; memory consolidation; REM deprivation; REM sleep; theta rhythm. (shrink)
In L'Arrêt de mort, as Derrida suggests, an ‘epochal suspension’ manifests itself, compulsively pulsating so as to conjure a certain spectrality beyond all consciousness, perception, or ordinary attentiveness. Re-reading Blanchot's text, I argue that it is on the borderlines of sleep that the ‘arrythmic pulsation’ of the arrêt de mort happens as impossible event – ‘the state of suspension in which it's over – and over again, and you'll never have done with that suspension itself’, to quote Derrida once (...) more. While ‘Living On’ makes little of sleep, however, I take this cue to follow a pathway which leads from Blanchot to Levinas. Blanchot's writing exposes the sleep of reason which occurs in the very promise of perfect day, a promise which mutates in the dream he associates with the ‘other night’, a dream which harbours the irrepressible return of ‘time's absence’, and which opens on to the very ‘outside’ which the world – and the self – lacks or wants (as much as ‘world’ or ‘self’ seek to overcome this ‘outside’ as such). Levinas, meanwhile, wants to think irremissible pure existing (il y a) in terms of insomnia; in contrast, consciousness seeks to assert itself over the unremitting presence of the ‘there is’ through its capacity for unconsciousness or sleep. This essay seeks to attend to the complexities of a certain ‘fatality of being’ that threatens to sweep away the ‘ego’ as consciousness's capacity to sleep is confronted by the radical vigilance of insomnia and the deep anonymity of the night (Existence and Existents). (shrink)
A new working hypothesis of sleep-wake cycle mechanisms is proposed, based on ontogeny and functional/anatomic compression of two stochastic neuronal models of information coding that complement each other in a key/lock fashion: the axonal arbor patterns (AAP – “hardware”) and the neuronal spike interval inequality patterns (SIIP – “software”). [Hobson et al.; Nielsen; Revonsuo; Solms; Vertes & Eastman].
Certain features of Stage NREM sleep – for example, rhythmic voltage oscillation in thalamic neurons – are physiologically inhospitable to “REM sleep processes.” In Stage 2, the sleep spindle and its refractory period must limit the incursion of “covert REM,” and thus the extent of REM-like cognition. If these hyperpolarization-dependent events also inform Stage NREM cognition, does a “1-gen” model suffice to account for REM-NREM differences? [Nielsen].
This commentary implicates the neostriatum in the production of the EEG sleep spindle and in the processing of motor procedural learning in sleep. Whether the sleep spindle may implement not only the consolidation-based enhancement of procedural learning, but also its initial consolidation, is considered; as is the fit between (1) corticostriatal anatomy and physiology, and (2) the physical properties of the sleep spindle.
In this chapter, we aimed at further characterizing the functional neuroanatomy of the human rapid eye movement (REM) sleep at the population level. We carried out a meta-analysis of a large dataset of positron emission tomography (PET) scans acquired during wakefulness, slow wave sleep and REM sleep, and focused especially on the brain areas in which the activity diminishes during REM sleep. Results show that quiescent regions are confined to the inferior and middle frontal cortex and (...) to the inferior parietal lobule. Providing a plausible explanation for some of the features of dream reports, these findings may help in refining the concepts, which try to account for human cognition during REM sleep. In particular, we discuss the significance of these results to explain the alteration in executive processes, episodic memory retrieval and self representation during REM sleep dreaming as well as the incorporation of external stimuli into the dream narrative. (shrink)
In this target article, Walker seeks to clarify the current state of knowledge regarding sleep and memory. Walker's review represents an impressively heuristic attempt to synthesize the relevant literature. In this commentary, we question the focus on procedural memory and the use of the term “consolidation,” and we consider the extent to which empirically testable predictions can be derived from Walker's model.
Both Solms and Nielsen acknowledge the difficulty of accounting for the similarities between REM and NREM sleep mentation with a two-generator model, and each link dreams, either explicitly (Solms) or implicitly (Nielsen), to brain activation. At present, however, no data indicate that brain activation can be demonstrated whenever vivid dream reports are obtained. [Nielsen; Solms].
The physicist J. Richard Gott has given an argument which, if good, allows one to make accurate predictions for the future longevity of a process, based solely on its present age. We show that there are problems with some of the details of Gott's argument, but we defend the core thesis: in many circumstances, the greater the present age of a process, the more likely a longer future duration.
