EEG Theta Activity Research Articles

Delta and theta eeg activity during resting state is altered in patients affected by major depression

IntroductionMajor depression (MD) is associated with cognitive and behavioral alterations in many domains. It is not well clear what cortical structures and functional alterations characterize MD patients during resting state, a condition during which mind wandering process is prevailing.ObjectivesIn MD patients with severe levels of depression we expected, during resting state, an altered asymmetry of cortical activity in the EEG bands that generally mark neurological impairment, i.e. Delta and Theta EEG bands.Methods30 MD patients under pharmacological treatment and 32 matched controls underwent an EEG recording (38 scalp sites) during 5 min resting state with open eyes. Eye movements were corrected by ICA modeling and the 5 min recording was divided in 2 sec epochs from which Delta and Theta spectral powers were extracted.ResultsSpectral analysis of the 5 min resting state revealed a significant difference between the two groups at the level of left temporal lobe. MD patients showed larger Delta and Theta spectral power in the left superior temporal gyrus at the level of Brodmann’s Areas 22 and 42.ConclusionsResults evidenced a cortical inhibition (greater EEG Delta and Theta activity) in left temporal linguistic areas in severe depression, a result pointing to a different mind wandering process and thought architecture in MD patients during resting state.

Effects of partially automated driving on the development of driver sleepiness

The objective of this study was to compare the development of sleepiness during manual driving versus level 2 partially automated driving, when driving on a motorway in Sweden. The hypothesis was that partially automated driving will lead to higher levels of fatigue due to underload. Eighty-nine drivers were included in the study using a 2 × 2 design with the conditions manual versus partially automated driving and daytime (full sleep) versus night-time (sleep deprived). The results showed that night-time driving led to markedly increased levels of sleepiness in terms of subjective sleepiness ratings, blink durations, PERCLOS, pupil diameter and heart rate. Partially automated driving led to slightly higher subjective sleepiness ratings, longer blink durations, decreased pupil diameter, slower heart rate, and higher EEG alpha and theta activity. However, elevated levels of sleepiness mainly arose from the night-time drives when the sleep pressure was high. During daytime, when the drivers were alert, partially automated driving had little or no detrimental effects on driver fatigue. Whether the negative effects of increased sleepiness during partially automated driving can be compensated by the positive effects of lateral and longitudinal driving support needs to be investigated in further studies.

Diabetic patients are deficient in intentional visuospatial learning and show different learning-related patterns of theta and gamma EEG activity

ABSTRACT Introduction: We hypothesized that diabetic patients without mild cognitive impairment would present deficiencies in visuospatial incidental/intentional memory processing and alterations in the underlying EEG alpha, theta and gamma patterns. Methods: Non-diabetic, diabetic-controlled, and diabetic-uncontrolled patients underwent a visuospatial incidental-intentional memory test under simultaneous recording of temporal, parietal, and frontal EEG. The test required patients to solve a maze, with eight objects irrelevant to the task, embedded in it, after an interference instruction, participants were asked to recall the positions of the objects (incidental test). Finally, the participants were explicitly told to study the object positions, and then were asked to recall the objects again (intentional test). Power from baseline, incidental learning, incidental memory, and intentional learning conditions was obtained in alpha, theta, and low-gamma bands. Comparisons were made across groups and conditions for each band, with age, sex, and years from the diagnosis as covariates (ANCOVA with blocking). Results: Diabetic patients showed spared incidental but deficient intentional visuospatial learning. Uncontrolled patients showed a more profound intentional learning deficit as they scored similar numbers of correct positions under incidental and intentional conditions; whereas, non-diabetic and diabetic-controlled patients increased their number after the intentional study. Non-diabetic participants showed increased power during intentional learning compared with the baseline condition in frontal theta, frontoparietal gamma (Fp2 and P4) and frontal alpha (F4) bands; whereas in diabetic patients the power increased in the theta band, in T5 (uncontrolled) and T5 and F7 (controlled). Conclusions: Diabetic patients without mild cognitive impairment show deficient intentional visuospatial learning which was worse in uncontrolled patients. Theta and gamma power increased in healthy participants during intentional learning principally in frontal areas. These EEG power changes were absent in diabetic patients. The reduced accuracy of diabetic patients in intentional visuospatial learning was associated with different EEG learning-related patterns.

