A New Method for Self-Regulation of Slow Cortical Potentials in a Timed Paradigm

A new method of slow cortical potential (SCP) biofeedback is described, in which subjects were presented with a sequence of two alternating tones. Subjects learned to adjust their SCPs with the 4-s rhythm of presented tones by producing directed SCP changes only in certain inter-tone intervals. Specifically, they learned to simultaneously produce two EEG signals: 1) positive or negative SCP shift at vertex, and 2) SCP asymmetry between the right and the left central area. After one training session, 13 healthy participants were able to differentiate significantly between the negativity and the positivity conditions; this differentiation was achieved within less than 300 ms after the discriminative signal, i.e. much faster than in previous studies employing traditional SCP biofeedback technique. However, these participants did not produce a significant hemispheric asymmetry in the first session. In the second experiment, five subjects participated in prolonged training (6 to 17 sessions). Highly significant control of SCP asymmetry over the precentral cortex was attained in four out of five participants. Advantages and disadvantages of the new method as compared with the classical SCP biofeedback technique are discussed.     

Deactivation of Brain Areas During Self-Regulation of Slow Cortical Potentials in Seizure Patients

This study investigates the neurophysiological basis of EEG feedback for patients with epilepsy. Brain areas are identified that become hemodynamically deactivated when epilepsy patients, trained in EEG self-regulation, generate positive slow cortical potentials (SCPs). Five patients were trained in producing positive SCPs, using a training protocol previously established to reduce seizure frequency in patients with drug refractory epilepsy. Patients attempted to produce positive SCP shifts in a functional magnetic resonance imaging (fMRI) scanner. Two patients were able to reliably produce positive SCP shifts. When these successful regulators were prompted to produce positive SCPs, blood oxygen level-dependent (BOLD) response indicated deactivation, in comparison to a control state, around the recording electrode, frontal lobe, and thalamus. Unsuccessful regulators’ BOLD response indicated no deactivation in cortical areas proximal to the active electrode. No thalamic deactivation was found in poor regulators. Decreased seizure frequency from SCP training may be the result of positively reinforced inhibition in cortical areas proximal to active electrode placement, the frontal cortex, and the thalamus.     

Self-regulation of Slow Cortical Potentials in Children with Migraine: An Exploratory Study

Migraine patients are characterized by increased amplitudes of slow cortical potentials (SCPs), representing pronounced excitability of cortical networks. The present study investigated the efficiency of biofeedback training of SCPs in young migraineurs. Ten children suffering from migraine without aura participated in 10 feedback sessions. They were compared with 10 healthy children for regulation abilities of cortical negativity and with 10 migraineurs from the waiting list for clinical efficacy. During the first two sessions, the migraine children were characterised by lacking ability to control cortical negativity, especially during transfer trials, compared with healthy controls. However, there was no difference following 10 sessions of training. Feedback training was accompanied by significant reduction of cortical excitability. This was probably responsible for the clinical efficacy of the training; a significant reduction of days with migraine and other headache parameters was observed. It is suggested that normalization of the threshold regulation of cortical excitability during feedback training may result in clinical improvement.     

Slow cortical potential biofeedback and the startle reflex

The negativity of slow cortical potentials (SCP) of the surface EEG is a measure of brain excitability, correlating with motor and cognitive preparation. Selfcontrol of SCP positivity has been shown to reduce seizure activity. Following SCP biofeedback from a central EEG electrode position, subjects gained bidirectional control over their SCP. The current study used a modified feedback methodology, and found a positive relationship between negativity and magnitude of EMG startle response (a measure of cortical and subcortical arousal, particularly aversive response disposition). Greater success in SCP differentiation was associated with self-report of less relaxation during negativity training.This research was supported by the Deutsche Forschungsgemeinschaft under grant No. SFB 307.     

Behavioral Psychophysiological Intervention in a Mentally Retarded Epileptic Patient with Brain Lesion

Behavioral psychophysiological treatment entailing Slow Cortical Potential (SCP) biofeed-back training and behavioral self-control training was conducted with a 27-year-old male epileptic patient (seizures for 23 years) with Wechsler IQ 64 who underwent callosotomy. The patient had 12/week secondary generalized tonic-clonic seizures. The treatment, consisting of 43 SCP training sessions and 22 behavioral control sessions, yielded a highly significant reduction of seizure frequency to about 7.5/week; such a decrease had never been observed after administration of new anticonvulsant drugs, nor after the callosotomy. During SCP feedback training, the patient was able to produce highly-significant cortical differentiation of SCPs of about 4 µV. In addition, he developed several new behaviors indicating growing ability of self-perception and self-regulation. These findings suggest that a combination of SCP biofeedback with behavioral treatment of epilepsy can be used even in mentally retarded patients with organic brain disorders.     

