Sleep pattern in the rook, Corvus frugilegus

In the rook, Corvus frugilegus, electrographic and behavioural correlates of sleep and wakefulness have been determined under natural lighting conditions. Slow wave sleep (SWS) was characterized by high amplitude slow EEG activity, low neck EMG, and behavioural inactivity. Paradoxical sleep (PS) was characterized by low amplitude fast EEG activity and inconsistent decrease in EMG. PS episodes always commenced with head downward. Several eye movements occurred activity were present. The rook spent in sleep 31.8% of the 24-h period. PS however, eye movements, high tonic neck EMG activity, and behavioural activity were present. The rook spent in sleep 31.8% of the 24-h period. PS constituted 1.8% of total sleep, while the rest of total sleep was occupied by SWS. On the average, episodes of SWS and PS lasted 10.8 min and 24 s respectively. The daily percentage of SWS was highly correlated with the mean episode duration. PS amount was better correlated with the number of episodes than with their mean duration. Our data suggest that over-short period of recovery from surgery and adaptation with implanted electrodes could lead to underestimation of sleep duration in rook.     

Sleep-waking cycle and behaviour after diethyldithiocarbamate in the rat

Young adult Louis rats were implanted for chronic sleep recording to test the effect of diethyldithiocarbamate (DDC) on sleep. Recordings of EEG and EMG were done continuously for 12 h during the 12 consecutive days. There were 2 days of baseline recording, 3 days of recording with a single daily injection of placebo, 3 days of recording with a single daily injection of DDC (500 mg/kg i.p.), and 3 days of DDC withdrawal recording with placebo injection. Placebo injections did not change the proportion of time spent in different behavioural states. With daily injection of DDC there was an increase in wakefulness, no change in slow-wave sleep and elimination or drastic reduction in paradoxical sleep (PS). There was no PS rebound during the DDC withdrawal days. These results suggest that the reduction of PS produced by DDC and the absence of PS rebound may be due to a lowering in norepinephrine in the brain. In other experiments rats were injected with DDC (500 mg/kg i.p.) daily for 3 days and whole brains were analysed chemically. Norepinephrine was significantly decreased, while 5-hydroxytryptamine, 5-hydroxyindolacetic acid, dopamine and homovanilic acid were unchanged. Seizure activity appeared during relaxed wakefulness in all rats treated with DDC. Taken together it seems that lowering of brain NE is responsible for the appearance of seizure activity and also, for PS reduction. PS reduction might, per se, produce seizure activity.     

Daily distribution of sleep states in the jackdaw, Corvus monedula

Polygraphic and behavioral studies of the jackdaws Corvus monedula have revealed a strong influence of the natural day-night cycle on their daily wakefulness-sleep activity. The jackdaws were behaviorally active during the light part of the photoperiod. The daily distribution of slow wave sleep (SWS) was symmetric and that of paradoxical sleep (PS) was asymmetric. The amount of PS was greater in the second half of the night than in the first. Short and intermediate length episodes occurred almost homogeneously throughout the night. The longest sleep episodes clustered toward the middle part of the night and did not occur in the periods following onset of sleep and before the end of sleep.     

Sleep pattern in the starling (Sturnus vulgaris)

Electrographic and behavioural observations were conducted on two male and two female captive starlings (Sturnus vulgaris) under natural illumination conditions during autumn. Polygraphically sleep and wakefulness of starling were similar to those of other birds. Starling's total sleep (TS) and slow wave sleep (SWS) lasted 39.0 +/- 1.4% and 38.3 +/- 1.7% of the 24-h period respectively. Paradoxical sleep (PS) was 1.8 +/- 0.2% of the total sleep time. The mean durations individual of TS, SWS and PS episodes were 6.8 +/- 0.2 min, 5.0 +/- 1.0 min and 18 +/- 3 s respectively. The daily percentage of SWS was correlated with the mean episode duration while that of PS was correlated with the number of episodes rather than with the mean episode duration. Starling females spent in sleep a greater percentage of the 24-h period than males.     

Is the pars intermedia of the hypophysis responsible for provoking paradoxical sleep in pontine cats with an isolated hypophysis?

In chronic pontine cats without hypothalamo-hypophysis, daily subcutaneous or intraventricular injection of total extracts of Bovine neuro-intermediate lobe increases both survival and quantity of paradoxical sleep, while synthetic Lysine vasopressin, Oxytocin or ACTH have no effect. Chronic pontine cats with "isolated hypophysis" have a longer survival and a more significant amount of paradoxical sleep than those without hypothalamo-hypophysis. Factor(s) liberated by pars intermedia are very likely to be responsible for the increase of PS since only pars intermedia remains functional in the "isolated hypophysis" as shown by immunocytochemical controls.     