Indices of cortical plasticity after therapeutic sleep deprivation in patients with major depressive disorder

BackgroundTherapeutic sleep deprivation (SD) presents a unique paradigm to study the neurobiology of major depressive disorder (MDD). However, the rapid antidepressant mechanism, which differs from today's slow first-line treatments, is not sufficiently understood. We recently integrated two prominent hypotheses of MDD and sleep, the synaptic plasticity hypothesis of MDD and the synaptic homeostasis hypothesis of sleep-wake regulation, into a synaptic plasticity model of therapeutic SD in MDD. Here, we further tested this model positing that homeostatically elevating net synaptic strength through therapeutic SD shifts the initially deficient inducibility of associative synaptic long-term potentiation (LTP)-like plasticity in patients with MDD into a more favorable window of associative plasticity. MethodsWe used paired associative stimulation (PAS), a transcranial magnetic stimulation protocol (TMS), to quantify cortical LTP-like plasticity after one night of therapeutic sleep deprivation in 28 patients with MDD. ResultsWe demonstrate a significantly different inducibility of associative plasticity in clinical responders to therapeutic SD (> 50% improvement on the 6-item Hamilton-Rating-Scale for Depression, n=13) compared to non-responders (n=15), which was driven by a long-term depression (LTD)-like response in SD-non-responders. Indices of global net synaptic strength (wake EEG theta activity, intracortical inhibition and BDNF serum levels) were increased after SD in both groups, with responders showing a generally lower intracortical inhibition than non-responders. LimitationsRepetitive assessments prior to and after treatment would be needed to further determine potential mechanisms. ConclusionAfter a night of therapeutic SD, clinical responders show a significantly higher inducibility of associative LTP-like plasticity than non-responders.

EEG Frontal Asymmetry and Theta Power in Unipolar and Bipolar Depression

BackgroundDistinguishing between unipolar and bipolar depression is of high clinical relevance. However, there is sparse research directly comparing these groups in terms of EEG activity. MethodWe investigated 87 participants’ left and right EEG frontal alpha-1, alpha-2, and theta activity related to happy and sad face stimuli in unipolar (UD, n=33) and bipolar (BD, n=22) depressed participants, and controls without depression (HC, n=32). ResultsPost-hoc analysis of an observed hemisphere x group interaction (p< .037) showed significant differences in alpha-1 asymmetry only for the comparison of UD and HC (p< .006). Further analysis of a significant emotion x group interaction (p= .001) revealed a differential impact of stimulus valence on theta power between the groups (p< .001). The valence dependent theta power of the BD differed from that of the UD (p< .0002) and the HC (p< .004).Alpha-1 asymmetry classified HC and both depressed groups with an accuracy of .69. Valence-related theta classified BD from UD with an accuracy of .83. Leave-one-out cross validation resulted in slightly reduced accuracy. LimitationsImportant limitations were the small sample size and that subjects were not medication-free. ConclusionsOur results demonstrate the value of simple, task related EEG activity for differentiating not only healthy individuals from those with depression, but also individuals with unipolar depression from those with bipolar depression.

