Lower Spectral Power Research Articles

Concussed Neural Signature is Substantially Different than Fatigue Neural Signature in Non-concussed Controls

Traumatic brain injuries can result in short-lived and long-lasting neurological impairment. Identifying the correct recovery timeframe is challenging, as balance-based metrics may be negatively impacted if testing is performed soon after exercise. Thirty-two healthy controls and seventeen concussed individuals performed a series of balance challenges, including virtual reality optical flow perturbation. The control group completed a backpacking protocol to induce moderate fatigue. Concussed participants had lower spectral power in the motor cortex and central sulcus when compared to fatigued controls. Moreover, concussed participants experienced a decrease in overall theta band spectral power while fatigued controls showed an increase in theta band spectral power. This neural signature may be useful to distinguish between concussed and non-concussed fatigued participants in future assessments.

Local sleep spindles in the human thalamus.

Sleep spindles have recently been shown to occur not only across multiple neocortical regions but also locally in restricted cortical areas. Here we show that local spindles are indeed present in the human posterior thalamus. Thalamic local spindles had lower spectral power than non-local ones. While non-local thalamic spindles had equal local and non-local cortical counterparts, local thalamic spindles had significantly more local cortical counterparts (i.e. occurring in a single cortical site). The preferential association of local thalamic and cortical spindles supports the notion of thalamocortical loops functioning in a modular way. Sleep spindles are believed to subserve many sleep-related functions, from memory consolidation to cortical development. Recent data using intracerebral recordings in humans have shown that they occur across multiple neocortical regions but may also be spatially restricted to specific brain areas (local spindles). The aim of this study was to characterize spindles at the level of the human posterior thalamus, with the hypothesis that, besides the global thalamic spindling activity usually observed, local spindles could also be present in the thalamus. Using intracranial, time-frequency EEG recordings in 17 epileptic patients, we assessed the distribution of thalamic spindles during natural sleep stages N2 and N3 in six thalamic nuclei. Local spindles (i.e. spindles present in a single pair of recording contacts) were observed in all the thalamic regions explored, and compared with non-local spindles in terms of intrinsic properties and cortical counterparts. Thalamic local and non-local spindles did not differ in density, frequency or duration, but local spindles had lower spectral power than non-local ones. Each thalamic spindle had a cortical counterpart. While non-local thalamic spindles had equal cortical local and non-local counterparts, local thalamic spindles had significantly more local cortical counterparts (i.e. occurring in a single cortical site). The preferential association of local thalamic and cortical spindles supports the notion of thalamocortical loops functioning in a modular way.

FKBP5 haplotypes and PTSD modulate the resting-state brain activity in Han Chinese adults who lost their only child

The stress-related gene FKBP5 has been related to dysregulated glucocorticoid receptor (GR) signaling, showing increased GR sensitivity in trauma-exposed subjects with post-traumatic stress disorder (PTSD) but not in those without PTSD. However, the neural mechanism underlying the effects of FKBP5 remains poorly understood. Two hundred and thirty-seven Han Chinese adults who had lost their only child were included. Four FKBP5 single nucleotide polymorphisms (rs3800373, rs9296158, rs1360780, and rs9470080) were genotyped. All 179 participants were successfully divided into three FKBP5 diplotype subgroups according to two major FKBP5 H1 and H2 yin yang haplotypes. Brain average spectral power was compared using a two-way (PTSD diagnosis and FKBP5 diplotypes) analysis of covariance within four separate frequency bands (slow-5, slow-4, slow-3, and slow-2). Adults with PTSD showed lower spectral power in bilateral parietal lobules in slow-4 and in left inferior frontal gyrus (IFG) in slow-5. There was significant FKBP5 diplotype main effect in anterior cingulate cortex (ACC) in slow-4 (H1/H1 higher than other two subgroups), and in precentral/postcentral gyri and middle cingulate cortex (MCC) in slow-3 (H2/H2 higher than other two subgroups). Also, there was a significant diagnosis × FKBP5 diplotype interaction effect in right parietal lobule in slow-3. These findings suggest that adults with PTSD have lower low-frequency power in executive control network regions. Lower power in ACC and greater power in the motor/sensory areas in FKBP5 high-risk diplotype group suggest a disturbance of emotional processing and hypervigilance/sensitization to threatening stimuli. The interaction effect of diagnosis × FKBP5 in parietal lobule may contribute to PTSD development.

