EEG spectral power during REM sleep in patients with frontal brain tumor.

BACKGROUND: The main objective of this research was to analyze the characteristics of electrical activity in the brain during REM (Rapid Eye Movements) sleep, by using an experimental model a pathology that affects the frontal lobes, such as brain tumors. In addition to determining the impact of variables such as the frontal area (dorsolateral, medial and orbital), laterality and size of the lesion; as well as the demographic and clinical characteristics of the patients evaluated. METHODS: By using polysomnographic recordings, 10 patients were evaluated. We obtained power spectra through a homemade program. For quantitative EEG (Electroencephalogram) (qEEG) analysis, the Fast Fourier Transform (FFT) algorithm was used to obtain the spectral power of each participant, channel, and frequency band. RESULTS: Sleep architecture and spectral power was found to be modified in patients compared to normative values. Other sociodemographic and clinical characteristics of the patients were also influenced, such as age range and antiepileptic drugs. CONCLUSIONS: Brain tumors in the frontal lobe can modify the rhythmogenesis of REM sleep, possibly due to changes of brain plasticity as an effect of the pathology. In addition to this, through this study we were able to show the association between neuroanatomical and functional changes, on the characteristics of brain electrical activity in patients with frontal brain tumor. Finally, this qEEG analysis technique allows, on the one hand, to deepen the knowledge and relationship between psychophysiological processes and, on the other hand, to be able to guide therapeutic decisions.

Human amygdala activation during rapid eye movements of rapid eye movement sleep: an intracranial study.

The amygdaloid complex plays a crucial role in processing emotional signals and in the formation of emotional memories. Neuroimaging studies have shown human amygdala activation during rapid eye movement sleep (REM). Stereotactically implanted electrodes for presurgical evaluation in epileptic patients provide a unique opportunity to directly record amygdala activity. The present study analysed amygdala activity associated with REM sleep eye movements on the millisecond scale. We propose that phasic activation associated with rapid eye movements may provide the amygdala with endogenous excitation during REM sleep. Standard polysomnography and stereo-electroencephalograph (SEEG) were recorded simultaneously during spontaneous sleep in the left amygdala of four patients. Time-frequency analysis and absolute power of gamma activity were obtained for 250 ms time windows preceding and following eye movement onset in REM sleep, and in spontaneous waking eye movements in the dark. Absolute power of the 44-48 Hz band increased significantly during the 250 ms time window after REM sleep rapid eye movements onset, but not during waking eye movements. Transient activation of the amygdala provides physiological support for the proposed participation of the amygdala in emotional expression, in the emotional content of dreams and for the reactivation and consolidation of emotional memories during REM sleep, as well as for next-day emotional regulation, and its possible role in the bidirectional interaction between REM sleep and such sleep disorders as nightmares, anxiety and post-traumatic sleep disorder. These results provide unique, direct evidence of increased activation of the human amygdala time-locked to REM sleep rapid eye movements.

Characterizing dynamic functional connectivity across sleep stages from EEG.

Following a nonlinear dynamics approach, we investigated the emergence of functional clusters which are related with spontaneous brain activity during sleep. Based on multichannel EEG traces from 10 healthy subjects, we compared the functional connectivity across different sleep stages. Our exploration commences with the conjecture of a small-world patterning, present in the scalp topography of the measured electrical activity. The existence of such a communication pattern is first confirmed for our data and then precisely determined by means of two distinct measures of non-linear interdependence between time-series. A graph encapsulating the small-world network structure along with the relative interdependence strength is formed for each sleep stage and subsequently fed to a suitable clustering procedure. Finally the delineated graph components are comparatively presented for all stages revealing novel attributes of sleep architecture. Our results suggest a pivotal role for the functional coupling during the different stages and indicate interesting dynamic characteristics like its variable hemispheric asymmetry and the isolation between anterior and posterior cortical areas during REM.

