Neuroelectric Activity Research Articles

Comparing the effect of hypercapnia and hypoxia on the electroencephalogram during wakefulness

ObjectiveHypoxia has been postulated as a key mechanism for neurocognitive impairment in sleep-disordered breathing. However, the effect of hypoxia on the electroencephalogram (EEG) is not clear. MethodsWe examined quantitative EEG recordings from 20 normal volunteers under three 5-min ventilatory control protocols: progressive hypercapnia with iso-hyperoxia (pO2=150mmHg) (Protocol 1), progressive hypercapnia with iso-hypoxia (pO2=50mmHg) (Protocol 2), and progressive hypoxia with a CO2 scrubber in the circuit (Protocol 3). Each protocol started with a 5-min session of breathing room air as baseline. ResultsIn Protocol 1, compared to its baseline, iso-hyperoxia hypercapnia led to a lower Alpha% and higher Delta/Alpha (D/A) ratio. Similarly, in Protocol 2, the iso-hypoxia hypercapnia induced a higher Delta%, a lower Alpha% and higher D/A ratio. No difference was found in any EEG spectral band including the D/A ratio when Protocols 1 & 2 were compared. In Protocol 3, the Delta%, Alpha% and D/A ratio recorded during hypoxia were not significantly different from baseline. ConclusionsWe found that hypercapnia, but not hypoxia, may play a key role in slowing of the EEG in healthy humans. SignificanceHypercapnia may be a greater influence than hypoxia on brain neuroelectrical activities.

Automated EEG signal analysis for identification of epilepsy seizures and brain tumour

Electroencephalography (EEG) is a clinical test which records neuro-electrical activities generated by brain structures. EEG test results used to monitor brain diseases such as epilepsy seizure, brain tumours, toxic encephalopathies infections and cerebrovascular disorders. Due to the extreme variation in the EEG morphologies, manual analysis of the EEG signal is laborious, time consuming and requires skilled interpreters, who by the nature of the task are prone to subjective judegment and error. Further, manual analysis of the EEG results often fails to detect and uncover subtle features. This paper proposes an automated EEG analysis method by combining digital signal processing and neural network techniques, which will remove error and subjectivity associated with manual analysis and identifies the existence of epilepsy seizure and brain tumour diseases. The system uses multi-wavelet transform for feature extraction in which an input EEG signal is decomposed in a sub-signal. Irregularities and unpredictable fluctuations present in the decomposed signal are measured using approximate entropy. A feed-forward neural network is used to classify the EEG signal as a normal, epilepsy or brain tumour signal. The proposed technique is implemented and tested on data of 500 EEG signals for each disease. Results are promising, with classification accuracy of 98% for normal, 93% for epilepsy and 87% for brain tumour. Along with classification, the paper also highlights the EEG abnormalities associated with brain tumour and epilepsy seizure.

Exercise mode and executive function in older adults: An ERP study of task-switching

The purpose of this study was to investigate the relationship between exercise mode and executive function and its effect on behavior and neuroelectric activity. Forty-eight older adults were classified into open-skill, closed-skill, and irregular exercise groups based on their experience of exercise participation. Executive function was measured via a task-switching paradigm, in which the behavioral indices and event-related potentials elicited by task-switching were assessed. The results revealed that the exercise groups, regardless of the exercise mode, exhibited faster reaction times in both global and local switches than the irregular exercise group, regardless of the within-task conditions. Similarly, larger P3 amplitudes were observed in both exercise groups compared to the irregular exercise group. Moreover, additional facilitation effects of open-skill exercises on global switch costs were observed, whereas no differences in local switch costs were found among the three groups. The results replicate previous studies that have reported generally improved executive function after participation in exercises; additionally, they extend the current knowledge by indicating that these cognitive improvements in specific aspects of executive function could also be obtained from open-skill exercises.

