Vocal accommodation in penguins (Spheniscus demersus) as a result of social environment.

The ability to vary the characteristics of one's voice is a critical feature of human communication. Understanding whether and how animals change their calls will provide insights into the evolution of language. We asked to what extent the vocalizations of penguins, a phylogenetically distant species from those capable of explicit vocal learning, are flexible and responsive to their social environment. Using a principal components (PCs) analysis, we reduced 14 vocal parameters of penguin's contact calls to four PCs, each comprising highly correlated parameters and which can be categorized as fundamental frequency, formant frequency, frequency modulation, and amplitude modulation rate and duration. We compared how these differed between individuals with varying degrees of social interactions: same-colony versus different-colony, same colony over 3 years and partners versus non-partners. Our analyses indicate that the more penguins experience each other's calls, the more similar their calls become over time, that vocal convergence requires a long time and relative stability in colony membership, and that partners' unique social bond may affect vocal convergence differently than non-partners. Our results suggest that this implicit form of vocal plasticity is perhaps more widespread across the animal kingdom than previously thought and may be a fundamental capacity of vertebrate vocalization.

Evaluation of the Effect of Chronic 94 GHz Exposure on Gene Expression in the Skin of Hairless Rats In Vivo.

Millimeter waves (MMW) are broadband frequencies that have recently been used in several applications in wireless communications, medical devices and nonlethal weapons [i.e., the nonlethal weapon, Active Denial Systems, (ADS) operating at 94-95 GHz, CW]. However, little information is available on their potential effects on humans. These radio-frequencies are absorbed and stopped by the first layer of the skin. In this study, we evaluated the effects of 94 GHz on the gene expression of skin cells. Two rat populations consisting of 17 young animals and 14 adults were subjected to chronic long-term 94 GHz MMW exposure. Each group of animals was divided into exposed and sham subgroups. The two independent exposure experiments were conducted for 5 months with rats exposed 3 h per day for 3 days per week to an incident power density of 10 mW/cm2, which corresponded to twice the ICNIRP limit of occupational exposure for humans. At the end of the experiment, skin explants were collected and RNA was extracted. Then, the modifications to the whole gene expression profile were analyzed with a gene expression microarray. Without modification of the animal's temperature, long-term chronic 94 GHz-MMW exposure did not significantly modify the gene expression of the skin on either the young or adult rats.

Effects of co-exposure to 900 MHz radiofrequency electromagnetic fields and high-level noise on sleep, weight, and food intake parameters in juvenile rats.

OBJECTIVE: Electrohypersensitive people attribute various symptoms to exposure of radiofrequency electromagnetic fields (RF-EMF); sleep disturbance is the most frequently cited. However, laboratory experiments have yielded conflicting results regarding sleep alterations. Our hypothesis was that exposure to RF-EMF alone would lead to slight or non-significant effects but that co-exposure to RF-EMFs and other environmental constraints (such as noise) would lead to significant effects. METHODS: 3-week-old male Wistar rats (4 groups, n = 12 per group) were exposed for 5 weeks to continuous RF-EMF (900 MHz, 1.8 V/m, SAR = 30 mW/kg) in the presence or absence of high-level noise (87.5 dB, 50-20000 Hz) during the rest period. After 5 weeks of exposure, sleep (24 h recording), food and water intakes, and body weight were recorded with or without RF-EMF and/or noise. At the end of this recording period, sleep was scored during the 1 h resttime in the absence of noise and of RF-EMF exposure. RESULTS: Exposure to RF-EMF and/or noise was associated with body weight gain, with hyperphagia in the noise-only and RF-EMF + noise groups and hypophagia in the RF-EMF-only group. Sleep parameters recording over 24 h highlighted a higher frequency of active wakefulness in the RF-EMF-only group and a lower non-rapid eye movement/rapid eye movement sleep ratio during the active period in the noise-only group. There were no differences in sleep duration in either group. During the 1-h, constraint-free sleep recording, sleep rebound was observed in the noise-only group but not in the RF-EMF-only and RF-EMF + noise groups. CONCLUSION: Our study showed effects of RF-EMF, regardless of whether or not the animals were also exposed to noise. However, the RF-EMF + noise group presented no exacerbation of those effects. Our results did not support the hypothesis whereby the effects of RF-EMF on physiological functions studied are only visible in animals exposed to both noise and RF-EMF.

