Quantitative EEG analysis of a single dose of psychotropic drugs in healthy probands

In a series of 74 experiments in a double blind study, 25 healthy test persons were medicated with a single dose of Clomipramin, Desipramin, Imipramin, Diazepam, Carbamazepin, Haloperidol, and a placebo. At the end of one hour, and again at the end of three hours, an EEG was made whose frequency analysis revealed significant changes in about half the test persons. The antidepressives induced an increase in the theta waves, the slow alpha waves, and the slow beta waves, and a decrease in the fast alpha waves. The factors influencing the EEG are discussed.     

Hemispheric Asymmetry and Regional Differences in Electroencephalographic Alpha Activity at the Wake-Sleep Transition

Electroencephalographic (EEG) alpha activity at the wake-sleep transition was studied in six right-handed adults in terms of hemispheric asymmetry and regional differences. Twelve-channel EEGs with linked mastoid references were recorded together with horizontal and vertical electro-oculograms (EOGs). Two types of alpha coefficient were obtained every 5.12 s by computing the relative proportion of right vs. left alpha band power and of anterior vs. posterior alpha band power. Four stages were scored using EEG sleep patterns (theta waves, vertex sharp waves, spindles, and K complex) and slow eye movement (SEM): stage W had neither EEG sleep patterns nor SEM; stage D1 had SEM and no EEG sleep patterns; stage D2 had theta waves or vertex sharp waves and SEM; stage S had spindles or K complex without SEM. It was found that the two types of alpha coefficient changed as a function of EEG-EOG stage and were correlated. Right-decreased and anterior-shifted alpha activities were manifest at stages D2 and S. Drowsiness was considered to be a heterogeneous state, exhibiting different spatial changes in alpha activity between stages D1 and D2.     

Developmental changes in application of the majority rule in group decisions

This study examined age-related changes in the child's application of the principle of majority rule in group decisions. Following a problem posed by Moessinger (1981), we enquired whether children routinely apply the majority rule when the majority consists of a shifting (variable) set of members across decisions, and alternate between majority and minority when the majority and minority is fixed, i.e. consists of the same individuals each time. In Geneva, Moessinger found that 8-year-olds failed to discriminate between fixed and shifting majorities, while most 13-year-olds (75 per cent) did so. An altered replication was conducted in Australia modifying Moessinger's procedure to control for extraneous variables such as ‘set’ and the need for variety in choice. It was found that on the task 7 per cent of 8-year-olds, 20 per cent of 10-year-olds, 32 per cent of 12-year-olds, and 39 per cent of 14-year-olds discriminated on a behavioural criterion between fixed and shifting majorities. Ten per cent of 8-year-olds, 40 per cent of 10-year-olds, 52 per cent of 12-year-olds, and 55 per cent of 14-year-olds made the discrimination on Moessinger's cognitive ‘reason’ criterion. The results show that development of the conceptual distinction between fixed and shifting majorities is gradual and continuous.     

Regional and inter-regional theta oscillation during episodic novelty processing

Recent event-related potential (ERP) and functional magnetic resonance imaging (fMRI) studies suggest that novelty processing may be involved in processes that recognize the meaning of a novel sound, during which widespread cortical regions including the right prefrontal cortex are engaged. However, it remains unclear how those cortical regions are functionally integrated during novelty processing. Because theta oscillation has been assumed to have a crucial role in memory operations, we examined local and inter-regional neural synchrony of theta band activity during novelty processing. Fifteen right-handed healthy university students participated in this study. Subjects performed an auditory novelty oddball task that consisted of the random sequence of three types of stimuli such as a target (1000 Hz pure tone), novel (familiar environmental sounds such as dog bark, buzz, car crashing sound and so on), and standard sounds (950 Hz pure tone). Event-related spectra perturbation (ERSP) and the phase-locking value (PLV) were measured from human scalp EEG during task. Non-parametric statistical tests were applied to test for significant differences between stimulus novelty and stimulus targets in ERSP and PLV. The novelty P3 showed significant higher amplitude and shorter latency compared with target P3 in frontocentral regions. Overall, theta activity was significantly higher in the novel stimuli compared with the target stimuli. Specifically, the difference in theta power between novel and target stimuli was most significant in the right frontal region. This right frontal theta activity was accompanied by phase synchronization with the left temporal region. Our results imply that theta phase synchronization between right frontal and left temporal regions underlie the retrieval of memory traces for unexpected but familiar sounds from long term memory in addition to working memory retrieval or novelty encoding.     

