Activity-Rest Circadian Rhythm of the Pearly Razorfish in Its Natural Habitat, before and during Its Mating.

Recent technological advances in marine biotelemetry have demonstrated that marine fish species perform activity-rest rhythms that have relevant ecological and evolutionary consequences. The main objective of the present report is to study the circadian rhythm of activity-rest of the pearly razorfish, Xyrichtys novacula in its own habitat, before and during the reproduction season using a novel biotelemetry system. This fish species is a small-bodied marine species that inhabits most shallow soft habitats of temperate areas and has a high interest for commercial and recreational fisheries. The activity of free-living fish was monitored by means of high-resolution acoustic tracking of the motor activity of the fish in one-minute intervals. The obtained data allowed the definition of the circadian rhythm of activity-rest in terms of classical non-parametric values: interdaily stability (IS), intradaily variability (IV), relative amplitude (RA), average activity during the most-active period of consecutive 10 h (M10), and average activity during the least-active period of consecutive 5 h (L5). We observed a well-marked rhythm, with little fragmentation and good synchrony with the environmental cycle of light-darkness, regardless of sex and the period studied. However, the rhythm was found to be slightly more desynchronized and fragmented during reproduction because of variations in the photoperiod. In addition, we found that the activity of the males was much higher than that of the females (p < 0.001), probably due to the peculiar behavior of the males in defending the harems they lead. Finally, the time at which activity began in males was slightly earlier than it was in females (p < 0.001), presumably due to the same fact, as differences in activity or for the individual heterogeneity of this species in the time of awakening are considered to be an independent axis of the fish's personality. Our work is novel, as it is one of the first studies of activity-rest rhythm using classical circadian-related descriptors in free-living marine fish using locomotory data facilitated by novel technological approaches.

Mammalian NREM and REM sleep: Why, when and how.

This report proposes that fish use the spinal-rhombencephalic regions of their brain to support their activities while awake. Instead, the brainstem-diencephalic regions support the wakefulness in amphibians and reptiles. Lastly, mammals developed the telencephalic cortex to attain the highest degree of wakefulness, the cortical wakefulness. However, a paralyzed form of spinal-rhombencephalic wakefulness remains in mammals in the form of REMS, whose phasic signs are highly efficient in promoting maternal care to mammalian litter. Therefore, the phasic REMS is highly adaptive. However, their importance is low for singletons, in which it is a neutral trait, devoid of adaptive value for adults, and is mal-adaptive for marine mammals. Therefore, they lost it. The spinal-rhombencephalic and cortical wakeful states disregard the homeostasis: animals only attend their most immediate needs: foraging defense and reproduction. However, these activities generate allostatic loads that must be recovered during NREMS, that is a paralyzed form of the amphibian-reptilian subcortical wakefulness. Regarding the regulation of tonic REMS, it depends on a hypothalamic switch. Instead, the phasic REMS depends on an independent proportional pontine control.

The Birth of the Mammalian Sleep.

Mammals evolved from small-sized reptiles that developed endothermic metabolism. This allowed filling the nocturnal niche. They traded-off visual acuity for sensitivity but became defenseless against the dangerous daylight. To avoid such danger, they rested with closed eyes in lightproof burrows during light-time. This was the birth of the mammalian sleep, the main finding of this report. Improved audition and olfaction counterweighed the visual impairments and facilitated the cortical development. This process is called "The Nocturnal Evolutionary Bottleneck". Pre-mammals were nocturnal until the Cretacic-Paleogene extinction of dinosaurs. Some early mammals returned to diurnal activity, and this allowed the high variability in sleeping patterns observed today. The traits of Waking Idleness are almost identical to those of behavioral sleep, including homeostatic regulation. This is another important finding of this report. In summary, behavioral sleep seems to be an upgrade of Waking Idleness Indeed, the trait that never fails to show is quiescence. We conclude that the main function of sleep consists in guaranteeing it during a part of the daily cycle.

Modifications in the Topological Structure of EEG Functional Connectivity Networks during Listening Tonal and Atonal Concert Music in Musicians and Non-Musicians.