Neuroelectrical Decomposition of Spontaneous Brain Activity Measured with Functional Magnetic Resonance Imaging

Spontaneous activity in the human brain occurs in complex spatiotemporal patterns that may reflect functionally specialized neural networks. Here, we propose a subspace analysis method to elucidate large-scale networks by the joint analysis of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) data. The new approach is based on the notion that the neuroelectrical activity underlying the fMRI signal may have EEG spectral features that report on regional neuronal dynamics and interregional interactions. Applying this approach to resting healthy adults, we indeed found characteristic spectral signatures in the EEG correlates of spontaneous fMRI signals at individual brain regions as well as the temporal synchronization among widely distributed regions. These spectral signatures not only allowed us to parcel the brain into clusters that resembled the brain's established functional subdivision, but also offered important clues for disentangling the involvement of individual regions in fMRI network activity.

Altered semantic integration in autism beyond language

Autism spectrum disorders (ASDs) are characterized by impaired communication, particularly pragmatic and semantic language, resulting in verbal comprehension deficits. Semantic processing in these conditions has been studied extensively, but mostly limited only to linguistic material. Emerging evidence, however, suggests that semantic integration deficits may extend beyond the verbal domain. Here, we explored cross-modal semantic integration using visual targets preceded by musical and linguistic cues. Particularly, we have recorded the event-related potentials to evaluate whether the N400 and late positive potential (LPP) components, two widely studied electrophysiological markers of semantic processing, are differently sensitive to congruence with respect to typically developing children. Seven ASD patients and seven neurotypical participants matched by age, education and intelligence quotient provided usable data. Neuroelectric activity was recorded in response to visual targets that were related or unrelated to a preceding spoken sentence or musical excerpt. The N400 was sensitive to semantic congruence in the controls but not the patients, whereas the LPP showed a complementary pattern. These results suggest that semantic processing in ASD children is also altered in the context of musical and visual stimuli, and point to a functional decoupling between the generators of the N400 and LPP, which may indicate delayed semantic processing. These novel findings underline the importance of exploring semantic integration across multiple modalities in ASDs and provide motivation for further investigation in large clinical samples.

Tracing the emergence of categorical speech perception in the human auditory system

Speech perception requires the effortless mapping from smooth, seemingly continuous changes in sound features into discrete perceptual units, a conversion exemplified in the phenomenon of categorical perception. Explaining how/when the human brain performs this acoustic-phonetic transformation remains an elusive problem in current models and theories of speech perception. In previous attempts to decipher the neural basis of speech perception, it is often unclear whether the alleged brain correlates reflect an underlying percept or merely changes in neural activity that covary with parameters of the stimulus. Here, we recorded neuroelectric activity generated at both cortical and subcortical levels of the auditory pathway elicited by a speech vowel continuum whose percept varied categorically from /u/ to /a/. This integrative approach allows us to characterize how various auditory structures code, transform, and ultimately render the perception of speech material as well as dissociate brain responses reflecting changes in stimulus acoustics from those that index true internalized percepts. We find that activity from the brainstem mirrors properties of the speech waveform with remarkable fidelity, reflecting progressive changes in speech acoustics but not the discrete phonetic classes reported behaviorally. In comparison, patterns of late cortical evoked activity contain information reflecting distinct perceptual categories and predict the abstract phonetic speech boundaries heard by listeners. Our findings demonstrate a critical transformation in neural speech representations between brainstem and early auditory cortex analogous to an acoustic-phonetic mapping necessary to generate categorical speech percepts. Analytic modeling demonstrates that a simple nonlinearity accounts for the transformation between early (subcortical) brain activity and subsequent cortical/behavioral responses to speech (>150-200 ms) thereby describing a plausible mechanism by which the brain achieves its acoustic-to-phonetic mapping. Results provide evidence that the neurophysiological underpinnings of categorical speech are present cortically by ~175 ms after sound enters the ear.

