The impact of prestimulus EEG frequency on auditory evoked potentials during sleep onset.

Assessed stimulus relevance vs rarity effects by investigating the N550 to stimuli identified as targets during wakefulness compared to the N550 in response to deviant stimuli with the same probability of occurrence without the target identification. Five Ss (mean age of 22.3 yrs) had their auditory evoked potentials recorded during wakefulness, Stage 1, and Stage 2 non-REM sleep using a 3-tone auditory oddball paradigm. Stage 1 sleep was divided into trials preceded by alpha and those preceded by theta. Results indicate that a negative wave peaking at about 100 ms, N1, displayed a significant decrease in amplitude with the onset of Stage 2 sleep. A later N2 peaked at about 250 ms in the waking state. This changed into a sleep-specific negative wave peaking at 300 ms (N300) at the alpha-theta transition within Stage 1. The P300 displayed a similar shift to become a P450 in Stage 2 sleep. N550 was specific to Stage 2, and was larger in response to rare, rather than frequent stimuli. There was no evidence of any enhancement to relevant rare stimuli compared with irrelevant rare stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evening administration of melatonin and bright light: interactions on the EEG during sleep and wakefulness

PROBLEM: Human leukocyte antigen (HLA)-G is uniquely expressed on extravillous cytotrophoblasts of the placenta and is postulated to be a mediator of maternal immune tolerance. Although it was originally considered to be nonpolymorphic, variations of the HLA-G DNA sequence have been reported, and a limited number of HLA-G alleles been defined. METHOD OF STUDY: The HLA-G wild-type sequence was compared with HLA-A2 with regard to the conservation of functionally essential parts of classical HLA-I molecules. HLA-G polymorphisms were analyzed under the aspect of ethnic differences, site, and consequences for postulated molecule functions. RESULTS: HLA-G exhibits a high degree of conservation relative to HLA-A2 in functionally relevant sites of HLA-class I molecules. However, polymorphic sites in HLA-G and classical HLA loci are not congruent. CONCLUSION: The type and localization of HLA-G polymorphisms suggest that different parts of HLA-G molecule underlie different selective constraints.     

Dynamical properties of the sleep EEG in different frequency bands

The information concerning the dynamic behavior of the sleep process gained by the usual evaluation of sleep EEGs according to the criteria of Rechtschaffen and Kales is limited. Therefore a new methodical approach is presented, which is a special case of spectral analyzed data processing. After digital band-pass filtering of the sleep EEG the root-mean-square (RMS) value of successive 20 s EEG epochs is calculated in defined frequency ranges. This procedure ensures to take into account the influence of the phase relation between different frequency components. The temporal course of these RMS values during the night reveals smooth curves with continuous transitions between different sleep states. In all frequency bands slow oscillations according to the sleep cycles are observable. Whereas the slow frequency bands have a temporal course with local maxima during non-REM and local minima during REM sleep, the fast frequency bands beta and gamma show the opposite behavior revealing higher RMS values during REM sleep. The relationship between the activities in different frequency bands is evaluated calculating the cross correlation coefficient. Taken together the procedure allows an objective and automated quantitative analysis of the sleep EEG. The main advantage of this approach is the characterization of the sleep cycle as a dynamic and continuous process. Compared to the classical analysis it provides a more detailed analysis of the sleep process, especially concerning the dynamics and microstructure of sleep.     

The systemic hemodynamics of waking and anesthetized male cats during noradrenaline infusion

Dynamics of arterial pressure and its hemodynamic components were shoen to dramatically differ in corscious and anesthetised animals. The data obtained suggest that corscious male cats, along with a baroreflex mechanism of resistance against involvement of the heart into the pressor response, have another mechanism acting in deficiency of baroreflex effects.     

Effects of accumbens m-chlorophenylbiguanide microinjections on sleep and waking in intact and 6-hydroxydopamine-treated rats

Effects of the 5-HT3 receptor agonist, m-chlorophenylbiguanide (10.0-40.0 microg), on sleep and waking were studied in control, vehicle-treated and 6-hydroxydopamine-injected rats. Bilateral injections of m-chlorophenylbiguanide into the nucleus accumbens of the control and the vehicle-infused animals significantly increased waking and reduced slow wave sleep. Rapid eye movement sleep (REM sleep) remained unchanged. Pretreatment with the selective 5-HT3 receptor antagonist, MDL 72222 (1aH,3a,5a, H-tropan-3-yl-3,5-dichloro-benzoate) (0.5 mg/kg, s.c.), reversed the effects of m-chlorophenylbiguanide (10.0-20.0 microg) on sleep and waking in the control group. Administration of the 5-HT3 receptor agonist to the 6-hydroxydopamine-treated animals modified only slightly the time spent in wakefulness and slow wave sleep, while REM sleep was significantly and dose dependently reduced. Our findings further support the proposal that increase of wakefulness and reduction of slow wave sleep after activation of 5-HT3 receptors, is partly related to the release of endogenous dopamine.     