Differential alpha coherence hemispheric patterns in men and women during pleasant and unpleasant musical emotions.

Potential sex differences in EEG coherent activity during pleasant and unpleasant musical emotions were investigated. Musical excerpts by Mahler, Bach, and Prodromidès were played to seven men and seven women and their subjective emotions were evaluated in relation to alpha band intracortical coherence. Different brain links in specific frequencies were associated to pleasant and unpleasant emotions. Pleasant emotions (Mahler, Bach) increased upper alpha couplings linking left anterior and posterior regions. Unpleasant emotions (Prodromidès) were sustained by posterior midline coherence exclusively in the right hemisphere in men and bilateral in women. Combined music induced bilateral oscillations among posterior sensory and predominantly left association areas in women. Consistent with their greater positive attributions to music, the coherent network is larger in women, both for musical emotion and for unspecific musical effects. Musical emotion entails specific coupling among cortical regions and involves coherent upper alpha activity between posterior association areas and frontal regions probably mediating emotional and perceptual integration. Linked regions by combined music suggest more working memory contribution in women and attention in men.

Brain activity and temporal coupling related to eye movements during REM sleep: EEG and MEG results.

EEG and MEG REM sleep gamma activity was studied immediately before rapid eye movement onset (PRE-EM), during REM sleep with eye movements away from eye movement onset -phasic-REM (Ph-REM)--and during REM sleep without eye movements, or tonic REM (T-REM). For this purpose, activity was segmented into three different time windows: of 62.5, 250 and 500 ms. Two strategies were used: one a statistical comparison of changes between T-REM, Ph-REM and PRE-EM; the other a descriptive approach using principal component analysis. Significant findings showed that both EEG and MEG gamma activity are higher directly before eye movement onset in PRE-EM periods and during Ph-REM than during T-REM; temporal coupling of electrical activity between the frontal and parietal regions is decreased, while temporal coupling between the right frontal and midline is increased. Just before eye movement onset, larger recording sites become related. For the first time, results showed a close temporal link between power and temporal coupling of fast oscillations andrapid eye movements in REM sleep, indicating increased activation, uncoupling between the left frontal executive areas and posterior sensory association regions and increased coupling between the right frontal attentional and midline alerting systems. Brain activity is reorganized by phasic events.

Electrical activity of the human amygdala during all-night sleep and wakefulness.

OBJECTIVE: The aim of the present work was to characterize the dynamics of the human amygdala across the different sleep stages and during wakefulness. METHODS: Simultaneous intracranial electrical recordings of the amygdala, hippocampus, and scalp electroencephalography during spontaneous sleep polysomnography in four patients suffering from epilepsy were analyzed. RESULTS: Power spectrum of the amygdala revealed no differences between rapid eye movement (REM) and wakefulness for all frequencies except higher power at 9 Hz during wakefulness and some low Gamma frequencies. Conversely, higher power was observed in non-REM (NREM) sleep than wakefulness for Delta, Theta and Sigma. CONCLUSIONS: Our results showed similar activity in the amygdala between wakefulness and REM sleep suggesting that the amygdala is as active in REM as during wakefulness. The higher power in Sigma frequencies during NREM sleep suggests that amygdala slow activity may play a significant role during NREM in concurrence with hippocampal activity. SIGNIFICANCE: While studies have described the metabolic activity of the human amygdala during sleep, our results show the corresponding electrical pattern during the whole night, pointing out an increase of slow activity during NREM sleep that might be subjected to similar influences as other subcortical brain structures, such as the hippocampus.

Metabolic and electric brain patterns during pleasant and unpleasant emotions induced by music masterpieces.

