Yolanda del Río-Portilla

EEG Bands During Wakefulness, Slow-Wave, and Paradoxical Sleep As a Result of Principal Component Analysis in the Rat

Rat EEG has been empirically divided in bands that frequently do not correspond with EEG generators nor with the functional meaning of EEG rhythms. Power spectra from wakefulness (W), slow-wave sleep (SWS), and paradoxical sleep (PS) of Wistar rats were submitted to Principal Component Analyses (PCA) to investigate which frequencies are covariant. Three independent eigenvectors were identified for SWS: a band between 1-6, an intermediate band between 7-15, and a fast band between 16-32 Hz (90.74% of the variance); two independent eigenvectors were extracted for PS: slow frequencies between 1-6 covarying together with frequencies between 11-16 Hz, and activity between 6-10 covarying together with fast frequencies between 17-32 Hz (80.38% of the variance); four eigen-vectors were obtained for W: 3-7, 8-9, 10-21 and 21-32 Hz (81.47% of the variance). Vigilance states showed significant differences in AP from 1 to 22 Hz. PCA extracted broad bands different for each vigilance state, which included the most representative EEG activities characteristic of them. These results indicate that during SWS, slow oscillations include frequencies up to 6 Hz, and spindle oscillations frequencies down to 7 Hz. No alpha frequencies were identified as an independent band. Frequencies within theta and beta were gathered in the same eigenvector during PS and in different eigenvectors during W suggesting coordinated activation of hippocampal and cortical systems during PS. These bands are consistent with the underlying neurophysiological mechanisms of sleep and wakefulness and with firing frequencies of generators of rhythmic activity obtained in cellular studies in animals.

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.

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.

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.

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.

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.

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.