Research Interests: Animal Behavior, Face recognition (Psychology), Recognition memory, Learning, Memory, and 19 moreBiological Sciences, Dissociation, Learning and Memory, Circadian Rhythm, Animals, Object Recognition, Male, Light, Rats, Rat, Learning Disorders, Short Term Memory, Long Term Memory, Wistar Rats, Locomotor Activity, Risk Evaluation, Control Group, Motor activity, and Avoidance Learning
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Sleep/wake cycle pattern and its relationship with anxiety in college students. This paper examines the relationship between the sleep/wake cycle and anxiety in medical students. The sleep/wake cycle and anxiety were evaluated in 37... more
Sleep/wake cycle pattern and its relationship with anxiety in college students. This paper examines the relationship between the sleep/wake cycle and anxiety in medical students. The sleep/wake cycle and anxiety were evaluated in 37 second year medical school students. The volunteers answered a morningness-eveningness questionnaire, Pittsburgh Sleep Quality Index - PSQI and state and trait of anxiety inventory - STAI;
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Research Interests: Chronobiology, Food, Signal Transduction, Ghrelin, Biological Sciences, and 17 moreBrain, Blood Glucose, Insulin, Glucagon, Mice, Circadian Rhythm, Animals, Leptin, Oscillations, Feeding Behavior, Rats, Animal models, Brain Structure, Photoperiod, Neural pathways, Suprachiasmatic Nucleus, and Vagus Nerve
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Rats exhibit ultradian as well as circadian rhythms in activity. Short‐term activity rhythms appear to result from bouts of feeding‐related behavior interspersed with periods of quiescence. We examined the relationship of activity to... more
Rats exhibit ultradian as well as circadian rhythms in activity. Short‐term activity rhythms appear to result from bouts of feeding‐related behavior interspersed with periods of quiescence. We examined the relationship of activity to feeding in 12 male Long‐Evans derived rats during ad lib and restricted feeding (RF) conditions to determine the effect of RF on both circadian and ultradian activity rhythms. By the end of 20 days of RF all animals exhibited an ultradian periodicity of approximately 12 hours. A twenty‐four hour rhythm in feeding persisted, apparently due to the rats adapting to the diurnal feeding period. General findings were that RF resulted in anticipatory activity prior to feeding and that short‐term activity fluctuations and investigations of the food bin continued during RF even though overall nocturnal activity decreased. The results suggest that male rats of this strain exhibit ultradian activity rhythms that appear to be strongly related to feeding.
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Chronotype is an established concept designed to identify distinct phase relationships between the expression of circadian rhythms and external synchronizers in humans. Although it has been widely accepted that chronotype is subjected to... more
Chronotype is an established concept designed to identify distinct phase relationships between the expression of circadian rhythms and external synchronizers in humans. Although it has been widely accepted that chronotype is subjected to ontogenetic modulation, there is no consensus on the interaction between age and gender. This study aimed to determine the relationship between age- and gender-related changes in the morningness-eveningness character in a large sample of people. A total of 14,650 volunteers were asked to complete the Brazilian version of the Horne and Östberg chronotype questionnaire. The data demonstrated that, on average, women were more morning-oriented than men until the age of 30 and there were no significant differences between men and women from 30 to 45 years of age. In contrast to the situation observed until the age of 30, women older than 45 years were more evening-oriented than men. These results suggest that the ontogenetic development of the circadian ...
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ABSTRACT The objective of the present study was to investigate the circadian and the ultradian rhythms of drinking behavior in Wistar rats maintained under conditions of constant darkness. Six mature male rats (weighing 270-350 g) were... more
ABSTRACT The objective of the present study was to investigate the circadian and the ultradian rhythms of drinking behavior in Wistar rats maintained under conditions of constant darkness. Six mature male rats (weighing 270-350 g) were exposed to light-dark 12:12-h cycles (LD 12:12, light on at 12:00 h) for 35 days and then switched to constant darkness (DD) conditions for at least 2 weeks. Drinking behavior was monitored continuously with a standard drinkometer circuit and the data was stored in 5-min bins. A modification of Enright's periodogram technique was used to evaluate the free-running drinking behavior circadian rhythm. Ultradian rhythms in drinking behavior were estimated by the Fast Fourier Transform (FFT) technique. Two of the animals (rats 4 and 6) showed no statistically significant circadian or ultradian rhythms and the other four showed free-running drinking circadian rhythm behavior shorter than 24 h (ranging from 23.333 to 23.967 h). Ultradian rhythms of drinking behavior of 12- and 8-h periods were detected in 4 (rats 1, 2, 3 and 5) and 2 (rats 1 and 5) animals, respectively. The relation of the compound structure of the circadian and ultradian rhythms is discussed demonstrating that drinking behavior is a good marker for studies of physiology of temporal organization.