Theta dominance in the power spectra of eeg in chronic neurogenic pain

To identify the theta over activity in power spectra of EEG in chronic neurogenic pain patients, spectral analysis of resting EEG of the patients (n=15, 41-64 years, median 48 years, 6 men) in the eye closed state was compared with that of healthy controls (n=15, 39-62 years, median 48 years, 6 men). The study was done with the approval of Institute Ethics Committee and after obtaining written informed consent from the study participants. The average power spectral density of all channels revealed higher spectral power (expressed as μV2/Hz) in the theta band (5-7 Hz frequency range) for the patient group (1.901 ± 1.687) when compared with that of the control group (1.559 ± 0.812). Lower spectral power in the alpha band (8-12 Hz frequency range) was also noted in the patient group (3.401±3.624) when compared to the control group (4.864±4.173). The limitation in sample size may have been the reason for not obtaining statistical significance (p value = 0.485 for theta power comparison and p value = 0.314 for alpha power comparison) for the differences noted between the two groups. Although the data obtained from power spectra of EEG is not confirmatory, increased theta activity and decreased alpha activity may underlie the pathophysiological mechanisms involved in chronic neurogenic pain.

Finger and forehead PPG signal comparison for respiratory rate estimation

Objective: An evaluation of the location of the photoplethysmogram (PPG) sensor for respiratory rate estimation is performed. Approach: Finger PPG, forehead PPG, and respiratory signal were simultaneously recorded from 35 subjects while breathing spontaneously, and during controlled respiration experiments at a constant rate from 0.1 Hz to 0.6 Hz, in 0.1 Hz steps. Four PPG-derived respiratory (PDR) signals were extracted from each one of the recorded PPG signals: pulse rate variability (PRV), pulse width variability, pulse amplitude variability and the respiratory-induced intensity variability (RIIV). Respiratory rate was estimated from each one of the four PDR signals for both PPG sensor locations. In addition, different combinations of PDR signals, power distribution of the respiratory frequency range and differences of the morphological parameters extracted from both PPG signals have been analysed. Main results: Results show better performance in terms of successful estimation and relative error when: (i) PPG signal is recorded in the finger; (ii) the respiratory rate is less than 0.4 Hz; (iii) RIIV signal is not considered. Furthermore, lower spectral power around the respiratory rate in the PDR signals recorded from the forehead was observed. Significance: These results suggest that respiratory rate estimation is better at lower rates (0.4 Hz and below) and that the finger is better than the forehead to estimate respiratory rate.

Features of EEG Spectral Parameters in Depressive Patients with Different Efficiencies of Decision-making

We analyzed the relationships between the EEG spectral parameters in depressed patients reflecting the functional state of the brain, and the efficiency of their decision-making based on both logic and emotional learning in order to clarify the neurophysiological mechanisms underlying decision-making impairments. As a result of multivariate cluster analysis based on 96 EEG spectral power parameters, two subgroups of depressive patients were identified. The groups differ in the EEG amplitude-frequency and spatial characteristics, but do not differ either in age or in severity of depression. The subgroup of depressive patients who formed cluster 2 and had higher spectral powers of the EEG ∆ (2–4 Hz), θ1 (4–6 Hz), θ2 (6–8 Hz), α1 (8–9 Hz) and α2 (9–11 Hz) subbands, as compared with the patients who formed cluster 1, had a higher level of cognitive test performance that requires decision-making: the Wisconsin Card Sorting Test (WCST), which evaluates logic-based decision-making, and the Iowa Gambling Task (IGT), which evaluates decision-making based on emotional learning. Cluster 2 patients also exhibited a better long-term memorization (in the ten-word long-term memory test) compared with those who formed cluster 1. Judging by the EEG parameters, the neurophysiological mechanisms of inhibition are more intact in patients forming cluster 2 than in cluster 1 patients who have lower spectral power values of the EEG ∆ (2–4 Hz), θ1 (4–6 Hz), θ2 (6–8 Hz), α1 (8–9 Hz), and α2 (9–11 Hz) subbands. The impairment of decision-making functions in depressive patients may, at least partially, be due to the deficit of the brain inhibition mechanisms that ensure normal integrative brain activity, including such higher mental functions as memory, attention, and decision-making.

Fractal properties of shoreline changes on a storm-exposed island

Extreme storm events and their consequent shoreline changes are of great importance for understanding coastal evolution and assessing storm hazards. This work investigates the fractal properties of the spatial distributions of shoreline changes caused by storms. Wavelet analysis and upper-truncated power law (UTPL) fitting are used to study the power spectra of shoreline changes and to evaluate the upper limits of the cross-shore erosion and accretion. During a period affected by storms, the alongshore shoreline change patterns are strong on the 15 km scale but are weak with lower spectral power on the 20 km scale. The areas adjacent to the eroded shoreline are usually accrete, and the cross-shore extent of erosion is larger than that of accretion when the coast is affected by storms. The fractal properties of shoreline changes due to storms are found to be temporally continuous: the effects of later storms build on the preceding shoreline conditions, including both the effects of previous storms and the subsequent shoreline recoveries. This work provides a new perspective on the various scales of the spatial variations of the morphodynamics of storm-affected shorelines.