功率谱熵在痫性发作大鼠脑电检测中的应用研究

目的:研究功率谱熵在痫性发作大鼠脑电检测中的应用。方法:采用青霉素在大鼠海马微注射制备急性痫性发作模型,以深部电极记录大鼠原始脑电信号,将24只SD大鼠随机分成四组,即正常组(A),对照组(B),单电极组(C),多电极组(D)。C、D组大鼠经致痫后观察未发作期、发作前期、发作期和发作后期四期脑电信号的变化,运用谱熵对四期脑电信号进行分析,并与A、B组进行对比。结果:C组和D组脑电功率谱熵显示两组发作期与未发作期、发作前期、发作后期比较有显著差异(P0.05),发作期明显低于其它各期;未发作期和发作前期相比有明显差异(P0.05),发作前期较未发作期降低;将D组大鼠海马致痫灶(a)及其同侧附近(b)、对侧(c)三点发作各期脑电功率谱熵进行对比分析,发作前期和发作期a、b、c三点比较有明显差异(P0.05),a点最低,c点的功率谱熵值最高。结论:功率谱熵可以预报痫性发作并可对癫痫病灶的定位提供一定的帮助。     

Electroencephalographic Biofeedback in the Treatment of Attention-Deficit/Hyperactivity Disorder

Historically, pharmacological treatments for attention-deficit/hyperactivity disorder (ADHD) have been considered to be the only type of interventions effective for reducing the core symptoms of this condition. However, during the past three decades, a series of case and controlled group studies examining the effects of EEG biofeedback have reported improved attention and behavioral control, increased cortical activation on quantitative electroencephalographic examination, and gains on tests of intelligence and academic achievement in response to this type of treatment. This review paper critically examines the empirical evidence, applying the efficacy guidelines jointly established by the Association for Applied Psychophysiology and Biofeedback (AAPB) and the International Society for Neuronal Regulation (ISNR). On the basis of these scientific principles, EEG biofeedback was determined to be “probably efficacious” for the treatment of ADHD. Although significant clinical improvement was reported in approximately 75% of the patients in each of the published research studies, additional randomized, controlled group studies are needed in order to provide a better estimate of the percentage of patients with ADHD who will demonstrate such gains in clinical practice.     

Brain Source Imaging in Preclinical Rat Models of Focal Epilepsy using High-Resolution EEG Recordings

Electroencephalogram (EEG) has been traditionally used to determine which brain regions are the most likely candidates for resection in patients with focal epilepsy. This methodology relies on the assumption that seizures originate from the same regions of the brain from which interictal epileptiform discharges (IEDs) emerge. Preclinical models are very useful to find correlates between IED locations and the actual regions underlying seizure initiation in focal epilepsy. Rats have been commonly used in preclinical studies of epilepsy¹; hence, there exist a large variety of models for focal epilepsy in this particular species. However, it is challenging to record multichannel EEG and to perform brain source imaging in such a small animal. To overcome this issue, we combine a patented-technology to obtain 32-channel EEG recordings from rodents² and an MRI probabilistic atlas for brain anatomical structures in Wistar rats to perform brain source imaging. In this video, we introduce the procedures to acquire multichannel EEG from Wistar rats with focal cortical dysplasia, and describe the steps both to define the volume conductor model from the MRI atlas and to uniquely determine the IEDs. Finally, we validate the whole methodology by obtaining brain source images of IEDs and compare them with those obtained at different time frames during the seizure onset.     

Modifications of Visual Evoked Potentials in Patients with Glaucoma

We compared the visual evoked EEG potentials (VEP) elicited by presentation of a reversal chess pattern in patients with glaucoma and in the control group. Amplitudes, peak latencies of the main VEP components (N75, P100, and N145), interpeak intervals, and interpeak magnitudes were measured, and a spectral analysis of the averaged VEP was performed. In patients suffering from glaucoma, the latencies of the N75 and P100 components were greater, while the interpeak intervals P100-N145 and N75-N145 were shorter, than those in the control group. Glaucoma-related changes in the VEP spectral characteristics, in particular a drop in the spectral power of oscillations corresponding to the alpha rhythm, were observed.     

Cortical Source Analysis of High-Density EEG Recordings in Children

EEG is traditionally described as a neuroimaging technique with high temporal and low spatial resolution. Recent advances in biophysical modelling and signal processing make it possible to exploit information from other imaging modalities like structural MRI that provide high spatial resolution to overcome this constraint¹. This is especially useful for investigations that require high resolution in the temporal as well as spatial domain. In addition, due to the easy application and low cost of EEG recordings, EEG is often the method of choice when working with populations, such as young children, that do not tolerate functional MRI scans well. However, in order to investigate which neural substrates are involved, anatomical information from structural MRI is still needed. Most EEG analysis packages work with standard head models that are based on adult anatomy. The accuracy of these models when used for children is limited², because the composition and spatial configuration of head tissues changes dramatically over development³. In the present paper, we provide an overview of our recent work in utilizing head models based on individual structural MRI scans or age specific head models to reconstruct the cortical generators of high density EEG. This article describes how EEG recordings are acquired, processed, and analyzed with pediatric populations at the London Baby Lab, including laboratory setup, task design, EEG preprocessing, MRI processing, and EEG channel level and source analysis.      