Brain correlates comparing pleasant and unpleasant states induced by three dissimilar masterpiece excerpts were obtained. Related emotional reactions to the music were studied using Principal Component Analysis of validated reports, fMRI, and EEG coherent activity. A piano selection by Bach and a symphonic passage from Mahler widely differing in musical features were used as pleasing pieces. A segment by Prodromidès was used as an unpleasing stimulus. Ten consecutive 30 s segments of each piece alternating with random static noise were played to 19 non-musician volunteers for a total of 30 min of auditory stimulation. Both brain approaches identified a left cortical network involved with pleasant feelings (Bach and Mahler vs. Prodromidès) including the left primary auditory area, posterior temporal, inferior parietal and prefrontal regions. While the primary auditory zone may provide an early affective quality, left cognitive areas may contribute to pleasant feelings when melodic sequences follow expected rules. In contrast, unpleasant emotions (Prodromidès vs. Bach and Mahler) involved the activation of the right frontopolar and paralimbic areas. Left activation with pleasant and right with unpleasant musical feelings is consistent with right supremacy in novel situations and left in predictable processes. When all musical excerpts were jointly compared to noise, in addition to bilateral auditory activation, the left temporal pole, inferior frontal gyrus, and frontopolar area were activated suggesting that cognitive and language processes were recruited in general responses to music. Sensory and cognitive integration seems required for musical emotion.

Waking EEG signs of non-restoring sleep in primary insomnia patients.

OBJECTIVE: Subjective feelings of insufficient and non-restorative sleep are core symptoms of primary insomnia. Sleep has a restorative effect on next-day waking EEG activity, whereas sleep loss has non-restorative effects in good sleepers. We proposed to explore waking EEG activity in primary insomniacs the evening before, and the morning after, a night of sleep, in order to detect signs of morning hyper-arousal and non-restoring sleep that might explain the subjective feelings despite the absence of objective signs in polysomnography. METHOD: Pre-sleep (10 pm) and post-sleep (10 am) waking EEG activity was analyzed in 10 non-medicated primary insomniacs and matched control subjects. Beta and Gamma absolute power and EEG temporal coupling were obtained. Participants also evaluated subjective sleep quantity and quality. RESULTS: Insomnia patients evaluated their sleep as non-restorative and insufficient. Compared to pre-sleep, during post-sleep control subjects exhibited significantly decreased Beta and Gamma power and reduced synchronization among anterior and posterior regions, consistent with restoring effects of sleep. Insomnia patients showed no beneficial effects of sleep on these EEG parameters. CONCLUSION: Insomniacs are hyper-aroused during morning wakefulness and they do not benefit from preceding sleep. SIGNIFICANCE: Our study adds new knowledge to our understanding of the physiopathology of insomnia.

[Biofeedback treatment for acute whiplash patients]. / Retroalimentación biológica para pacientes con esguince cervical agudo.

BACKGROUND: The aim of this study is to evaluate the physiological and psychological effect after an electromyographic biofeedback treatment in combination with progressive muscular relaxation training in patients with acute whiplash. METHODS: Twelve patients with acute whiplash volunteered to participate in a quasi-experimental design and a control group. INCLUSION CRITERIA: Two months maximum after car accident, severity levels II and I. EXCLUSION CRITERIA: previous history of persistent pain or serious previous injury. The groups were randomly divided in two (treatment and waiting list groups). We used electromyographic measures of the trapezius muscles with psychometric tests: Beck Anxiety and Depression Inventory; Oswestry Pain Disability Questionnaire; Visual Analog Scale of Pain; TAMPA Scale for Kinesiophobia. The treatment consisted in electromyographic biofeedback after progressive muscular relaxation training. RESULTS: There were significant intra-group differences before and after treatment in muscular symmetry and subjective pain perception in the treatment group. CONCLUSIONS: We achieved a significant change (clinical and statistical) in subjective pain perception and muscular symmetry. This study highlights the importance of multidisciplinary work in acute pain patients and the effectiveness of clinical psychophysiological strategies with acute whiplash patients.

