EEG coherence and power spectra during REM sleep related to melatonin intake in mild-to-moderate Alzheimer's disease: a pilot study.

It has been reported that melatonin diminishes rapid eye movement (REM) sleep latency in patients with Alzheimer's disease (AD). Pharmacological studies suggest that melatonin promotes prompt sleep installation through interaction with GABA receptors, and that it is associated with acute suppression of neural electrical activity. Nevertheless, melatonin's effects on electroencephalographic (EEG) activity related to REM sleep onset in AD patients have not been analyzed. Thus, in this pilot study we analyzed the effects of melatonin on EEG activity during the first episode of REM sleep in eight patients treated with 5-mg of fast-release melatonin.During a single-blind, placebo-controlled study, polysomnographic recordings were obtained from frontal, central, temporal, and occipital scalp derivations. REM sleep latency, as well as the relative power (RP) and EEG coherences of six EEG bands, were compared between the placebo and melatonin conditions.Results showed that melatonin intake in AD patients decreased REM sleep onset, and that this was associated with lower RP and coherence of the ß and γ EEG bands.The possibility that the inhibitory GABAergic pathways related to REM sleep generation are well-preserved in mild-to-moderate AD is discussed. We conclude that the short REM sleep onset related to melatonin intake in AD patients is associated with a significant decrease in both RP and EEG coherence, mainly in the fast frequencies.

Cognitive training on the solving of mathematical problems: an EEG study in young men / Entrenamiento cognitivo en la resolución de problemas matemáticos: un estudio de EEG en hombres jóvenes

Abstract. Objective. This study characterized the electroencephalographic correlation (rEEG) between prefrontal and parietalcortices in young men while solving logical-mathematical problems after 18 sessions of cognitive training. Method. Two training groups were formed: one trained with gradually increased complexity (CT), the other with no increase in complexity (ST). Results. CT had a greater number of correct responses in the post-training evaluation than ST and showed a higher correlation between the left frontopolar-parietal cortices in almost all EEG bands, and between the dorsolateral-parietal cortices in the alpha1 band while solving math problems post-training. Results suggest that major functional synchronization between the left prefrontal and parietal cortices plays an important role in improving mathematical problem-solving after cognitive training.

Resumen Objetivo. El presente estudio caracteriza la correlación electroencefalográfica (rEEG) entre las cortezas prefrontal y parietal en hombres jóvenes durante la resolución de problemas lógico-matemáticos después de 18 sesiones de entrenamiento cognitivo. Método. Se formaron dos grupos de entrenamiento: uno entrenado con un incremento gradual de complejidad (CT) y el otro sin incremento de complejidad (ST). Resultados. El grupo CT presentó un mayor número de respuestas correctas que el grupo ST en la evaluación post entrenamiento, a su vez mostró un incremento en la correlación entre las cortezas frontopolar y parietal izquierdas en la mayoría de las bandas, así como entre las cortezas dorsolateral y parietal en la banda alfa1 durante la resolución de problemas posterior al entrenamiento. Los resultados sugieren que el incremento en la sincronización funcional entre las cortezas prefrontal y parietal izquierdas juega un rol importante en la resolución de problemas matemáticos después del entrenamiento cognitivo.

Topographic distribution of the EEG ad hoc broad bands during sleep and wakefulness in the spider monkey (Ateles Geoffroyi).

There is evidence that research on sleep among New World monkeys may provide important knowledge related to the evolution of sleep more broadly in the primate order. Digital electroencephalographic (EEG) analyses provide essential knowledge on sleep in the spider monkey. Recently, specific EEG bands related to sleep in these animals have been obtained using principal component analysis, but the exact spatio-temporal distribution of these EEG bands in this species has not yet been analyzed. This study determined the topographic distribution of the EEG spectral power of ad hoc broad bands during rapid eye movement sleep, nonrapid eye movement sleep, and wakefulness. Superficial EEG activity was obtained from the occipital, frontal, and central areas of six young adult male monkeys housed in a laboratory. During wakefulness, occipital areas showed high absolute power in the 1-3, 3-12, and 11-30 Hz ranges, while during nonrapid eye movement 1 sleep the highest absolute power was in the 13-30 Hz range. During nonrapid eye movement 3 sleep, frontal and central areas showed a high absolute power in the 18-19 Hz range. Finally, the right central area showed a high absolute power in the 20-30 Hz range during rapid eye movement sleep. This topographic distribution of EEG bands could represent the brain organization required for arousal and mnemonic processing during sleep in the spider monkey.