The present work aims to demonstrate the hypothesis that atonal music modifies the topological structure of electroencephalographic (EEG) connectivity networks in relation to tonal music. To this, EEG monopolar records were taken in musicians and non-musicians while listening to tonal, atonal, and pink noise sound excerpts. EEG functional connectivities (FC) among channels assessed by a phase synchronization index previously thresholded using surrogate data test were computed. Sound effects, on the topological structure of graph-based networks assembled with the EEG-FCs at different frequency-bands, were analyzed throughout graph metric and network-based statistic (NBS). Local and global efficiency normalized (vs. random-network) measurements (NLE|NGE) assessing network information exchanges were able to discriminate both music styles irrespective of groups and frequency-bands. During tonal audition, NLE and NGE values in the beta-band network get close to that of a small-world network, while during atonal and even more during noise its structure moved away from small-world. These effects were attributed to the different timbre characteristics (sounds spectral centroid and entropy) and different musical structure. Results from networks topographic maps for strength and NLE of the nodes, and for FC subnets obtained from the NBS, allowed discriminating the musical styles and verifying the different strength, NLE, and FC of musicians compared to non-musicians.

Bright Light Therapy and Circadian Cycles in Institutionalized Elders.

BACKGROUND: Bright light therapy has been found to be an efficient method to improve the main parameters of circadian rhythms. However, institutionalized elders may suffer reduced exposure to diurnal light, which may impair their circadian rhythms, cognitive performance, and general health status. OBJECTIVES: To analyze the effects of 5 days of morning exposure for 90 min to bright light therapy (BLT) applied to institutionalized elderly subjects with mild/moderate cognitive impairment. SUBJECTS: Thirty-seven institutionalized subjects of both sexes, aged 70-93 years. METHODS: The study lasted three consecutive weeks. During the second week the subjects were submitted to BLT (7000-10,000 lux at eye level) on a daily basis. Cognition, attention, and sleep quality were evaluated at the beginning of the first and third week. Circadian variables were recorded continuously throughout the 3 weeks. Non-invasive holders and validated tests were used to analyze the variables studied. RESULTS: After BLT we have found significant improvements in general cognitive capabilities, sleep quality and in the main parameters of the subject's circadian rhythms. The results show that merely 90 min of BLT for five days seems to achieve a significant improvement in a constellation of circadian, sleep, health, and cognitive factors. CONCLUSION: Bright light therapy is an affordable, effective, fast-acting therapy for age-related disturbances, with many advantages over pharmacological alternatives. We hypothesize these effects were the result of activating the residual activity of their presumably weakened circadian system.

Uso del índice digital D2:D4 como indicador biológico del trastorno específico del lenguaje / Use of the 2 D: 4 D digit ratio as a biological marker of specific language disorders

INTRODUCCIÓN: Encontrar marcadores biológicos del trastorno específico del lenguaje facilitaría su detección e intervención precoz. En este sentido, el índice digital D2:D4 es considerado un indicador indirecto de la exposición prenatal a la testosterona, y estudios previos lo han relacionado con la competencia lingüística y la conducta agresiva, por lo que podría ser un candidato a marcador biológico. El objetivo es comparar el valor de este índice digital en niños con trastorno específico del lenguaje (TEL) frente a sujetos con desarrollo típico del lenguaje, estableciendo en qué medida correlacionan los valores del índice biológico con la conducta (lingüística, cognitiva, social...) de dichos sujetos. Sujetos y métodos: Se comparó el índice D2:D4, el lenguaje, la cognición y la conducta social en un grupo de niños con TEL (n = 15) con un grupo de niños sin dificultades del lenguaje (n = 16) de la misma la misma edad (entre 5-8 años), sexo (masculino) y nivel sociocultural. RESULTADOS: Los niños con TEL mostraron valores significativamente más altos en el índice D2:D4 de la mano derecha, y una correlación negativa entre el índice D2:D4 de la mano derecha y la competencia lingüística. Aunque los niños con TEL mostraron peores habilidades adaptativas y conductas internalizantes, aunque no mayor agresividad, estas medidas no se correlacionaron con el índice D2:D4, y sí con los valores de lenguaje y de cognición. CONCLUSIONES: Un valor más alto del índice biológico D2:D4 (menor exposición intrauterina a la testosterona) parece estar asociado con las dificultades del lenguaje de los niños con TEL, pero no con sus dificultades conductuales. Las dificultades conductuales de estos niños parecen ser consecuencia de sus dificultades lingüísticas y de su nivel de cognición