0327 NREM Sleep EEG in Typically Developing and Drug-Naïve ADHD Adolescents: Data from a Longitudinal Study

Abstract Introduction Structural MRI studies suggest delayed brain maturation in children with attention deficit hyperactivity disorder (ADHD). The steep adolescent decline in sleep slow wave EEG activity provides an opportunity to investigate brain electrophysiological evidence for this maturational delay. Most ADHD sleep EEG studies have been cross-sectional. Here we present data from an ongoing longitudinal study of the maturational trajectories of sleep EEG in drug-naïve ADHD and typically developing adolescents. Methods Nine children diagnosed with ADHD (combined subtype, DSM-V criteria, mean age 12.39±0.61 years), and nine typically developing controls (12.07±0.35 years) were recruited. Subjects underwent an adaptation night and all night polysomnography twice yearly at the Laboratory. Sleep EEG was analyzed using fast Fourier transform. NREM delta and theta EEG activity were compared across first two recordings. Results Group effects (ADHD vs. control) on all night delta and theta energy, and delta power were not significant (p&amp;gt;0.2 for all). All night theta power was lower (p=0.035) for the ADHD group, and all night NREM sleep duration trended (p=0.060) toward being lower for the ADHD group. Controlling for sleep duration differences by examining only the first 5 h of NREM sleep showed no group effect on delta power (p=0.77) and a trend toward lower theta power (p=0.057) for the ADHD group. Conclusion At age 12 to 13 years, NREM sleep delta EEG did not differ between ADHD and control subjects. Theta power, which declines at a younger age than delta, was lower in control subjects. The two recordings thus far differ only by 6 months. The entire study will provide 5 semiannual recordings and allow us to determine if the higher theta power in the ADHD group will hold and if delta power will be greater as well, and thus provide electrophysiological support for the delayed brain maturation suggested by MRI findings. Support Shota Rustaveli National Science Foundation Grant FR17_94; Subjects Recruitment Support - Mental Health Service in Tbilisi “Kamara”.

Aging-related changes in motor response-related theta activity

It has been suggested that a distributed oscillatory system in the brain operating in the theta (3.5–7 Hz) frequency range plays a major role in coordinating motor actions. The major objective of the present study was to explore the effects of human aging on the neurodynamics of motor-related EEG theta activity during correct motor response generation. Response-related potentials of young and older adults elicited in auditory and visual four-choice sensorimotor tasks were analyzed in the time-frequency domain. The phase-locking factor and total power were computed at motor cortical regions contra- and ipsilateral to the movement and at the midline to reflect phase synchronization and power of motor theta oscillations. Major results demonstrated that in both young and older adults, a pronounced response-locked theta activity (3.5–7 Hz) was generated at premotor, motor and sensorimotor cortical regions contra-lateral to the responding hand. Aging was associated with a decreased lateral asymmetry in the phase synchronization of only the left-hand responses. Also, there was a strong aging-related suppression of theta power at the medial fronto-central region that was specifically enhanced and correlated with response speed only in young adults. These results confirm the involvement of theta oscillations in movement generation in relation to action coordination in humans. Also, they show that aging is associated with a dysfunction of the oscillatory theta system for motor action regulation due to a strong suppression of a medial frontal integrating mechanism and an impaired balance in the functional control of responses with the right and the left hand.

SEROTONIN LEVEL IN PERIPHERAL BLOOD AND THE BRAIN’S BIOELECTRICAL ACTIVITY IN YOUNG PEOPLE 15-17 YEARS

The purpose of the work is to evaluate the features of the organization of the bioelectrical activity of the brain with different levels of serotonin in the serum of peripheral blood in young people 15-17 years old. The study involved 93 healthy girls and boys (15-17 years) of the Arkhangelsk region and the Nenets autonomous okrug. A serotonin level is determined in serum by enzyme immunoassay using a set of “Serotonin ELISA”. The electroencephalogram (EEG) power spectrum (PS) in the alpha, beta and theta frequencies ranges was recorded using an electroencephalograph “Encephalan” (Medicom, Taganrog). Age-dependent electroencephalogram (EEG) patterns is associated with the level of serotonin in peripheral blood in adolescents. On the background of a higher level of serotonin in the blood, compared to girls, boys have localized associations of theta and beta1 activity of EEG and serotonin levels, mainly in the right frontal-temporal region. In girls, the spectral power level of the EEG theta activity is more dependent on the level of serotonin in the blood, and a greater number of brain areas are involved in correlation interactions in comparison with young men (temporal regions on the left and frontal, central, parietal regions of both hemispheres of the brain).

Bilateral Theta Transcranial Alternating Current Stimulation (tACS) Modulates EEG Activity: When tACS Works Awake It Also Works Asleep.