Impacts of Subchronic, High-Level Noise Exposure on Sleep and Metabolic Parameters: A Juvenile Rodent Model.

BACKGROUND: Noise is an environmental factor that has been associated with metabolic and sleep disorders. Sleep is a vital function, since it underpins physiologic processes and cognitive recovery and development. However, the effects of chronic noise exposure on the developing organism are still subject to debate. OBJECTIVE: The objective of the present study was to assess the effects of subchronic, high-level noise exposure on sleep, apnea, and homeostasis in juvenile rats. METHODS: Twenty-four 3-wk-old male Wistar rats were exposed to noise [[Formula: see text], [Formula: see text]] for 5 wk and 2 d during the 12-h rest period. Data on sleep stages, food and water intake, apnea, and body and organ weight were recorded. RESULTS: Five weeks of high-level noise exposure were associated with hyperphagia ([Formula: see text]), body weight gain ([Formula: see text]), a heavier thymus ([Formula: see text]), and heavier adrenal glands ([Formula: see text]). A sleep analysis highlighted microstructural differences in the active period: in particular, the mean daily amount of rapid eye movement (REM) sleep as a proportion of total sleep time (TST) was higher. The mean daily amount of non-REM (NREM) sleep was lower in the exposed group, meaning that the intergroup difference in the TST was not significant. During a 1-h, noise-free plethysmographic recording during the rest period, the mean total amount of active wakefulness (AW) was lower in the exposed group (by 9.1 min), whereas the mean duration of an episode of REM sleep was higher (by 1.8 min), and the TST was higher (by 10.7 min). DISCUSSION: Subchronic exposure of juvenile rats to high-intensity noise during the rest period was associated with some small but significant sleep disturbances, greater food and water intakes, greater body weight gain, and greater thymus and adrenal gland weights. The main effects of noise exposure on sleep were also observed in the 1-h plethysmography session after 5 wk of exposure. https://doi.org/10.1289/EHP4045.

Validation of 'Somnivore', a Machine Learning Algorithm for Automated Scoring and Analysis of Polysomnography Data.

Manual scoring of polysomnography data is labor-intensive and time-consuming, and most existing software does not account for subjective differences and user variability. Therefore, we evaluated a supervised machine learning algorithm, SomnivoreTM, for automated wake-sleep stage classification. We designed an algorithm that extracts features from various input channels, following a brief session of manual scoring, and provides automated wake-sleep stage classification for each recording. For algorithm validation, polysomnography data was obtained from independent laboratories, and include normal, cognitively-impaired, and alcohol-treated human subjects (total n = 52), narcoleptic mice and drug-treated rats (total n = 56), and pigeons (n = 5). Training and testing sets for validation were previously scored manually by 1-2 trained sleep technologists from each laboratory. F-measure was used to assess precision and sensitivity for statistical analysis of classifier output and human scorer agreement. The algorithm gave high concordance with manual visual scoring across all human data (wake 0.91 ± 0.01; N1 0.57 ± 0.01; N2 0.81 ± 0.01; N3 0.86 ± 0.01; REM 0.87 ± 0.01), which was comparable to manual inter-scorer agreement on all stages. Similarly, high concordance was observed across all rodent (wake 0.95 ± 0.01; NREM 0.94 ± 0.01; REM 0.91 ± 0.01) and pigeon (wake 0.96 ± 0.006; NREM 0.97 ± 0.01; REM 0.86 ± 0.02) data. Effects of classifier learning from single signal inputs, simple stage reclassification, automated removal of transition epochs, and training set size were also examined. In summary, we have developed a polysomnography analysis program for automated sleep-stage classification of data from diverse species. Somnivore enables flexible, accurate, and high-throughput analysis of experimental and clinical sleep studies.

c-Fos expression in the limbic thalamus following thermoregulatory and wake-sleep changes in the rat.