Statistical Comparison of Band Spectral Power: An Aid in Stochastical Analysis of Brain Electrical Activity Part 1: Approximation of the distribution of broad band power by a χ2-distribution

In this study the distribution of estimated broad band spectral power is evaluated. Under weak assumptions it is possible to appropriate this distribution by a χ2-distribution and to construct tolerance intervals with great statistical accuracy. The theoretical results implicate a new methodical basis for statistical comparison of spectral parameters in EEG analysis.     

Hyperventilation Test-Related Changes of EEG in Children: Peculiarities Detected Using Periodometric Analysis

Computer periodometric analysis of EEG recorded from 169 healthy schoolchildren allowed us to calculate the quantitative indices characterizing the direction and intensity of dynamic changes in cerebral electrical activity induced by a hyperventilation test. Three main types of EEG reactions to hyperventilation observed in children of different age groups have been classified. The dependence of the frequency of types of EEG reactions of healthy children to the hyperventilation test on the age of the tested subjects and EEG type in the resting state was demonstrated.     

Effects of 45-Hz magnetic fields on the functional state of the human brain

The influence of sinusoidal 45-Hz magnetic fields on the brain functions of 20 volunteers was investigated in a double-blind study using spectral analysis of EEG and measurements of Omega potentials and reaction time (RT). The field strength was 1,000 A/m (1.26 mT) and the duration of exposure was 1 h. Ten volunteers were exposed to a continuous field and ten received an intermittent exposure (1 s on/1 s off). Each person received one real and one sham exposure. One half of the volunteers got the real exposure first and the sham treatment after at least 24 h. For the rest, the sequence was inverse. The measurements of EEG, omega potentials and RT were performed before and after each exposure. Several statistically significant changes were observed, most of them after intermittent exposure. In the EEG, an increase of alpha (7.6–13.9 Hz) activity and a decrease of delta (1.5–3.9 Hz) activity were observed. β waves (14.2–20 Hz) increased in the frontal derivations as did the total power in occipital derivations. The mean and peak frequencies of EEG increased mainly in the frontal derivations. No direct effects on RT were seen. Learning to perform the RT test (decrease of RT in repeated trials), however, seemed to be affected by the exposure. The persons who received real exposure first learned more slowly than those who got sham exposure first. Further experiments are necessary to confirm the findings and for understanding the mechanisms of the effects. © 1993 Wiley-Liss. Inc.     

Correlation between the Activity of Dopaminergic Neurons of the Ventral Tegmentum and Spectral Power of the EEG Rhythms in Awake Cats

We studied correlations between the frequency of background impulse activity (BIA) of dopaminergic (DAergic) neurons of the ventral tegmentum (VT) and spectral power (SP) of the frequency components of EEG samples recorded in awake cats. The EEG was recorded monopolarly (electrodes were fixed in the cranial bones) from the frontal, occipital, and right and left temporal regions of the cortex. In a great majority of the cases, the BIA frequency of VT DA-ergic neurons demonstrated significant positive correlations with changes in the SPs of the alpha and beta EEG rhythms. The closest correlations of the spiking frequency of DA-ergic cells with the SP of the alpha rhythm was observed in the occipital region, while those with the beta SP were found in the frontal area. Correlations of the activity of DA-ergic neurons with the SPs of the alpha and beta rhythms in the left temporal cortical zone were closer, as compared with those in the symmetrical right zone. Correlations of the SPs of the delta, theta, and gamma EEG components with the discharge frequency of VT DA neurons were of opposite directions, and in most cases such correlations did not reach the level of significance. The results of this study show that, in some cases, specific EEG patterns can be considered indicators of the state of the cerebral VT DA-ergic system. Neirofiziologiya/Neurophysiology, Vol. 40, No. 4, pp. 359–367, July–August, 2008.     

EEG Spectral Analysis of Relaxation Techniques

The acute central nervous system effects of relaxation techniques (RT) have not been systematically studied. We conducted a controlled, randomized study of the central nervous system effects of RT using spectral analysis of EEG activity. Thirty-six subjects were randomized to either RT or a music comparison condition. After listening to an RT audiotape or music audiotapes daily for 6 weeks, the acute central nervous system effects of RT and music were measured using power spectral analysis of alpha and theta EEG activity in all cortical regions. RT produced significantly greater increases in theta activity in multiple cortical regions compared to the music condition. These findings are consistent with widespread reductions in cortical arousal during RT. They extend previous findings and suggest that theta, and not alpha, EEG may be the most reliable marker of the central nervous system effects of RT. These findings demonstrate that RT produce greater reductions in central nervous system activity than a credible comparison condition. The findings suggest that RT represent a hypoactive central nervous system state that may be similar to Stage 1 sleep and that RT may exert their therapeutic effects, in part, through cerebral energy conservation/restoration.     