Relationship of temporal lobe volumes to neuropsychological test performance in healthy children

Ecological validity of neuropsychological assessment includes the ability of tests to predict real-world functioning and/or covary with brain structures. Studies have examined the relationship between adaptive skills and test performance, with less focus on the association between regional brain volumes and neurobehavioral function in healthy children. The present study examined the relationship between temporal lobe gray matter volumes and performance on two neuropsychological tests hypothesized to measure temporal lobe functioning (visual perception-VP; peabody picture vocabulary test, third edition-PPVT-III) in 48 healthy children ages 5-18 years. After controlling for age and gender, left and right temporal and left occipital volumes were significant predictors of VP. Left and right frontal and temporal volumes were significant predictors of PPVT-III. Temporal volume emerged as the strongest lobar correlate with both tests. These results provide convergent and discriminant validity supporting VP as a measure of the "what" system; but suggest the PPVT-III as a complex measure of receptive vocabulary, potentially involving executive function demands.     

Circumcerebral application of weak complex magnetic fields with derivatives and changes in electroencephalographic power spectra within the theta range: implications for states of consciousness

Relative power within the delta, theta, low-alpha, high-alpha, and gamma electroencephalographic spectra of 8 human volunteers was recorded over the left and right frontal, temporal, parietal, and occipital lobes during and after the circumcerebral application through an array of 8 solenoids of 6 different configurations of weak (5 to 10 microTesla) magnetic fields. The solenoids were equally spaced around the subject's head along a horizontal plane above the ears. An approximately 30% increase in power within the theta band occurred transcerebrally during the application of a specific configuration, previously shown to affect subjective time, involving 20-msec. rates of change in the duration of delivery of the magnetic fields to each successive solenoid. Compared to the left hemisphere, the right hemisphere displayed a 20% increase in power within the 5.0- to 5.9-Hz range for all 6 configurations. The results suggest that very complex magnetic fields with the appropriate temporal parameters rotated around and within brain space can interact with the cerebral processes, measured as specific hands of frequencies, generating consciousness. Implications for the roles of hippocampal theta activity, cortical resonance, and Goldstone bosons in these processes are discussed.     

Electrophysiological spatiotemporal dynamics during implicit visual threat processing

Numerous studies have found evidence for corticolimbic theta band electroencephalographic (EEG) oscillations in the neural processing of visual stimuli perceived as threatening. However, varying temporal and topographical patterns have emerged, possibly due to varying arousal levels of the stimuli. In addition, recent studies suggest neural oscillations in delta, theta, alpha, and beta-band frequencies play a functional role in information processing in the brain. This study implemented a data-driven PCA based analysis investigating the spatiotemporal dynamics of electroencephalographic delta, theta, alpha, and beta-band frequencies during an implicit visual threat processing task. While controlling for the arousal dimension (the intensity of emotional activation), we found several spatial and temporal differences for threatening compared to nonthreatening visual images. We detected an early posterior increase in theta power followed by a later frontal increase in theta power, greatest for the threatening condition. There was also a consistent left lateralized beta desynchronization for the threatening condition. Our results provide support for a dynamic corticolimbic network, with theta and beta band activity indexing processes pivotal in visual threat processing.     

I see what you mean: theta power increases are involved in the retrieval of lexical semantic information

An influential hypothesis regarding the neural basis of the mental lexicon is that semantic representations are neurally implemented as distributed networks carrying sensory, motor and/or more abstract functional information. This work investigates whether the semantic properties of words partly determine the topography of such networks. Subjects performed a visual lexical decision task while their EEG was recorded. We compared the EEG responses to nouns with either visual semantic properties (VIS, referring to colors and shapes) or with auditory semantic properties (AUD, referring to sounds). A time-frequency analysis of the EEG revealed power increases in the theta (4-7Hz) and lower-beta (13-18Hz) frequency bands, and an early power increase and subsequent decrease for the alpha (8-12Hz) band. In the theta band we observed a double dissociation: temporal electrodes showed larger theta power increases in the AUD condition, while occipital leads showed larger theta responses in the VIS condition. The results support the notion that semantic representations are stored in functional networks with a topography that reflects the semantic properties of the stored items, and provide further evidence that oscillatory brain dynamics in the theta frequency range are functionally related to the retrieval of lexical semantic information.     