Spindle frequency activity in the sleep EEG: individual differences and topographic distribution

Focal magnetic transcranial stimulation (TCS) is employed for mapping of the motor cortical output to abductor digiti minimi (ADM) muscle. The aim of this study was to evaluate the interhemispheric asymmetries in normals. Motor maps were obtained through motor evoked potentials (MEPs) recordings from ADM muscle in 20 healthy subjects in right and left hemispheres TCS. Measurement of several indexes such as excitability threshold, MEPs amplitude, MEPs latency, and silent period duration did not show differences between the hemispheres. Moreover, no interhemispheric asymmetries were found when the amplitude ratio values were analyzed. The hand motor cortical area, as represented by the number of responsive sites (3.6 vs. 3.5) and the "hot spot" site localization presented a fairly symmetrical organization. Absolute values displayed a relatively wide intersubject variability, while their interhemispheric differences were extremely restricted. This observation can offer a new tool in diagnosing and following up neurological disorders affecting the central motor system, mainly for those concerning monohemispheric lesions.     

Effects of the 1989 San Francisco earthquake on frequency and content of nightmares.

In a systematic evaluation of the effects of a natural disaster on nightmares, nightmare frequency was found to be about twice as high among 92 San Francisco Bay area college students as among 97 control Ss in Tucson, Arizona, after the 1989 Loma Prieta earthquake. Ss in California had not only more nightmares in general but substantially more nightmares about earthquakes. Over a 3-wk period, about 40% of those in the San Francisco Bay area reported one or more nightmares about an earthquake, as compared with only 5% of those in Arizona. However, nightmares about earthquakes were not more emotionally intense than other nightmares. These findings support the long-held view that the experience of a potentially traumatic event can result in more frequent nightmares, particularly about the event itself, but contradict the common opinion that nightmares about such events are unusually intense. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes in EEG alpha frequency and evoked response latency during solitary confinement.

1 wk. of solitary confinement of 20 18-45 yr. old prison inmates produced significant changes in their EEG frequency and visual evoked potentials (VEP) that parallel those reported in laboratory studies of sensory deprivation. EEG frequency declined in a nonlinear manner over the 7-day period. VEP latency, which decreased with continued solitary confinement, was shorter for these Ss than for control Ss whose VEP latency did not change over the same period. Experimental Ss who had been in prison longer had shorter VEP latencies than relative newcomers to the prison. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dynamics of EEG spindle frequency activity during extended sleep in humans: relationship to slow-wave activity and time of day

The dynamics of EEG spindle frequency activity (SFA; spectral power density in the 12.25-15.0 Hz range) and its relationship to slow-wave activity (SWA; 0.75-4.5 Hz) were investigated in long sleep episodes (> 12 h). Young healthy men went to bed at either 19:00 h (early sleep; prior waking 36 h, n = 9) or 24:00 h (late sleep; prior waking 17 h, n = 8). In both nights, SWA in non-rapid-eye-movement sleep (NREMS) decreased over the first three to four 1.5-h intervals and remained at a low level in the subsequent five to six 1.5-h intervals. In contrast, the changes of SFA were more variable and differed between the lower (12.25-13.0 Hz), middle (13.25-14.0 Hz) and higher frequency bin (14.25-15.0 Hz). A pronounced influence of time of day was present in the lower and higher SFA bin, when the dynamics were analyzed with respect to clock time. In both the early and late sleep condition, power density in the lower bin was highest between 2:00 and 5:00 h in the morning and decreased thereafter. In the higher bin, power density was low in the early morning hours and increased as sleep was extended into the daytime hours. The results provide further evidence for a frequency-specific circadian modulation of SFA which becomes more evident at a time when SWA is low.     

REM sleep facilitation of adaptive waking behavior: A review of the literature.

Reviews the literature on REM sleep in regard to whether REM sleep prepares the S for subsequent learning or facilitates the retention of learning and/or the adaptation to prior stimulation. It is concluded that when studies are classified paradigmatically, E. M. Dewan's (1969) REM sleep metaprogramming hypothesis provides a useful conceptual scheme for interpreting the relevant literature. Suggested modifications to this hypothesis and anticipated future ones are discussed. (90 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of systemic morphine on lamina I spinothalamic tract neurons in the cat