Differences in brain activity during olfactory testing of female body odors between young men with and without sexual experience

Olfactory testing was performed in two groups of young men aged 18–22 years with and without sexual experience. Multichannel EEG was recorded at rest and upon the presentation of 45 natural body odors of young women in different phases of the menstrual cycle. The odors were either intact or mixed with J’Adore L’Absolu perfume (Christian Dior) with or without a female pheromone. Changes in spectral power within narrow frequency ranges in response to olfactory stimulation were estimated by multivariate analysis of variance. It was found that background electrical activity of the brain in young men with regular sex life had lower spectral power in all frequency ranges. The EEG responses to the intact olfactory stimuli in all young men were associated with a decrease in spectral power in the majority of the frequency ranges and especially in the θ2 and high- and low-frequency α rhythms. Presentation of female odors masked with a perfume resulted in bidirectional EEG responses; i.e., the spectral power in the θ1 and β1 ranges increased or decreased depending on the sexual experience of men and the menstrual cycle phase of a female donor as compared with an intact odor. The comparison of the EEG responses to intact or perfume-masked odors showed that individual odor remains dominant.

Electrical activity of the neocortex in adult rats after prenatal hypoxia and in epilepsy model

Changes in electrical activity of neocortex after prenatal hypoxia (day 14 of embryogenesis - E14, 7 % 02 for 3 hours) and these combined with intracortical microinjection of epileptogenic 4-aminopyridine (4-AP) have been studied in adult rats. We analyzed the frequency-time parameters of electrocorticogram (ECoG) during sleep and wakefulness as well as spike-wave discharge (SWD) in 4-AP-induced epileptiform model. The results showed that in rats subjected to prenatal hypoxia the theta rhythm had a lower frequency and sleep spindles were characterized by lower spectral power in low-frequency domain in comparison with the control group. In rats with prenatal pathology delayed onset of epileptiform activi- ty and altered frequency distribution of the spectral power of 4-AP-induced SWD were revealed.

Мозговые механизмы воображения при выполнении вербальных творческих задач

In the present study, EEG spectral analysis was used to examine the brain mechanisms of imagination in student actors and student non-actors under three experimental conditions: when subjects created a coherent story based on a presented picture (STORY), listed the details of the presented picture (DETAIL) and executed simple calculation while they looked at neutral background (COUNT). Statistical comparison of STORY and DETAIL conditions revealed significantly higher spectral power in alpha1 (7.5-10 Hz) and alpha2 (10-12.5 Hz) bands in the most of investigated cortical areas in actors and non-actors. By contrast, in comparisons STORY-COUNT and DETAIL-COUNT significantly lower spectral power in the same frequency bands in all investigated cortical areas in both groups was obtained. The most prominent differences in comparison STORY-DETAIL were revealed over the central parietal area. The most prominent differences in comparisons STORY-COUNT and DETAIL-COUNT were revealed mainly over the occipital areas. These EEG changes were found in both groups of subjects. Taking this fact into account we consider parietal areas to be stable element of the brain system which maintain verbal creativity in actors and non-actors. The discussion of our results with respect to those obtained in previous studies leads to conclusion that parietal areas are involved into the mechanism of selective inhibition of visual information processing during imagination.

Corticomuscular Coherence Reflects Interindividual Differences in the State of the Corticomuscular Network During Low-Level Static and Dynamic Forces

In the investigation of corticomuscular coherence (CMC), it remained unclear why some subjects do not present significant CMC. We predicted that such subjects will develop CMC as a result of learning as indexed by improved performance during a visuomotor task. We investigated CMC, cortical motor spectral power (SP), and performance in 14 subjects during isometric compensation of a static force or dynamic force (DF) with their right index finger. We compared data from the beginning of the experiment (Time-Period 1) and after learning (Time-Period 2). Eight subjects (Group CMC++) presented CMC during Period 1 which increased during Period 2. Six subjects (Group CMC-+) presented CMC only during Period 2. Group CMC-+ was "more desynchronized" (lower SP, and stronger task-related desynchronization) than Group CMC++. The performance was better in Group CMC++ than in Group CMC-+. Learning was associated with higher SP, higher CMC, and better performance in both groups. However, in the more complicated DF condition, Group CMC++ learned better than Group CMC-+. The present study demonstrates the presence of CMC in all subjects tested and evidence that this is due to the fact that individuals may fall into 2 different groups in terms of oscillatory motor control: Group CMC-+ presents CMC only after learning.