EEG correlates of posthypnotically controlled degrees of cognitive arousal

Experimental control over five degrees of cognitive (as opposed to organismic) arousal has been developed by hypnotic programming techniques. Previously, these posthypnotic manipulations have been applied to the investigation of diverse topics such as visual discrimination, performance on the Stroop test, selective concentration on color vs. form of consonants, and cognitive “reverberation.” The present study explored electroencephalographic (EEG) correlates of the five degrees of cognitive arousal in a task requiring participants to visualize objects for l-rain periods while lying on a couch with their eyes closed. Analysis of data from the occipital area in left and right hemispheres revealed that the highest degree of arousal was accompanied by larger amplitudes of alpha and beta power and smaller amplitudes of theta. This pattern of results was similar in both hemispheres, although more marked in the left. The findings, which provide an independent source of support for validity of the hypnotic programming, are discussed in relation to EEG literature on cognitive activity.     

Theta activity and meditative states: spectral changes during concentrative meditation

Brain oscillatory activity is associated with different cognitive processes and plays a critical role in meditation. In this study, we investigated the temporal dynamics of oscillatory changes during Sahaj Samadhi meditation (a concentrative form of meditation that is part of Sudarshan Kriya yoga). EEG was recorded during Sudarshan Kriya yoga meditation for meditators and relaxation for controls. Spectral and coherence analysis was performed for the whole duration as well as specific blocks extracted from the initial, middle, and end portions of Sahaj Samadhi meditation or relaxation. The generation of distinct meditative states of consciousness was marked by distinct changes in spectral powers especially enhanced theta band activity during deep meditation in the frontal areas. Meditators also exhibited increased theta coherence compared to controls. The emergence of the slow frequency waves in the attention-related frontal regions provides strong support to the existing claims of frontal theta in producing meditative states along with trait effects in attentional processing. Interestingly, increased frontal theta activity was accompanied reduced activity (deactivation) in parietal–occipital areas signifying reduction in processing associated with self, space and, time.     

Modification of EEG power spectra and EEG connectivity in autobiographical memory: a sLORETA study

The aim of the present study was to explore the modifications of scalp EEG power spectra and EEG connectivity during the autobiographical memory test (AM-T) and during the retrieval of an autobiographical event (the high school final examination, Task 2). Seventeen healthy volunteers were enrolled (9 women and 8 men, mean age 23.4 ± 2.8 years, range 19–30). EEG was recorded at baseline and while performing the autobiographical memory (AM) tasks, by means of 19 surface electrodes and a nasopharyngeal electrode. EEG analysis was conducted by means of the standardized LOw Resolution Electric Tomography (sLORETA) software. Power spectra and lagged EEG coherence were compared between EEG acquired during the memory tasks and baseline recording. The frequency bands considered were as follows: delta (0.5–4 Hz); theta (4.5–7.5 Hz); alpha (8–12.5 Hz); beta1 (13–17.5 Hz); beta2 (18–30 Hz); gamma (30.5–60 Hz). During AM-T, we observed a significant delta power increase in left frontal and midline cortices (T = 3.554; p < 0.05) and increased EEG connectivity in delta band in prefrontal, temporal, parietal, and occipital areas, and for gamma bands in the left temporo-parietal regions (T = 4.154; p < 0.05). In Task 2, we measured an increased power in the gamma band located in the left posterior midline areas (T = 3.960; p < 0.05) and a significant increase in delta band connectivity in the prefrontal, temporal, parietal, and occipital areas, and in the gamma band involving right temporo-parietal areas (T = 4.579; p < 0.05). These results indicate that AM retrieval engages in a complex network which is mediated by both low- (delta) and high-frequency (gamma) EEG bands.     