Interaction between light-dark cycles and circadian rhythm on sleep and wakefulness in albino rats

This study investigated the role of the circadian phase in modulating the effect of short light-dark cycles (LDc) on sleep and wakefulness. Six male albino rats of the Sprague-Dawley strain were implanted with electrodes for standard electrophysiological recordings performed during baseline (12 - 12 h LDc), short LDc treatment, and recovery (12 - 12 h LDc) for 4 days each. In the short LDc treatment, 15 - 15 min LDc were applied, respectively, in mid-periods of inactive and active phases to maintain an entrained circadian rhythm. The results showed that the 15 - 15 min LD ratio of both non-rapid eye movement sleep (NREM) and paradoxical sleep (PS) did not vary with the circadian phase. In contrast, changes in both the NREM and PS amounts in the short LDc treatment varied with the circadian phase. It is argued in the Discussion section that the circadian phase-related changes in the sleep amount did not result from the circadian rhythm effect but from the interactions between the habitual 24 h lighting schedule and the habitual LD distribution of the sleep and wakefulness amounts. On the other hand, this study found that both waking (W) and PS response to short LDc varied with time courses. The 15 min dark period strongly enhanced the W time only when it occurred for the first time in the inactive phase while it consistently facilitated PS across the remaining time periods in both the active and inactive phases. Furthermore, a residual effect of short LDc on PS was revealed in this study. Compared to the baseline, the 12 - 12 h LD ratio of PS was significantly decreased during recovery compared to the short LDc treatment.     

Differential action upon sleep states of ventrolateral and central areas of pontine tegmental field

In order to study oral pontine mechanisms of the sleep- wakefulness cycle (SWC), modifications in the total amount, frequency, and duration of episodes of wakefulness (W), drowsiness (D), slow sleep (SS) and paradoxical sleep (PS) together with modifications in the hourly distribution of both sleep states were analyzed in 15 adult cats. Three animals were used as sham-operated controls. Six of them, Group I, received unilateral lesions in ventral and lateral areas of the nucleus reticularis pontis oralis (RPO) and rostral nucleus reticularis pontis caudalis (RPC). The remaining 6 cats, Group II, had unilateral lesions in the central part of the same nuclei. After ventrolateral lesions (Group I) decrease of PS and SS occurred, but only PS changes reached statistically significant values; while, on the contrary, a significant increase of SS and PS followed central lesions (Group II). Hourly distribution analysis indicated that in Group I decrease of both sleep states took place mainly at night, while in Group II increase of both SS and PS occurred during day. These results suggest a complex and non- uniform influence of the pontine tegmental area on SWC mechanisms. Effects obtained after unilateral lesions, precisely located in ventral and lateral or central parts, point to the existence of two functionally distinct, although almost overlapping, systems, at this level.     

Circadian rhythms of slow-wave sleep and paradoxical sleep are in opposite phase in genetically hypoprolactinemic rats

In eleven genetically hypoprolactinemic rats (IPL nude rats) and five control rats (OFA), the sleep-waking cycle was continuously registered for 14 days at two ambient temperatures. At 23 degrees C, the slow wave sleep (SWS) duration of IPL rats was significantly higher (+6.8%, t = 5.4, p less than 0.001) than that of control rats, while the paradoxical sleep (PS) duration was lowered by 31.8% (t = 9.4, p less than 0.001). The circadian rhythm of PS disappeared while that of SWS persisted unchanged. At 30 degrees C, both sleep durations reached the level of control rats. The circadian rhythm of PS was however completely reversed: the PS acrophase was at 01 h while that of SWS was at 12 hrs. This first observation of spontaneous dissociation of the two states of sleep supports the hypothesis of two distinct circadian clocks, one for SWS, another for PS. It is suggested that hypothalamic prolactin and/or other still unknown genetic alterations might be responsible for the observed change in the PS circadian rhythm.     