Introducción: el objetivo de este trabajo consistió en evaluar el efecto fisiológico y psicológico de la retroalimentación biológica de electromiografía de superficie (RB de EMGs) en combinación con relajación muscular progresiva (RMP) en pacientes con esguince cervical (EC) agudo. Métodos: Un total de 12 pacientes con EC agudo participaron voluntariamente en el estudio, con diseño cuasiexperimental, y grupo control. Criterios de inclusión: máximo dos meses del accidente automovilístico; gravedad I y II. Se excluyeron: pacientes con historia previa de dolor persistente, o que hayan tenido lesión seria. Se dividió en dos grupos aleatoriamente (de intervención y en lista de espera). Se realizó un registro psicofisiológico de los músculos trapecios con EMGs, en conjunto con instrumentos psicométricos: inventario de ansiedad y depresión de Beck; índice de incapacidad de Oswestry; escala visual análoga y de miedo al movimiento. La intervención consistió aplicar RB de EMGs, posterior a un entrenamiento en RMP. Resultados: el grupo de intervención disminuyó significativamente su valor de simetría muscular (permaneciendo dentro de lo normal) así como su percepción subjetiva del dolor, intragrupo antes/después de la intervención. Conclusiones: se produjo un cambio significativo (tanto clínico como estadístico) en la percepción del dolor y la actividad conjunta de músculos pares. Igualmente, muestra la relevancia de atender un problema agudo multidisciplinariamente; así como la utilidad de las estrategias psicofisiológicas clínicas en pacientes agudos de EC.

Effect of 38 h of total sleep deprivation on the waking EEG in women: sex differences.

38 h of sleep deprivation in women resulted in decreased alpha, increased theta and increased intrahemispheric correlation during rest and increased theta and reaction time during task. F3-O1 coherent activity was selectively decreased consistent with the role of sleep for recovery of frontal functions. Sleep deprivation effects were milder in women than in men, however, recovery was not complete suggesting that women need more sleep than men to recover.

Rendimiento cognitivo en mujeres con síndrome de ovario poliquístico: un estudio piloto / Cognitive Performance in Women with Polycystic Ovarian Syndrome: A Pilot Study

Resumen El Síndrome de ovario poliquístico (SOP) es la enfermedad endocrina-metabólica más frecuente en las mujeres en edad reproductiva. A pesar de su alta prevalencia, hay pocas investigaciones que analizan los efectos de los cambios hormonales sobre la cognición de pacientes con SOP. Objetivo: comparar el rendimiento en habilidades cognitivas y los niveles de hormonas sexuales de un grupo de pacientes con SOP y con las de un grupo control. Método: Participaron 20 mujeres mayores de 21 años, sin tratamiento hormonal, dividas en dos grupos, el primero compuesto por 10 pacientes diagnosticadas con SOP según los criterios de Rotterdam (GSOP) y el otro, de control, compuesto por 10 mujeres sin diagnóstico de SOP (GCT). Se aplicaron las pruebas WAIS III y fluidez verbal semántica y fonológica de la batería NEUROPSI Atención y memoria, y se realizaron análisis sanguíneos de hormonas sexuales. Resultados: Las pacientes del GSOP obtuvieron puntajes inferiores a las del GCT en el CI Verbal (p=0.009), CI Total (p=0.029), índice de comprensión verbal (p=0.005), índice de memoria de trabajo (p=0.023) y en la prueba de fluidez verbal semántica (p=0.029). No se encontraron diferencias significativas en los niveles hormonales. Conclusión: el GSOP presentó menor rendimiento que el GCT en pruebas de tipo verbal, aunque no se presentó déficit en su ejecución. Se sugiere estudiar la relación de la insulinorresistencia con la cognición en pacientes con SOP.