Hypnotic pseudomemories,prehypnotic warnings,and the malleability of suggested memories

This study used Orne's nocturnal events paradigm to test the effects of warning highly hypnotizable participants about the possibility of hypnotic false memories. We found that warnings reduced suggestibility but not false memories during hypnosis. Fewer warned participants (12/32, 38 per cent) than unwarned participants (12/16, 75 per cent) accepted the suggestion to hear a noise that awakened them when they were age-regressed to a night of the previous week. However, an analysis of only those persons who accepted the suggestion during hypnosis showed that the warning had no effect on their posthypnotic pseudomemories: among this group, 75 per cent of warned versus 58 per cent of unwarned persons stated immediately after hypnosis that the noise occurred in reality (i.e., reported a pseudomemory). During a final confidential assessment, 58 per cent of the warned participants who had accepted the noise suggestion reported a pseudomemory, versus 50 per cent of the unwarned participants. Comparing pseudomemory rates across all participants, regardless of whether they passed or failed the noise suggestion, 28 per cent of warned participants versus 44 per cent of unwarned participants reported pseudomemories, a nonsignificant difference. Finally, warned and unwarned participants were equally confident in their false memories. © 1998 John Wiley & Sons, Ltd.     

Right to left hemispheric shift in occipital electroencephalographic responses to repeated Kimura figures

Gordon and Carmon (1976) reported that repeated presentations of an initially novel stimulus were associated with a transfer of cerebral dominance over time (trials) from the right to the left hemisphere. To test the generalizability of these results the proportions of alpha rhythms over the left and right occipital and parietal lobes were measured following the presentation of recurring and nonrecurring complex visual patterns (the Kimura Figures) to the upper or lower, left or right peripheral visual fields. Analysis showed increased electrical activation (as inferred by attenuated proportions of alpha rhythms) of the left occipital lobe but decreased activation of the right occipital lobe. This shift occurred during repeated presentations of the same stimuli but not during single presentations of different novel stimuli. There was no significant shift in this activity over the parietal lobes. These results are consistent with the reports of other researchers who have found a shift of dominant neuroelectrical activity from the right to the left hemisphere as the novelty of a visuospatial stimulus decreases.     

Expectancy in melody: tests of children and adults

Melodic expectancies among children and adults were examined. In Experiment 1, adults, 11-year-olds, and 8-year-olds rated how well individual test tones continued fragments of melodies. In Experiment 2, 11-, 8-, and 5-year-olds sang continuations to 2-tone stimuli. Response patterns were analyzed using 2 models of melodic expectancy. Despite having fewer predictor variables, the 2-factor model (E. G. Schellenberg, 1997) equaled or surpassed the implication-realization model (E. Narmour, 1990) in predictive accuracy. Listeners of all ages expected the next tone in a melody to be proximate in pitch to the tone heard most recently. Older listeners also expected reversals of pitch direction, specifically for tones that changed direction after a disruption of proximity and for tones that formed symmetric patterns.     

Neural correlates of feigned memory impairment are distinguishable from answering randomly and answering incorrectly: an fMRI and behavioral study

Previous functional magnetic resonance imaging (fMRI) studies have identified activation in the prefrontal-parietal-sub-cortical circuit during feigned memory impairment when comparing with truthful telling. Here, we used fMRI to determine whether neural activity can differentiate between answering correctly, answering randomly, answering incorrectly, and feigned memory impairment. In this study, 12 healthy subjects underwent block-design fMRI while they performed digit task of forced-choice format under four conditions: answering correctly, answering randomly, answering incorrectly, and simulated feigned memory impairment. There were three main results. First, six areas, including the left prefrontal cortex, the left superior temporal lobe, the right postcentral gyrus, the right superior parietal cortex, the right superior occipital cortex, and the right putamen, were significantly modulated by condition type. Second, for some areas, including the right superior parietal cortex, the right postcentral gyrus, the right superior occipital cortex, and the right putamen, brain activity was significantly greater in feigned memory impairment than answering randomly. Third, for the areas including the left prefrontal cortex and the right putamen, brain activity was significantly greater in feigned memory impairment than answering incorrectly. In contrast, for the left superior temporal lobe, brain activity was significantly greater in answering incorrectly than feigned memory impairment. The results suggest that neural correlates of feigned memory impairment are distinguishable from answering randomly and answering incorrectly in healthy subjects.     