Neuromodulation of Early Multisensory Interactions in the Visual Cortex

Merging information derived from different sensory channels allows the brain to amplify minimal signals to reduce their ambiguity, thereby improving the ability of orienting to, detecting, and identifying environmental events. Although multisensory interactions have been mostly ascribed to the activity of higher-order heteromodal areas, multisensory convergence may arise even in primary sensory-specific areas located very early along the cortical processing stream. In three experiments, we investigated early multisensory interactions in lower-level visual areas, by using a novel approach, based on the coupling of behavioral stimulation with two noninvasive brain stimulation techniques, namely, TMS and transcranial direct current stimulation (tDCS). First, we showed that redundant multisensory stimuli can increase visual cortical excitability, as measured by means of phosphene induction by occipital TMS; such physiological enhancement is followed by a behavioral facilitation through the amplification of signal intensity in sensory-specific visual areas. The more sensory inputs are combined (i.e., trimodal vs. bimodal stimuli), the greater are the benefits on phosphene perception. Second, neuroelectrical activity changes induced by tDCS in the temporal and in the parietal cortices, but not in the occipital cortex, can further boost the multisensory enhancement of visual cortical excitability, by increasing the auditory and tactile inputs from temporal and parietal regions, respectively, to lower-level visual areas.

Computational representation of a realistic head and brain volume conductor model: electroencephalography simulation and visualization study

Computational head and brain volume conductor modeling is a practical and non-invasive method to investigate neuroelectrical activity in the brain. Anatomical structures included in a model affect the flow of volume currents and the resulting scalp surface potentials. The influence of different tissues within the head on scalp surface potentials was investigated by constructing five highly detailed, realistic head models from segmented and processed Visible Human Man digital images. The models were: (1) model with 20 different tissues, that is, skin, dense connective tissue (fat), aponeurosis (muscle), outer, middle and inner tables of the scalp, dura matter, arachnoid layer (including cerebrospinal fluid), pia matter, six cortical layers, eye tissue, muscle around the eye, optic nerve, temporal muscle, white matter and internal air, (2) model with three main inhomogeneities, that is, scalp, skull, brain, (3) model with homogeneous scalp and remaining inhomogeneities, (4) model with homogeneous skull and remaining inhomogeneities, and (5) model with homogeneous brain matter and remaining inhomogeneities. Scalp potentials because of three different dipolar sources in the parietal-occipital lobe were computed for all five models. Results of a forward solution revealed that tissues included in the model and the dipole source location directly affect the simulated scalp surface potentials. The major finding indicates that significant change in the scalp surface potentials is observed when the brain's distinctions are removed. The other modifications, for example, layers of the scalp and skull are important too, but they have less effect on the overall results.

Working memory training: Improving intelligence – Changing brain activity

The main objectives of the study were: to investigate whether training on working memory (WM) could improve fluid intelligence, and to investigate the effects WM training had on neuroelectric (electroencephalography – EEG) and hemodynamic (near-infrared spectroscopy – NIRS) patterns of brain activity. In a parallel group experimental design, respondents of the working memory group after 30h of training significantly increased performance on all tests of fluid intelligence. By contrast, respondents of the active control group (participating in a 30-h communication training course) showed no improvements in performance. The influence of WM training on patterns of neuroelectric brain activity was most pronounced in the theta and alpha bands. Theta and lower-1 alpha band synchronization was accompanied by increased lower-2 and upper alpha desynchronization. The hemodynamic patterns of brain activity after the training changed from higher right hemispheric activation to a balanced activity of both frontal areas. The neuroelectric as well as hemodynamic patterns of brain activity suggest that the training influenced WM maintenance functions as well as processes directed by the central executive. The changes in upper alpha band desynchronization could further indicate that processes related to long term memory were also influenced.

