On the origin of the EEG alpha rhythm.
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Alpha Rhythm↗
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[Contribution to dynamic study of the alpha rhythm].
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Alpha Rhythm↗
Individual differences in alpha rhythm responsivity: inter-task consistency and relationships to cardiovascular and dispositional variables.
Individual differences in EEG alpha rhythm responsivity were examined with respect to: (1) consistency of response across cognitive tasks; (2) relationships to cardiovascular responsivity; and (3) relationships to dispositional variables. Inter-task correlations revealed a significant degree of stability in subjects' alpha responses to four "sensory rejection" tasks: mental arithmetic, time estimation and imagining oneself as cold or warm. Individuals evidencing greater suppression of alpha activity during mental arithmetic also displayed greater heart rate increase and greater digital vasoconstriction, as well as obtaining higher scores on the Activity subscale of the EASI-III Temperament Survey and on the "Hard Striving" subscale of the Jenkins Activity Survey for Health Prediction, a measure of the Coronary-Prone Behavior Pattern. Alpha responsivity in the time estimation and warm imagery tasks was also associated with greater heart rate increase. The results suggest that alpha responsivity is related to individual differences affecting one's attentiveness or involvement in experimental tasks.
Alpha Rhythm↗
Human movement-related potentials vs desynchronization of EEG alpha rhythm: a high-resolution EEG study.
Movement-related potentials (MRPs) and event-related desynchronization (ERD) of alpha rhythm were investigated with an advanced high-resolution electroencephalographic technology (128 channels, surface Laplacian estimate, realistic head modeling). The working hypothesis was that MRPs and alpha ERD reflect different aspects of sensorimotor cortical processes. Both MRPs and alpha ERD modeled the responses of primary sensorimotor (M1-S1), supplementary motor (SMA), and posterior parietal (PP, area 5) areas during the preparation and execution of unilateral finger movements. Maximum responses were modeled in the contralateral M1-S1 during both preparation and execution of the movement. The SMA and PP responses were modeled mainly from the MRPs and alpha ERD, respectively. The modeled ipsilateral M1-S1 responses were larger and stronger in the alpha ERD than MRPs. These results may suggest that alpha ERD reflects changes in the background oscillatory activity in wide cortical sensorimotor areas, whereas MRPs represent mainly increased, task-specific responses of SMA and contralateral M1-S1.
Adult↗
[Alpha rhythm during open eye derivation in infantile brain damaged and normal children].
1. The behavior of the occipital alpha rhythm during open-eye derivation was studied on nine- to twelve-year-old boys of normal intelligence, of whom ten were free from brain injuries and eleven had been suffering from brain injuries in early childhood. 2. There was observed a marked tendency of the alpha index to differ in dependence upon the time of testing, the cause of which was believed to be a weakness of vigilance on the part of brain-injured children. 3. Application of this simple method of examination to group comparisons makes it possible to neurophysiologically determine an important part of chronic cerebropsychic axis syndromes.
Alpha Rhythm↗
EEG alpha rhythm and eyelid flutter.
A single case of one-to-one correspondence between eyelid flutter and EEG alpha rhythm is reported. It arose during a battery of experiments into possible personality correlates of eyelid conditioning, EEG evoked potential and skin potential habituation, involving over 400 subjects. The reported phenomenon lasted for one burst of 24 sec. and another of 6 sec. during 40 min. of recording on one subject. The observation is considered in the light of reported cases of links between EEG alpha and epileptic seizure and also between EEG alpha, Parkinsonism, and finger tremor. A time-keeping role for EEG alpha in the brain is postulated.
Adult↗
Is the alpha rhythm a control parameter for brain responses?
The main goal of the present study is to develop a conceptual analysis of alpha response in the brain based on single sweep evaluation. A new method was employed to estimate a set of single-sweep parameters and quantify the oscillatory behaviour of single, electroencephalograph (EEG) sweeps. It was aimed to demonstrate that brain alpha responses are governed by spontaneous alpha activity and to validate the principle of brain response excitability. Because the spontaneous alpha activity depends on both the topology of recording and the subject's age, topology and age models were used. Spontaneous and evoked alpha activity were recorded at frontal and occipital sites in three groups of subjects: 3-year-old children, young adults and middle-aged subjects. Amplitude, enhancement and phase-locking of single alpha responses to visual stimuli were analysed. Major results showed that; (1) visual alpha responses could be recorded only if the alpha rhythm was developed in the spontaneous EEG independent of electrode location; (2) middle-aged adults showed more expressed frontal spontaneous alpha activity in comparison with young adults; (3) accordingly, alpha responses with higher amplitude and stronger phase-locking were produced over the frontal brain area in middle-aged than young adults. These results validate the principle of brain response excitability and demonstrate that a shift towards frontal brain areas for both the spontaneous and evoked alpha activity occurs with increasing age in adults. The results are discussed in the context of the diffuse and distributed alpha system of the brain. Age-dependent changes in frontal alpha activity are suggested to be related to frontal brain functioning during aging.
Adult↗
On the presence of a peculiar alpha rhythm in the olfactory tubercle of waking armadillos.