Abstract Polycystic ovarian syndrome (PCOS) is the most common endocrine-metabolic disease in women of reproductive age. Despite its high prevalence, little research analyzes the effects of hormonal changes on cognition in patients with PCOS. Objective: To compare the performance in cognitive abilities and sexual hormone levels of a group of patients with PCOS and those of a control group. Method: Twenty women older than 21 years, without hormone treatment, divided in two groups, the first consisting by 10 patients diagnosed with PCOS according to the Rotterdam criteria (GSOP), and the other composed of 10 women without diagnosis of PCOS (GCT). WAIS III and semantic and phonological verbal fluency tests of the NEUROPSI attention and memory test battery were applied, and blood analyzes of sexual hormones were analyzed. Results: The GSOP patients obtained lower scores than the GCT in Verbal IQ (p=0.009), full scale IQ (p=0.029), verbal comprehension index (p=0.005), working memory index (p=0.023) and semantic verbal fluency test (p=0.029). No significant differences were found in sexual hormone levels. Conclusion: the GSOP showed lower performance than the GCT in verbal tests, although there was not deficit in its execution. It is suggested to study the relationship of insulin resistance with cognition in patients with GSOP.

Enhanced emotional reactivity after selective REM sleep deprivation in humans: an fMRI study.

Converging evidence from animal and human studies suggest that rapid eye movement (REM) sleep modulates emotional processing. The aim of the present study was to explore the effects of selective REM sleep deprivation (REM-D) on emotional responses to threatening visual stimuli and their brain correlates using functional magnetic resonance imaging (fMRI). Twenty healthy subjects were randomly assigned to two groups: selective REM-D, by awakening them at each REM sleep onset, or non-rapid eye movement sleep interruptions (NREM-I) as control for potential non-specific effects of awakenings and lack of sleep. In a within-subject design, a visual emotional reactivity task was performed in the scanner before and 24 h after sleep manipulation. Behaviorally, emotional reactivity was enhanced relative to baseline (BL) in the REM deprived group only. In terms of fMRI signal, there was, as expected, an overall decrease in activity in the NREM-I group when subjects performed the task the second time, particularly in regions involved in emotional processing, such as occipital and temporal areas, as well as in the ventrolateral prefrontal cortex, involved in top-down emotion regulation. In contrast, activity in these areas remained the same level or even increased in the REM-D group, compared to their BL level. Taken together, these results suggest that lack of REM sleep in humans is associated with enhanced emotional reactivity, both at behavioral and neural levels, and thus highlight the specific role of REM sleep in regulating the neural substrates for emotional responsiveness.

Enhanced frontoparietal synchronized activation during the wake-sleep transition in patients with primary insomnia.

INTRODUCTION: Cognitive and brain hyperactivation have been associated with trouble falling asleep and sleep misperception in patients with primary insomnia (PI). Activation and synchronization/temporal coupling in frontal and frontoparietal regions involved in executive control and endogenous attention might be implicated in these symptoms. METHODS: Standard polysomnography (PSG) and electroencephalogram (EEG) were recorded in 10 unmedicated young patients (age 19-34 yr) with PI with no other sleep/medical condition, and in 10 matched control subjects. Absolute power, temporal coupling, and topographic source distribution (variable resolution electromagnetic tomography or VARETA) were obtained for all time spent in waking, Stage 1 and Stage 2 of the wake-sleep transition period (WSTP), and the first 3 consecutive min of N3. Subjective sleep quality and continuity were evaluated. RESULTS: In comparison with control subjects, patients with PI exhibited significantly higher frontal beta power and current density, and beta and gamma frontoparietal temporal coupling during waking and Stage 1. CONCLUSION: These findings suggest that frontal deactivation and disengagement of brain regions involved in executive control, attention, and self-awareness are impaired in patients with PI. The persistence of this activated and coherent network during the wake-sleep transition period (WSTP) may contribute to a better understanding of underlying mechanisms involved in difficulty in falling asleep, in sleep misperception, and in the lighter, poorer, and nonrefreshing sleep experienced by some patients with PI.

Diazepam-induced changes in EEG oscillations during performance of a sustained attention task.