The relationship between sleep circadian rhythm and central feedback mechanism of gonadal steroid in female guinea pigs

To examine the relationship between the sleep rhythm and the gonadal feedback system in the guinea pig, the effects of estrous cycle, gonadal steroids and brain deafferentiations on the sleep rhythm were studied and the following results were obtained; 1) the guinea pigs did not show an apparent circadian rhythmicity in the sleep-wakefulness cycle but showed an ultradian rhythm, whereas, the activity rhythm was circadian, 2) the rhythm in paradoxical sleep(PS) showed changes associated with the estrous cycle which were characterized by a decrease and rebound-like increase in PS amounts on the day of proestrus, 3) the horizontal deafferentation above the medial preoptic area at the level of the anterior commissure (MPO roof cut) did not disrupt the estrous cycle dependent changes in the PS rhythm, but the prechiasmatic deafferentiation of the medial basal hypothalamus (PCD) and the large complete deafferentation of the medial basal hypothalamus (CDL) disrupted them, 4) ovariectomy (OVX) did not result in any changes in sleep and activity rhythms, 5) an administration of estradiol benzoate (E2) to OVX guinea pig caused a decrease in the amount of PS and an administration of progesterone (P) 48h after E2 caused a more pronounced decrease and rebound-like increase in the amount of PS, 6) the MPO roof cut did not affect the steroidal modification of the PS rhythm and the PCD disrupted it, while the CDL-animal also showed a E2-induced PS decrease. From these results, it appears that the guinea pig may be a circadian animal, but this may not be seen in the sleep-wakefulness cycle, and the estrous cycle dependent changes in the PS rhythm may be the reflection of steroidal modification of the sleep rhythm and the site of action may be the inside of the medial preoptic anterior hypothalamic structures, but this area may also be affected by the output from the medial basal hypothalamus.     

Antipredator vigilance of juvenile and adult thirteen-lined ground squirrels and the role of nutritional need

Juvenile thirteen-lined ground squirrels, Spermophilus tridecemlineatus, are less vigilant (i.e. they spend less time visually scanning the environment) than adults. To determine whether nutritional need was a potential cause of this difference, we supplemented two groups of free-ranging juveniles during the predispersal stage, while juveniles were still near and around the natal burrows. The high-energy food group (HEF: 11 squirrels) received peanut butter and oats while the low-energy food group (LEF: seven squirrels) received lettuce. Adults (14 squirrels) were also supplemented, but due to their greater home range sizes, it was not feasible to classify them as either HEF or LEF. To evaluate the effect of supplementation on antipredator vigilance, the behavioural act of visually scanning for predators, we videotaped individuals while they were foraging above ground during 5-min observation periods. Each squirrel was observed and weighed during three time periods over 23 days. From the videotape, we extracted measures of time spent vigilant, locomoting and foraging. All three categories of squirrels gained mass over the study period, but the HEF juveniles rapidly exceeded that of the LEF juveniles. Early in the study, LEF and HEF juveniles did not significantly differ in either body mass or time budgets, and, initially, both juvenile groups were similar to adults in the amount of time devoted to vigilance. Later in the study, the behaviour of HEF juveniles closely resembled that of adults (increased time devoted to vigilance and decreased time devoted to foraging), while LEF juveniles decreased vigilance and increased their foraging time. This study indicates that for thirteen-lined ground squirrels the lower vigilance of juveniles is due, at least in part, to the greater nutritional needs of young animals with consequent increases in foraging, which is largely incompatible with vigilance. Copyright 2000 The Association for the Study of Animal Behaviour.     

Effects of electrolytic lesion of hypothalamic paraventricular nucleus and its related areas on the sleep waking cycle in the cat

In order to study putative hypothalamic mechanisms of sleep waking cycle regulation we destroyed, by electrolytic coagulation, a large part of the medial hypothalamus overlapping the paraventricular nucleus in 6 adult cats. We never observed any modification of light slow wave sleep. Three of the six cats presented no paradoxical sleep (PS) impairment, despite an almost total destruction of neurophysin-immunoreactive cells of PVN in two cats and marked signs of diabetes insipidus in the third. Further, in the other three animals a statistically significant decrease of daily quantities of PS and deep slow wave sleep (SWS2) were related to an extensive destruction of the anterior hypothalamic area. These results suggest lack of influence of the PVN in sleep regulation and an involvement of the anterior hypothalamus in the onset of SWS2 and PS.     