PurposeRecent studies demonstrate that 5-Hz bilateral transcranial alternating current stimulation (θ-tACS) on fronto-temporal areas affects resting EEG enhancing cortical synchronization, but it does not affect subjective sleepiness. This dissociation raises questions on the resemblance of this effect to the physiological falling asleep process. The current study aimed to evaluate the ability of fronto-temporal θ-tACS to promote sleep.Subjects and methodsTwenty subjects (10 F/10 M; mean age: 24.60 ± 2.9 y) participated in a single-blind study consisting of two within-subject sessions (active/sham), one week apart in counterbalanced order. Stimulation effects on EEG were assessed during wake and post-stimulation nap. The final sample included participants who fell asleep in both sessions (n=17).ResultsGroup analyses on the whole sample reported no θ-tACS effects on subjective sleepiness and sleep measures, while a different scenario came to light by analysing data of responders to the stimulation (ie, subjects actually showing the expected increase of theta activity in the wake EEG after the θ-tACS, n=7). Responders reported a significant increase in subjective sleepiness during wakefulness after the active stimulation as compared to the sham. Moreover, the sleep after the θ-tACS compared to sham in this sub-group showed: (1) greater slow-wave activity (SWA); (2) SWA time-course revealing increases much larger as closer to the sleep onset; (3) stimulation-induced changes in SWA during sleep topographically associated to those in theta activity during wake.ConclusionSubjects who show the expected changes during wake after the stimulation also had a consistent pattern of changes during sleep. The enhancement of cortical synchronization by θ-tACS during wakefulness actually corresponds to increased sleep pressure, but it occurs only in some individuals. Thus, θ-tACS can enhance sleep, although individual factors to be further investigated affect the actual responsiveness to this treatment.

Ketamine effects on default mode network activity and vigilance: A randomized, placebo-controlled crossover simultaneous fMRI/EEG study.

In resting‐state functional connectivity experiments, a steady state (of consciousness) is commonly supposed. However, recent research has shown that the resting state is a rather dynamic than a steady state. In particular, changes of vigilance appear to play a prominent role. Accordingly, it is critical to assess the state of vigilance when conducting pharmacodynamic studies with resting‐state functional magnetic resonance imaging (fMRI) using drugs that are known to affect vigilance such as (subanesthetic) ketamine. In this study, we sought to clarify whether the previously described ketamine‐induced prefrontal decrease of functional connectivity is related to diminished vigilance as assessed by electroencephalography (EEG). We conducted a randomized, double‐blind, placebo‐controlled crossover study with subanesthetic S‐Ketamine in N = 24 healthy, young subjects by simultaneous acquisition of resting‐state fMRI and EEG data. We conducted seed‐based default mode network functional connectivity and EEG power spectrum analyses. After ketamine administration, decreased functional connectivity was found in medial prefrontal cortex whereas increased connectivities were observed in intraparietal cortices. In EEG, a shift of energy to slow (delta, theta) and fast (gamma) wave frequencies was seen in the ketamine condition. Frontal connectivity is negatively related to EEG gamma and theta activity while a positive relationship is found for parietal connectivity and EEG delta power. Our results suggest a direct relationship between ketamine‐induced functional connectivity changes and the concomitant decrease of vigilance in EEG. The observed functional changes after ketamine administration may serve as surrogate end points and provide a neurophysiological framework, for example, for the antidepressant action of ketamine (trial name: 29JN1556, EudraCT Number: 2009‐012399‐28).

Role of GABAA receptors in EEG activity and spatial recognition memory in aged APP and PS1 double transgenic mice

Alzheimer's disease (AD) is a leading cause of dementia, with no effective treatment currently available. However, targeting the aging mechanism may improve outcomes and γ-aminobutyric acid (GABA) system alteration could have implications for treatment of cognitive decline in old age. We studied the effects of the GABA system on brain activity in aged APP and PS1 transgenic mice. Low dose (0.1 mg/kg i.p.) GABAA agonist muscimol and antagonist bicuculline were administered for moderate system activation and inhibition, respectively. EEGs from the hippocampus (Hip) and prefrontal cortex (PFC) were recorded under spontaneous state and during Y-maze performance. Basally, AD mice exhibited increased spontaneous EEG delta (2–4 Hz) and decreased spontaneous EEG alpha (8–12 Hz) activity in the Hip, and decreased Y-maze EEG theta (4–8 Hz) activity in the PFC. Interestingly, GABAA activation and inhibition in AD mice reduced EEG delta activity and increased EEG theta activity in the PFC, and behaviorally improved spatial recognition memory during Y-maze testing. Decreased spontaneous EEG delta activity was also observed in the PFC. Specifically, GABAA activation primarily affected low frequency EEG (2–12 Hz) activity in the PFC, whereas inhibition affected EEG activity across many frequencies in the PFC and Hip. These data provide evidence for slower brain activity in AD mice. Importantly, improved spatial memory after GABAA activation and inhibition may be explained by brain rhythm recovery in certain regions. Our study highlights the potential clinical use of GABAA drugs to improve cognitive disorders and restore neural network activity in AD.