A cellular degeneration of two thalamic nuclei belonging to the "limbic thalamus", i.e., the anteroventral (AV) and mediodorsal (MD) nuclei, has been shown in patients suffering from Fatal Familial Insomnia (FFI), a lethal prion disease characterized by autonomic activation and severe insomnia. To better assess the physiological role of these nuclei in autonomic and sleep regulation, c-Fos expression was measured in rats during a prolonged exposure to low ambient temperature (Ta, - 10 °C) and in the first hours of the subsequent recovery period at normal laboratory Ta (25 °C). Under this protocol, the thermoregulatory and autonomic activation led to a tonic increase in waking and to a reciprocal depression in sleep occurrence, which was more evident for REM sleep. These effects were followed by a clear REM sleep rebound and by a rebound of Delta power during non-REM sleep in the following recovery period. In the anterior thalamic nuclei, c-Fos expression was (1) larger during the activity rather than the rest period in the baseline; (2) clamped at a level in-between the normal daily variation during cold exposure; (3) not significantly affected during the recovery period in comparison to the time-matched baseline. No significant changes were observed in either the MD or the paraventricular thalamic nucleus, which is also part of the limbic thalamus. The observed changes in the activity of the anterior thalamic nuclei appear, therefore, to be more specifically related to behavioral activation than to autonomic or sleep regulation.

Wake-sleep and cardiovascular regulatory changes in rats made obese by a high-fat diet.

Obesity is known to be associated with alterations in wake-sleep (WS) architecture and cardiovascular parameters. This study was aimed at assessing the possible influence of diet-induced obesity (DIO) on sleep homeostasis and on the WS state-dependent levels of arterial pressure (AP) and heart rate in the rat. Two groups of age-matched Sprague-Dawley rats were fed either a high-fat hypercaloric diet, leading to DIO, or a normocaloric standard diet (lean controls) for 8 weeks. While under general anesthesia, animals were implanted with instrumentation for the recording of electroencephalogram, electromyogram, arterial pressure, and deep brain temperature. The experimental protocol consisted of 48h of baseline, 12h of gentle handling, enhancing wake and depressing sleep, and 36-h post-handling recovery. Compared to lean controls, DIO rats showed: i) the same amount of rapid-eye movement (REM) and non-REM (NREM) sleep in the rest period, although the latter was characterized by more fragmented episodes; ii) an increase in both REM sleep and NREM sleep in the activity period; iii) a comparable post-handling sleep homeostatic response, in terms of either the degree of Delta power increase during NREM sleep or the quantitative compensation of the REM sleep loss at the end of the 36-h recovery period; iv) significantly higher levels of AP, irrespectively of the different WS states and of the changes in their intensity throughout the experimental protocol. Overall, these changes may be the reflection of a modification in the activity of the hypothalamic areas where WS, autonomic, and metabolic regulations are known to interact.

Wake-sleep, thermoregulatory, and autonomic effects of cholinergic activation of the lateral hypothalamus in the rat: a pilot study.

A major role in the wake-promoting effects of the activation of the lateral hypothalamus (LH) has been ascribed to a population of orexin (ORX)-containing neurons that send projections to central areas which regulate Wake-Sleep and autonomic function. Since, in the rat, a substantial amount of ORX neurons receive cholinergic projections from cells involved in Wake-Sleep regulation, the aim of this study was to assess the role played by LH cholinoceptive cells in Wake-Sleep and autonomic regulations. To this end, the effects of a microinjection of the cholinergic agonist Carbachol (CBL) into the LH were compared to those obtained through the activation of a wider cell population by the microinjection of the GABAA antagonist GABAzine (GBZ). The results of this pilot study showed that both drugs elicited the same behavioral and autonomic effects, those caused by GBZ being larger and longer-lasting than those following administration of CBL. Briefly, wakefulness was enhanced and sleep was depressed, and brain temperature and heart rate consistently increased, while mean arterial pressure showed only a mild increment. Surprisingly, the administration of the drug vehicle (SAL) elicited a similar pattern of Wake-Sleep effects which, although much smaller, were sufficient to mask any statistical significance between treatment and control data. In conclusion, the results of this work show that the arousal elicited by LH disinhibition by GABAzine is concomitant with autonomic responses set by the intervention of cold-defense mechanisms. Since the same response is elicited at a lower level by CBL administration, the hypothesis of an involvement of cholinoceptive ORX neurons in its generation is discussed.