Melatonin effects on EEG activity during non-rapid eye movement sleep in mild-to-moderate Alzheimer´s disease: a pilot study.

INTRODUCTION: There is evidence to suggest that melatonin diminishes non-rapid eye movement sleep (NREMS) latency in patients with Alzheimer´s disease (AD). However, melatonin's effects on cortical activity during NREMS in AD have not been studied. The objective of this research was to analyze the effects of melatonin on cortical activity during the stages of NREMS in 8 mild-to-moderate AD patients that received 5-mg of fast-release melatonin. METHODS: During a single-blind, placebo-controlled crossover study, polysomnographic recordings were obtained from C3-A1, C4-A2, F7-T3, F8-T4, F3-F4 and O1-O2. Also, the relative power (RP) and EEG coherences of the delta, theta, alpha1, alpha2, beta1, beta2 and gamma bands were calculated during NREMS-1, NREMS-2 and NREMS-3. These sleep latencies and all EEG data were then compared between the placebo and melatonin conditions. RESULTS: During NREMS-2, a significant RP increase was observed in the theta band of the left-central hemisphere. During NREMS-3, significant RP decreases in the beta bands were recorded in the right-central hemisphere, compared to the placebo group. After melatonin administration, significant decreases of EEG coherences in the beta2, beta1 and gamma bands were observed in the right hemisphere during NREMS-3. DISCUSSION: We conclude that short NREMS onset related to melatonin intake in AD patients is associated with a significant RP increase in the theta band and a decrease in RP and EEG coherences in the beta and gamma bands during NREMS-3. These results suggest that the GABAergic pathways are preserved in mild-to-moderate AD.

Calea zacatechichi Schltdl. (Compositae) produces anxiolytic- and antidepressant-like effects, and increases the hippocampal activity during REM sleep in rodents.

ETHNOPHARMACOLOGICAL RELEVANCE: Calea zacatechichi is a plant with an extensive popular and ritual use in Mexico. In healthy volunteers, it induces well-being and tranquility senses, and facilitates superficial stages of sleep. However, anxiolytic, and antidepressant-like effects and changes on the sleep-waking stages have not been explored. AIM: To determine anxiolytic and antidepressant-like effects of an aqueous extract of C. zacatechichi (CZ) in rodents and to analyze their effects on hippocampal activity in the rat sleep-waking cycle. MATERIAL AND METHODS: CZ anxiolytic- and antidepressant-like effects were evaluated in several mice and rat behavioral paradigms. CZ effects on temporal distribution of sleep were described, and hippocampus EEG frequency patterns were analyzed during the sleep-waking cycle; absolute and relative powers were analyzed during Rapid Eye Movements (REM) and non-REM sleep stages. CZ chemical analysis was performed by UPLC-ESI-MS. RESULTS: CZ produced specific and robust anxiolytic- and antidepressant-like effects in mice and rats, similar to those of prototypical drugs, at doses ranging from 0.5 to 50 mg/kg. CZ at 100 mg/kg produced visible mild sedative effects in rats, associated with a significant increase in Slow Wave Sleep episodes during a 6 h recording, and enhanced fast frequencies of hippocampus (gamma-band:31-50 Hz) during REM sleep. CONCLUSION: Results could support the well-being and tranquility senses reported by healthy consumers, and to explain the oneiric content during dreams and some improvements in cognitive processes described by consumers. Anxiolytic- and antidepressant-like effects of this species, reported for first time in this study could improve some aspects of mental health.

Principal component analysis of electroencephalographic activity during sleep and wakefulness in the spider monkey (Ateles geoffroyi).

The study of electroencephalographic (EEG) activity during sleep in the spider monkey has provided new insights into primitive arboreal sleep physiology and behavior in anthropoids. Nevertheless, studies conducted to date have maintained the frequency ranges of the EEG bands commonly used with humans. The aim of the present work was to determine the EEG broad bands that characterize sleep and wakefulness in the spider monkey using principal component analysis (PCA). The EEG activity was recorded from the occipital, central, and frontal EEG derivations of six young-adult male spider monkeys housed in a laboratory setting. To determine which frequencies covaried and which were orthogonally independent during sleep and wakefulness, the power EEG spectra and interhemispheric and intrahemispheric EEG correlations from 1 to 30 Hz were subjected to PCA. Findings show that the EEG bands detection differed from those reported previously in both spider monkeys and humans, and that the 1-3 and 2-13 Hz frequency ranges concur with the oscillatory activity elucidated by cellular recordings of subcortical regions. Results show that applying PCA to the EEG spectrum during sleep and wakefulness in the spider monkey led to the identification of frequencies that covaried with, and were orthogonally independent of, other frequencies in each behavioral vigilance state. The new EEG bands differ from those used previously with both spider monkeys and humans. The 1-3 and 2-13 Hz frequency ranges are in accordance with the oscillatory activity elucidated by cellular recordings of subcortical regions in other mammals.

