Developmental transition of EEG spectra to alpha band in a sample of children with developmental disabilities

Developmental transition of EEG spectra to alpha band of 14 children with developmental disabilities (from 7 yr. and 3 mo. to 16 yr. and 1 mo. of age at the first EEG recording: M= 13.2, SD=2.6; 6 girls and 8 boys) was studied by auto-power spectrum analysis longitudinally. The results showed the mean age (14.1 yr. to 14.8 yr. in the four regions of the frontal, central, parietal, and occipital regions) for subjects and their mean frequency (4.2 Hz to 4.7 Hz in the 4 regions) at which EEG shift started from theta band, and those means (15.1 yr. to 15.7 yr. and 9.5 Hz to 9.6 Hz in the 4 regions) at which EEG shift reached the alpha band. Prior EEG research on healthy children has shown that approximately 10 years of age is critical for developmental transition of EEG spectra to alpha frequencies. It is suggested that the present data showed a delay of this critical age for this sample of children with developmental disabilities relative to 10 years for healthy children reported by Katada, et al. and Benninger, et al.     

Intellectual disabilities and developmental EEG transition to alpha band: a comment on Shibagaki, et al. (2006)

In 2006 Shibagaki, et al. estimated mean chronological age at which dominant EEG frequency reached alpha band in 11 children with intellectual disabilities (M age, 15 yr.). Consistent with previous studies, the results showed a delay in the critical age relative to healthy children and earlier maturation at posterior scalp sites, with the exception of several children who persistently showed EEG slower than alpha band. A flaw in the study might be that having only 2 children younger than 10 yr. was insufficient. A remaining problem for researchers would be to identify whether the developmental delay in EEG correlates with IQ in intellectually disabled children.     

Frontal EEG alpha band asymmetry as a predictor of reasoning deficiency in depressed people

Cognitive deficits in depression are mostly apparent in executive functions, especially when integration of information and reasoning is required. In parallel, there are also numerous studies pointing to the frontal alpha band asymmetry as a psychophysiological marker of depression. In this study, we explored the role of frontal alpha asymmetry as a potential factor explaining the cognitive problems accompanying depression. Twenty-six depressed and 26 control participants completed a reasoning task and underwent 5 minutes of electroencephalography recording. In line with the previous studies, depressed people showed difficulties with reasoning but we did not observe the relationship between frontal asymmetry in the alpha band and depression. However, we found that in the depressed group the frontal alpha asymmetry index was characterised by larger variance than in the control group, and it was also a strong predictor of cognitive functioning exclusively in the depressed group. Our results point to the disruption of a psychophysiological balance, reflected in changed frontal alpha asymmetry (into more left-sided frontal asymmetry in the alpha band, reflecting more right-sided cortical activity) as a possible brain correlate of cognitive disturbances present in depressive disorders.     

EEG alpha asymmetry and creativity

Results of 3 experiments examining the relationship between creativity and left-hemisphere and right-hemisphere EEG activity are reported. Creativity has been hypothesized to involve the use of primary-process cognition, and such cognition is hypothetically accompanied by activation of the right cerebral hemisphere. In light of these hypotheses, we predicted that highly-creative people should exhibit greater right-hemisphere than left-hemisphere EEG activity during creative performance and that this pattern would not be found in less-creative people. All 3 experiments supported this prediction. This difference in asymmetry was specific to creative performance. It was not present during basal recordings or during a non-creative task.     

EEG alpha reactivity and extraversion-introversion

Spectral characteristics of spontaneous EEG and characteristics of the alpha attenuation response (AAR) induced by acoustic stimulation, were analyzed for two groups of subjects selected on the basis of their scores on the extraversion-introversion scale of the Eysenck Personality Questionnaire. While no significant differences were found in basic alpha rhythm, significant differences were manifested in the AAR characteristics. Extraverted subjects habituated to the auditory stimulus while introverts did not. Introverts were generally more responsive to stimulation. The results are discussed in relation to the arousability model proposed by Eysenck and Gray, verifying the relationships with typological dimensions of Superior Nervous Activity, elaborated by the Soviet school.     

Parametric interactions in EEG period analysis

Off-line statistical analysis of computer-generated EEG period distribution parameters indicates the presence of important interactions within the traditional frequency bands and that confounded psychological variables null out highly significant results.     