INTRODUCTION: The finding of biological markers of specific language impairment would facilitate their detection and early intervention. In this sense, the 2 D:4 D finger ratio is considered an indirect indicator of prenatal exposure to testosterone. Previous studies have related it to linguistic competence and aggressive behaviour, and could be a candidate for a biological marker of language impairment. The aim was to compare the value of the 2 D:4 D ratio in children with Specific Language Impairment (SLI) with those of children with typical language development, as well as to establish to what extent this biological index correlates with the behaviour (linguistic, cognitive, social,...) in both groups. Subjects and methods: 2 D:4 D ratio, language, cognition and social behaviour were compared in a group of children with SLI (n = 15), with a group of children without language difficulties (n = 16) of the same age (between 5-8 years), gender (male), and socio-cultural level. RESULTS: Children with SLI showed significantly higher values of 2 D:4 D ratio of the right hand, and a negative correlation between this ratio and their linguistic competence. Although the children with SLI showed impaired adaptive abilities, but not more aggressive behaviour, these measurements did not correlate with the 2 D:4 D index. Nevertheless, social behaviour correlated with language and cognition competence. CONCLUSIONS: A higher value of the biological 2 D:4 D ration (lower intrauterine exposure to testosterone) seems to be associated with language difficulties in boys with SLI, but not with their behavioural difficulties. Their behavioural difficulties seem to be a consequence of their linguistic difficulties and their level of cognition

[Use of the 2D:4D digit ratio as a biological marker of specific language disorders]. / Uso del índice digital D2:D4 como indicador biológico del trastorno específico del lenguaje.

INTRODUCTION: The finding of biological markers of specific language impairment would facilitate their detection and early intervention. In this sense, the 2D:4D finger ratio is considered an indirect indicator of prenatal exposure to testosterone. Previous studies have related it to linguistic competence and aggressive behaviour, and could be a candidate for a biological marker of language impairment. The aim was to compare the value of the 2D:4D ratio in children with Specific Language Impairment (SLI) with those of children with typical language development, as well as to establish to what extent this biological index correlates with the behaviour (linguistic, cognitive, social,...) in both groups. SUBJECTS AND METHODS: 2D:4D ratio, language, cognition and social behaviour were compared in a group of children with SLI (n=15), with a group of children without language difficulties (n=16) of the same age (between 5-8 years), gender (male), and socio-cultural level. RESULTS: Children with SLI showed significantly higher values of 2D:4D ratio of the right hand, and a negative correlation between this ratio and their linguistic competence. Although the children with SLI showed impaired adaptive abilities, but not more aggressive behaviour, these measurements did not correlate with the 2D:4D index. Nevertheless, social behaviour correlated with language and cognition competence. CONCLUSIONS: A higher value of the biological 2D:4D ration (lower intrauterine exposure to testosterone) seems to be associated with language difficulties in boys with SLI, but not with their behavioural difficulties. Their behavioural difficulties seem to be a consequence of their linguistic difficulties and their level of cognition.

Effects of differences in the availability of light upon the circadian rhythms of institutionalized elderly.

The aim of this study was to compare the availability of diurnal and nocturnal light in two residences for aged persons (R1 and R2, Palma de Mallorca, Illes Balears, Spain). We found that the R1 inmates were exposed to lower amounts of light during waking time and higher amounts during sleeping time. The main traits of the circadian rhythms and the quality of sleep in the inmates of the two residences were found to be positively related to the availability of light during waking time and negatively to the increased light exposure during bed time. In addition, the sleep of R1 inmates suffered higher disturbances as a consequence of the different policy for nocturnal diapers check and change. Altogether, these two factors may explain the differences observed in the two residences regarding the circadian rhythms, health status and quality of life. Two conclusions stem from these results: (1) the circadian rhythms of aged people are particularly sensitive to the contrast between diurnal and nocturnal light and (2) the nursing staff of institutions for aged people must receive specific formation on the best practices for maintaining the circadian health of aged people.

Altered Functional Performance in Patients with Fibromyalgia.