Annual changes in the copulatory behavior of male rats maintained under constant laboratory conditions.

The objective of the present study was to evaluate the sexual behavior of male rats kept under constant laboratory conditions for one entire year. A total of 213 sexually-inexperienced, male Wistar rats were maintained in controlled environmental conditions from birth. Depending the month in which they reached the age 3-month-old, the male rats were divided into 12 groups, one for each month of the year, and their sexual behavior was evaluated. Records of their sexual behavior were made from 09:00 to 11:00 hrs am. The following parameters were recorded: mount (latency and number), intromission (latency and number), ejaculation latency, and intromission rate. During the months of March, June, July and September, the rats showed lower mount and intromission latencies than in January, February, April, May and October-to-December. Similarly, in March, June, July and August they had higher copulatory efficiency than in January, February, April and December. Results suggest that male rats exposed to controlled environmental conditions could have endogenous mechanisms that regulate sexual behavior but are independent of seasonal environmental signals. The annual variability in the sexual behavior of male rats maintained under constant laboratory conditions should be considered when planning research and experiments.

EEG correlation during the solving of simple and complex logical-mathematical problems.

Solving logical-mathematical word problems is a complex task that requires numerous cognitive operations, including comprehension, reasoning, and calculation. These abilities have been associated with activation of the parietal, temporal, and prefrontal cortices. It has been suggested that the reasoning involved in solving logical-mathematical problems requires the coordinated functionality of all these cortical areas. In this study was evaluated the activation and electroencephalographic (EEG) correlation of the prefrontal, temporal, and parietal regions in young men while solving logical-mathematical word problems with two degrees of difficulty: simple and complex. During the solving of complex problems, higher absolute power and EEG correlation of the alpha and fast bands between the left frontal and parietal cortices were observed. A temporal deactivation and functional decoupling of the right parietal-temporal cortices also were obtained. Solving complex problems probably require activation of a left prefrontal-parietal circuit to maintain and manipulate multiple pieces of information. The temporal deactivation and decreased parietal-temporal correlation could be associated to text processing and suppression of the content-dependent reasoning to focus cognitive resources on the mathematical reasoning. Together, these findings support a pivotal role for the left prefrontal and parietal cortices in mathematical reasoning and of the temporal regions in text processing required to understand and solve written mathematical problems.

Melatonin Effects on EEG Activity During Sleep Onset in Mild-to-Moderate Alzheimer's Disease: A Pilot Study.

There is evidence demonstrating that 5-mg of fast-release melatonin significantly reduces nocturnal sleep onset in patients with mild-to-moderate Alzheimer's disease (AD). However, the physiological mechanism that could promote sleep installation by melatonin in patients with AD is still poorly understood. The present pilot study was designed to analyze the effects of melatonin on cortical activity during the sleep onset period (SOP) in eight mild-to-moderate AD patients treated with 5-mg of fast-release melatonin. Electroencephalographic recordings were obtained from C3-A1, C4-A2, F7-T3, F8-T4, F3-F4, and O1-O2. The relative power (RP), interhemispheric, intrahemispheric, and fronto-posterior correlations of six electroencephalographic bands were calculated and compared between two conditions: placebo and melatonin. Results show that at F7-T3, F3-F4, and C3-A1, melatonin induced an increase of the RP of the delta band. Likewise, in F7-T3, melatonin induced a decrease of the RP in the alpha1 band. Similarly, results show a lower interhemispheric correlation between the F7-T3 and F8-T4 derivations in the alpha1 band compared to the placebo condition. We conclude that the short sleep onset related to melatonin intake in AD patients was associated with a lower RP of the alpha1, a higher RP of the delta band (mainly in the left hemisphere) and a decreased interhemispheric EEG coupling in the alpha1 band. The possible role of the GABAergic neurotransmission as well as of the cascade of neurochemical events that melatonin triggers on sleep onset are discussed.

Alpha electroencephalographic activity during rapid eye movement sleep in the spider monkey (Ateles geoffroyi): An index of arousal during sleep?