Psychophysics of EEG alpha state discrimination

Nearly all research in neurofeedback since the 1960s has focused on training voluntary control over EEG constructs. By contrast, EEG state discrimination training focuses on awareness of subjective correlates of EEG states. This study presents the first successful replication of EEG alpha state discrimination first reported by Kamiya (1962). A 150-s baseline was recorded in 106 participants. During the task, low (<30th percentile of the baseline) and high alpha events (>70th percentile) triggered a prompt. Participants indicated "high" or "low" with a keypress response and received immediate feedback. Seventy-five percent of participants achieved significant discrimination within nine sessions, with a significant learning curve effect. Performance was significantly related to physical properties of the EEG signal, including magnitude, duration, and absolute vs. relative amplitude. These results are consistent with a conceptualization of EEG state discrimination as a sensory modality, although it is also intricately related to voluntary control of these states.     

Extraversion,impulsiveness, and EEG alpha activity

Measures of spontaneous EEG activity in the 8–14-Hz band (alpha) obtained while subjects opened and closed their eyes on instruction were related to scores on the EPQ-E scale and scales of narrow and broad impulsiveness. Subjects with high scores on narrow impulsiveness were found to show less alpha activity than subjects with low scores. No significant relationships with alpha activity emerged for the other personality scales. It is concluded that impulsiveness rather than EPQ-E is the major correlate of differences in EEG-defined arousal.     

Differences in EEG alpha activity related to giftedness

In three experiments, differences in EEG alpha activity between gifted (mean IQ = 137) and average (mean IQ = 105) individuals were investigated. EEG activity was monitored over 16 scalp locations. A fast Fourier transform was performed on 15 artifact-free 2-second chunks of data to derive a spectral power average in the alpha band (7.5–13 Hz). In the first experiment, EEG of gifted and average individuals during two relaxation phases—eyes closed and eyes open—was recorded. Gifted individuals showed higher EEG alpha power only while resting with eyes open. In the second experiment, gifted and average individuals solved two problems that were divided into phases of problem solving and preparing for problem solving (reading, making a plan of how to solve the problem). Significant differences were obtained only for the problem-solving stages. Gifted individuals in comparison with average ones showed higher alpha power (less mental effort) while solving the two problems. The third experiment investigated whether the lower mental activity displayed by gifted individuals was related to their ability to form more abstract schemata. For that purpose EEG was recorded while gifted and average individuals memorized lists of words and pictures that either allowed, or did not allow, for classification into more abstract categories. For both types of lists, gifted individuals displayed higher alpha power than average ones. The results obtained confirm the hypothesis that the higher EEG alpha power during information processing displayed by gifted individuals may derive from the nonuse of many brain areas not required for the problem at hand.     

Psychiatrically noticeable anxiety, EEG alpha index, alpha feedback and relaxation

In a follow-up study (first investigation: KIRSCHBAUM u. GISTL, arch. Psychol. 1973, 125, 263-273) fifteen patients with psychiatric or neurological disorders were examined for correlations between anxiety (clinical rating), scores from MAS and MMQ, and EEG-Alpha-percentage alterations during an unspecific relaxation training with or without Alpha-Biofeedback. Clinically and psychometrically high anxious patients (n = 10) showed under both conditions significant diminuation of Alpha-percentage in contrast to earlier examined students whose Alpha-rates had increased (significantly). Theoretical explanations of these results are discussed.     

EEG alpha asymmetry: task difficulty and hypnotizability

Parieto-occipital EEG alpha was recorded bilaterally, while 20 high- and 20 low-hypnotizable women performed one left-hemisphere and one right-hemisphere task of low difficulty and two other comparable tasks of high difficulty. Every task was performed twice, once with eyes open and once with eyes closed. All subjects were right-handed. The tasks were originally selected to be of high and low difficulty. The subjective rating of task-difficulty was also evaluated. The integrated amplitude alpha and the alpha ratio (R-L/R + L) were the dependent variables. The highly hypnotizable women showed significantly higher alpha amplitude in eyes-closed condition than the low scorers; this difference disappeared during task performance and in the eyes-open condition. The left-tasks showed lower alpha amplitude in both hemispheres than right-tasks and baseline. The right-hemisphere alpha amplitude was lower than left in all experimental conditions. On tasks of high and low difficulty there was different hemispheric behavior on right and left tasks. Performance reflecting the right and left hemispheres in the low-difficulty condition showed no changes between baseline, right- and left-tasks, while under high difficulty there was a decrease in alpha amplitude in the right and even more marked decrease in the left hemisphere during left-tasks. The pattern of task effects for ratio scores was the same as for alpha amplitude, however, despite the analysis of alpha scores, an interaction of hypnotizability X task-difficulty was detected. The highly hypnotizable women showed less negative alpha ratio during a task of low difficulty than during tasks of high difficulty; the reverse was true for the low-hypnotizable women. Finally, the highly hypnotizable subjects showed less subjective difficulty during performance than the low scorers.     