Fibromyalgia is a common chronic pain condition that exerts a considerable impact on patients' daily activities and quality of life. Objectives: The main objective of the present study was to evaluate kinematic parameters of gait, functional performance, and balance in women with fibromyalgia syndrome. Methods: The study included 26 female patients with fibromyalgia (49.2 ± 8.0 years) according to the criteria of the American College of Rheumatology, as well as 16 pain-free women (43.5 ± 8.5 years). Gait and balance parameters were extracted from video recordings of participants performing several motor tasks. Non-linear dynamic of body sway time series was also analyzed by computing the Hurst exponent. In addition, functional performance and clinical pain were obtained by using standardized motor tests (Berg's balance scale, 6-min walking test, timed up and go task, Romberg's balance test) and self-report questionnaires (Fibromyalgia Impact Questionnaire). Results: Walking speed was significantly diminished (p < 0.001) in FM patients as compared to pain-free controls, probably due to significant reductions in stride length (p < 0.001) and cycle frequency (p < 0.001). Analyses of balance also revealed significant differences between fibromyalgia and pain-free controls on body sway in the medial-lateral and anterior-posterior axes (all ps < 0.01). Several parameters of gait and balance were significantly associated with high levels of pain, depression, stiffness, anxiety, and fatigue in fibromyalgia. Conclusion: Our data revealed that both gait and balance were severely impaired in FM, and that subjective complaints associated with FM could contribute to functional disability in these patients. These findings suggest that optimal rehabilitation and fall prevention in fibromyalgia require a comprehensive assessment of both psychological responses to pain and physical impairments during postural control and gait.

Comparing the Behavioural Effects of Exogenous Growth Hormone and Melatonin in Young and Old Wistar Rats.

Growth hormone (GH) and melatonin are two hormones with quite different physiological effects. Curiously, their secretion shows parallel and severe age-related reductions. This has promoted many reports for studying the therapeutic supplementation of both hormones in an attempt to avoid or delay the physical, physiological, and psychological decay observed in aged humans and in experimental animals. Interestingly, the effects of the external administration of low doses of GH and of melatonin were surprisingly similar, as both hormones caused significant improvements in the functional capabilities of aged subjects. The present report aims at discerning the eventual difference between cognitive and motor effects of the two hormones when administered to young and aged Wistar rats. The effects were tested in the radial maze, a test highly sensitive to the age-related impairments in working memory and also in the rotarod test, for evaluating the motor coordination. The results showed that both hormones caused clear improvements in both tasks. However, while GH improved the cognitive capacity and, most importantly, the physical stamina, the effects of melatonin should be attributed to its antioxidant, anxiolytic, and neuroprotective properties.

Assessment of risk factors and test performance on malnutrition prevalence at admission using four different screening tools.

BACKGROUND & AIMS: Malnutrition is very common in patients when admitted to the hospital. The aim of the present study was: a) to determine the prevalence of malnutrition at admission in a tertiary care hospital and identify risk factors for malnutrition, and b) to test the sensitivity and specificity of different screening tests for malnutrition compared to subjective global assessment (SGA). METHODS: We conducted a prospective study at 24h of admission in order to assess malnutrition in 537 adult subjects (56.4% males, mean age of 61.3±17.7 years) using 4 different screening tools: mininutritional assessment short form (MNA-SF), nutritional risk screening 2002 (NRS2002), malnutrition universal screening tool (MUST), and SGA. Anthropometrics and co-morbidities were registered. RESULTS: The overall rate of undernutrition was 47.3%. Specific rates were 54.2% in patients > 65y vs. 40.7% < 65y (p = 0.002) and 63.4% in medical vs. 34.0% surgical department (p < 0.001). Identified risk factors of malnutrition at admission were: the presence of heart disease (OR 1.74 CI 95% 1.16-2.60 p = 0.007) for MNASF (AUC 0.62); liver disease (OR 4.45 CI 95% 1.9410.22 p < 0.001), > 65y (OR 2.10 CI 95% 1.19-3.93 p = 0.011), medicine department (OR 3.58 CI 95% 1.93-6.62 p < 0.001) for SGA (AUC 0.96); lung disease (OR 3.34 CI 95% 1.45-7.73 p = 0.005), medicine department (OR 2.55 CI 95%1.09-5.98 p = 0.032) for NRS 2002 (AUC 0.97). Recent unintentional weight loss was a common factor. CONCLUSIONS: Undernourishment at hospital admission is frequent. Comorbidities may contribute to the presence of undernutrition at admission. Nonetheless, SGA, NRS2002, MNA-SF or MUST can be used in our setting.