A very regular 8-12 rhythm was found in the olfactory tubercle of the armadillo Chaetophractus villosus. The rhythm was observed during wakefulness. Considerable sinusoidal activity was also observed not only during wakefulness, but during synchronized (slow) and desynchronized (paradoxical) sleep. The significance of this novel rhythm is discussed together with considerations that establish an important difference between it and the other 'alpha rhythms' known.
Alpha Rhythm↗
EEG alpha rhythm, intention and oculomotor control.
A replication of Wertheim's (1981) visual pursuit tracking study examined the reactivity of the posterior EEG alpha rhythm to two tracking tasks. Twelve subjects visually tracked a light spot moving in a predictable or an unpredictable path. The EEG was recorded from O1, O2, P3, P4, T5, and T6, referenced to linked mastoids, and power for the alpha frequency band was calculated for 60 s trial epochs. Results showed significantly higher occipital and posterior temporal alpha power during the predictable tracking trials in agreement with Wertheim's findings. The significance of this for his attention/intention model is discussed.
Adult↗
Feedback control of human alpha rhythm from the central area.
Twenty subjects, aged 17 to 25, were given from 5 to 10 sessions of training in controlling alpha. They were divided into three groups, respectively reinforced for increasing alpha from the central area, reinforced for decreasing alpha from the central area, and given noncontingent reinforcement. Compared with the initial baseline, the alpha of the noncontingent subjects did not change, while those reinforced for increases were reliably higher and those reinforced for decreases reliably lower than the noncontingent group. A slight trend toward improvement during successive sessions was not reliable. Since the experiment was conducted in the Soviet Union, the subjects had no expectations of an "alpha experience." Although tests showed a slight elevation in mood at the end of the sessions, there were no differences among the groups. There was an increase in reports of fatigue after the training sessions. There were no reports of using visual or somatomotor maneuvers as a means of controlling alpha. Furthermore, alpha rhythm control was not found to be consistently correlated with changes in heart rate, respiration, or mood, as determined by cross-correlation analysis.
Adolescent↗
[Trajectories of alpha rhythm dipoles shifting over the human brain cortex].
Dynamic study of 3D localization of the equivalent current dipoles (ECD)--sources of the EEG alpha rhythm in the human brain was performed in seven subjects with closed eyes using a one-dipole model. An exact localization of ECDs was obtained by combination of EEG and MRI mapping that allowed tracing of ECD shifts over the cortex with 4 ms step. Our data confirmed localization of these ECDs mainly in the occipital cortex and revealed their successive shift over this area during generation of each alpha-wave. Typical trajectories of these shifts were revealed and quantitatively compared by the hierarchical cluster analysis. The data obtained directly proved periodical rhythmic alpha-wave spreading process in the human visual cortex and an external control of this process. The data are discussed in terms of the "scanning hypothesis" (Pitts W., McCulloch W.H. Bull. Math. Biophys. 1947. V. 9. P. 127) which predicted a certain functional meaning of the alpha activity for cortical processing of sensory information in the human brain.
Adult↗
Anticipatory electroencephalography alpha rhythm predicts subjective perception of pain intensity.
UNLABELLED: This high-resolution electroencephalography (EEG) study tested the hypothesis that the suppression of rolandic alpha power before predictable painful stimulation affects the subject's subsequent evaluation of pain intensity, as a reflection of the influence of expectancy processes on painful stimulus processing. High-resolution EEG data were recorded (126 channels) from 10 healthy adult volunteers during the expectancy of a painful CO(2)-laser stimulation at the right wrist. Surface laplacian estimation enhanced the EEG spatial information content over 6 scalp regions of interest (left frontal, right frontal, left central, right central, left parietal, and right parietal areas). Spectral power was computed for 3 alpha sub-bands with reference to the individual alpha frequency peak (about 5-7 Hz for alpha 1, 7-9 Hz for alpha 2, and 9-11 Hz for alpha 3). The suppression of the alpha power before the painful stimulation [as reflected by the event-related desynchronization (ERD)] indexed the anticipatory cortical processes. Results showed maximum (negative) correlations between the alpha 2 and alpha 3 ERD amplitude at the left central area and the subjective evaluation of pain intensity (P < .001). The stronger the anticipatory alpha 2 and alpha 3 ERD, the higher the subjective evaluation of pain intensity. For alpha 3, that correlation was confirmed even when the effect of habituation across the recording session was taken into account. These results suggest that the anticipatory suppression of the alpha rhythms over the contralateral primary sensorimotor cortex predicts subsequent subjects' evaluation of pain intensity, in line with its crucial role for the discrimination of that intensity. PERSPECTIVE: This electroencephalographic study showed that anticipatory activation/deactivation of sensorimotor cortex roughly predicts subjective evaluation of pain. This motivates further investigation on possible implications for the understanding of central chronic pain. Chronic pain patients might exaggerate the anticipatory activation of sensorimotor cortex to negligible pain stimuli.
Adult↗
The thalamus as the generator and modulator of EEG alpha rhythm: a combined PET/EEG study with lorazepam challenge in humans.