Lamina I spinothalamic tract (STT) neurons are an integral component of the central representation of pain and temperature and thus their sensitivity to various analgesics needs to be examined. In the present study, the effects of successive, cumulative doses (0.125-2.0 mg/kg) of intravenous morphine sulfate on the quantitative stimulus-response properties of nociceptive lamina I STT cells have been tested in the intact, barbiturate-anesthetized cat. Both nociceptive-specific (n = 7) and multireceptive (heat, pinch and cold sensitive; n = 7) lamina I STT cells were inhibited in a dose-dependent manner. Parallel dose-dependent effects on responses to noxious heat and pinch were generally observed that reduced ongoing discharge levels and the slopes of the stimulus-response functions. However, non-STT lamina I cells (n = 5) differed significantly; the responses of one multireceptive (heat, pinch and cold-sensitive) cell and the responses to pinch of 3 of 4 wide dynamic range cells were not inhibited. In addition, two-thirds of the nociceptive lamina I STT cells showed enhanced responses at the lowest dose of morphine (0.125 mg/kg). These results contrast with the varied effects of morphine reported for superficial dorsal horn cells with uncharacterized projections and they support the role of lamina I STT cells in pain. Furthermore, these observations are consistent with previous findings indicating that lamina I STT neurons are a distinct subpopulation of lamina I cells. These results support previous evidence that opiatergic modulation of sensory activity in lamina I is functionally organized.     

C-fos expression in the pons and medulla of the cat during carbachol-induced active sleep

Microinjection of carbachol into the rostral pontine tegmentum of the cat induces a state that is comparable to naturally occurring active (REM, rapid eye movement) sleep. We sought to determine, during this pharmacologically induced behavioral state, which we refer to as active sleep-carbachol, the distribution of activated neuron within the pons and medulla using c-fos immunocytochemistry as a functional marker. Compared with control cats, which were injected with saline, active sleep-carbachol cats exhibited higher numbers of c-fos-expressing neurons in (1) the medial and portions of the lateral reticular formation of the pons and medulla, (2) nuclei in the dorsolateral rostral pons, (3) various raphe nuclei, including the dorsal, central superior, magnus, pallidus, and obscurus, (4) the medial and lateral vestibular, prepositus hypoglossi, and intercalatus nuclei, and (5) the abducens nuclei. On the other hand, the mean number of c-fos-expressing neurons found in the masseter, facial, and hypoglossal nuclei was lower in carbachol-injected than in control cats. The data indicate that c-fos expression can be employed as a marker of state-dependent neuronal activity. The specific sites in which there were greater numbers of c-fos-expressing neurons during active sleep-carbachol are discussed in relation to the state of active sleep, as well as the functional role that these sites play in generating the various physiological patterns of activity that occur during this state.     

Respiratory responses to tracheobronchial stimulation during sleep and wakefulness in the adult cat

The response to tracheal stimulation (50 microliters of tap water) during wakefulness, non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep was investigated in adult cats. In wakefulness, repetitive coughing occurred on 80% of the trials. In NREM and REM sleep, the most frequent response (approximately 69% and 58% of the trials, respectively) was arousal, followed by coughing. Apneas occurred following the stimulus and before arousal in 11% and 24% of the trials in NREM and REM sleep, respectively. In NREM sleep, the tracheal stimulus sometimes evoked expiratory efforts following a normal inspiratory effort (11% of the trials). These were much weaker than the expiratory efforts during coughing in wakefulness. In REM sleep, stimulation in 11% of the trials elicited increased inspiratory efforts. Although these may have been diminutive preparatory inspirations for coughing, they were much smaller than preparatory inspirations associated with coughing in wakefulness, and they were never followed by active expiratory efforts. Arousal from either NREM or REM sleep in response to tracheal stimulation was sometimes associated with an augmented breath. This response, which is common upon spontaneous arousal, may lead to deeper aspiration of the tracheal fluid. We conclude that in cats coughing requires wakefulness and that airway stimuli in sleep cause a variety of respiratory responses, some of which may be maladaptive.     

Topographic analysis of coherence and propagation of EEG activity during sleep and wakefulness

Overnight sleep EEG recorded from 21 derivations was studied in 8 healthy subjects. The vector autoregressive model was fitted to all 21 channels simultaneously. Ordinary, multiple and partial coherences and directed transfer functions were estimated for sleep stages and wakefulness. Ordinary coherences give rather trivial information that coherence decreases with distance. Partial coherences revealed specific structure that was well repeatable for the subjects studied. Differences in coherence patterns between sleep stages were found by means of statistical tests. An increase of coherence was found for sleep stages 2, 3 and 4. Directed transfer function made possible the identification of the main centers from which EEG activity is spreading during sleep and wakefulness. During sleep the influence of subcortical structures was manifested by propagation of activity from the fronto-central region. The range of this interaction was highest in sleep stages 3 and 4. An EEG analysis, based on the approach of treating time series as a realization of one process and on the simultaneous (not pair-wise) evaluation of signals offers new possibilities in the investigation of synchronization and functional relations in the brain.     

The mismatch negativity to frequency deviants during the transition from wakefulness to sleep.