Antecedentes y objetivos: La desnutrición es muy frecuente en los pacientes que ingresan en el hospital. El objetivo de nuestro estudio es a) determinar la prevalencia de desnutrición al ingreso en un hospital de tercer nivel e identificar los factores de riesgo para desnutrición. b) Estudiar la sensibilidad y especifidad de diferentes test de cribado de desnutrición comparados con las valoración global subjetiva (VGS). Material y métodos: Realizamos un estudio prospectivo a las 24 h del ingreso hospitalario a individuos (56.4% hombres con una edad media de 61,3 ± 17 años) utilizando 4 test de cribado diferentes: mininutritional assessment short form (MNA-SF), nutritional risk screening 2002 (NRS2002), malnutrition universal screening tool (MUST) y VGS. Además, se recogieron medidas antropométricas y comorbilidades. Resultados: La prevalencia global de desnutrición fue de 47.3%. Las tasas específicas fueron 54,2% para > 65 años, 40,7% en < 65 años (p = 0,002), 63,4% en las áreas médicas, 34,0% áreas quirúrgicas (p < 0,001). Los factores que influían en la presencia de desnutrición al ingreso fueron: cardiopatía (OR 1,74 IC 95% 1,16-2,60 p = 0,007) en el MNA-SF (AUC 0,62); hepatopatía (OR 4,45 IC 95% 1.9410,22 p < 0,001), > 65años (OR 2,10 IC 95% 1,19-3,93 p = 0,011), áreas médicas (OR 3,58 IC 95% 1,93-6,62 p < 0,001) en la VGS (AUC 0,96); neumopatía (OR 3,34 IC 95% 1,45-7,73 p = 0,005), áreas médicas (OR 2,55 IC 95% 1,09-5,98 p = 0,032) en el NRS 2002 (AUC 0,97). La pérdida de peso involuntaria fue común a todos los test. Conclusiones: La desnutrición es frecuente al ingreso hospitalario. La presencia de comorbilidades puede influir en la presencia de desnutrición al ingreso, sin embargo, podemos utilizar cualquiera de los tests propuestos para su detección en nuestro hospital.

Assessment of risk factors and test performance on malnutrition prevalence at admission using four different screening tools / Valoración de los factores de riesgo y validez de cuatro tests de cribaje sobre la prevalencia de desnutrición al ingreso hospitalario

Background & aims: Malnutrition is very common in patients when admitted to the hospital. The aim of the present study was: a) to determine the prevalence of malnutrition at admission in a tertiary care hospital and identify risk factors for malnutrition, and b) to test the sensitivity and specificity of different screening tests for malnutrition compared to subjective global assessment (SGA). Methods: We conducted a prospective study at 24h of admission in order to assess malnutrition in 537 adult subjects (56.4% males, mean age of 61.3±17.7 years) using 4 different screening tools: mininutritional assessment short form (MNA-SF), nutritional risk screening 2002 (NRS2002), malnutrition universal screening tool (MUST), and SGA. Anthropometrics and comorbidities were registered. Results: The overall rate of undernutrition was 47.3%. Specific rates were 54.2% in patients > 65y vs.40.7% < 65y (p = 0.002) and 63.4% in medical vs.34.0% surgical department (p < 0.001). Identified risk factors of malnutrition at admission were: the presence of heart disease (OR 1.74 CI 95% 1.16-2.60 p = 0.007) for MNA-SF (AUC 0.62); liver disease (OR 4.45 CI 95% 1.9410.22 p < 0.001), > 65y (OR 2.10 CI 95% 1.19-3.93 p = 0.011), medicine department (OR 3.58 CI 95% 1.93-6.62 p < 0.001) for SGA (AUC 0.96); lung disease (OR 3.34 CI 95% 1.45-7.73 p = 0.005), medicine department (OR 2.55 CI 95%1.09-5.98 p = 0.032) for NRS 2002 (AUC 0.97). Recent unintentional weight loss was a common factor. Conclusions: Undernourishment at hospital admission is frequent. Comorbidities may contribute to the presence of undernutrition at admission. Nonetheless, SGA, NRS2002, MNA-SF or MUST can be used in our setting (AU)