It is suggested that Walker's consolidation-based enhancement of memory during REM sleep corresponds to the simulated annealing technique used for function optimization, and that robotic and AI design could benefit from inclusion of a deliberate REM-like memory optimization phase.
We address the notion of integration of new memory representations and the potential dependence of this phenomenon on sleep, in light of recent findings on the lexicalization of spoken words. A distinction is introduced between measures tapping directly into the strength of the newly acquired knowledge and indirect measures assessing the influence of this knowledge on spoken word identification.
If reports given on experimental awakenings validly represent mental activity that was underway before the awakening, REM sleep is neither necessary nor sufficient for dreaming. Another intuitively attractive hypothesis for its function – that REM consolidates or otherwise modifies memory traces acquired while awake – is not supported by the preponderant evidence. There is growing acceptance of the possibility that REM functions to support sleep rather than waking brain processes. [Hobson et al.; Nielsen; Solms; Vertes & Eastman].
The descriptive “null” hypothesis is strengthened by the fact that during dreaming sleep stage, the primary visual cortex is deactivated as compared with other sleep stages.
The target articles by Hobson et al., by Solms, and by Nielsen can be combined to further our understanding of the neurological basis of dreaming during REM and, notably, NREM sleep. Revonsuo adds to our understanding of the function of dreams from the perspective of behavioral biology but overstates its importance. Vertes & Eastman fail in their effort to discount memory enhancement as a function of REM sleep. [Hobson et al.; Nielsen; Revonsuo; Solms; Vertes & Eastman].
Nielsen's concept of “covert REM sleep” accounts for more of the complexity in sleep psychophysiology than its conceptual predecessors such as the tonic-phasic model. With new neuroimaging findings, such concepts lead to more precise sleep psychophysiology including both traditional polysomnographic signs and neuronal activity in greater proximity to the actual point sources and distributed networks which generate dreaming. [Hobson et al.; Nielsen].
Dreams are used figuratively throughout Greek literature to refer to something fleeting and/or unreal. In Plato, this metaphorical language is specifically used to describe an epistemological distinction: the one who has false knowledge or opinion is said to be dreaming while the one who has true knowledge is said to be awake. These figures are also central to Philo of Alexandria's philosophical language in De somniis 1-2 and De Iosepho . Although scholars have documented these epistemological metaphors in Plato and (...) related treatments of the concept of sleep in Heraclitus, it has not been discussed in any detail in relation to Philo's treatment of Joseph in these two treatises. In De somniis 1-2, Philo primarily emphasizes his role as a dreamer and thus one incapable of true knowledge. In De Iosepho , Joseph is a dream interpreter who is not only awake but also capable of interpreting the figurative dream of life to which most people are subject. Although some scholars have considered these treatises contradictory in terms of their treatments of Joseph, an analysis of Philo's figurative use of sleep and dreaming reveals that they are a part of a coherent exegetical framework. (shrink)
The phenomenon of dreamless sleep and its philosophical consequences, particularly deep sleep's relevance to such issues as Self, Consciousness, Personal Identity, Unity of Subject, and Disembodied Life, are explored through a discussion, in varying detail, of certain noted doctrines and views--for example of Advaita Vedānta, Hegel, and H. D. Lewis. Finally, with a cue from Leibniz and McTaggart, the suggestion is made that at no stage during sleep is the self without some perceptions, however indeterminate. Support for (...) this hypothesis is claimed from the current psychoanalytic opinion that mental activity does not cease during any part of sleep and that human beings continue to dream even in the so-called dreamless state. (shrink)
In this commentary the “incredibly robust” evidence for the relationship between sleep and procedural memory is questioned; inconsistencies in the existing data are pointed out. In addition, some suggestions about extending research are made, for example, studying REM sleep augmentation or memory consolidation in patients with sleep disorders. Last, the possibility of a relationship between dreaming and memory processes is discussed.
Does sleep restore brain function or does it consolidate memory? I argue that memory consolidation during sleep is an offshoot of restitution. Continual learning causes local synapse-specific neural fatigue, which then masks expression of that learning, especially on time-limited tests of procedural skills. Sleep serves to restore the fatigued synapses, revealing the consolidation-based enhancement observed as a “latent” overnight improvement in learning.