Electroencephalography when meditation advances: a case-based time-series analysis

Increased alpha and theta activities in electroencephalography (EEG) have been found during various forms of meditation. However, advanced stage of meditation drew less attention to date. We aimed at exploring EEG characteristics during advanced meditation. Bilateral absolute alpha and theta EEG powers were recorded when a single meditator at rest, exercising breath meditation, and reaching the advanced meditative stage in 10 sessions of meditation. Averaged time-series data were analyzed using simulation modeling analysis to compare the powers during different meditative phases. During breath meditation, significantly higher activities compared with baseline were found only in bilateral theta (P = 0.0406, 0.0158 for left and right sides, respectively), but not in alpha (P = 0.1412, 0.0978 for left and right sides, respectively) bands. When meditation advanced, significantly increased activities were found both in bilateral alpha (P = 0.0218, 0.0258 for left and right sides, respectively) and theta (P = 0.0308, 0.0260 for left and right sides, respectively) bands compared against breath meditation. When advanced meditation compared against baseline, bilateral alpha (P = 0.0001, 0.0001 for left and right sides, respectively) and theta (P = 0.0001, 0.0001 for left and right sides, respectively) bands revealed significantly increased activities. Our findings support that internalized attention manifested as theta activity continuingly enhances significantly in sequential phases of meditation, while relaxation manifested as alpha activity is significant only after the advanced meditative phase is reached.     

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.     

Speech dominance and handedness in the normal human

Spectral analysis was used to measure the coherence or similarity of form between occipital and temporal evoked potentials. In both right- and left-handers, coherence was greater in the left hemisphere for click stimuli and in the right hemisphere for flash stimuli. Similar asymmetries occurred in left but not right speech dominant patients whose speech lateralization has been determined by the intracarotid amytal test. Right-handers and males, however, showed significantly larger amplitudes of auditory responses in the right hemisphere. Left-handers and females reversed this pattern. It was concluded that within a basically left speech dominant organization, males and right-handers would emphasize the verbal, temporal structure of auditory information and the nonverbal, spatial structure of visual information. Females and left-handers would tend to reverse this emphasis.     

Distinct brain systems underlie the processing of valence and arousal of affective pictures

Valence and arousal are thought to be the primary dimensions of human emotion. However, the degree to which valence and arousal interact in determining brain responses to emotional pictures is still elusive. This functional MRI study aimed to delineate neural systems responding to valence and arousal, and their interaction. We measured neural activation in healthy females (N = 23) to affective pictures using a 2 (Valence) × 2 (Arousal) design. Results show that arousal was preferentially processed by middle temporal gyrus, hippocampus and ventrolateral prefrontal cortex. Regions responding to negative valence included visual and lateral prefrontal regions, positive valence activated middle temporal and orbitofrontal areas. Importantly, distinct arousal-by-valence interactions were present in anterior insula (negative pictures), and in occipital cortex, parahippocampal gyrus and posterior cingulate (positive pictures). These data demonstrate that the brain not only differentiates between valence and arousal but also responds to specific combinations of these two, thereby highlighting the sophisticated nature of emotion processing in (female) human subjects.     

Combining computer adaptive testing technology with cognitively diagnostic assessment

A major advantage of computerized adaptive testing (CAT) is that it allows the test to home in on an examinee's ability level in an interactive manner. The aim of the new area of cognitive diagnosis is to provide information about specific content areas in which an examinee needs help. The goal of this study was to combine the benefit of specific feedback from cognitively diagnostic assessment with the advantages of CAT. In this study, three approaches to combining these were investigated: (1) item selection based on the traditional ability level estimate (theta), (2) item selection based on the attribute mastery feedback provided by cognitively diagnostic assessment (alpha), and (3) item selection based on both the traditional ability level estimate (theta) and the attribute mastery feedback provided by cognitively diagnostic assessment (alpha). The results from these three approaches were compared for theta estimation accuracy, attribute mastery estimation accuracy, and item exposure control. The theta- and alpha-based condition outperformed the alpha-based condition regarding theta estimation, attribute mastery pattern estimation, and item exposure control. Both the theta-based condition and the theta- and alpha-based condition performed similarly with regard to theta estimation, attribute mastery estimation, and item exposure control, but the theta- and alpha-based condition has an additional advantage in that it uses the shadow test method, which allows the administrator to incorporate additional constraints in the item selection process, such as content balancing, item type constraints, and so forth, and also to select items on the basis of both the current theta and alpha estimates, which can be built on top of existing 3PL testing programs.