The primary aim of the present study was to test diazepam (DZ) effect, a benzodiazepine (BDZ) usually prescribed to reduce anxiety and to induce sleep, on EEG activity while performing a visual sustained attention task. The EEG activity was recorded in a double-blind placebo experiment, and prestimulus spectral power and inter- and intrahemispheric temporal coupling were assessed during visual sustained attention task performance. A single DZ dose (5 mg) was enough to increase reaction times during visual sustained attention task responses. DZ decreased prestimulus EEG power in the 1- to 6-, 8- to 12-, and 19- to 35-Hz bands and disrupted right intrahemispheric temporal coupling in the α-frequency range (8-12 Hz). The combined reduction in power and temporal coupling suggests both local and interregional DZ-induced disruption of neuronal synchronicity especially in the right hemisphere in agreement with the prominent attention-related networks in this hemisphere. These data support the notion that the influence of DZ on behavior goes beyond sedative effects and can potentially compromise higher cognitive functions with negative consequences to daily life situations.

La actividad Alfa frontal en insomnes primarios con dificultad para iniciar el sueño / Frontal alpha activity in primary insomniacs with sleep onset difficulties

Difficulty in sleep initiation, with or without objective signs, is one of the most frequent complaints in primary insomniacs. The electroencephalographic (EEG) activity characteristic of waking (beta and alpha oscillations) is gradually replaced by the EEG signs of sleep (sleep spindles and theta/delta waves) during the sleep onset period (SOP) in normal subjects. The decrease in fast oscillations occurs at the first signs of stage 1, whereas theta and delta increase occurs later, indicating that waking promoting mechanisms are turned off before sleep-promoting mechanisms are fully started. It could be therefore hypothesized that difficulty in sleep initiation in insomniacs might be due to either a hyperactivation of waking promoting systems, a weakness of sleep promoting mechanisms or an imbalance between them. Quantitative EEG analysis has revealed higher beta during wakefulness, as well as during sleep and lower slow (delta) activity in insomniacs. The presence of alpha activity during cognitive information processing, especially of slow alpha activity in relation to attention, as well as in some pathologies associated to sleep disturbances, has suggested that alpha activity during sleep is a sign of activation; however, alpha activity during sleep has been less studied in insomniacs. Only broad bands have been considered in all of the aforementioned studies, and in almost all of them the analyses were restricted to central regions. It is therefore important to study the entire frequency spectrum of EEG activity in insomniacs. Sleep initiation does not occur simultaneously over the entire cortex but starts as a local process which gradually invades the rest of the cortex, in which the frontal lobes play a crucial role. Frontal and parietal regions are part of an important network involved in attention and conduction of thought. Thus, quantitative analysis of narrow EEG bands and their distribution in the cerebral cortex may contribute to a better understanding of neural mechanisms compromised in etiology of sleep initiation in primary insomnia. The main objective of the present investigation was, therefore, to analyze the spectral power of narrow EEG bands in the 19 derivations of the 10-20 International System during SOP in primary insomniacs with difficulty in sleep initiation. Given that one of the main complaints of insomniacs is the difficulty to initiate sleep and that hyperarousal is one of the factors proposed to be involved in the etiology of insomnia, EEG activity during SOP of the first night in the laboratory was analyzed to control activating effects of surrounding circumstances and isolate permanent EEG characteristics. Subjects were 