Do you perform the multiple sleep latency test according to the guidelines? A case with multiple sleep onset REM periods

Sleep and Biological Rhythms - The patient was a 21-year-old male who complained of daytime sleepiness. His multiple sleep latency test (MSLT) showed multiple sleep onset REM periods (SOREMPs). The...     

Characteristics of rapid eye movement sleep behavior disorder in narcolepsy

The basal forebrain (BF) plays an important role in regulating cortical activity and sleep/wake states. Both cholinergic and non-cholinergic neurons of the BF project to the cerebral cortex and hippocampus, whereas the hypothalamus and brainstem nuclei are mostly innervated by non-cholinergic BF neurons. Neurons in the BF show various discharge profiles in relation to cortical activity and behavioral states and are differentially modulated by neurotransmitters of other sleep/wake regulatory neurons. Recent technical advances have made it possible to correlate discharge profiles of single BF neurons during sleep/wake states with their neurochemical phenotypes, and to make selective lesions of certain cell types. The goal of this review is to summarize the current knowledge of the anatomy and sleep/wake regulatory functions of cholinergic and non-cholinergic BF neurons. We will first review the anatomical heterogeneity of BF neurons, and then discuss recent evidence for the firing patterns of BF cholinergic and non-cholinergic neurons during natural sleep–wake patterns, and finally, discuss their roles in sleep homeostasis. It is proposed that through different neurotransmitters, projections, and state-regulated activity, the cholinergic and non-cholinergic BF neurons collectively and differently regulate cortical activity and sleep-wake states.

     

Cortical regions activated after rapid eye movements during REM sleep

The present study investigated the cortical regions activated during rapid eye movement (REM) sleep by identifying the sources of electric currents of brain potentials related to rapid eye movements using low-resolution brain electromagnetic tomography (LORETA). The brain potentials measured were the lambda response (P1 and P2) during wakefulness and the lambda-like response (P1r and P2r) during REM sleep. Fifteen healthy university students participated in this study. During wakefulness, the sources of the electric current of the lambda response (P1 and P2) were estimated to be in the primary and secondary visual cortices (BA 17, 18). During REM sleep, the P1r has a source in a higher order visual area (precuneus; BA 7, 31) and P2r comes from the primary and secondary visual cortices (BA 17, 18). In addition, the density of electric current in the premotor and fronto-central regions including anterior cingulate gyrus was higher after rapid eye movements, which was a discriminative feature of REM sleep. The results of this study suggest that these activities that occur after rapid eye movements might underlie the generation of vivid visual images of dreaming.

     

Respiratory changes associated with rapid eye movements in normo- and hypercapnia during sleep

Rapid eyemovements during rapid-eye-movement (REM) sleep are associated withrapid, shallow breathing. We wanted to know whether thiseffect persisted during increased respiratory drive byCO₂. In eight healthy subjects, werecorded electroencephalographic, electrooculographic, andelectromyographic signals, ventilation, and end-tidalPCO₂ during the night. InspiratoryPCO₂ was changed to increaseend-tidal PCO₂ by 3 and 6 Torr. During normocapnia, rapid eye movements were associated with a decreasein total breath time by 0.71 ± 0.19 (SE) s(P < 0.05) because of shortenedexpiratory time (0.52 ± 0.08 s,P < 0.001) and with a reduced tidalvolume (89 ± 27 ml, P < 0.05) because of decreased rib cage contribution (75 ± 18 ml, P < 0.05). Abdominal (11 ± 16 ml, P = 0.52) and minuteventilation (0.09 ± 0.21 ml/min, P = 0.66) did not change. Inhypercapnia, however, rapid eye movements were associated with afurther shortening of total breath time. Abdominal breathing was alsoinhibited (79 ± 23 ml, P < 0.05), leading to a stronger inhibition of tidal volume and minuteventilation (1.84 ± 0.54 l/min,P < 0.05). We conclude thatREM-associated respiratory changes are even more pronounced duringhypercapnia because of additional inhibition of abdominal breathing.This may contribute to the reduction of the hypercapnic ventilatory response during REM sleep.

     

EEG of striate cortex in blind monkeys: effects of eye movements and sleep.

After control studies, using electrodes permanently implanted in the central visual system, squirrel monkeys and macaques were in most instances blinded by acute glaucoma. This permitted subsequent observation of eye movements. Ocular nystagmus developed in all cases. Beginning immediately upon recovery from anesthesia, and persisting for at least 1 year, the EEG of the striate cortex was characterized by totally flat periods up to several seconds in duration which were ended abruptly by a sharp "spike" trailed in turn by a ragged high voltage, slow pattern for another second or two. The great majority of these "spikes" from the blind striate cortex occurred within 60-200 msec after a saccadic eye movement, made either in nystagmus or attempted fixation. They were not dependent upon proprioception from the extraocular muscles. It is suggested that they represent a "corollary discharge" for movement of the eyes. The blind striate cortex was judged to be hyperexcitable on the basis of these saccade-associated "spikes", not often observable in intact monkeys, and from the increase both in response evoked by electrical stimulation of optic radiation and amplitude of the EEG in sleep.     