There is evidence that some animal species have developed physiological and behavioral mechanisms to monitor potential predatory threats during rapid eye movement sleep (REMS). Nevertheless, it has not been reported in arboreal primates. The present study analyzed the sleeping postures, as well as the electromyographic and electroencephalographic (EEG) activities during three conditions: REMS, non-REMS (N-REMS), and wakefulness in spider monkeys. The study included six monkeys, whose EEGs were recorded at the O1-O2, C3, C4, F3, and F4 derivations to analyze relative power (RP) and interhemispheric, intrahemispheric, frontoposterior, and central-posterior coherence of frequency bands, which has been considered an index of arousal states. The bands analyzed were theta (4.0-7.0 Hz), alpha1 (8.0-10.5 Hz), alpha2 (11.0-13.5 Hz), and beta (14.0-30.0 Hz). Spider monkeys adopt a vertical posture during sleep, and in REMS a lack of muscular atonia was observed. The RP of the alpha bands at O1-O2 was higher during REMS than that during wakefulness, N-REMS1, and N-REMS2. At the C3 derivation, the RP of alpha1 was higher during REMS than that during N-REMS2. The RP of both alpha bands at the F4 derivation was higher during REMS than that during wakefulness, whereas REMS was characterized by a higher coherence between the F3 and O1-O2 derivations of the alpha2 band. These prevalences and the higher coherence of alpha bands during REMS could represent a correlate of behavioral traits and activated cortical areas related to a possible arousal state in spider monkeys while sleeping.

Cortical beta EEG oscillations related to changes in muscle tone activity during sleep in spider monkey (Ateles geoffroyi).

BACKGROUND: The physiological mechanisms that allow for sleeping in a vertical position, which is primordial for arboreal primates, have not been studied yet. METHODS: A non-invasive polysomnographic study of 6 spider monkeys (Ateles geoffroyi) was conducted. The relative beta power of the motor cortex and its linear relation with muscle tone in the facial mentalis muscle and the abductor caudae medialis muscle of the tail during wakefulness and sleep stages were calculated. RESULTS: A strong negative linear relationship (r = -.8, P = .03) was found between the relative power of the beta2 band in the left motor cortex and abductor caudae medialis muscle tone during delta sleep. CONCLUSIONS: The left motor cortex, through beta2 band activity, interacts with abductor caudae medialis muscle tonicity during delta sleep. This interaction takes part in the mechanisms that regulate the sleep postures.

Sleep in the spider monkey (Ateles geoffroyi): A semi-restrictive, non-invasive, polysomnographic study.

The normal sleep patterns of the spider monkey (Ateles geoffroyi) have not been described yet. The objective of this study was to characterize the electrophysiological patterns, sleeping postures, and sleep-wake cycle in semi-restricted spider monkeys. Continuous 24-hr polysomnographic (PSG) recordings, involving simultaneous recording of non-invasive electroencephalographic (EEG), electro-oculographic (EOG), and electromyographic (EMG) activities, were carried out in captive monkeys living in outdoor rainforest enclosures. Electrode placement was done according to the human international 10-20 system. Specific behaviors displayed by monkeys during the sleep-wake cycles were correlated with the PSG recordings. The nycthemeral distribution of the sleep-wake cycle was also calculated. The results show that electrophysiological N-REM sleep patterns in spider monkeys are similar to those observed in other primates, including human beings. Furthermore, a vertical semi-fetal posture was observed during N-REM and REM sleep phases. The amount of nocturnal sleep was significantly higher than that of the diurnal period, showing that the spider monkey is a diurnal primate. An outstanding finding was the absence of muscular atonia during the spider monkey's REM sleep, which suggests that arboreal primates have developed a neuromuscular mechanism specialized for sleeping in a vertical posture.

El origen y las funciones de los sueños a partir de los potenciales PGO / The origin and functions of dreams based on the PGO activity

Understanding the phenomenon of sleep and dreams has fascinated humans always. However, the scientific study of sleep is relatively recent. In 1953, Aserinsky and Kleitman found that slow wave sleep (SWS) was periodically interrupted by episodes of rapid EEG activity, which are accompanied by rapid eye movements (REMs), and named this sleep phase as REM sleep. Subsequently, in 1957, Dement and Kleitman discovered that these rapid eye movements coincided with the appearance of dreams. By using animal experimental models, the subcortical mechanisms underlying REM sleep have been studied, and it has been demonstrated that this activity depends on the serotonergic activity from wakefulness, which promotes the formation of peptides that trigger certain structures of the brainstem, where cholinergic mechanisms of REM sleep are integrated. In turn, on the pontine region monophasic phasic potentials (300-400 uV) are generated that can also be recorded on the lateral geniculate body and in the occipital cortex; hence the name of ponto-geniculo-occipital waves (PGO). These potentials spread to the oculomotor system to provoke the REMs of REM sleep and possibly give rise to visual hallucinatory phenomena. Furthermore, it has been shown that certain limbic structures related to emotion and memory are activated by these potentials. This suggests that PGO waves generate mnemonic and emotional components of dreams. Several aspects of the functions of these PGO waves remains to be determined, but knowledge about the origin of brain phenomena that generate dreams has had a breakthrough from its study. In the present work we review the literature concerning the work done over PGO waves and its contribution to the knowledge of the origin and functions of dreams.