19-34 years old, right-handed with primary sleep insomnia, which were thoroughly screened via structured psychiatric, medical and sleep interviews and scales. Subjects were younger and the age range was narrower than in other EEG frequency spectral content studies of primary insomniacs to avoid confounding effects of changes in sleep architecture or in EEG generated by development. All patients met the criteria for primary insomnia with sleep onset difficulty and impaired daytime function on three or more nights per week for at least six months and with no medical, psychiatric or neurological conditions; they were not medicated and had no other sleep disorders. Participants taking sleep medications or other drugs (urine test), respiratory or sleep disorders such as apnea and periodic limb movements (PSG) were excluded. The control group (n = 9) was matched for age and dexterity, but had no complaints of insomnia and reported their sleep as restorative and satisfactory. All participants underwent a single night of standard polysomnography (EEG, EOG and EMG) in the laboratory. In addition, the 19 electrode sites of the 10-20 International System referred to ipsilateral earlobes, oral-nasal airflow and anterior tibialis EMG were recorded. PSG was scored in 30 sec epochs, blind to the subject group according to Rechtschaffen and Kales criteria. EEG from SOP (lights out to consolidate sleep), defined as 3 consecutive minutes of delta sleep, was digitized at 1024 Hz with 12 bits resolution and filter settings of 0.03-70 Hz. EEG was segmented into two-sec non-overlapping epochs and inspected for artifacts. All artifact-free epochs were Fast Fourier Transformed and absolute (AP) and relative power (RP: AP in each Hz bin/total spectrum power × 100) was obtained for 1 Hz bins. AP and RP was log-transformed before statistical analysis, and was averaged over each derivation and sleep stage of SOP. Group differences were compared by means of Student's t tests and probability level was set at p<0.05. In contrast with healthy controls, insomniac patients exhibited higher alpha RP (7 and 8 Hz) over all frontal derivations during stage 2 of SOP and higher RP of isolated beta and gamma frequencies during wakefulness. PSG of both groups showed the <> with decreased total sleep time, decreased sleep efficiency index and REM sleep percentage compared to normal values for the 20-30 age decade; PSG variables were not significantly different between the two groups except for wakefulness percentage during SOP. Insomniacs did differ from controls in subjective estimation of sleep quality and continuity in spite of similar PSG. The absence of significant differences between insomniacs and controls in sleep EEG activity (delta, theta and sigma frequencies) suggests that sleep homeostatic function is preserved in insomniacs, which agrees with results obtained in other studies after partial sleep deprivation. The absence of a stronger promoting effect of insomnia in the insomniac group by the first recording night indicates that EEG characteristics found in this group cannot be attributed to external stimuli nor surrounding circumstances and rather suggests a more stable alteration; however, further studies of larger groups and other age spans are needed to confirm present results. The evidence mentioned above suggests an imbalance between waking and sleep promoting mechanisms in primary insomniacs with difficulty in sleep initiation and sleep perception. Attention depends not only on vigilance level, but also on frontal regions which, together with posterior association areas, conform an essential network for purposive endogenously guided attention. The presence in insomniacs of alpha activity in frontal regions, which is a sign of top-down control of attention, and its absence in posterior regions during stage 2 suggests the persistence of a certain level of endogenous attention during stage 2 of SOP, which contributes in turn to the subjective perception of sleep onset difficulties and bad sleep quality.

