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Five cocaine-dependent individuals completed a 22-day inpatient study of sleep and cognition. Following 3 days of drug-free baseline, participants underwent 3 days of twice-daily smoked cocaine base self-administration (6 50-mg doses, 14 minutes apart), followed by 15 days of abstinence. Each morning and afternoon, the CDR repeatable, multiple-version, computerized cognitive battery (whose stability following practice has been documented) was administered. During abstinence, performance deteriorated on vigilance tasks (especially reaction time) as well as on immediate and delayed verbal recognition tasks but not on working memory tasks. Declines were most evident in the afternoon. Data suggest that abstinence can unmask cognitive deficits induced by chronic cocaine use and circadian factors may mediate their severity. Keywords: Cocaine, abstinence, binge, cognition, attention, memory, repeated assessments, INTRODUCTION Much concern has been raised recently regarding possible adverse effects of cocaine on cognitive functioning (1-9). In general, these studies have compared abstinent cocaine abusers to matched controls with [...]

Loneliness predicts morbidity and mortality from broad-based causes, but the reasons for this effect remain unclear. Few differences in traditional health behaviors (e.g., smoking, exercise, nutrition) have been found to differentiate lonely and nonlonely individuals. We present evidence that a prototypic restorative behavior--sleep--does make such a differentiation, not through differences in time in bed or in sleep duration, but through differences in efficacy: In the study we report here, lonely individuals evinced poorer sleep efficiency and more time awake after sleep onset than nonlonely individuals. These results, which were observed in controlled laboratory conditions and were found to generalize to the home, suggest that lonely individuals may be less resilient than nonlonely individuals in part because they sleep more poorly. These results also raise the possibility that social factors such as loneliness not only may influence the selection of health behaviors but also may modulate the salubrity of restorative behaviors.

As a normal psychological event, dreaming is an object of fascination and of conflicting explanation. In biopsychological terms, this article compares 3 explanations of 1 salient feature of dream cognition. Physical movement can be measured in dream reports, can be understood in physiologic terms, and can provide a focus for comparing dream theories. In addition, dreamed motion may have functional importance. The authors discuss dream motor data that conflict with Freud's explanation of dream movement and with a distributed activation explanation but coincide with an activation-synthesis hypothesis. Because physiologic models of sleep intersect with physiologic models of psychopathology, this approach may be relevant to psychopathological dreaming.

The evolution of sleep patterns in developing kittens was studied using time-lapse video technology and direct observation. The duration, frequency, and onset of the behavioural states and interactions of the cats were analyzed and then organized into phases that represent major changes in developmental structure during the first 6 weeks of kitten life. We have demonstrated that the kittens began exhibiting adult bi-cyclic sleep patterns on approximately Day 30 of development. During the 10-day period that preceded this consolidation of sleep pattern, REM sleep decreased by half, with a reciprocal increase in NREM sleep. These changes were coincident with an increase in kitten pattern motor behaviour and an increase in stimulation of the kittens by the mother during her bi-cyclic active periods.

The exclusion of thinking from recent studies of sleep mentation has hindered a full appreciation of how cognitive activity differs across the states of waking and sleep. To overcome this limitation, this study investigated thoughts and hallucinations using experience sampling, home-based sleep-wake monitoring, and formal analyses of the psychological data. The prevalence of thoughts decreased gradually from waking through sleep onset and non-REM sleep, to reach its nadir in REM sleep, whereas hallucinations increased sharply across these states. Furthermore, multiple occurrences of hallucinations but not of thoughts increased significantly from sleep onset through non-REM sleep, to a peak in REM sleep. This reciprocity in thoughts and hallucinations might reflect a progressive shift from high to low aminergic-to-cholinergic neuromodulatory ratios across wake-sleep states, accompanied by an array of changes in the regional activation patterns of the brain.

Definitions of dreaming are not required to map formal features of mental activity onto brain measures. While dreaming occurs during all stages of sleep, intense dreaming is largely confined to REM. Forebrain structures and many neurotransmitters can contribute to sleep and dreaming without negating brainstem and aminergic-cholinergic control mechanisms. Reductionism is essential to science and AIM has considerable heuristic value. Recent findings support sleep's role in learning and memory. Emerging technologies may address long-standing issues in sleep and dream research.

Recent neuropsychological data indicating that an absence of dreaming follows lesions of frontal subcortical white matter have been interpreted by Solms as supportive of Freud's wish-fulfillment, disguise-censorship dream theory. The purpose of this commentary is to call attention to Solms's commitment to Freud and to challenge and contrast his specific arguments with the simpler and more complete tenets of the activation-synthesis hypothesis. [HOBSON ET AL.; NIELSEN; SOLMS]

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. Keywords: consciousness, dreaming, neuroimaging, neuromodulation, NREM, phenomenology, qualia, REM, sleep

Abstract * Performance on a visual discrimination task shows longterm improvement after a single training session. When tested within 24 hr of training, improvement was not observed unless subjects obtained [...]

The notion that dreaming might alter the strength of associative links in memory was first proposed almost 200 years ago. But no strong evidence of such altered associative links has been obtained. Semantic priming can be used to quantify the strength of associative links between pairs of words; it is thought to measure the automatic spread of activation from a 'node' representing one word to nodes representing semantically related words. Semantic priming could thus be used to test for global alterations in the strengths of associative links across the wake-sleep cycle. Awakenings from REM and nonREM (NREM) sleep produce a period of state carry-over during which performance is altered as a result of the brain's slow transition to full wakefulness, and cognitive testing in this period can provide information about the functioning of the brain during the prior sleep period. when subjects were tested across the night - before and after a night's sleep as well as immediately following forced awakenings from REM and NREM sleep - weak priming (e.g., thief-wrong) was found to be state dependent (p = 0.016), whereas strong priming (e.g., hot-cold) was not (p = 0.89). Weak primes were most effective in the prosleep and REM sleep conditions and least effective in NREM and postsleep conditions. Most striking are analyses comparing weak and strong priming within each wake-sleep state. Contrary to the normal pattern of priming, subjects awakened from REM sleep showed greater priming by weak primes than by strong primes (p = 0.01). This result was seen in each of three protocols. In contrast, strong priming exceeded weak priming in NREM sleep. The shift in weak priming seen after REM sleep awakenings suggests that cognition during REM sleep is qualitatively different from that of waking and NREM sleep and may reflect a shift in associative memory systems, a shift that we hypothesize underlies the bizarre and hyperassociative character of REM-sleep dreaming. Known changes in brainstem activity that control the transition into and maintenance of REM sleep provide a possible explanation of this shift., INTRODUCTION Sleep, especially REM sleep, provides an exceptional opportunity to study the brain basis of cognitive processes. As one proceeds from waking into nonREM (NREM) and then REM sleep, a [...]