Giuseppe Barbato

Extended sleep in humans in 14 hour nights (LD 10:14): relationship between REM density and spontaneous awakening

The sleep patterns of 8 normal subjects living in a winter-type photoperiod (10 h light and 14 h darkness; LD 10:14) for 4 weeks were characterized by the presence of periods of spontaneous wakefulness alternating with periods of spontaneous sleep. Transitions from sleep to wakefulness occurred much more frequently out of REM sleep than out of NREM sleep (P < 0.002). REM periods that terminated in wakefulness showed shorter REM durations (P < 0.0005) and higher REM densities (P < 0.0005) than REM periods that did not terminate in wakefulness. The authors discuss these results in terms of a possible relationship between REM density and arousal level. The higher REM density preceding wakefulness and the increased number of REM periods terminating in spontaneous awakenings could reflect an enhanced level of a brain arousing process, resulting from reduced sleep pressure in the extended nights.

Increased spontaneous eye blink rate following prolonged wakefulness.

Sleep deprivation (SD) is a technique of sleep-wake manipulation which has been used to treat depression. Changes in neurotransmitter systems, that are also involved in the effects of the antidepressant drugs, have been suggested as the possible mechanisms of action of SD. However, the therapeutic effect of SD is acute and transient, while antidepressant effects of drug treatments are gradual and stable. SD might work throughout mechanisms that are different from those mediating drugs effects. In the present study we analyzed the role of dopamine activity in SD. Spontaneous eye blink rate provides a non invasive measure of central dopamine activity. We assessed eye blink rate across prolonged wakefulness (from 10:00 a.m. to 07:00 a.m.) in 25 young normal subjects. Eye blink rate increased at the end of the wakefulness period. Blink rates and sleepiness as assessed by Karolinska Sleepiness Scale correlated positively with time spent awake. We propose that increased blink rate might reflect a dopamine activation that counteracts sleep drive. Antidepressant effects of sleep deprivation might be related to activation of the physiological mechanisms which regulate wake maintenance.

Indoor artificial lighting: Prediction of the circadian effects of different spectral power distributions

The study presented in this paper aims to evaluate if and how the environment affects the circadian impact of a light source by predicting circadian stimulus (CS) resulting from the exposure to different light scenes, using equations reported in studies by Rea et al. The main findings are: (1) Above 600 lx at eye level the increase of CS is little; (2) Between 50 lx and 200 lx at the eye level an increase of only 50 lx determines a significant increase of CS; (3) Light sources with correlated colour temperatures between 2900 K and 4200 K have similar impacts on the circadian system according to the calculation method used; (4) Even an almost neutral environment affects the circadian impact of a light source.

Dopamine activation in Neuroticism as measured by spontaneous eye blink rate

Personality dimensions have been associated with different psychobiological systems. However, no agreement exists in literature on a specific role of a single neurotransmitter for each of the dimensions investigated. We studied the relationship of Neuroticism, Extraversion and Psychoticism as assessed by Eysenck Personality Inventory (EPI) with spontaneous eye blink rate (BR), a non-invasive measure of central dopamine activity. A total of sixty-three healthy subjects (40 females, 23 males, mean age 24.2±3.9) were studied. Spontaneous blink rate and time of blink suppression were assessed by EOG measurement. Levels of Extraversion and Neuroticism were inversely correlated. In contrast with previous findings, a significant correlation between blink rate measures and Neuroticism was found. No significant correlation between blink measures and either Extraversion, or Psychoticism were found. The results appear consistent with a lower threshold for activation in neuroticism as suggested by Eysencks original model.

Diurnal variation of spontaneous eye blink rate in the elderly and its relationships with sleepiness and arousal

Sleep-wake rhythms in the elderly are deeply modified compared to young subjects, irrespective of physical or mental illnesses. However, still controversial are the results about age-related circadian variations of sleepiness levels. The objective of this study is to investigate the profile of diurnal sleepiness in healthy elderly subjects through subjective scales and by measuring spontaneous eye-blink rate (BR). In fact, we have previously found that BR, a reliable and non-invasive peripheral measure of central dopamine activity, increases in the young at times when subjective sleepiness is increased. Twelve healthy elderly volunteers (F=9, M=3, age range 64-79) participated in the experiment. At four times during the day (10a.m., 1.30p.m., 5p.m., 8.30p.m.), Karolinska sleepiness scale and a visual analogue scale for mood were administered to the subjects and BR was measured through vertical EOG. Alpha EEG power was used as objective measure of sleepiness. Sleepiness significantly changes across the day; according to post hoc contrasts, this is due to more sleepiness at 5p.m. Future research should be aimed at clarifying whether this peak is related to phase-advanced core body temperature in elderly people. Differently from the young, no significant differences were found in BR across the day, suggesting that an age-related modification of dopaminergic arousal mechanisms counteracting the rising sleep drive should be further explored.

Dynamics of electroencephalographic slow wave activity and body temperature during monophasic and biphasic human sleep

Dynamics of electroencephalographic (EEG) slow wave activity (0.5-4.5 Hz) and body temperature, as estimates, respectively, of the process S and process C, regulating sleep and waking alternate occurrence, were measured during monophasic and biphasic sleep patterns that occurred spontaneously in a 35-year-old woman who lived for 105 days in a winter-type photoperiod (10-14 h light-dark). In monophasic nights, rate of EEG synchronization showed a decreasing trend across the first three non-rapid eye movement (NREM) periods. In biphasic nights, rate of EEG synchronization increased during the third NREM period which precedes the nocturnal awakening. Temperature cycle was not different between biphasic and monophasic nights. Those results confirm that EEG dynamics reflects homeostatic sleep regulatory mechanism, and suggest that the period of prolonged wakefulness in the middle of biphasic night is pre-programmed.

Effects of Prolonged Wakefulness: The Role of PERIOD3 Genotypes and Personality Traits

The roles of personality traits, as assessed by Eysenck Personality Inventory, and of the clock gene PERIOD3 (PER3) were analysed on the subjective effects of prolonged wakefulness. A sample of 70 healthy participants (7 men, 63 women; M age = 24.2 yr., SD = 3.2) was studied during forced wakefulness between 7:30 p.m. and 9:30 a.m. According to Eysencks arousal model, it was hypothesized that prolonged wakefulness might affect in a different way those classified as Introverted and Extraverted. During the forced wakefulness period, the Introverted group showed greater decrease in subjective measures of vigilance than did the Extraverted group, but no differences were observed between groups with high and low scores on Psychoticism and Neuroticism. Prolonged wakefulness had a negative effect on subjective sleepiness and mood in all three PER3 polymorphisms analysed.

SEASONAL CHANGES IN MOOD AND CREATIVE ACTIVITY AMONG EMINENT ITALIAN WRITERS

A sample of 33 eminent Italian writers was studied. They were nominees of three of the most important literary Italian awards (Strega, Campiello, and Viareggio). The Seasonal Pattern Assessment Questionnaire was mailed to 105 writers during the period October 2003 and January 2004, of whom 39 replied. 33 (M age = 54.5 yr., SD=12.5; 8 women and 25 men) completed the questionnaire. Among respondents, spring and summer months showed highest ratings of “feel best.” During the summer a decline in creativity was not significant; respondents also reported sleeping least. Scores on the Global Seasonality Score suggested writers appeared to show higher seasonal sensitivity than the general population. Seasonal changes were considered as a problem by a majority of them. Although writers showed high seasonal sensitivity, no significant relationship was found between the seasonal pattern of mood and self-reported creativity.