Enhanced slow-wave EEG activity and thermoregulatory impairment following the inhibition of the lateral hypothalamus in the rat.

Neurons within the lateral hypothalamus (LH) are thought to be able to evoke behavioural responses that are coordinated with an adequate level of autonomic activity. Recently, the acute pharmacological inhibition of LH has been shown to depress wakefulness and promote NREM sleep, while suppressing REM sleep. These effects have been suggested to be the consequence of the inhibition of specific neuronal populations within the LH, i.e. the orexin and the MCH neurons, respectively. However, the interpretation of these results is limited by the lack of quantitative analysis of the electroencephalographic (EEG) activity that is critical for the assessment of NREM sleep quality and the presence of aborted NREM-to-REM sleep transitions. Furthermore, the lack of evaluation of the autonomic and thermoregulatory effects of the treatment does not exclude the possibility that the wake-sleep changes are merely the consequence of the autonomic, in particular thermoregulatory, changes that may follow the inhibition of LH neurons. In the present study, the EEG and autonomic/thermoregulatory effects of a prolonged LH inhibition provoked by the repeated local delivery of the GABAA agonist muscimol were studied in rats kept at thermoneutral (24°C) and at a low (10°C) ambient temperature (Ta), a condition which is known to depress sleep occurrence. Here we show that: 1) at both Tas, LH inhibition promoted a peculiar and sustained bout of NREM sleep characterized by an enhancement of slow-wave activity with no NREM-to-REM sleep transitions; 2) LH inhibition caused a marked transitory decrease in brain temperature at Ta 10°C, but not at Ta 24°C, suggesting that sleep changes induced by LH inhibition at thermoneutrality are not caused by a thermoregulatory impairment. These changes are far different from those observed after the short-term selective inhibition of either orexin or MCH neurons, suggesting that other LH neurons are involved in sleep-wake modulation.

SCOPRISM: a new algorithm for automatic sleep scoring in mice.

BACKGROUND: Scoring of wake-sleep states by trained investigators is a time-consuming task in many sleep experiments. We aimed to validate SCOPRISM, a new open-source algorithm for sleep scoring based on automatic graphical clustering of epoch distribution. METHODS: We recorded sleep and blood pressure signals of 36 orexin-deficient, 7 leptin knock-out, and 43 wild-type control mice in the PRISM laboratory. Additional groups of mice (n=14) and rats (n=6) recorded in independent labs were used to validate the algorithm across laboratories. RESULTS: The overall accuracy, specificity and sensitivity values of SCOPRISM (97%, 95%, and 94%, respectively) on PRISM lab data were similar to those calculated between human scorers (98%, 98%, and 94%, respectively). Using SCOPRISM, we replicated the main sleep and sleep-dependent cardiovascular findings of our previous studies. Finally, the cross-laboratory analyses showed that the SCOPRISM algorithm performed well on mouse and rat data. COMPARISON WITH EXISTING METHODS: SCOPRISM performed similarly or even better than recently reported algorithms. SCOPRISM is a very simple algorithm, extensively (cross)validated and with the possibility to evaluate its efficacy following a quick and easy visual flow chart. CONCLUSIONS: We validated SCOPRISM, a new, automated and open-source algorithm for sleep scoring on a large population of mice, including different mutant strains and on subgroups of mice and rats recorded by independent labs. This algorithm should help accelerate basic research on sleep and integrative physiology in rodents.

Thermoregulatory correlates of nausea in rats and musk shrews.

