Relatively poor memory for dreams is important evidence for Hobson et al.'s model of conscious states. We describe the time-gap experience as evidence that everyday memory for waking states may not be as good as they assume. As well as being surprisingly sparse, everyday memories may themselves be systematically distorted in the same manner that Revonsuo attributes uniquely to dreams. [Hobson et al.; Revonsuo].

Solms shows the cortical basis for why dreams reflect waking concerns and goals, but with deficient volition. I argue the latter relates to Hobson et al.'s process I as well as M. A memory function for REM sleep is possible, but may be irrelevant to dream characteristics, which, contrary to Revonsuo, mirror the range of waking emotions, positive and negative. [Hobson et al.; Nielsen; Solms; Revonsuo; Vertes & Eastman].

Since the discovery that the characteristics of dreaming sleep are far stronger in Stage 1 rapid eye movement sleep than in any other biological state, investigators have attempted to determine the relative responsibility of the tonic versus the phasic properties of REM sleep for the different characteristics of dreaming–features such as the amount of information in the dream report, the brightness and clarity of the visual images, shifts in thematic continuity, and incongruities of image and meaning. The present experiment is (...) designed to identify dream characteristics that are specifically associated with tonic changes in level of cortical activation within sleep. It samples reports of imagery and thought during spontaneous variations within one phase of the 24-h diurnal rhythm and across the REM-NREM sleep cycle in order to identify the independent and joint contributions of the two cycles to imagery and thought. The rising phase of the diurnal cycle in the late night and morning was estimated from clock time during the late night and early morning and was varied by delaying the sleep onset and waking time of the subjects. Considered together with other studies, the results suggest that the major determinant of vivid visual imagery and enhanced cognitive activity during sleep is a pattern of subcortical and cortical activation that is common to both the REM phase of the REM-NREM cycle and the activated phase of the 24-h diurnal wake-sleep cycle. (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)

Task unrelated thought (TUT) refers to thought directed away from the current situation, for example a daydream. Three experiments were conducted on healthy participants, with two broad aims. First, to contrast distributed and encapsulated views of cognition by comparing the encoding of categorical and random lists of words (Experiments One and Two). Second, to examine the consequences of experiencing TUT during study on the subsequent retrieval of information (Experiments One, Two, and Three). Experiments One and Two demonstrated lower levels of (...) TUT and higher levels of word-fragment completion whilst encoding categorical relative to random stimuli, supporting the role of a distributed resource in the maintenance of TUT. In addition the results of all three experiments suggested that experiencing TUT during study had a measurable effect on subsequent retrieval. TUT was associated with increased frequency of false alarms at retrieval (Experiment One). In the subsequent experiments TUT was associated with no advantage to retrieval based on recollection, by manipulating instructions at encoding (Experiment Two), and/or at retrieval (Experiment Three). The implications of the results of all three experiments are discussed in terms of recent accounts of memory retrieval and conscious awareness. (shrink)

From the neurophysiological perspective, thinking in dreaming and the quality of dream thought have been considered hallucinatory, bizarre, illogical, improbable, or even impossible. This empirical phenomenological research concentrates on testing whether dream thought can be defined as rational in the sense of an intervening mental process between sensory perception and the creation of meaning, leading to a conclusion or to taking action. From 10 individual dream journals of male participants aged 22–59 years and female participants aged 25–49 years, we delimited (...) four dreams per journal and randomly selected five thought units from each dream for scoring. The units provided a base for testing a hypothesis that the thought processes of dream construction are rational. The results support the hypothesis and demonstrate that eight fundamental rational thought processes can be applied to the dreaming process. (shrink)

Dreams are a remarkable experiment in psychology and neuroscience, conducted every night in every sleeping person. They show that the human brain, disconnected from the environment, can generate an entire world of conscious experiences by itself. Content analysis and developmental studies have promoted understanding of dream phenomenology. In parallel, brain lesion studies, functional imaging and neurophysiology have advanced current knowledge of the neural basis of dreaming. It is now possible to start integrating these two strands of research to address fundamental (...) questions that dreams pose for cognitive neuroscience: how conscious experiences in sleep relate to underlying brain activity; why the dreamer is largely disconnected from the environment; and whether dreaming is more closely related to mental imagery or to perception. (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)

Thinking is known to be state dependent but a systematic study of how thinking in dreams differs from thinking while awake has not been done. The study consisted of analyzing the dream reports of 26 subjects who, in addition to providing dream reports also provided answers to questions about their thinking within the dream. Our hypothesis was that thinking in dreams is not monolithic but has two distinct components, one that is similar to wake-state cognition, and another that is fundamentally (...) different. We found that cognition within a dream scenario was similar to that of wake-state cognition, but that thinking about the scenario itself was deficient and very different than wake-state thinking. (shrink)

Two experiments employed experience sampling to examine the factors associated with a prospective and retrospective focus during mind wandering. Experiment One explored the contribution of working memory and indicated that participants generally prospect when the task does not require continuous monitoring. Experiment Two demonstrated that in the context of reading, interest in what was read suppressed both past and future-related task-unrelated-thought. Moreover, in disinterested individuals the temporal focus during mind wandering depended on the amount of experience with the topic matter—less (...) experienced individuals tended to prospect, while more experienced individuals tended to retrospect. Together these results suggest that during mind wandering participants’ are inclined to prospect as long as the task does not require their undivided attention and raise the intriguing possibility that autobiographical associations with the current task environment have the potential to cue the disinterested mind. (shrink)

Pierre Maquet1,2,6, Steven Laureys1,2, Philippe Peigneux1,2,3, Sonia Fuchs1, Christophe Petiau1, Christophe Phillips1,6, Joel Aerts1, Guy Del Fiore1, Christian Degueldre1, Thierry Meulemans3, André Luxen1, Georges Franck1,2, Martial Van Der Linden3, Carlyle Smith4 and Axel Cleeremans5.