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 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)

The implicit-explicit distinction is applied to knowledge representations. Knowledge is taken to be an attitude towards a proposition which is true. The proposition itself predicates a property to some entity. A number of ways in which knowledge can be implicit or explicit emerge. If a higher aspect is known explicitly then each lower one must also be known explicitly. This partial hierarchy reduces the number of ways in which knowledge can be explicit. In the most important type of implicit knowledge, (...) representations merely reflect the property of objects or events without predicating them of any particular entity The dearest cases of explicit knowledge of a fact are representations of one's own attitude of knowing that fact. These distinctions are discussed in their relationship to similar distinctions such as procedural-declarative, conscious unconscious, verbalizable-nonverbalizable, direct-indirect tests, and automatic voluntary control. This is followed by an outline of how these distinctions can be used to integrate and relate the often divergent uses of the implicit-explicit distinction in different research areas. We illustrate this for visual perception, memory, cognitive development, and artificial grammar learning. (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.

A Nobel Prize-winning scientist and a leading brain researcher show how the brain creates conscious experience.

Clinical and experimental evidence suggests that hippocampal damage causes more severe disruption of episodic memories if those memories were encoded in the recent rather than the more distant past. This decrease in sensitivity to damage over time might reflect the formation of multiple traces within the hippocampus itself, or the formation of additional associative links in entorhinal and association cortices. Physiological evidence also supports a two-stage model of the encoding process in which the initial encoding occurs during active waking and (...) deeper consolidation occurs via the formation of additional memory traces during quiet waking or slow-wave sleep. In this article I will describe the changes in cholinergic tone within the hippocampus in different stages of the sleep-wake cycle and will propose that these changes modulate different stages of memory formation. In particular, I will suggest that the high levels of acetylcholine that are present during active waking might set the appropriate dynamics for encoding new information in the hippocampus, by partially suppressing excitatory feedback connections and so facilitating encoding without interference from previously stored information. By contrast, the lower levels of acetylcholine that are present during quiet waking and slow-wave sleep might release this suppression and thereby allow a stronger spread of activity within the hippocampus itself and from the hippocampus to the entorhinal cortex, thus facilitating the process of consolidation of separate memory traces. (shrink)

The function of REM, or any other stage of sleep, can currently only be conjectured. A rational evaluation of the role of REM in memory processing requires systematic testing of hypotheses that are optimally derived from a complete synthesis of existing knowledge. Our view is that the large number of studies supporting a relationship between REM-related brain activity and memory is not easily explained away. [Vertes & Eastman].

This Hartley applies to man, and observes, that as man cannot comprehend his own nature, he must imagine a finite being superior to him that can ...