Initial claims that REM sleep is important in the consolidation of all memories have been revised and reduced to the claim that sleep has a role only in the consolidation of procedural learning. Now, Walker hypothesizes that sleep has no role in the “stabilization phase of consolidation” but only in the “enhanced learning” phase of procedural learning. Evidence for this vague, truncated hypothesis remains as inconsistent as that for prior claims.
By assuming that REM sleep either plays a critical role in all memory consolidation or no role in any, Vertes & Eastman have chosen to reject, rather than explain, robust experimental findings of a role for sleep in memory and learning. In contrast, Nielsen has attempted to integrate conflicting findings in the dispute over REM versus NREM mentation. Researchers must trust the data more and the theories less, and build integrative rather than exclusionary models if they hope to (...) resolve these knotty problems effectively. [Nielsen; Vertes & Eastman]. (shrink)
Cellular mechanisms hypothesized to underlie sleep-dependent memory consolidation are expressed throughout the brain during sleep. Use of sleep deprivation to evaluate the functional importance of these mechanisms is confounded by degradation in waking performance resulting from impaired vigilance. There is a need for methods that will permit disruption of specific mechanisms during sleep only in the neuronal circuits most critically involved in learning. This should be accomplished without global sleep disruption and with preservation of the (...) restorative aspects of sleep. (shrink)
The most distinctive activities of humankind and the source of its greatest achievements are the scientific investigation of the world and the creation of art. Newton's Sleep examines their complementary roles in contemporary life and defends both against those who assert that science is spiritually empty and inherently dangerous and that art is trivialised by a lack of social mission.
(1) Substituting (as Solms does) forebrain for brainstem in the search for a dream “controller” is counterproductive, since a distributed system need have no single controller. (2) Evidence against episodic memory consolidation does not show that REM sleep has no role in other types of memory, contra Vertes & Eastman. (3) A generalization of Revonsuo's “threat simulation” model in reverse is more plausible and is empirically testable. [Hobson et al.; Solms; Revonsuo; Vertes & Eastman].
The WEAVER++ model discussed by Levelt et al. assumes incremental encoding and articulation following complete encoding. However, many of the response latency results can also be accounted for by assuming incremental articulation. Another temporal variable, initial segment duration, can distinguish WEAVER++'s incremental encoding account from the incremental articulation account.
Robert Koch (1843–1910) discovered the causal agents for tuberculosis, cholera, and anthrax. The 1905 Nobel Prize acknowledged Koch's criteria for identifying the causal agent of an infectious disease. These criteria remain useful and the data reviewed below show that the cholinergic contributions to REM sleep control are confirmed by Koch's postulates. [Hobson et al.].
We consider Walker's thorough review in the context of thinking about future research on the relation between sleep and memory. We first address methodological issues including type of memory and sleep-stage dependency. We suggest a broader investigation of potential signaling molecules that may be critical to sleep-related consolidation. A brief review of the importance of the stress hormone cortisol illustrates this point.
Little is known about how to generate plausible new scientific ideas. So it is noteworthy that 12 years of self-experimentation led to the discovery of several surprising cause-effect relationships and suggested a new theory of weight control, an unusually high rate of new ideas. The cause-effect relationships were: (1) Seeing faces in the morning on television decreased mood in the evening (>10 hrs later) and improved mood the next day (>24 hrs later), yet had no detectable effect before that (0–10 (...) hrs later). The effect was strongest if the faces were life-sized and at a conversational distance. Travel across time zones reduced the effect for a few weeks. (2) Standing 8 hours per day reduced early awakening and made sleep more restorative, even though more standing was associated with less sleep. (3) Morning light (1 hr/day) reduced early awakening and made sleep more restorative. (4) Breakfast increased early awakening. (5) Standing and morning light together eliminated colds (upper respiratory tract infections) for more than 5 years. (6) Drinking lots of water, eating low-glycemic-index foods, and eating sushi each caused a modest weight loss. (7) Drinking unflavored fructose water caused a large weight loss that has lasted more than 1 year. While losing weight, hunger was much less than usual. Unflavored sucrose water had a similar effect. The new theory of weight control, which helped discover this effect, assumes that flavors associated with calories raise the body-fat set point: The stronger the association, the greater the increase. Between meals the set point declines. Self-experimentation lasting months or years seems to be a good way to generate plausible new ideas. Key Words: breakfast; circadian; colds; depression; discovery; fructose; innovation; insomnia; light; obesity; sitting; standing; sugar. (shrink)
The relationship between sleep and memory has been controversial since the 1950s. Studies on delayed dream recall and long-term retention of pre-sleep stimuli indicate that sleep may have a positive role in the consolidation of information. This positive indication counterbalances the negative one from the studies on the effects of REM deprivation. [Vertes & Eastman].