El fenómeno del sueño y de los sueños es algo que siempre ha fascinado al hombre. Sin embargo, el estudio científico del sueño es relativamente reciente. En 1953, Aserinsky y Kleitman encontraron que el sueño de ondas lentas (SOL) es interrumpido periódicamente por episodios de actividad EEG rápida, que se acompañan de movimientos oculares rápidos (MORs), y denominaron a esta fase "sueño MOR". Posteriormente, Dement y Kleitman, en 1957, descubrieron que estos movimientos oculares rápidos coinciden con la aparición de los sueños. Utilizando animales de experimentación se han estudiado los mecanismos subcorticales que subyacen al sueño MOR y se ha demostrado que éste depende de una actividad serotoninérgica de la vigilia, que promueve la formación de péptidos que ponen en marcha ciertas estructuras de la región pontina del tallo cerebral en donde se integran los mecanismos colinérgicos del sueño MOR. En la región pontina, a su vez, se generan potenciales monofásicos de alto voltaje (300-400 pV) que también pueden registrarse en el cuerpo geniculado lateral y en la corteza occipital, de allí el nombre de potenciales ponto-genículo-occipitales (PGO). Estos potenciales se propagan hacia el sistema oculomotor para provocar los MORs y posiblemente den origen a los fenómenos oníricos visuales. Además se ha demostrado que ciertas estructuras del sistema límbico, relacionadas con las emociones y la memoria, son activadas por dichos potenciales. Lo anterior sugiere que los potenciales PGO generan los componentes mnésicos y emocionales de los sueños. Quedan aún por determinarse varios aspectos sobre las funciones de estos potenciales, pero el conocimiento sobre el origen de los fenómenos cerebrales que generan los sueños ha tenido un gran avance a partir de su estudio. En el presente artículo se revisa la bibliografía concerniente a los trabajos realizados sobre los potenciales PGO y su aportación al conocimiento del origen y las funciones de los sueños.

Efectos de la melatonina sobre la macro-arquitectura del sueño en pacientes con demencia tipo Alzheimer / Melatonin effects on macro arquitecture sleep in Alzheimer's disease patients

The objective of the present study was to evaluate the 5 mg. melatonin effects on the sleep macro-architecture in eight patients with middle to moderate Alzheimer's disease (DTA). Using the polysomnography technique (PSG), we made a simple-blind, non-randomized, controlled with placebo study. The PSG was carried out according to the following order: night 1: placebo administration; night 2 and 3: continues melatonin administration. In the first night with melatonin treatment, the sleep latency to the first episode of Stage 2, Delta and REM sleep, was significantly diminished as compared with placebo (≤.05). No significant difference in total time of each sleep stage and sleep efficiency was observed. Nevertheless, a tendency to diminish the total time of nocturnal wake and increase of the total sleep time in the second night with melatonin treatment was observed. We conclude that melatonin can improve sleep in patients with middle to moderate DTA.

El objetivo del presente estudio fue determinar los efectos de 5 mg. de melatonina de liberación inmediata sobre la macro-arquitectura del sueño en ocho pacientes con diagnóstico de Demencia Tipo Alzheimer (DTA) de media a moderada. Utilizando la técnica polisomnográfica (PSG) se realizó un estudio simple ciego, no aleatorio, controlado con placebo. Los registros PSG se llevaron a cabo de la siguiente manera: Noche 1: administración de placebo; noche 2 y 3: administración continua de melatonina (5 mg). Observamos que el tratamiento con melatonina durante la primera noche de administración disminuyó significativamente la latencia de la fase 2, del sueño de ondas delta y el sueño de MOR al ser comparadas con el placebo (P ≤.05). No se observaron diferencias significativas en el tiempo total de cada fase de sueño; tampoco se observaron diferencias en la eficiencia del sueño en presencia de la melatonina. Sin embargo se observó una tendencia a la disminución del tiempo total de vigilia y un aumento del tiempo total de sueño, principalmente durante la segunda noche de tratamiento. Concluimos que la melatonina puede mejorar el sueño en pacientes con DTA de media a moderada.