Differential behavioral, stress, and sleep responses in mice with different delays of fear extinction.

Sleep, in particular rapid eye movement (REM), has been linked to fear learning and extinction; however, their relationship is poorly understood. We determined how different delays of extinction training (ET) impact fear-conditioned behaviors, changes in sleep, and stress responses. EEG activity, movement, and body temperature in mice were monitored via telemetry. Following contextual fear conditioning (shock training [ST]), separate groups of mice were reexposed to the context at 24-hour post-ST (24h ET-1) and at 48-hour post-ST (48h ET-1). Post-ET sleep amount and sleep-associated EEG (delta and theta) activity were compared to baseline and to post-ST sleep. Freezing, locomotion, grooming, and rearing were monitored to determine effects of ET on fear behaviors. Body temperature immediately after ET was monitored to assess stress-induced hyperthermia (SIH). 24h ET-1 and 48h ET-1 produced similar freezing and REM reductions, but dissimilar rearing activity and SIH. 24h ET-1 was followed by periods of suppressed REM-associated theta (REM-θ) activity, immediately after ET and during the subsequent dark period. Suppressed REM-θ was specific to sleep after 24h ET-1, and did not occur after ST, nor after 48h ET-1. ET-1 at 24 and 48 hours after ST was associated with similar freezing and REM amounts, but with differences in other overt behaviors, in REM-θ, and in SIH. Freezing was not predictive of changes in other fear-associated responses. This study demonstrated that consideration of time delay from fear acquisition to extinction is important when assessing the relationships between extinction and behavior, sleep, and stress responses.

A preliminary investigation of the role of slow-wave activity in modulating waking EEG theta as a marker of sleep propensity in major depressive disorder

BackgroundBoth EEG slow-wave activity (SWA) during sleep and EEG theta activity during waking have been shown to increase with extended waking, and decrease following sleep, suggesting that both are markers of sleep propensity. In individuals with major depressive disorder (MDD), however, altered patterns of SWA have been noted, suggesting that sleep homeostasis is dysregulated. This study aimed to examine if slow-wave disruption would alter sleep propensity differently in healthy controls (HC) and those with MDD. Methods25 individuals (13 diagnosed with MDD and 12 HC) participated. Following one night of adaptation sleep, participants underwent one night of baseline sleep, and one night of selective slow-wave disruption by auditory stimuli. In the evening, before sleep, and in the morning following sleep, waking EEG was recorded from participants in an upright position, with eyes open. ResultsRepeated measures ANOVA revealed a significant three-way interaction, such that AM theta activity was significantly lower following slow-wave disruption in those with MDD, but not in HC. Additionally, SWA was not correlated with theta activity in MDD. LimitationsThese data are based on a relatively small sample size of unmedicated individuals with MDD. ConclusionsThese data may suggest that SWA plays a differential role in the homeostatic regulation of sleep in HC, and in MDD, and provide additional evidence that the presence of SWA may be maladaptive in MDD.

The Dorsal Hippocampus Neuronal Lesion Does not Affect Theta Activity in the Cortical Network