Antecedentes y objetivos: La desnutrición es muy frecuente en los pacientes que ingresan en el hospital. El objetivo de nuestro estudio es a) determinar la prevalencia de desnutrición al ingreso en un hospital de tercer nivel e identificar los factores de riesgo para desnutrición. b) Estudiar la sensibilidad y especificidad de diferentes test de cribado de desnutrición comparados con las valoración global subjetiva (VGS). Material y métodos: Realizamos un estudio prospectivo a las 24 h del ingreso hospitalario a individuos (56.4% hombres con una edad media de 61,3 ± 17 años) utilizando 4 test de cribado diferentes: mininutritional assessment short form (MNA-SF), nutritional risk screening 2002 (NRS2002), malnutrition universal screening tool (MUST) y VGS. Además, se recogieron medidas antropométricas y comorbilidades. Resultados: La prevalencia global de desnutrición fue de 47.3%. Las tasas específicas fueron 54,2% para > 65 años, 40,7% en < 65 años (p = 0,002), 63,4% en las áreas médicas, 34,0% áreas quirúrgicas (p < 0,001). Los factores que influían en la presencia de desnutrición al ingreso fueron: cardiopatía (OR 1,74 IC 95% 1,16-2,60 p = 0,007) en el MNA-SF (AUC 0,62); hepatopatía (OR 4,45 IC 95% 1.9410,22 p < 0,001), > 65 años (OR 2,10 IC 95% 1,19-3,93 p = 0,011), áreas médicas (OR 3,58 IC 95% 1,93-6,62 p < 0,001) en la VGS (AUC 0,96); neumopatía (OR 3,34 IC 95% 1,45-7,73 p = 0,005), áreas médicas (OR 2,55 IC 95% 1,09-5,98 p = 0,032) en el NRS 2002 (AUC 0,97). La pérdida de peso involuntaria fue común a todos los test. Conclusiones: La desnutrición es frecuente al ingreso hospitalario. La presencia de comorbilidades puede influir en la presencia de desnutrición al ingreso, sin embargo, podemos utilizar cualquiera de los tests propuestos para su detección en nuestro hospital (AU)

Asymmetric sleep in apneic human patients.

Unilateral sleep in marine mammals has been considered to be a defense against airway obstruction, as a sentinel for pod maintenance, and as a thermoregulatory mechanism. Birds also show asymmetric sleep, probably to avoid predation. The variable function of asymmetric sleep suggests a general capability for independence between brain hemispheres. Patients with obstructive sleep apnea share similar problems with diving mammals, but their eventual sleep asymmetry has received little attention. The present report shows that human sleep apnea patients also present temporary interhemispheric variations in dominance during sleep, with significant differences when comparing periods of open and closed airways. The magnitude of squared coherence, an index of interhemispheric EEG interdependence in phase and amplitude, rises in the delta EEG range during apneic episodes, while the phase lag index, a measure of linear and nonlinear interhemispheric phase synchrony, drops to zero. The L index, which measures generalized nonlinear EEG interhemispheric synchronization, increases during apneic events. Thus, the three indexes show significant and congruent changes in interhemispheric symmetry depending on the state of the airways. In conclusion, when confronted with a respiratory challenge, sleeping humans undergo small, but significant, breathing-related oscillations in interhemispheric dominance, similar to those observed in marine mammals. The evidence points to a relationship between cetacean unihemispheric sleep and their respiratory challenges.

Asymmetric sleep in rats.

Five Wistar rats were surgically implanted with cortical and parietal electrodes for conventional polysomnography to test for sleep-related EEG asymmetries during 48 hours of continuous recording. When the animals were grouped not according to right-left dominance (which would represent a population bias) but instead according to preferred vs non-preferred hemisphere, significant light/dark circadian changes in side dominance were found in delta power during NREM; in theta and beta power during REM; and in alpha 1, alpha 2, and theta power during wakefulness. The changes have been interpreted as a response to temporal variations in the capability to respond to environmental challenges.

Evolution of wakefulness, sleep and hibernation: from reptiles to mammals.

Thus far, most hypotheses on the evolutionary origin of sleep only addressed the probable origin of its main states, REM and NREM. Our article presents the origin of the whole continuum of mammalian vigilance states including waking, sleep and hibernation and the causes of the alternation NREM-REM in a sleeping episode. We propose: (1) the active state of reptiles is a form of subcortical waking, without homology with the cortical waking of mammals; (2) reptilian waking gave origin to mammalian sleep; (3) reptilian basking behaviour evolved into NREM; (4) post-basking risk assessment behaviour, with motor suspension, head dipping movements, eye scanning and stretch attending postures, evolved into phasic REM; (5) post-basking, goal directed behaviour evolved into tonic REM and (6) nocturnal rest evolved to shallow torpor. A small number of changes from previous reptilian stages explain these transformations.

