Arousal and Vigilance: Do They Differ?
Study in a Sleep Inertia Paradigm
Patricia Tassi, Anne Bonnefond, Alain Hoeft,
Roland Eschenlauer, Alain Muzet

The present experiment was conducted to determine whether vigilance and arousal are different functional entities, even though the two concepts are usually confounded. Our hypothesis is that vigilance is a state specifically associated with attentional availability, whereas arousal is a state independent of attention and based on neuronal activation. If this is true, differential effects on performance can be expected. Namely, we propose that arousal essentially affects speed of information processing, whereas vigilance is more linked to accuracy and/or omissions. The sleep inertia paradigm has been chosen to distinguish the effects of low arousal and hypovigilance. We compared performance in either sleep deprived or non sleep-deprived subjects in the Descending Subtraction Test (DST) presented in a complex and simple version. Speed and error indices were the dependent variables. Results showed that speed was deteriorated in both groups during the first 15 min after awakening, but only in the simple task, suggesting a slowing down of mental processing. By contrast, the error index reflecting accuracy showed, in the complex task only, increased errors during the first and last 15-min period in the sleep-deprived subjects but not in the Control Group. All together, these data are in favor of a functional difference between arousal and vigilance, and these two functions could affect performance in specific ways.

Stage at Awakening, Sleep Inertia, and Performance
Corrado Cavallero and Francesco Versace

Our purpose was to verify if the differential effect of final stage at awakening varies with the amount of sleep reduction and if this effect goes beyond the boundaries of sleep inertia. Seven university students were paid for their participation. The design included two conditions, REM (three consecutive nights) and NREM (three consecutive nights). Sleep length was progressively curtailed to 6 hrs, 4.5 hrs and 3 hrs for the first, second and third night, respectively. In the REM condition, participants were awakened during REM sleep, while in the NREM condition, participants were awakened during Stage 2. Days following experimental nights were devoted to the assessment of performance. Test sessions were scheduled upon awakening and then every three hours thereafter. Performance was measured by means of a Simple Reaction Time task and a Four Choice reaction time task. Results show that sleep inertia after NREM awakenings is more pronounced than after REM awakenings. Sleep curtailment enhances this differential effect and prolongs it beyond sleep inertia boundaries. Final stage at awakening not only exerts a differential influence on performance within the sleep inertia phase, but also impairs performance after NREM awakenings following inertia dissipation, especially when sleep is curtailed.

Melatonin Treatment for Insomnia in Parkinson's Disease: A Pilot Study
Glenna A. Dowling, Judith Mastick and Michael J. Aminoff

Complaints of insomnia are common in patients with Parkinson's disease (PD). Melatonin has been shown to improve insomnia in some populations but has not been well studied in patients with PD. The primary aims of this pilot study were to assess endogenous melatonin secretion in PD patients by determining the time of dim-light melatonin onset (DLMO), and to compare the effect of exogenous melatonin (5 mg) therapy with placebo on nocturnal sleep in patients who complained of insomnia. A double-blind, placebo-controlled, cross-over trial was employed. Subjects (n=8) with PD and no evidence of depression, cognitive impairment, or primary sleep disorders participated in the 4-week protocol. During a 1-week treatment period, subjects took melatonin (5 mg) or placebo capsules (administered in random order) 30 minutes before bedtime, with a 1-week washout between treatments. DLMO was determined by RIA of blood samples. Nocturnal sleep was assessed by actigraphy. Subjective sleep quality was assessed with daily diaries and a weekly questionnaire. The mean DLMO was 21:05. During the melatonin treatment week there was a nonsignificant decrease in nocturnal waketime (20 minutes) and an increase in sleep efficiency (3%). Six subjects (75%) reported that they slept better during the melatonin treatment week. Results of this pilot study do not indicate that melatonin administration improves objective sleep in PD patients who complain of insomnia.

Whole-head Measures of Sleep from MEG Signals and the Ubiquitous <1Hz "Slow Oscillation"
Norman R. Simon, Bob Kemp, Ilonka Manshanden, and Fernando H. Lopes da Silva

The whole-head MEG sleep records for each of three subjects were separated into segments of 5.12 seconds and then grouped according to sleep phase ranging from drowsiness-sleep onset to deep slow-wave sleep. Spectral decomposition was employed to find "collective modes," defined as narrow frequency ranges at which all or nearly all of the MEG detectors displayed easily discernable power peaks. To follow these collective modes, we developed a normalized multichannel parameter s based upon the density of the MEG records and shown to track the classic progression of NREM sleep. The most prevalent collective mode appeared in the two lowest frequency bins at 0.49 and 0.98 Hz, respectively, almost certainly corresponding to the "slow oscillation" first described by Steriade et al. (1993). This mode was extremely strong in all subjects for all phases of true sleep and seemed to be present even in drowsiness and sleep onset. As sleep progressed, power in the two lowest bins grew rapidly, until, in the deepest slow-wave phase, these frequencies totally dominated the spectrum. The flow of power into the two lowest frequency bins was found to occur all over the head, but, particularly, at non-peripheral temporal locations in both hemispheres.

Extracellular Serotonin in the Rat Hippocampus during REM Sleep Deprivation
Faustino Lopez-Rodriguez, Charles Wilson, Nigel Maidment, Rusell Poland, Michael H. Chase and Jerome Engel, Jr.

Rapid eye movement (REM) sleep deprivation exerts activating effects in humans and rats. The mechanisms of action of these effects are not well understood. In the present report, we used in vivo microdialysis in the rat to test the hypothesis that REM sleep deprivation increases extracellular levels of serotonin (5HT) in the hippocampus. Rats were REM deprived for 24 hours with the platform technique (rats on a small platform surrounded by water). Changes in dialysate 5HT concentration in these rats were compared with those found in stress-control rats (rats on large platform, surrounded by water), and cage-control rats. All rats were food deprived during the 24 hours of the experimental paradigm. No significant differences were found in 5HT levels in the hippocampus among the three groups of rats. There was a significant increase in 5HT levels after the rats were returned to the home cages, but again this increase was not different among the three groups, suggesting that REM sleep deprivation does not increase 5HT release. These results do not support the hypothesis that the activating effects of REM sleep deprivation are due to an increase in 5HT release.