Examined the changes in the mismatch negativity (MMN) during the transition from a waking, conscious state to one of sleep and unconsciousness. Auditory event-related potentials were recorded from 8 Ss, 21–32-yrs old, during the sleep onset period. A 1,000 Hz-standard stimulus was presented every 600 ms. At random, on 20% of the trials, the standard was changed to either a large 2,000-Hz or a small 1,100-Hz deviant. Results indicate that during wakefulness, the large deviant elicited a larger, long-lasting MMN than the small deviant. Following the large deviant during relaxed wakefulness and Stage 2 sleep, the MMN continued to be elicited although it was reduced in amplitude. No significant MMN was recorded for either deviant in Stages 1 and slow wave sleep. The loss of consciousness therefore appears to have a marked effect on the MMN. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of motivation on the relationship between heart rate and sensorimotor tasks.

Evaluated the effects of motivation on tonic and phasic heart rate (HR) changes during motor-perceptual tasks. 40 male undergraduates were randomly assigned to 2 groups. In Phase I of the experiment, Ss were given counterbalanced programmed series of reaction time and time estimation trials. While controls worked under the same conditions in Phase II, experimental Ss performed the same tasks under increased motivation, receiving 10-cent tokens for a good performance on each trial. Results indicate that the HR deceleration, already known to take place in the preparatory interval of the reaction time task, also occurs just before the response in time estimation trials. For both tasks, the Phase II motivation increase produces both a greater foreperiod deceleration and a large acceleration immediately after the motor response. Results are discussed in terms of the motivational significance of HR variations, with reference to the cardiosomatic hypothesis of P. A. Obrist (1976) and the intake-rejection hypothesis of J. I. Lacey and B. C. Lacey (1978). (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of current-concern- and nonconcern-related waking suggestions on nocturnal dream content

In previous research, presleep suggestions influenced nocturnal dream content. It was hypothesized that suggesting topics associated with participants' current concerns would influence dream content more than suggesting other topics. Ten students spent 4 nights in a sleep laboratory: an adaptation night, a baseline night, and 2 nights under suggestions to dream about a concern-related or other topic. Concern-related suggestions influenced dream content--largely its central imagery--more than did other suggestions, which did not differ from nonsuggestion. Number of transformations within dreams was uncorrelated with dream vividness, contrary to extended activation-synthesis theory. Thus, the concern-related status of suggestions moderates their effectiveness and, inconsistent with extended activation-synthesis theory but consistent with current-concerns and distributed-activation theories, motivational and volitional processes actively influence dream content.     

Habituation of the EEG arousal response in rats: Short- and long-term effects, frequency specificity, and wake–sleep transfer.

In 3 experiments with 78 male Holtzman albino rats, presentation of auditory stimuli over interstimulus intervals (ISIs) of several minutes to sleeping Ss produced significant habituation of the EEG arousal response. The arousal response habituated to an asymptote after only 2 or 3 stimulus presentations. Little or no spontaneous recovery occurred between sessions separated by 24 or 72 hrs. The habituation produced by a single stimulus presentation was retained for at least 24 hrs, and orderly habituation was shown with a 24-hr ISI. Approximately 90% retention of habituation was shown 32 days following 10 stimulus presentations, and some degree of retention was shown for as long as 50 days. After habituation had reached a long-term asymptote, 600 stimulus presentations over 2-sec ISIs produced further response decrements, but these decrements recovered completely within a matter of minutes and responsiveness returned to the previously established long-term asymptote. Habituation was shown to be frequency-specific over both 24-hr and 32-day intervals. Habituation produced by stimulus presentations to awake Ss transferred to the condition in which stimuli were presented to sleeping Ss. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The long-term course of spike and wave complexes in the waking EEG of chronic schizophrenics

Nineteen chronic schizophrenics (8 males and 11 females) showed at least one spike and wave complex (SpW) in their rested-awake EEGs during long-term neuroleptic treatment. The age at the first appearance of the SpW ranged from 16 to 60 years, and the duration of neuroleptic medication preceding its appearance was from 1 to 35 years. Two types of SpW waveform were discriminated; one was a diffuse high voltage isolated 3.5-4 Hz SpW complex, and the other a diffuse moderate voltage 5-6 Hz SpW burst. In EEG studies repeated over the long-term, the presence of SpW was transient in 11 cases, intermittent in 5 cases, and continuous in 3 cases. Three patients had generalized tonic-clonic clinical seizures; two of their EEGs did not show SpW until after the onset of seizures. All three responded well to adjunctive anticonvulsant therapy. The other 16 patients exhibited SpW but did not have clinical seizures with or without prophylactic use of anticonvulsants. The SpW in the EEG of chronic schizophrenics might be an indicator of predisposition for seizure, but it is not a good predictor of seizure.