The hippocampal theta activity represents the oscillatory field potentials within the range of 4–10 Hz, which mainly appears during wakefulness and rapid eye moment (REM) sleep. The synchronization of theta activity between the hippocampus and other parts of the brain is essential for learning and memory. Theta waves can be recorded from the different cortical areas, which exhibit a consistent phase relationship with hippocampal rhythmicity. It has been postulated that the synchronized theta activity in the cortico-hippocampal networks could be essential for communication of memory information between hippocampus and cortex. It is, however, not known if the dorsal hippocampus (DH) contributes in propagating theta waves in the cortical network. In this study, we have investigated the effects of DH lesion on theta activity during different vigilant states in the frontoparietal cortical network. Rats were surgically prepared for chronic polysomnographic recordings and drug injections. After recovery from surgery, animals were divided into two groups: (a) DH-non-lesioned and (b) DH-lesioned groups. DH was lesioned with microinjection of ibotenic acid. We found that the DH neuronal damage did not significantly alter cortical EEG theta activity. There were only marginal changes in the power of theta (5–9 Hz) and high-frequency oscillatory waves (10–40 Hz) that too only during REM sleep in the DH-lesioned animals. Although the hippocampal theta rhythm plays an important role the cortical–hippocampal synchrony, it is likely that in the absence of DH, the cortical theta oscillation can be modulated by some non-hippocampal theta generators such as the septum-diagonal band of Broca or the supramammillary body.

Rocking Promotes Sleep in Mice through Rhythmic Stimulation of the Vestibular System

Rocking has long been known to promote sleep in infants and, more recently, also in adults, increasing NREM sleep stage N2 and enhancing EEG slow waves and spindles. Nevertheless, whether rocking also promotes sleep in other species, and what the underlying mechanisms are, has yet to be explored. In the current study, C57BL/6J mice equipped with EEG and EMG electrodes were rocked laterally during their main sleep period, i.e., the 12-h light phase. We observed that rocking affected sleep in mice with a faster optimal rate than in humans (1.0 versus 0.25Hz). Specifically, rocking mice at 1.0Hz increased time spent in NREM sleep through the shortening of wake episodes and accelerated sleep onset. Although rocking did notincrease EEG activity in the slow-wave and spindle-frequency ranges in mice, EEG theta activity (6-10Hz) during active wakefulness shifted toward slower frequencies. To test the hypothesis that the rocking effects are mediated through the vestibular system, we used the otoconia-deficient tilted (tlt) mouse, which cannot encode linear acceleration. Mice homozygous for the tlt mutation were insensitive to rocking at 1.0Hz, while the sleep and EEG response of their heterozygous and wild-type littermates resembled those of C57BL/6J mice. Our findings demonstrate that rocking also promotes sleep in the mouse and that this effect requires input from functional otolithic organs of the vestibule. Our observations also demonstrate that the maximum linear acceleration applied, and not the rocking rate per se, is key in mediating the effects of rocking on sleep.

Sleep orchestrates indices of local plasticity and global network stability in the human cortex.

Animals and humans spend on average one third of their lives in sleep, but its functions remain to be specified. Distinct lines of research propose that sleep promotes local strengthening of information-bearing synapses (plasticity) and global downscaling of synaptic strength (stability) in neural networks-prerequisites for adaptive behavior in a changing environment. However, the potential orchestration of these processes, particularly in humans, needs to be further characterized. Here, we use electrophysiological, behavioral, and molecular indices to noninvasively study cortical plasticity and network stability in humans. We observe indices of local strengthening of prior induced long-term potentiation-like plasticity (paired associative stimulation induced change in motor-evoked potential) and global network stabilization (homeostatic regulation of wake EEG theta activity) after brief periods of nonrapid eye movement sleep compared with wakefulness. The interplay of local sleep slow oscillations and spindle activity, previously related to synaptic refinements during sleep, is identified as a potential mechanism. Our findings are consistent with the notion that sleep-specific brain activity patterns reduce the plasticity-stability dilemma by orchestrating local plasticity and global stability of neural assemblies in the human cortex. Future studies are needed to further decipher the neural mechanisms underlying our indirect observations.

Daytime Acute Non-Visual Alerting Response in Brain Activity Occurs as a Result of Short- and Long-Wavelengths of Light

