New bands in the sleep stages of spider monkeys (Ateles geoffroyi): Electroencephalographic correlations and spatial distribution

The study of electroencephalographic (EEG) signals in nonhuman primates has led to important discoveries in neurophysiology and sleep behavior. Several studies have analyzed digital EEG data from primate species with prehensile tails, like the spider monkey, and principal component analysis has led to the identification of new EEG bands and their spatial distribution during sleep and wakefulness in these monkeys. However, the spatial location of the EEG correlations of these new bands during the sleep-wake cycle in the spider monkey has not yet been explored. Thus, the objective of this study was to determine the spatial distribution of EEG correlations in the new bands during wakefulness, rapid eye movement (REM) sleep, and non-REM sleep in this species. EEG signals were obtained from the scalp of six monkeys housed in experimental conditions in a laboratory setting. Regarding the 1-21 Hz band, a significant correlation between left frontal and central regions was recorded during non-REM 2 sleep. In the REM sleep, a significant correlation between these cortical areas was seen in two bands: 1-3 and 3-13 Hz. This reflects a modification of the degree of coupling between the cortical areas studied, associated with the distinct stages of sleep. The intrahemispheric EEG correlation found between left perceptual and motor regions during sleep in the spider monkey could indicate activation of a neural circuit for the processing of environmental information that plays a critical role in monitoring the danger of nocturnal predation.

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 β 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.

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.

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.

Emotional facial expressions during REM sleep dreams

Although motor activity is actively inhibited during rapid eye movement (REM) sleep, specific activations of the facial mimetic musculature have been observed during this stage, which may be associated with greater emotional dream mentation. Nevertheless, no specific biomarker of emotional valence or arousal related to dream content has been identified to date. In order to explore the electromyographic (EMG) activity (voltage, number, density and duration) of the corrugator and zygomaticus major muscles during REM sleep and its association with emotional dream mentation, this study performed a series of experimental awakenings after observing EMG facial activations during REM sleep. The study was performed with 12 healthy female participants using an 8-hr nighttime sleep recording. Emotional tone was evaluated by five blinded judges and final valence and intensity scores were obtained. Emotions were mentioned in 80.4% of dream reports. The voltage, number, density and duration of facial muscle contractions were greater for the corrugator muscle than for the zygomaticus muscle, whereas high positive emotions predicted the number (R² 0.601, p = 0.0001) and voltage (R² 0.332, p = 0.005) of the zygomaticus. Our findings suggest that zygomaticus events were predictive of the experience of positive affect during REM sleep in healthy women.

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.

El origen y las funciones de los sueños a partir de los potenciales PGO

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 µV) 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

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 diagnostico de Demencia Tipo Alzheimer (DTA) de media a moderada. Utilizando la técnica polisomnográfica (PSG) se realizo 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 disminuyo significativamente la latencia de la fase 2, del sueño de ondas delta y el sueno 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 sueno en pacientes con DTA de media a moderada.

Sleep characterization of a one-month-old freely moving stumptail macaque (Macaca arctoides): a pilot study

Electroencephalographic (EEG) activity during both human and adult primates' sleep has been proven to be similar and consequently, it could be assessed under similar parameters. However, there is no information regarding this EEG activity in the early stages of development in non-human primates. Therefore, the aim of this study was to describe EEG sleep patterns in a 1-month-old Macaca arctoides with a non-invasive and free-movement method. Sleep stages were initially scored using the criteria of quiet sleep and active sleep. This procedure allowed us to observe graphoelements to distinguish sleep phases as described in adult macaques. Afterwards, the final score was recorded following the Slow Wave Sleep and Rapid Eye Movement Sleep criteria. The present results suggest that sleep features of this monkey are similar to those of a 2-month-old human neonate.

Long-lasting enhancement of rapid eye movement sleep and pontogeniculooccipital waves by vasoactive intestinal peptide microinjection into the amygdala temporal lobe

STUDY OBJECTIVES

The effect of a vasoactive intestinal peptide (VIP) microinjection into the amygdaloid central (CN) and basal nuclei (BN) on sleep organization and on the number and pattern of occurrence of pontogeniculooccipital (PGO) waves was analyzed.

DESIGN

One group of 8 cats was studied in baseline conditions and after the microinjection of two doses of VIP applied into the CN and BN.

SETTING

Sleep research laboratory. PARTCIPANTS AND INTERVENTIONS: Eight cats were prepared with sleep-recording electrodes and with guide tubes in both amygdalae for saline and VIP microinjections. Neuropeptide doses of 0.10 microg/1 microl (30 microM) and 0.33 microg/1 microl (99.24 microM) were employed.

MEASUREMENTS AND RESULTS

Once the microinjection was applied, 23-hour polygraphic sleep recordings were performed for 5 consecutive days. Concomitantly the PGO waves were tape-recorded on each day and computationally analyzed. Results show that the 0.10 microg/1 microl microinjection produced no change. Unilateral VIP 0.33 microg/1 microl injection into the CN provoked a significant and lasting increase in the percentage of slow-wave sleep with PGO waves. Bilateral application of VIP increased the percentage of slow-wave sleep with PGO waves and rapid eye movement sleep for 5 days. Bilateral microinjection of the neuropeptide into the BN only enhanced the percentage of slow wave sleep with PGO waves. For both amygdaloid nuclei, we observed that VIP increased the number and modified the PGO wave pattern of occurrence during slow-wave sleep with PGO waves and during rapid eye movement sleep.

CONCLUSIONS

The VIP microinjection into both the CN and BN induces increased amounts of rapid eye movement sleep, PGO waves, and slow-wave sleep with PGO waves, having a more robust effect on all of these three variables when applied into the CN.