Recently, several papers have shown that a small subset of retinal ganglion cells (RGCs), which project to the suprachiasmatic nucleus (SCN) and contain a new photopigment called melanopsin, are the photoreceptors involved in light-dark... more
Recently, several papers have shown that a small subset of retinal ganglion cells (RGCs), which project to the suprachiasmatic nucleus (SCN) and contain a new photopigment called melanopsin, are the photoreceptors involved in light-dark entrainment in rodents. In our primate colony, we found a couple of common marmosets (Callithrix jacchus) that had developed progressive and spontaneous visual deficiency, most likely because of retinal degeneration of cones and/or rods. In this study, we evaluated the photoresponsiveness of the circadian system of these blind marmosets. Two blind and two normal marmosets were kept in cages with a controlled light-dark cycle (LD) to study photoentrainment, masking, and phase response to a dark pulse. Blind marmosets were entrained with the new LD cycle when light onsets were delayed and advanced by 6 hours. In constant light conditions, blind marmosets free-ran with a period of 23.2 hours, while normal animals free-ran with a period of 23.6 hours. Al...
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The present study aimed to assess changes in the circadian and homeostatic control of the sleep-wake pattern in stroke patients and correlations with quality of life. Participants were 22 patients (55 ± 12 years) and 24 healthy subjects... more
The present study aimed to assess changes in the circadian and homeostatic control of the sleep-wake pattern in stroke patients and correlations with quality of life. Participants were 22 patients (55 ± 12 years) and 24 healthy subjects (57 ± 11 years). Instruments used were: the Pittsburgh Sleep Quality Index, SF-36 Questionnaire and Actigraphy. Data were analyzed by Mann-Whitney test and Spearman's correlation. Results identified a significant difference in sleep quality and quality of life between patients and healthy subjects, with patients on average exhibiting poor sleep quality (patients: 8.4 ± 3.4; healthy subjects: 6.2 ± 2.5; p = 0.0001) and low quality of life scores (p < 0.001). Correlation analysis detected an association between circadian variables (total activity, start and finish times of activity) and quality of life (p < 0.001). Associations between homeostatic variables (sleep duration, latency and efficiency) and quality of life were also significant (p < 0.001). In conclusion, results in this study showed compromised sleep quality and quality of life in the patients evaluated, associated with circadian and homeostatic alterations. This suggests that complaints regarding poor sleep quality be taken into consideration when planning the rehabilitation of stroke patients.
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ABSTRACT Today it is recognized that changes in circadian rhythmicity can cause cardiovascular disorders, digestive disorders, and endocrine disorders, as well as psychiatric disorders. Such evidence of the relevance of circadian... more
ABSTRACT Today it is recognized that changes in circadian rhythmicity can cause cardiovascular disorders, digestive disorders, and endocrine disorders, as well as psychiatric disorders. Such evidence of the relevance of circadian rhythmicity and the changes of this rhythmicity to human health is generally derived from temporal challenges that the human organism faces in today’s society. Thus, knowledge of functional mechanisms of circadian rhythmicity regulation is important so we can clinically intervene in the intrinsic disorders of circadian rhythmicity as well as for its application in medicine, both for diagnosis and at the therapeutic level. The most studied animal models are the rodents, which have nocturnal habits and polyphasic sleep, indicating the need for an animal model that is diurnal and presents monophasic sleep, more similar to humans, such as the marmoset, Callithrix jacchus. In this chapter we describe in detail the recent experimental findings produced in our laboratory and reported in the scientific literature, which allow us to propose the marmoset as a potential model for the study of circadian rhythmicity.
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Research Interests: CEP and Clinical Sciences
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Este artigo relata as conclusões da reunião de consenso com médicos especialistas sobre diagnóstico de narcolepsia baseada na revisão dos artigos sobre narcolepsia listados no Medline entre 1980 e 2010. A narcolepsia é uma doença crônica... more
Este artigo relata as conclusões da reunião de consenso com médicos especialistas sobre diagnóstico de narcolepsia baseada na revisão dos artigos sobre narcolepsia listados no Medline entre 1980 e 2010. A narcolepsia é uma doença crônica de início entre a primeira e segunda ...