Abstract. Very recent preliminary findings concerning the alerting capacities of light stimulus with long-wavelengths suggest the existence of neural pathways other than melatonin suppression that trigger the nonvisual response. Though the nonvisual effects of light during the daytime have not been investigated thoroughly, they are definitely worth investigating. The purpose of the present study is to enrich existing evidence by describing how quantitative electroencephalography (EEG) signal analysis can give insight into the measurement of the acute nonvisual response observed in brain states generated during daytime exposure to light (when melatonin secretion is negligible). EEG changes were assessed in 19 subjects during the daytime while being exposed to both short- (blue, 72 μW/cm2) and long-wavelength (red, 18 μW/cm2) radiation. We showed that artificial light stimulus as low as 40 lux decreases the synchronization in the upper theta, lower alpha, and upper alpha EEG activity spectrum. The direction of change was consistent with an increased level of alertness. We can conclude that EEG analysis is an indicator of the acute nonvisual response to daytime light. Surprisingly, the response was more spread over the scalp during exposure to red light than to blue light. According to our study, the response to long-wavelength stimulus that inhibits sleepiness, thereby inducing alertness, also takes place at the bright part of the 24-hr day when human beings are naturally predisposed to be exposed to a high level of sunlight: between 12 and 4 PM. The absorption spectrum of the nonvisual system seems to have different characteristics than was previously suspected: it is not dominated by the short-wavelengths, but involves long-wavelengths. Since we observed the predominance of the red-light alerting effect over the blue-light in this experiment, we conclude that more than one mechanism, beyond the melatonin pathway, must be involved.

0245 Examining the Effects of Slow-wave Activity Disruption on Waking EEG Theta Activity

0245 Examining the Effects of Slow-wave Activity Disruption on Waking EEG Theta Activity

Two Different Populations within the Healthy Elderly: Lack of Conflict Detection in Those at Risk of Cognitive Decline.

During healthy aging, inhibitory processing is affected at the sensorial, perceptual, and cognitive levels. The assessment of event-related potentials (ERPs) during the Stroop task has been used to study age-related decline in the efficiency of inhibitory processes. Studies using ERPs have found that the P300 amplitude increases and the N500 amplitude is attenuated in healthy elderly adults compared to those in young adults. On the other hand, it has been reported that theta excess in resting EEG with eyes closed is a good predictor of cognitive decline during aging 7 years later, while a normal EEG increases the probability of not developing cognitive decline. The behavioral and ERP responses during a Counting-Stroop task were compared between 22 healthy elderly subjects with normal EEG (Normal-EEG group) and 22 healthy elderly subjects with an excess of EEG theta activity (Theta-EEG group). Behaviorally, the Normal-EEG group showed a higher behavioral interference effect than the Theta-EEG group. ERP patterns were different between the groups, and two facts are highlighted: (a) the P300 amplitude was higher in the Theta-EEG group, with both groups showing a P300 effect in almost all electrodes, and (b) the Theta-EEG group did not show an N500 effect. These results suggest that the diminishment in inhibitory control observed in the Theta-EEG group may be compensated by different processes in earlier stages, which would allow them to perform the task with similar efficiency to that of participants with a normal EEG. This study is the first to show that healthy elderly subjects with an excess of theta EEG activity not only are at risk of developing cognitive decline but already have a cognitive impairment.

Temporal Courses in EEG Theta and Alpha Activity in the Dynamic Health Qigong Techniques Wu Qin Xi and Liu Zi Jue.

Health Qigong is a common technique of Traditional Chinese Medicine applied to strengthen mental and physical health. Several studies report increases in EEG theta and alpha activity after meditative Qigong techniques indicating a relaxed state of mind. To date, little is known on the effects of dynamic Health Qigong techniques that comprise bodily movements on brain activity. In the current study, we compared effects of two dynamic Health Qigong techniques on EEG brain activity. Subjects performed the techniques Wu Qin Xi (five animals play) and Liu Zi Jue (six healing sounds) in a within-subjects design. Eyes-open and eyes-closed resting EEG was recorded before and immediately after each 15-min practice block. Additionally, the Profile of Mood States (POMS) questionnaire was administered at pretest, and after each 15-min practice block. Results show a decrease in alpha activity after 15 min, followed by an increase after 30 min in the Health Qigong technique Liu Zi Jue. Theta activity was decreased after 15 min, followed by an increase after 30 min in the technique Wu Qin Xi. Results of the POMS indicated an increased vigor-activity level with decreased fatigue and tension-anxiety levels in both techniques after 30 min of practice. Our results demonstrate different temporal dynamics in EEG theta and alpha activity for the Health Qigong techniques Wu Qin Xi and Liu Zi Jue. We hypothesize that the found brain activation patterns result from different attentional focusing styles and breathing techniques performed during the investigated Health Qigong techniques.