BACKGROUND: Purpose of this study was to investigate the functional relationship between electroencephalographic (EEG) alpha power and cerebral glucose metabolism before and after pharmacological alpha suppression by lorazepam. METHODS: Ten healthy male volunteers were examined undergoing two F18-fluorodeoxyglucose (18-FDG) positron emission tomography (PET) scans with simultaneous EEG recording: 1x placebo, 1x lorazepam. EEG power spectra were computed by means of Fourier analysis. The PET data were analyzed using SPM99, and the correlations between metabolism and alpha power were calculated for both conditions. RESULTS: The comparison lorazepam versus placebo revealed reduced glucose metabolism of the bilateral thalamus and adjacent subthalamic areas, the occipital cortex and temporo-insular areas (P < 0.001). EEG alpha power was reduced in all derivations (P < 0.001). Under placebo, there was a positive correlation between alpha power and metabolism of the bilateral thalamus and the occipital and adjacent parietal cortex (P < 0.001). Under lorazepam, the thalamic and parietal correlations were maintained, whereas the occipital correlation was no longer detectable (P < 0.001). The correlation analysis of the difference lorazepam-placebo showed the alpha power exclusively correlated with the thalamic activity (P < 0.0001). CONCLUSIONS: These results support the hypothesis of a close functional relationship between thalamic activity and alpha rhythm in humans mediated by corticothalamic loops which are independent of sensory afferences. The study paradigm could be a promising approach for the investigation of cortico-thalamo-cortical feedback loops in neuropsychiatric diseases.
Adult↗
Topographic quantitative analysis of the intrinsic alpha rhythm in chronic obstructive pulmonary disease.
Twenty-two patients with documented COPD and no other significant illnesses were studied to assess the effect of varying degrees of COPD on the intrinsic alpha rhythm. The severity of COPD was determined by spirometry with assessment of FEV1, FVC, and FEV1/FVC. The alpha frequency for COPD patients was slower than that which characterizes age equated normals and averages 1.6 S.D. below normative data base mean values (range -0.43 S.D. to -1.85 S.D.). Impairment of pulmonary functioning significantly correlated with the degree of alpha frequency slowing over the posterior cortical regions, and the slowest alpha frequencies occurred in those COPD patients with the lowest FEV1/FVC ratios. Impairment of cognitive functioning is thus an important clinical consideration in treatment of patients with COPD but may go unrecognized until late in the course of the disease.
Aged↗
Correlates of alpha rhythm in functional magnetic resonance imaging and near infrared spectroscopy.
We used simultaneous electroencephalogram-functional magnetic resonance imaging (EEG-fMRI) and EEG-near infrared spectroscopy (NIRS) to investigate whether changes of the posterior EEG alpha rhythm are correlated with changes in local cerebral blood oxygenation. Cross-correlation analysis of slowly fluctuating, spontaneous rhythms in the EEG and the fMRI signal revealed an inverse relationship between alpha activity and the fMRI-blood oxygen level dependent signal in the occipital cortex. The NIRS-EEG measurements demonstrated a positive cross-correlation in occipital cortex between alpha activity and concentration changes of deoxygenated hemoglobin, which peaked at a relative shift of about 8 s. Our data suggest that alpha activity in the occipital cortex is associated with metabolic deactivation. Mapping of spontaneously synchronizing distributed neuronal networks is thus shown to be feasible.
Adult↗
[The characteristics of the alpha-rhythm electroencephalogram in patients with liver cirrhosis].
The brain functional state in patients with liver cirrhosis was investigated, the correlational dependence between the intrinsically present alpha-rhythm of electroencephalogram pattern of examined patients and the brain reactions signs while the functional tests conduction was studied up. The data obtained are compared with the results of such investigations, conducted in healthy persons. The results of investigations witness the brain functional possibilities lowering in patients with liver cirrhosis. The test with photostimulation is pathognomonic for this disease.
Adult↗
Magnetoencephalography: evidence of magnetic fields produced by alpha-rhythm currents.
Weak alternating magnetic fields outside the human scalp, produced by alpha-rhythm currents, are demonstrated. Subject ard magnetic detector were housed in a multilayer magnetically shielded chamber. Background magnetic noise was reduced by signal-averaging. The fields near the scalp are about 1 x 10(-9) gauss (peak to peak). A course distribution shows left-right symmetry for the particular averaging technique used here.
Brain↗
[Possible mechanism of the thalamic pacemaker of alpha-rhythm and fusiform activity].
Proceedings from the analysis of known experimental data on theta-rhythm (fusiform activity) a determinate model of its generator is proposed. It is based on the mechanism of beats frequencies. The model consists of 2 united identical moduli generating harmonic (rhythmical) oscillations alpha-rhythms of approximating frequencies v1 and v2 = v1 + delta v. The working regime of the generator is determined by the trigger pulse frequency. The proposed quantitative relationships between theta-rhythm parameters--T, n and frequencies of constituent oscillations v and delta v are checked up by analysing oscillograms of barbiturate activity in EEG of dogs. The results obtained are in favour of determinate rather than stochastic mechanism of theta-rhythm.
Alpha Rhythm↗