Nausea is a prominent symptom and major cause of complaint for patients receiving anticancer chemo- or radiation therapy. The arsenal of anti-nausea drugs is limited, and their efficacy is questionable. Currently, the development of new compounds with anti-nausea activity is hampered by the lack of physiological correlates of nausea. Physiological correlates are needed because common laboratory rodents lack the vomiting reflex. Furthermore, nausea does not always lead to vomiting. Here, we report the results of studies conducted in four research centers to investigate whether nausea is associated with any specific thermoregulatory symptoms. Two species were studied: the laboratory rat, which has no vomiting reflex, and the house musk shrew (Suncus murinus), which does have a vomiting reflex. In rats, motion sickness was induced by rotating them in their individual cages in the horizontal plane (0.75 Hz, 40 min) and confirmed by reduced food consumption at the onset of dark (active) phase. In 100% of rats tested at three centers, post-rotational sickness was associated with marked (~1.5°C) hypothermia, which was associated with a short-lasting tail-skin vasodilation (skin temperature increased by ~4°C). Pretreatment with ondansetron, a serotonin 5-HT3 receptor antagonist, which is used to treat nausea in patients in chemo- or radiation therapy, attenuated hypothermia by ~30%. In shrews, motion sickness was induced by a cyclical back-and-forth motion (4 cm, 1 Hz, 15 min) and confirmed by the presence of retching and vomiting. In this model, sickness was also accompanied by marked hypothermia (~2°C). Like in rats, the hypothermic response was preceded by transient tail-skin vasodilation. In conclusion, motion sickness is accompanied by hypothermia that involves both autonomic and thermoeffector mechanisms: tail-skin vasodilation and possibly reduction of the interscapular brown adipose tissue activity. These thermoregulatory symptoms may serve as physiological correlates of nausea.

Provocative motion causes fall in brain temperature and affects sleep in rats.

Neural substrate of nausea is poorly understood, contrasting the wealth of knowledge about the emetic reflex. One of the reasons for this knowledge deficit is limited number and face validity of animal models of nausea. Our aim was to search for new physiological correlates of nausea in rats. Specifically, we addressed the question whether provocative motion (40-min rotation at 0.5 Hz) affects sleep architecture, brain temperature, heart rate (HR) and arterial pressure. Six adult male Sprague­Dawley rats were instrumented for recordings of EEG, nuchal electromyographic, hypothalamic temperature and arterial pressure. Provocative motion had the following effects: (1) total abolition of REM sleep during rotation and its substantial reduction during the first hour post-rotation (from 20 ± 3 to 5 ± 1.5%); (2) reduction in NREM sleep, both during rotation (from 57 ± 6 to 19 ± 5%) and during the first hour post-rotation (from 56 ± 3 to 41 ± 9%); (3) fall in the brain temperature (from 37.1 ± 0.1 to 36.0 ± 0.1 °C); and (4) reduction in HR (from 375 ± 6 to 327 ± 7 bpm); arterial pressure was not affected. Ondansetron, a 5-HT3 antagonist, had no major effect on all observed parameters during both baseline and provocative motion. We conclude that in rats, provocative motion causes prolonged arousing effects, however without evidence of sympathetic activation that usually accompanies heightened arousal. Motion induced fall in the brain temperature complements and extends our previous observations in rats and suggests that similar to humans, provocative motion triggers coordinated thermoregulatory response, leading to hypothermia in this species.

Waking and sleeping in the rat made obese through a high-fat hypercaloric diet.

Sleep restriction leads to metabolism dysregulation and to weight gain, which is apparently the consequence of an excessive caloric intake. On the other hand, obesity is associated with excessive daytime sleepiness in humans and promotes sleep in different rodent models of obesity. Since no consistent data on the wake-sleep (WS) pattern in diet-induced obesity rats are available, in the present study the effects on the WS cycle of the prolonged delivery of a high-fat hypercaloric (HC) diet leading to obesity were studied in Sprague-Dawley rats. The main findings are that animals kept under a HC diet for either four or eight weeks showed an overall decrease of time spent in wakefulness (Wake) and a clear Wake fragmentation when compared to animals kept under a normocaloric diet. The development of obesity was also accompanied with the occurrence of a larger daily amount of REM sleep (REMS). However, the capacity of HC animals to respond to a "Continuous darkness" exposure condition (obtained by extending the Dark period of the Light-Dark cycle to the following Light period) with an increase of Sequential REMS was dampened. The results of the present study indicate that if, on one hand, sleep curtailment promotes an excess of energy accumulation; on the other hand an over-exceeding energy accumulation depresses Wake. Thus, processes underlying energy homeostasis possibly interact with those underlying WS behavior, in order to optimize energy storage.