A technique for accurate identification of alpha frequency in the EEG

An economical and highly accurate electronic filter for the detection of narrow frequency bands in the electroencephalogram (EEG) is described. The apparatus employs solid state integrated circuits and digital logic to detect and provide feedback output. In the example given, this device acts as an alpha rhythm discriminator and provides the accuracy of a more expensive computer simulated filter.     

EEG alpha asymmetry in dyslexics during speaking and block design tasks

Lateral specialization for speech and spatial construction was investigated in a highly screened group of dyslexic and normal-reading boys, age 9-13, by examining the extent to which their EEG alpha asymmetry changed from one task to the other. EEG was recorded from central, midtemporal, and parietal leads during several minutes of spontaneous narrative speech, and while the child constructed block designs. The dyslexics showed the same strongly task-dependent asymmetry as the normal readers, comparable to that observed in our adult populations. The observations were confirmed with a second independently chosen cohort of subjects. This result is discussed in terms of the constraints it places on models of dyslexia which invoke disorders of lateral specialization and hemisphere integration.     

Generalization of skills between operant control and discrimination of EEG alpha

While biofeedback is often said to increase self-control of physiological states by increasing awareness of their subjective correlates, relatively few studies have analyzed the relationship between control (standard biofeedback) and awareness (a discrimination paradigm). We hypothesized that the two skills would generalize and facilitate each other for 8–12 Hz EEG amplitude (alpha). Participants were given 7 sessions of training to either control or discriminate Pz alpha followed by 3 sessions of the other paradigm. Another group was given 7 sessions with time divided equally between the two types of training. The control-training first group showed significant generalization of skills to the discrimination task. However, the reverse was not true, and the combined task group did no better in either task than the other two groups. These results provide ambivalent support for the role of awareness in biofeedback, and suggest possible improvements in the discrimination paradigm.     

The self and dreams during a period of transition

The content of dreams and changes to the self were investigated in students moving to University. In study 1, 20 participants completed dream diaries and memory tasks before and after they had left home and moved to university, and generated self images, “I am…” statements (e.g. I am an undergraduate), reflective of their current self. Changes in “I ams” were observed, indicating a newly-formed ‘university’ self. These self, images and related autobiographical knowledge were found to be incorporated into recent dreams but not into dreams from other periods. Study 2 replicated these findings in a different sample (N = 55). We suggest that these data reflect a period of self-consolidation in which new experiences and self images are incorporated into autobiographical memory knowledge structures representing personal goals during sleep.     

EEG alpha activity and hallucinatory experience during sensory deprivation.

The relationship between hallucinatory experiences under sensory deprivation and EEG alpha activities was studied. Each of seven male students lived alone in an air conditioned, soundproof dark room for 72 hours. When hallucinatory experiences occurred, the students pressed a button at once. If they could not press the button during the experience, they were required to press it two times when the hallucinatory experience was finished. Spectral analysis was performed on the consecutive EEG samples from just before button-presses to 10 min. before them, and the average alpha band amplitudes were obtained for the four epochs (0-.5, .5-2, 2-5, 5-10 min.). For the single button-presses, the amplitude of alpha band increased 2 min. before the button-presses. Right-hemisphere EEG activation was observed in the occipital area for the double button-presses. The results suggest an association between the hallucinatory experiences under sensory deprivation and the amount of EEG alpha activity.     

Imagery-induced negative affect,social touch and frontal EEG power band activity

Social touch seems to modulate emotions, but its brain correlates are poorly understood. Here, we investigated if frontal power band activity in the electroencephalogram (EEG) during aversive mental imagery is modulated by social touch from one’s romantic partner and a stranger. We observed the highest theta and beta power when imaging alone, next so when being touched by a stranger, with lowest theta and beta activity during holding hands with the loved one. Delta power was higher when being alone than with a stranger or a partner, with no difference between the two. Gamma power was highest during the stranger condition and lower both when being alone and with the partner, while alpha power did not change as a function of social touch. Theta power displayed a positive correlation with electrodermal activity supporting its relation to emotional arousal. Attachment style modulated the effect of touch on the EEG as only secure but not insecure partner bonding was associated with theta power reductions. Because theta power was sensitive to the experimental perturbations, mapped onto peripheral physiological arousal and reflected partner attachment style we suggest that frontal theta power might serve as an EEG derived bio-marker for social touch in emotionally significant dyads.