Androgens and eye movements in women and men during a test of mental rotation ability

Eye movements were monitored in 16 women and 20 men during completion of a standard diagram-based test of mental rotation ability to provide measures of cognitive function not requiring conscious, decisional processes. Overall, women and men allocated visual attention during task performance in very similar, systematic ways. However, consistent with previous suggestions that sex differences in attentional processes during completion of the mental rotation task may exist, eye movements in men compared to women indicated greater discrimination and longer processing of correct alternatives during task performance. Other findings suggested that androgens may enhance cognitive processes that are recruited differentially by women and men as a function of the task. Specifically, smaller (i.e., more masculine) digit ratios were associated with men's shorter fixations on distracters, suggesting that perinatal androgen action may influence brain systems that facilitate the identification of relevant task stimuli. In women, higher circulating testosterone levels appeared to contribute to more general processes engaged during task performance, for example higher levels of visual persistence. It is possible that variability in the relative contribution of such hormone sensitive cognitive processes to accuracy scores as a function of different sample characteristics or assessment methods may partially account for the inconsistent findings of previous research on hormonal factors in mental rotation ability.     

The 'scanning hypothesis' of rapid eye movements during REM sleep: a review of the evidence

Rapid eye movements (REMs) and visual dreams are salient features of REM sleep. However, it is unclear whether the eyes scan dream images. Several lines of evidence oppose the scanning hypothesis: REMs persist in animals and humans without sight (pontine cats, foetus, neonates, born-blinds), some binocular REMs are not conjugated (no focus point), REMs occur in parallel (not in series) with the stimulation of the visual cortex by ponto-geniculo-occipital spikes, and visual dreams can be obtained in non REM sleep. Studies that retrospectively compared the direction of REMs to dream recall recorded after having awakened the sleeper yielded inconsistent results, with a concordance varying from 9 to 80%. However, this method was subject to methodological flaws, including the bias of retrospection and neck atonia that does not allow the determination of the exact direction of gaze. Using the model of RBD (in which patients are able to enact their dreams due to the absence of muscle atonia) in 56 patients, we directly determined if the eyes moved in the same directions as the head and limbs. When REMs accompanied goal-oriented motor behaviour during RBD (e.g., framing something, greeting with the hand, climbing a ladder), 90% were directed towards the action of the patient (same plane and direction). REMs were however absent in 38% of goal-oriented behaviours. This directional coherence between limbs, head and eye movements during RBD suggests that, when present, REMs imitate the scanning of the dream scene. Because REMs index and complexity were similar in patients with RBD and controls, this concordance can be extended to normal REM sleep. These results are consistent with the model of a brainstem generator activating simultaneously images, sounds, limbs movements and REMs in a coordinated parallel manner, as in a virtual reality.     

Fractal property of eye movements in schizophrenia

 On the basis of a temporal model of animal behavior we conducted temporal analysis of eye movements in schizophrenic subjects (n=10) and normal controls (n=10). We found a fractal property in schizophrenic subjects, the fixation time of eye movement during reading ambiguous and difficult sentences showing a clear inverse power law distribution. An exponential distribution of a nonfractal nature was found in normal controls. Received: 21 July 1995/Accepted in revised form: 30 April 1996     

Relationship between dim light melatonin onset and the timing of sleep in sleep onset insomniacs

Sleep and Biological Rhythms - Dim light melatonin onset (DLMO), a phase marker of the circadian system can be estimated from sleep diaries of good sleepers. Previous studies have shown a strong...     

What are birds looking at? Head movements and eye use in chickens

Using video recordings of hens, Gallus gallus domesticus, as they approached different kinds of objects, I examined how change in object distance is associated with a change from lateral to binocular viewing. The birds tended to view distant objects laterally while they preferentially viewed objects less than 20-30 cm away frontally; this was true whether they were looking at another bird or at an inanimate object. However, as well as switching between lateral and frontal viewing, the hens also swung their heads from side to side with movements so large that the same object appeared to be viewed with completely different parts of the retina, and even with different eyes, in rapid succession. When confronted with a novel object, the hens walked more slowly but continued to show large head movements. This suggests that, unlike mammals, which gaze fixedly at novel objects, hens investigate them by moving the head and looking at them with different, specialized, parts of their eyes. Many aspects of bird behaviour, such as search image formation, vigilance and visual discriminations, may be affected by the way they move the head and eyes. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

The direction of rapid eye movements as an indication of hemispheric asymmetry during REM sleep. II

The hypothesis of right hemisphere predominance in REM sleep and of an increase in left activity throughout the night have been tested by analyzing the distribution of vertical and of horizontal rapid eye movements (REMs) to the right and to the left during the first and the last REM periods in 5 right-handed subjects. Neither the expected superiority of REMs to the left nor variations along the REM periods were found. For vertical eye movements our data suggest a superiority of upward movements during REM. In waking some empirical evidences suggest a relationship between upward eye movements and right hemisphere functioning although to date no hemispheric model can explain it.     

Computer analysis of rapid eye movements

Simulation of the saccadic eye movement mechanism and, more recently, diagnosis of neuromuscular disorders associated with saccades rely on accurate recording and analysis of saccade characteristics. Traditionally, eye movements are monitored objectively by registering a transduced voltage correlate of eye position on a pen or cathode ray oscillograph. Analysis of the record obtained is tedious and often inaccurate. The advent of small digital computers with analog-to-digital capability permits more efficient recording. However, computer programs reviewed are limited to the analysis of specific saccade parameters or partly depend on manual operations. The computer program described stores the entire saccadic event of each eye between pre-defined limits including the pre- and post-saccade intervals. Preliminary operations including artifact identification, location of onset, elimination of RC decay, DC offset and amplitude scaling prepare the data for display and subsequent analysis. The program also includes a subroutine to derive the mean and standard deviation of successive saccades.