Event-related Potentials During Target-response Tasks to Study Cognitive Processes of Upper Limb Use in Children with Unilateral Cerebral Palsy

Unilateral Cerebral Palsy (CP) is a neurodevelopmental disorder that is a very common cause of disability in childhood. It is characterized by unilateral motor impairments that are frequently dominated in the upper limb. In addition to a reduced movement capacity of the affected upper limb, several children with unilateral CP show a reduced awareness of the remaining movement capacity of that limb. This phenomenon of disregarding the preserved capacity of the affected upper limb is regularly referred to as Developmental Disregard (DD). Different theories have been postulated to explain DD, each suggesting slightly different guidelines for therapy. Still, cognitive processes that might additionally contribute to DD in children with unilateral CP have never been directly studied. The current protocol was developed to study cognitive aspects involved in upper limb control in children with unilateral CP with and without DD. This was done by recording event-related potentials (ERPs) extracted from the ongoing EEG during target-response tasks asking for a hand-movement response. ERPs consist of several components, each of them associated with a well-defined cognitive process (e.g., the N1 with early attention processes, the N2 with cognitive control and the P3 with cognitive load and mental effort). Due to its excellent temporal resolution, the ERP technique enables to study several covert cognitive processes preceding overt motor responses and thus allows insight into the cognitive processes that might contribute to the phenomenon of DD. Using this protocol adds a new level of explanation to existing behavioral studies and opens new avenues to the broader implementation of research on cognitive aspects of developmental movement restrictions in children.     

Correlations between the content of toxic and essential metals in the organism and characteristics of EEG potentials in youths under conditions of an urban environment

In 18-to 19-year-old students, the content of a number of microelements, as well as of calcium, in biologically stable tissues (hair samples) was measured using X-ray fluorescent analysis. In the tested persons, we observed a certain deficit of main elements (calcium, copper, and zinc), while in some persons the levels of toxic lead and strontium were exceeded. Correlation analysis of the parameters of EEG potentials (current EEG and evoked and event-related potentials, EPs and ERPs, respectively) showed the existence of a few significant (or close to those) correlations of the spectral powers of some rhythms and derivatives of a few indices of the background EEG and more numerous cases of correlations of the parameters of EPs and ERPs (latencies and amplitudes) with the contents of the studied elements. The physiological importance of metals, according to the number of characteristics of EEG potentials that correlate with their contents, can be arranged in descending order as follows: As, Zn > Ca > Cd > Pb > Sr. None of the studied parameters of EEG phenomena correlated with the level of copper. The strength of correlations varied from weak to mild (0.29 < R < 0.50). The densest correlations were observed for the concentrations of toxic lead and cadmium. With respect to the characteristics of ERPs, some of the elements under study demonstrated synergism (e.g., lead and arsenic), while others were in an antagonistic relation (cadmium and calcium). Neirofiziologiya/Neurophysiology, Vol. 38, No. 2, pp. 167–174, March–April, 2006.     

Correlation of the characteristics of EEG potentials with the indices of attention in 12-to 13-year-old children

We studied correlations of the spectral characteristics of EEG with the indices characterizing the level of attention in 60 children (12 to 13 years old). Indices of voluntary attention were measured using a complex of psychological tests, including a Bourdon’s test (correcture test), a two-stimulus go/no-go test, a computer test (a modification of the Bourdon’s test for characterization of concentration and stability of attention), and Schulte’s tables. Children manifesting a good working ability (corresponding to the results of the go/no-go test and correcture test) showed relatively high values of the ratio of spectral powers (SPs) of the beta 1 and theta rhythms. These ratios were greater in the right hemisphere; this is probably indicative of a greater contribution of neuronal mechanisms of this hemisphere to providing watchfulness and stability of attention. Children demonstrating increased impulsivity (according to the results of the go/no-go test) were characterized by low modal frequencies of the alpha rhythm in the occipital brain regions, while children with relatively high values of this frequency in various cerebral regions demonstrated high indices of attentiveness and rates of the cognitive processes. Children performing the test task with especially high accuracy were characterized by high ratios of SPs of the low-frequency beta rhythm vs theta rhythm (mostly in the central and parietal regions of both hemispheres). The approach we have applied can be used for measuring the objective indices characterizing the state of the attention sphere in children. Neirofiziologiya/Neurophysiology, Vol. 38, No. 3, pp. 248–256, May–June, 2006.