Validation of daily increment formation in otoliths of juvenile and adult European anchovy

The otoliths of juveniles and adults of European anchovy Engraulis encrasicolus held in aquaria were marked by immersion in oxytetracycline hydrochloride (OTC) at concentrations between 350 and 410 mg l⁻¹ for 12 h. Counts of microincrements between fluorescent bands validated the daily otolith increment formation. The otolith increments were easily readable at ×400 with average increment widths of c . 1·1 µm. Validation was successfully demonstrated in juveniles and adults maintained for short periods in the aquaria in the summer. For European anchovy captured as juvenile and reared to adults, however, increment formation appeared less than daily. The daily periodicity of the otoliths in juvenile European anchovy implies that counting of microincrements can be used to study their birth dates. The application of this technique to adults, however, may lead to the underestimation of actual age and further research needs to be done to clarify the reasons for the apparent loss of the daily rhythm over long periods.     

Crop selection, feeding skills and risks taken by adult and juvenile Rooks Corvus frugilegus

During July and August, adult Rooks Corvus frugilegus predominantly foraged on pastures while most juveniles fed on storm-flattened barley. The rate at which barley grains were consumed by both adults and juveniles increased from early July to late July and August. Adult birds consumed barley at a faster rate than juveniles in early July, but there was no difference in the rate at which barley was consumed by adults and juveniles later in the season. No differences in feeding rates could be detected between adults and juveniles that foraged on pasture. Adult Rooks were more vigilant than juveniles when feeding in barley fields.     

Study of sleep of shift workers with alternating schedules: adaptation and recovery in case of rapid shift rotation (3-4 days) (author's transl)

An electroencephalographic study of the sleep of shift workers (3 x 8) was performed in a French oil refinery. The recordings of diurnal sleep showed: a severe disorganization of the first day sleep (very short duration, decrease of PS and SWS in absolute amount); a trend towards better sleep characteristics (duration, PS and SWS amount) through the day-sleep period. Recovery night sleep appeared different when following curtailed night sleep (morning shift) and when following curtailed day sleep (night shift). Nocturnal sleep following immediately the diurnal sleep shows only partly the characteristics of a real recovery. Thus there seems to be a beginning adaptation to schedule reversal. This result supports a rapid shift alternation (3-4 days) which restrains both the cumulated sleep deficit and the adaptation to schedule reversal.     

Autumn migration of robins (Erithacus rubecula) in Hungary

The purpose of this study was to describe the autumn migration dynamics of juvenile (n = 3075) and adult (n = 596) robin Erithacus rubecula in Hungary. Capturing and ringing of birds took place at five bird ringing stations of Actio Hungarica between 13 August and 27 October, 2004. The number of captured juvenile and adult individuals rated to one net was the lowest in the reeds of Izsák and the highest in the woody areas of Szalonna, where adults were present at a higher proportion. The migration dynamics of the robin showed that the end of September and the beginning of October was the peak time for passing through Hungary. Based on the estimated time of the 10% of daily capture, it can be stated that juvenile birds started their migration as early as the end of August or at the beginning of September while the migration of the adults started later. The migration started earliest in Szalonna and latest in Izsák. The comparison of daily catch dynamics (based on the estimated time of 10% and 50% of daily captures) of juveniles and adults between study sites showed that similarity of daily capture was higher in the case of juveniles. The five study sites had different qualities from the point of view of the robins’ habitat preference. Our results showed that the reed-bed of Izsák had only peripheral importance while the other forest and bushy study areas played a key role in resting and feeding during the migration of the robin.     

Sleep: approaching the fundamental questions

Our 'sleep need' may be defined as the daily amount of sleep we require to be fully awake during daytime. A recent study has shown that both sleep need and daytime sleepiness decline in older adults.     

Sleep and eating behavior in adults at risk for type 2 diabetes

Insufficient quantity and quality of sleep may modulate eating behavior, everyday physical activity, overall energy balance, and individual risk of obesity and type 2 diabetes. We examined the association of habitual sleep quantity and quality with the self-reported pattern of eating behavior in 53 healthy urban adults with parental history of type 2 diabetes (30 F/23 M; mean (s.d.) age: 27 (4) years; BMI: 23.9 (2.3) kg/m(2)) while taking into consideration the amount of their everyday physical activity. Participants completed 13 (3) days of sleep and physical activity monitoring by wrist actigraphy and waist accelerometry while following their usual lifestyle at home. Overnight laboratory polysomnography was used to screen for sleep disorders. Subjective sleep quality was measured with the Pittsburgh Sleep Quality Index. Eating behavior was assessed using the original 51-item and the revised 18-item version of the Three-Factor Eating Questionnaire including measures of cognitive restraint, disinhibition, hunger, and uncontrolled and emotional eating. In multivariable regression analyses adjusted for age, BMI, gender, race/ethnicity, level of education, habitual sleep time measured by wrist actigraphy and physical activity measured by waist accelerometry, lower subjective sleep quality was associated with increased hunger, more disinhibited, uncontrolled and emotional eating, and higher cognitive restraint. There was no significant association between the amount of sleep measured by wrist actigraphy and any of these eating behavior factors. Our findings indicate that small decrements in self-reported sleep quality can be a sensitive indicator for the presence of potentially problematic eating patterns in healthy urban adults with familial risk for type 2 diabetes.     