Learning procedural skills involves improvement in speed and accuracy. Walker proposes two stages of memory consolidation: enhancement, which requires sleep, and stabilization, which does not require sleep. Speed improvement for a motor learning task but not accuracy occurs after sleep-dependent enhancement. We discuss this finding in the context of computational models and underlying sleep mechanisms.
In this manuscript Hobson et al. propose a model exploring qualitative differences between the three states of consciousness, waking, NREM sleep, and REM sleep, in terms of state-related brain activity. The model consists of three factors, each of which varies along a continuum, creating a three-dimensional space: activation (A), information flow (I), and mode of information processing (M). Hobson has described these factors previously (1990; 1992a). Two of the dimensions, activation and modulation, deal directly with subcortical influences upon (...) cortical structures – the reticular activation system, with regard to the activation dimension and the locus coeruleus and the pontine raphe neuclei, with regard to the modulation dimension. The focus of this review is a further exploration of the interaction between dreaming and the cortical and subcortical structures relevant to REM sleep eye movements. [Hobson et al. ]. (shrink)
This article argues that corporate management in the United States has expanded its scope beyond office walls and encompasses many aspects of workers' daily lives. One new element of corporate training is the micromanagement of sleep; self-help books, newspaper reports, magazine articles, and consulting firms currently advise workers and supervisors on optimizing productivity by cultivating certain sleep habits. Although consultants and self-help books make specific recommendations about sleep, most medical research is inconclusive about sleep's benefits for (...) human performance. Using the ideas of Michel Foucault and Gilles Deleuze as a philosophical backdrop, this article examines the complex and often contradictory links between self-help, medicine, and corporate governance. (shrink)
In this series of articles, several new hypotheses on sleep and dreaming are presented. In each case, we feel the data do not adequately support the hypothesis. In their lengthy discourse, Hobson et al. represent to us the familiar reciprocal interaction model dressed in new clothes, but expanded beyond reasonable testability. Vertes & Eastman have proposed that REM sleep is not involved in memory consolidation. However, we do not find their arguments persuasive in that limited differences in activity (...) in REM and waking do not lend credence to the idea that memory consolidation occurs in one state and not the other. Solms makes an argument that dreams are generated from the dopaminergic forebrain based largely on pathological lesion studies in humans. We recognize that this argument has some intuitive appeal and agree with some of the tenets but we do not feel that the arguments are completely convincing due to the lack of anatomical controls, including symmetry and laterality. On the whole, there are interesting arguments put forward in these target articles but the evidence does not convince us that new vistas are opened. No Holy Grail of sleep here! [Hobson et al.; Solms; Vertes & Eastman]. (shrink)
We model the optimal copulation duration in the yellow dungflyScathophaga stercoraria, assuming that males optimize their reproductive success per day. The independent state-variables of a male are the actual sperm reserves, the female encounterrate and the time of the day. We used stochastic dynamic programming to predict the optimal copulation duration. The model predicts that copulation duration should increase (i) for larger males, (ii) for males with a better previous diet (iii) for males accepting more females (iv) (...) for males staying away from the dung during a whole day. It also predicts that (v) males on a restricted diet should accept fewer matings, (vi) testes size should shrivel during the day, (vii) the correlation coefficient between copulation duration and sequence number should decrease with increasing initial sperm reserve and with increasing number of copulations performed on a given day.There are two essential differences between our model and a model of Parker (1992). (i) Our model assumes that males optimize per day. Parker's model assumes that males optimize per mating bout, one bout comprising many days. (ii) Since all the important state variables depend only on the moment of the copulation, our model does not assume a long-time memory in dungflies, and it is more flexible than Parker's model. Overall, both models explain the data available equally well. (shrink)