An Integrative Assessment of the Psychophysiologic Alterations in Young Women With Recurrent Major Depressive Disorder

Alterations in neuroelectrical activities coincide with major depressive disorder (MDD). This study examines the pattern of cerebral activity and cardiac autonomic parameters of euthymic women with recurrent MDD. Resting electroencephalograms and electrocardiograms were recorded from 20 women with MDD receiving escitalopram and 40 matched and healthy women. We computed frontal alpha asymmetry to evaluate the interhemispheric balance. Parameters of heart rate variability were extracted to assess cardiac autonomic control. Sample entropy was used to assess the complexity of neurocardiac dynamics. The relationship between cardiovagal activity and alpha electroencephalogram was examined with a coherence analysis. Multivariable analysis of variance revealed a differential pattern of psychophysiologic variables between MDD patients and controls (p = .03). MDD was associated with a tendency toward lower left frontal activity (-0.06 [standard deviation = 0.14] versus 0.04 [0.17] lnμV(2), p = .04). Discriminant analysis demonstrated more right frontal activation, a lower high-frequency heart rate power spectrum, and a higher ratio of the low- to high-frequency heart rate power spectrum in patients with MDD compared with controls. Residual depressive symptoms (r = -0.09 to 0.11, p = .63-.99) and escitalopram dosage (r = -0.09 to 0.28, p = .22-.84) were not correlated with autonomic measures. Coherence between normalized high-frequency component of the heart rate power spectrum and alpha power was not significant (F3, p = .27; F4, p = .16). Euthymic women with recurrent MDD have a distinctive psychophysiologic profile. This profile may reflect altered frontal activation and a reduced cardiovagal tone in depression.

Vertically aligned carbon nanofiber as nano-neuron interface for monitoring neural function

Neural chips, which are capable of simultaneous multisite neural recording and stimulation, have been used to detect and modulate neural activity for almost thirty years. As neural interfaces, neural chips provide dynamic functional information for neural decoding and neural control. By improving sensitivity and spatial resolution, nano-scale electrodes may revolutionize neural detection and modulation at cellular and molecular levels as nano-neuron interfaces. We developed a carbon-nanofiber neural chip with lithographically defined arrays of vertically aligned carbon nanofiber electrodes and demonstrated its capability of both stimulating and monitoring electrophysiological signals from brain tissues in vitro and monitoring dynamic information of neuroplasticity. This novel nano-neuron interface may potentially serve as a precise, informative, biocompatible, and dual-mode neural interface for monitoring of both neuroelectrical and neurochemical activity at the single-cell level and even inside the cell. From the Clinical EditorThe authors demonstrate the utility of a neural chip with lithographically defined arrays of vertically aligned carbon nanofiber electrodes. The new device can be used to stimulate and/or monitor signals from brain tissue in vitro and for monitoring dynamic information of neuroplasticity both intracellularly and at the single cell level including neuroelectrical and neurochemical activities.

A typology of human neuro-electric brain activity and its relation to personality and ability

La ricerca ha indagato la possibilitŕ di definire una tipologia di attivitŕ elettrica cerebrale, che potesse spiegare differenze di personalitŕ e abilitŕ. Misure di potenza e coerenza di 331 partecipanti, divise in 7 bande di frequenza determinate individualmente, sono state sottoposte ad analisi fattoriali, che hanno prodotto una soluzione ad 8 fattori. I coefficienti fattoriali Bartlett cosě ottenuti sono stati utilizzati come variabili di input per un'analisi "cluster". Questa analisi ha rivelato come ottimale una soluzione a 3 cluster. I 2 cluster piů numerosi (C1 e C2) differivano rispetto ai valori di potenza; il pattern di potenza e coerenza del cluster C3 era piů complesso. I 3 cluster ottenuti differivano anche rispetto alla variabili di abilitŕ e personalitŕ. Sono state osservate differenze nei pattern dei fattori di personalitŕ e abilitŕ, e in misura minore in un singolo fattore. Questi pattern erano piů omogenei per i fattori di personalitŕ e piů eterogenei per le abilita generali e per i fattori di intelligenza emozionale.