Parasite mediated mortality and host immune response explain age-related differences in blood parasitism in birds

An important pattern in host-parasite assemblages is a higher intensity of parasites in juveniles than in adults, but the reasons for these differences remain obscure. Three non-mutually exclusive hypotheses have been proposed: (1) heavily parasitized juveniles die before being recruited into the adult population ('selection' hypothesis); (2) the development of an acquired immunity by the host in front of the parasite reduces the intensity of the parasite in adult hosts ('immunity' hypothesis); and (3) differences in behavior makes adults less exposed to the parasite than juveniles ('vector exposure' hypothesis). Having rejected the 'vector exposure' hypothesis in a previous study, here we tested the 'selection' and 'immunity' hypotheses in feral pigeons (Columba livia) infected by the blood parasite Haemoproteus columbae. In agreement with the 'selection' hypothesis, young (but not adult) pigeons that were highly parasitized had a lower probability of surviving until adulthood, independent of their body condition. However, selection was not strong enough to account for the observed differences in parasite intensity between age-classes, and after selection parasite intensity of survivors still remained 85% higher in juveniles than in adults. In contrast, the 'immunity' hypothesis offered a greater explanatory power. The intensity of blood parasites in young pigeons, but not in adults, decreased over time so dramatically that by the time they had become adults their intensities were indistinguishable from that typically seen in adults. Therefore, while selection against highly parasitized juveniles can contribute to some extent to a reduction in parasitism seen in the adult population, age-specific blood parasitism in feral pigeons is best explained as a transitory phase just before the host develops an effective immune response.     

Groups of passive and active control state in longitudinal experiments: an electrophysiological study

Long-term electrophysiological experiments were carried out with rats with chronically implanted electrodes into dopaminergic brain structures. Within 4 weeks after surgery, the relative spectral power of electrical activity in the delta1 and delta2 frequency bands decreased, while the relative spectral power in the alpha, beta1 and beta2 bands increased. A delayed (to the 4-5th week after surgery) increase in the total amount of sleep and REM sleep percent was observed in the sleep architecture of these animals. Multiple (during 2 weeks daily) intraperitoneal saline injections altered the dynamic of electrophysiological indices on the 2nd-3rd postsurgery weeks. The total sleep amount being not increased, the total and mean REM sleep durations increased, and the dynamic of the relative spectral power of electrical activity in the dopaminergic brain structures in the delta1, alpha and beta2 bands was found to be changed.     

Biology of a "babysitting" symbiosis in brittle stars: analysis of the interactions between Ophiomastix venosa and Ophiocoma scolopendrina

Abstract. "Babysitting" symbioses between brittle star species involve juveniles of one species and adults of another. During this phenomenon, reported from many localities in the Indo-Pacific Ocean, juveniles are attached to the disk or lie in the bursa of the adults. The symbiosis between members of Ophiomastix venosa and their host, Ophiocoma scolopendrina , was investigated on the Great Barrier Reef of Toliara (Madagascar) during a 14-month period. The population of O. scolopendrina only occurs on rocky spurs that frequently emerge at low tide, while the population of O. venosa lies in adjacent surge channels that are always immersed. Only juveniles of O. venosa associated with adults of O. scolopendrina may occur on the rocky spurs. Analyses conducted on the populations of the two species showed that (1) the symbiosis is facultative and that symbiotic juveniles migrate into the channels when they reach a disc diameter of 6 mm, and (2) recruitment in the channels occurs in April. Host choice experiments, Y-tube experiments, and experiments assessing the resistance of the ophiuroids to air-drying were conducted in the laboratory. The experiments clearly demonstrated that (1) symbiotic juveniles of O. venosa specifically recognize adults of O. scolopendrina , while free juveniles of the same size do not, and (2) juveniles of O. venosa would not survive air-drying conditions similar to those observed on the spurs at low tides if they were not in symbiosis with adults of O. scolopendrina .