Association of EEG alpha variants and alpha power with alcohol dependence in Mexican American young adults

Several studies support an association between electroencephalogram (EEG) voltage and alcohol dependence. However, the distribution of EEG variants also appears to differ depending on an individual's ethnic heritage, suggesting significant genetic stratification of this EEG phenotype. The present study's aims were to investigate the incidence of EEG alpha variants and spectral power in the alpha frequency range in Mexican American young adults based on gender, and personal and family history of alcohol dependence. Clinical ratings (high-, medium-, and low alpha voltage variants) and spectral characteristics of the EEG in the alpha frequency range (7.5–12Hz) were investigated in young adult (age 18–25 years) Mexican American men (n=98) and women (n=138) who were recruited from the community. Nineteen percent (n=45) of the participants had a low-voltage alpha EEG variant, 18% had a high-voltage variant, and 63% had a medium-voltage variant. There were no significant differences in the distribution of the EEG variants based on family history of alcohol dependence. There was a significant relationship between gender and the three alpha variants (χ2=9.7; df=2; P<.008), and there were no male participants with alcohol dependence with high alpha variants (χ2=5.8; df=2; P<.056). Alcohol dependence, but not a family history of alcohol dependence, was associated with lower spectral power in the alpha frequency range in the right (F=4.4; df=1,96; P<.04) and left (F=5.3; df=1.96; P<.02) occipital areas in the men but not in the women. In conclusion, in this select population of Mexican American young adults, male gender and alcohol dependence are associated with an absence of high-voltage alpha variants and lower alpha power in the EEG. These data suggest that EEG low voltage, a highly heritable trait, may represent an important endophenotype in male Mexican Americans that may aid in linking brain function with genetic factors underlying alcohol dependence in this ethnic group.

Characteristics of the θ and α EEG Bands in 15- to 17-Year-Old Adolescents

A neurophysiological study included 16 males aged 15–17 years and 12 psychologically and neurologically healthy men. The EEG was recorded under conditions of quiet wakefulness (eyes closed), total activation (eyes open), and aversive acoustic stimulation. Under all conditions, the adolescents showed a significantly higher spectral power (SP) in the θ1 and θ2 EEG bands and a lower SP in the α1 and α2 bands as compared to the adults. Under all conditions and in all frequency bands, the level of interhemispheric coherence (ICOH) between the frontotemporal regions (F 7/8) in the adolescents significantly surpassed that in the adults, whereas, in all other areas, ICOH was lower than in the adults. The opening of the eyes and aversive acoustic stimulation were associated with a decrease in SP in all groups. This decrease was more pronounced in the θ1 and θ2 bands in the adolescents compared to the adults and less significant in the α2 band. The EEG was characterized by significant differences in both the initial parameters of the θ and α bands and their activation-induced reactive changes in the adolescents compared to the adults. This finding was explained by brain immaturity in the adolescents of this age group.

Comparisons of EEG spectral and correlation measures between healthy term and preterm infants

Continuous 12-hour electroencephalography (EEG)-sleep studies were acquired by a computerized monitoring system under environmentally controlled conditions for 2 groups of neonates. Eighteen healthy preterm infants at a postconceptional term age were matched to 18 term infants. These 2 groups were also matched for gender, race, and socioeconomic class. For the entire 12-hour recording, relative spectral power values (i.e., ratio of specific EEG power in specific frequency band compared to total EEG power) were significantly reduced in the preterm group for θ ( P ≤ .007), α ( P ≤ .001), and β ( P ≤ .018) frequency bands, while δ remained unchanged. Correlations between 91 pairs of EEG channels were also calculated and the preterm infants had significantly higher correlation values in 27 of the 91 pairs of channels ( P < .05); 14 interhemispheric, 8 intrahemispheric, and 5 sagittal combinations, while 3 intrahemispheric combinations were higher in the term group. Fewer functional neuronal aggregates generate less oscillatory potential (i.e., lower spectral power) in the θ through β frequency ranges in the preterm infant, while greater cortical connectivity (i.e., higher correlations) exists in many brain regions by postconceptional term ages in this group. These findings suggest a functional alteration in brain development of the preterm infant as a result of prolonged extrauterine experience and/or prematurity.