What, if anything do dreams tell us about ourselves? What is the relationship between types of sleep and types of dreams? Does dreaming serve any purpose? Or are dreams simply meaningless mental noise--'unmusical fingers wandering over the piano keys'? With expertise in philosophy, psychology, and neuroscience, Owen Flanagan is uniquely qualified to answer those questions. And in Dreaming Souls he provides both an accessible survey of the latest research on sleep and dreams and a compelling new theory about (...) the nature and function of dreaming. Flanagan argues that while sleep has a clear biological function and adaptive value, dreams are merely side effects, 'free-riders', irrelevant from an evolutionary point of view. But dreams are hardly unimportant. Indeed, Flanagan argues that dreams are self-expressive, the result of our need to find or create meaning, even when we are sleeping. Rejecting Freud's theory of manifest and latent content--of repressed wishes appearing in disguised form--Flanagan shows how brainstem activity during sleep generates a jumbled profusion of memories, images, thoughts, emotions, and desires, which the cerebral cortex then attempts to shape into a more or less coherent story. Such dream narratives range from the relatively mundane worries of non-REM sleep tot he fantastic confabulations of deep REM that resemble pyschotic episodes in their strangeness. But, however bizarre these narratives may be, they can shed light on our mental life, our well being, and our sense of self. Written with clarity, lively wit, and remarkable insight, Dreaming Souls offers a fascinating new way of apprehending one of the oldest mysteries of mental life. (shrink)
Ischemic stroke involves numerous and complex pathophysiological mechanisms including blood flow reduction, ionic exchanges, spreading depressions and cell death through necrosis or apoptosis. We used a mathematical model based on these phenomena to study the influences of intensity and duration of ischemia on the final size of the infarcted area. This model relies on a set of ordinary and partial differential equations. After a sensibility study, the model was used to carry out in silico experiments in various ischemic conditions. (...) The simulation results show that the proportion of apoptotic cells increases when the intensity of ischemia decreases, which contributes to the model validation. The simulation results also show that the influence of ischemia duration on the infarct size is more complicated. They suggest that reperfusion is beneficial when performed in the early stroke but may be either inefficacious or even deleterious when performed later after the stroke onset. This aggravation could be explained by the depolarisation waves which might continue to spread ischemic damage and by the speeding up of the apoptotic process leading to cell death. The effect of reperfusion on cell death through these two phenomena needs to be further studied in order to develop new therapeutic strategies for stroke patients. (shrink)
The role of brain monoamines may be important for the neurobiology of the alterations of visual alertness in recurrent complex visual hallucinations (RCVH). This is evidenced by sleep research, neurophysiologic, and clinical data. Hence, the mechanisms of RCVH may not be simply explained by acetylcholine underactivity only.
Matthew Walker's article has prompted us to consider neuropsychiatric disorders and pharmacological effects associated with sleep alterations, and aspects of memory affected. Not all disorders involving insomnia show memory impairment, and hypersomnias can be associated with memory deficits. The use of cholinergic medication in dementia indicates that consideration of the link between sleep and memory is more than academic.
Nancy Cartwright views models as blueprints for nomological machines ? machines that, if properly shielded, generate law?like behaviour or regularities. Marcel Boumans has argued that we can look for devices inside models, which enable us to measure aspects of these regularities. Therefore, if models do produce regular behaviour (Cartwright), they might perhaps generate numbers about phenomena in the world, provided we can locate a good measuring device in the model (Boumans). How do they do this? Models are often (...) understood to consist of internal principles and bridge principles. Both of these play a role in the measuring process. This paper suggests that we can understand the internal principles to be responsible for generating the regularities displayed by the model ? and for many users of the model, this is sufficient use. The bridge principles (following Cartwright ? ?the real bridge principles?) are a matter of picking the right mathematical representation to make the model work with respect to some real world case at hand. These ?real? bridge principles may enable the model to generate numbers and so serve to make the model into a measuring device. This paper explores this construction of a measuring device of duration dependence of unemployment. Since search theory cannot be made operational for this purpose duration models, which model of the outflow process of unemployment with a Weibull function, are taken as a representation of reservation wage setting in search models. As I show, this Weibull function serves as a bridge principle to make a measure of the elasticity of response between unemployment benefit and duration of unemployment. It enables measurement to take place by modelling behaviour according to some assumptions, which operate as constraints. While this Weibull function serves this purpose, its assumptions are arbitrary rather than connected to theory, and measurements generated with this bridge principle turn out to be highly sensitive to its specification. The Weibull function does enable the model to function as a measuring device, but the lack of ability to make newly invoked unobservable variables operational makes it of dubious worth. (shrink)