Responding to Unfair Offers Made by a Friend: Neuroelectrical Activity Changes in the Anterior Medial Prefrontal Cortex

When receiving unfair monetary offers from another person, the most common response is punishment. Existing literature on the Ultimatum Game indicates that individuals frequently refuse unfair offers even when this results in a loss for themselves. Here, we present behavioral and neurophysiological evidence demonstrating that friendship substantially modifies this response. When the proposer was a friend rather than an unknown person, unfair offers were less frequently rejected and the medial frontal negativity (MFN) typically associated with unfair offers was reversed to positive polarity. The underlying generators were located in inferior-mesial and right inferior- and medial-lateral frontal regions (BA10 and BA11). These findings highlight the fundamental role of the anterior prefrontal cortex in interpersonal economic interaction and, particularly, present new evidence on the effects of social distance on the MFN.

EEG-Based Cognitive Interfaces for Ubiquitous Applications: Developments and Challenges

Technical advances in the neuroelectric recordings and in the computational tools for the analysis of the brain activity and connectivity make it now possible to follow and to quantify, in real time, the interactive brain activity in a group of subjects engaged in social interactions. The degree of interaction between persons can then be assessed by "reading" their neuroelectric activities. Imaging the social brain can thus open a new area of study in neuroscience.

From social behaviour to brain synchronization: Review and perspectives in hyperscanning

Recently, the neuroscience field took a particular interest in the use of a neuroimaging technique called ‘hyperscanning’. This new technique consists in the simultaneous recording of the hemodynamic or neuroelectric activities of multiple subjects. Behind this small technical step lays a giant methodological leap. Groundbreaking insight in the understanding of social cognition shall be achieved if the right paradigms are implemented. A growing number of studies demonstrate the potential of this recent technique. In this paper, we will focus on current issues and future perspectives of brain studies using hyperscanning. We will also add to this review two studies initiated by Line Garnero. These studies will illustrate the promising possibilities offered by hyperscanning through two different key phenomena pertaining to social interaction: gesture imitation and joint attention.

The Effect of Temporal EEG Signals While Listening to Quran Recitation

Human brain which is one of the most complex organic systems, involves billons of interacting physiological and chemical process that will give rise to experimentally observed neuroelectrical activity, which is called an electroencephalogram (EEG). Many researchers have investigated the effect of various events to the EEG signals such as meditation and classical music [1]-[3]. From their analysis result, they claimed that meditation and classical music can help a person to be in relaxing conditions. This study is performed in order to extend the research findings of the effect of religious activities to the human brain. EEG signals from subject at rests, as well as in different cognitive states; listening to Quran recitation and listening to hard music are measured and analysed. Statistical analysis using SPSS software is performed in order to test the validity of obtained data. The analysis results from this study show that listening to Quran recitation can generate alpha wave and can help a person always in relax condition compared with listening to hard rock music.

Manifestações eletrofisiológicas em adultos com HIV/AIDS submetidos e não-submetidos à terapia anti-retroviral

auditory evoked potentials (AEP) assess the neuroelectric activity on the auditory pathway -from the auditory nerve to the cerebral cortex - in response to an acoustic stimulus or event. Studies have demonstrated electrophysiological abnormalities in individuals with HIV/AIDS. to characterize the hearing electrophysiological manifestations in adults with HIV/AIDS by comparing the results obtained in the group exposed to antiretroviral therapy with those obtained in the group not exposed to such treatment. electrophysiological evaluation of hearing (Auditory Brainstem Response - ABR, Auditory Middle Latency Response - AMLR and P300) was conducted in 56 individuals with HIV/AIDS: 24 participants composed group I (not exposed to antiretroviral treatment) and 32 participants composed group II (exposed to treatment). alterations in every AEP were observed in individuals with HIV/ AIDS, especially in the ABR. Indeed, the group exposed to antiretroviral treatment presented more alterations. individuals with HIV/AIDS may present alterations on the central and peripheral auditory nervous system. The group exposed to antiretroviral therapy presents more alterations on the brainstem auditory pathway.