Apneas de sueño en la especie humana y reflejos de buceo en animales: el eslabón comparativo / Human sleep apneas and animal diving reflexes: the comparative link

La evolución de los vertebrados debe haber favorecido las adaptaciones para soportar períodos de acceso limitado al oxígeno. Un ejemplo paradigmático de estas adaptaciones son los animales buceadores, quienes pueden soportar períodos de anoxia prolongados y repetidos. El medio interno de estos animales resiste lo que debería ser considerado un severo desajuste gaseoso. Estos animales disponen de tres estrategias principales: mantienen elevadas reservas de oxígeno, son capaces de resistir la asfixia y tienen la capacidad de reducir notablemente su metabolismo durante los períodos de apnea. Estas repuestas han aparecido por evolución a partir de respuestas para la supervivencia muy antiguas y que deben haber sido utilizadas en muchas otras ocasiones. Por su parte, las apneas de sueño probablemente comparten muchas adaptaciones fisiológicas con los animales buceadores. Esta revisión analiza la extensión de estas similitudes, ofrece evidencias de su existencia y sugiere posibles líneas de investigación que pueden mejorar el conocimiento clínico de las apneas de sueño (AU)

The evolution of vertebrates should have favoured adaptations to periodic limitations in the availability of oxygen. A paradigmatic example could be observed in diving animals that can support prolonged and repeated periods of anoxia, leading to severe gaseous unbalances in the internal medium. Animals developed three main mechanisms to achieve such goal: maintaining high oxygen stores, supporting asphyxia and reducing the energetic metabolism during apneic periods. These capacities should have been developed from very old evolutionary survival responses which could have been useful in many different situations involving respiratory stress. Accordingly, sleep apneas should share many physiological adaptations with diving animals. This review shows evidence of such similarities, analyzes their extension and suggests further research lines to improve the clinical consequences of sleep apneas (AU)

The trivial function of sleep.

Rest in poikilothermic animals is an adaptation of the organism to adjust to the geophysical cycles, a doubtless valuable function for all animals. In this review, we argue that the function of sleep could be trivial for mammals and birds because sleep does not provide additional advantages over simple rest. This conclusion can be reached by using the null hypothesis and parsimony arguments. First, we develop some theoretical and empirical considerations supporting the absence of specific effects after sleep deprivation. Then, we question the adaptive value of sleep traits by using non-coding DNA as a metaphor that shows that the complexity in the design is not a definitive proof of adaptation. We then propose that few, if any, phenotypic selectable traits do exist in sleep. Instead, the selection of efficient waking has been the major determinant of the most significant aspects in sleep structure. In addition, we suggest that the regulation of sleep is only a mechanism to enforce rest, a state that was challenged after the development of homeothermy. As a general conclusion, there is no direct answer to the problem of why we sleep; only an explanation of why such a complex set of mechanisms is used to perform what seems to be a simple function. This explanation should be reached by following the evolution of wakefulness rather than that of sleep. Sleep could have additional functions secondarily added to the trivial one, although, in this case, the necessity and sufficiency of these sleep functions should be demonstrated.

Mammalian sleep may have no adaptive advantage over simple activity-rest cycles.

The adaptive value of sleep remains unknown in spite of the intense research performed throughout the last decades. However, few sleep researchers are aware of the difficulties posed by the blind acceptance of an extreme adaptationist viewpoint. Under this philosophy, every anatomical and functional detail present in a living being should have a positive adaptive value, a position that has been considered as rather doubtful. In this report, it is proposed that most of the physiological changes used for mammalian sleep definition could be mere by-products of other true adaptations, such as the ontogenetic and phylogenetic development of the nervous system. As a result, complex mammalian sleep could have no adaptive value over that of the simplest forms of rest-activity cycles present in all living forms. In addition, it is proposed that the absence of adaptive value should, by default, be the first option regarding the function of sleep. Besides, the burden of the proof should be always charged over the proponents of every particular adaptive function. As this proof has not been reached, it is the absence of function for sleep which should be taken for granted.

Evidence of state-dependent interhemispheric relationships in lizard EEG during the awake state.

The electroencephalogram (EEG) from both hemispheres of eight Canary lizards Gallotia galloti was registered at 25 degrees C and 35 degrees C during awake state with open eyes (OE) and closed eyes. The possible interdependence between the recorded EEGs was assessed by means of newly developed methods of multivariate nonlinear time-series analysis. The interdependence turned out to be significant and greater for the OE state at both temperatures, although it was of linear type in most of the cases. We conclude that the methods can be successfully applied to study the interdependence between noisy, low-amplitude EEGs.