La dificultad para conciliar el sueño es uno de los síntomas más frecuentes del insomnio primario. La apreciación subjetiva de un periodo prolongado de latencia al sueño, aun en presencia de signos de sueño, puede deberse a la coexistencia de los mecanismos promotores de la vigilia y del sueño, y la lucha por el predominio de uno de ellos. La red de atención ejecutiva, conformada por las áreas de asociación frontales y parietales, cumple un papel de particular importancia en el control endógeno de la atención y en la regulación del alertamiento por parte de la corteza. Las frecuencias del EEG en el rango de actividad alfa lenta (7 y 8 Hz) participan en los procesos cognoscitivos activos de la vigilia, especialmente en la atención y la memoria, y son indicadoras del control corticofugo, o top-down, de estos procesos. Sin embargo, el análisis cuantitativo del EEG durante el proceso de conciliación del sueño en los insomnes se ha centrado fundamentalmente en la actividad delta, theta y beta, y únicamente en las regiones centrales (C3 y C4), de tal forma que el análisis de banda estrecha del EEG y su distribución en toda la corteza podría contribuir a una mejor comprensión de los mecanismos neurales comprometidos en la etiología del insomnio primario. El objetivo principal de esta investigación es, por lo tanto, analizar el espectro de frecuencias con resolución de 1 Hz en todas las derivaciones del Sistema Internacional 10-20 en insomnes primarios crónicos durante el periodo inicial del sueño (PIS) y comparar a estos últimos con un grupo control. Con el fin de aislar las características del EEG de los insomnes de causas circunstanciales, se analizará la primera noche de PSG igualando en ambos grupos el efecto activador que ejerce el medio circundante sobre el Sistema Nervioso Central, el estado psicológico y la arquitectura del sueño. Se estudiaron nueve pacientes insomnes primarios cuya queja principal era la dificultad para iniciar el sueño y nueve sujetos controles libres de problemas de sueño, diestros y entre 19-34 años de edad. Se realizó la PSG durante la primera noche en el laboratorio siguiendo los procedimientos estándar y adicionalmente se registraron las 19 derivaciones del Sistema Internacional 10-20. Se obtuvieron los espectros de potencia del EEG de todas las derivaciones con resolución de 1 Hz del PIS (tiempo comprendido entre las buenas noches y el sueño consolidado: 3 minutos consecutivos de sueño delta). Los insomnes tuvieron mayor actividad alfa lenta (7 y 8 Hz) en las regiones frontales durante la etapa 2 del PIS y de algunas frecuencias rápidas (beta y gamma) en la vigilia; subestimaron la calidad de sueño; y mostraron el mismo efecto de primera noche que los controles. La ausencia de diferencias entre los dos grupos en el EEG típico del sueño (delta, theta y sigma) sugiere que los insomnes tienen preservada la función homeostásica del sueño. La ausencia de diferencias en la PSG de los insomnes y controles indica que la dificultad para conciliar el sueño del grupo de insomnes no se encuentra en estímulos externos ambientales ni en condiciones circunstanciales y sugiere que se debe a alteraciones más permanentes. El conjunto de estas evidencias apunta hacia una alteración de la vigilia en concordancia con las hipótesis que proponen que el insomnio tiene un componente primordial de activación fisiológica y psicológica. La atención depende, además del nivel de vigilancia, de las regiones frontales que, junto con las áreas posteriores de asociación, conforman una red esencial para la atención dirigida endogenamente. La presencia de ritmo alfa en las regiones frontales y su ausencia en las áreas posteriores durante la etapa 2 en los insomnes podría reflejar la permanencia de cierto nivel de atención endógena durante la etapa 2 del PIS y podría constituir un mecanismo alterado del sistema frontal subyacente a la dificultad para iniciar el sueño.

MEG tomography of human cortex and brainstem activity in waking and REM sleep saccades.

We recorded the magnetoencephalographic (MEG) signal from three subjects before, during and after eye movements cued to a tone, self-paced, awake and during rapid eye movement (REM) sleep. During sleep we recorded the MEG signal throughout the night together with electroencephalographic (EEG) and electromyographic (EMG) channels to construct a hypnogram. While awake, just prior to and during eye movements, the expected well time-locked physiological activations were imaged in pontine regions, with early 3 s priming. Activity in the frontal eye fields (FEF) was identified in the 300 ms before the saccade onset. Visual cortex activation occurred 200 ms after saccades. During REM, compared to the eyes closed awake condition, activity was higher in supplementary motor area (SMA) and lower in inferior parietal and precuneus cortex. Electro-occulographic (EOG) activity just prior to REM saccades correlated with bilateral pontine and FEF activity some 250-400 ms before REM saccade onset, which in turn was preceded 200 ms earlier by reciprocal activation of the pons and FEF. An orbitofrontal-amygdalo-parahippocampal-pontine sequence, possibly related to emotional activation during REM sleep, was identified in the last 100 ms leading to the REM saccade, but not linked to saccade initiation.