Intrauterine tobacco exposure may alter auditory brainstem responses in newborns

This study of tobacco exposure and auditory processes was conducted in a predominantly low-income population of 40 pregnant women and their newborns. Urinary cotinine concentrations and self-reported smoking status were obtained from the mother during the first prenatal care visit. Auditory brainstem-evoked responses (ABRs) were recorded in neonates to assess neuroelectrical activity of the auditory nerve following a sound stimulus. Infants of mothers with the highest cotinine concentrations (> 1,000 ng/ml) responded at a rate that was four times greater (hazard ratio 4.1, 95% confidence interval 1.4-11.5) than infants of non-smoking mothers (cotinine <or= 15 ng/ml). Associations with more moderate cotinine concentrations (> 15-1,000 ng/ml) were not observed. Enhanced ABRs may disrupt auditory processes related to speech perception, negatively affecting reading and language development during childhood. The results suggest that tobacco exposure during pregnancy may impair auditory function.

Sequence effects in the Go/NoGo task: Inhibition and facilitation

Facilitation and inhibition are asymmetric aspects of attention that differentially affect response times (RTs), accuracy and neuroelectric activity in many experimental tasks. Both vary as a function of stimulus context, with stimulus repetitions, for example, often resulting in facilitation in terms of speed, accuracy or reduced neural activity. Although inhibition has been extensively studied in the Go/NoGo task, facilitation has been overlooked. Twenty healthy adults performed an adapted Go/NoGo task which manipulated levels of facilitation and inhibition. Event-related potential (ERP) and behavioural measures were averaged according to preceding stimulus sequences. Established Go/NoGo effects for N2 and P3 components were replicated. Behavioural and ERP measures, however, showed strong sequence effects. Correlates of facilitation included reduced P1 and N1 latencies, and topographic effects in P1, to Go stimulus repetitions. Manipulations of inhibitory load through increasing Go before NoGo stimuli resulted in incremental increases in N1, P2 and N2 latencies. Several additional ERP and RT measures showed quadratic effects, with indications of facilitation or inhibition which reversed towards the end of longer stimulus trains. The results suggest that both facilitatory and inhibitory processes underlie performance in the Go/NoGo task. As Go stimuli are typically more frequently repeated than NoGo stimuli, the two processes may be confounded when sequence effects are not considered. Additionally, analysing stimuli by context indicates that the timing of the Go-P3 latency is closely related to responses, and the prolongation of N1, P2 and N2 with increasing difficulty of inhibition supports a possible relation of these components to inhibition.

EEG-based assessment of vigilance regulation in patients with depression, and healthy controls

A recently presented approach suggested that manic behaviour could partly be interpreted as an autoregulatory attempt to stabilize vigilance regulation, which was found to be unstable in manic patients. In depressed patients, a hyperstable vigilance regulation was reported in one work, potentially explaining the typical withdrawal and sensation avoidance in depression. The study compares the vigilance regulation of depressed patients without medication (preliminary n=11; age: 33.1, SD 13.2) and age-, sex-, and education-matched healthy controls (preliminary n=11; age: 33.3, SD 13.3). Depressive symptoms, sleep quality and wakefulness are assessed (SCID-I, HAMD, BDI, MFI, SF-A, VAS). The awake resting EEGs are analyzed via an algorithm which classifies EEG segments into different vigilance stages, based on the frequency and topographical distribution of the neuroelectric activity. Depressive Patients showed significantly more higher vigilance stages (A1-A3) than healthy controls (p=0.032). The lower vigilance stages B2/3 occurred in 72.7% of the healthy controls, and in 36.4% of the depressive patients. When B2/3 stages occurred in depressive patients, it was later than in healthy controls (481.5 vs. 185.3 mean seconds). Preliminary results indicate that depressive patients differ from healthy controls regarding the vigilance regulation in showing fewer declines to low vigilance levels. Confirmatory tests will be conducted, if the survey sample size reaches n=30 per group.