Enhanced dynamic complexity in the human EEG during creative thinking

Age-dependent functional development pattern in neonatal brain: An fMRI-based brain entropy study

The relationship between brain entropy (BEN) and early brain development has been established through animal studies. However, it remains unclear whether the BEN can be used to identify age-dependent functional changes in human neonatal brains and the genetic underpinning of the new neuroimaging marker remains to be elucidated. In this study, we analyzed resting-state fMRI data from the Developing Human Connectome Project, including 280 infants who were scanned at 37.5-43.5 weeks postmenstrual age. The BEN maps were calculated for each subject, and a voxel-wise analysis was conducted using a general linear model to examine the effects of age, sex, and preterm birth on BEN. Additionally, we evaluated the correlation between regional BEN and gene expression levels. Our results demonstrated that the BEN in the sensorimotor-auditory and association cortices, along the 'S-A' axis, was significantly positively correlated with postnatal age (PNA), and negatively correlated with gestational age (GA), respectively. Meanwhile, the BEN in the right rolandic operculum correlated significantly with both GA and PNA. Preterm-born infants exhibited increased BEN values in widespread cortical areas, particularly in the visual-motor cortex, when compared to term-born infants. Moreover, we identified five BEN-related genes (DNAJC12, FIG4, STX12, CETN2, and IRF2BP2), which were involved in protein folding, synaptic vesicle transportation and cell division. These findings suggest that the fMRI-based BEN can serve as an indicator of age-dependent brain functional development in human neonates, which may be influenced by specific genes.

Time course of EEG power during creative problem-solving with insight or remote thinking

Problem-solving often requires creativity and is critical in everyday life. However, the neurocognitive mechanisms underlying creative problem-solving remain poorly understood. Two mechanisms have been highlighted: the formation of new connections among problem elements and insight solving, characterized by sudden realization of a solution. In this study, we investigated EEG activity during a modified version of the remote associates test, a classical insight problem task that requires finding a word connecting three unrelated words. This allowed us to explore the brain correlates associated with the semantic remoteness of connections (by varying the remoteness of the solution word across trials) and with insight solving (identified as a Eurêka moment reported by the participants). Semantic remoteness was associated with power increase in the alpha band (8-12 Hz) in a left parieto-temporal cluster, the beta band (13-30 Hz) in a right fronto-temporal cluster in the early phase of the task, and the theta band (3-7 Hz) in a bilateral frontal cluster just prior to participants' responses. Insight solving was associated with power increase preceding participants' responses in the alpha and gamma (31-60 Hz) bands in a left temporal cluster and the theta band in a frontal cluster. Source reconstructions revealed the brain regions associated with these clusters. Overall, our findings shed new light on some of the mechanisms involved in creative problem-solving.

Neural and cognitive correlates of performance in dynamic multi-modal settings

The endeavour to understand human cognition has largely relied upon investigation of task-related brain activity. However, resting-state brain activity can also offer insights into individual information processing and performance capabilities. Previous research has identified electroencephalographic resting-state characteristics (most prominently: the individual alpha frequency; IAF) that predict cognitive function. However, it has largely overlooked a second component of electrophysiological signals: aperiodic 1/ƒ activity. The current study examined how both oscillatory and aperiodic resting-state EEG measures, alongside traditional cognitive tests, can predict performance in a dynamic and complex, semi-naturalistic cognitive task. Participants' resting-state EEG was recorded prior to engaging in a Target Motion Analysis (TMA) task in a simulated submarine control room environment (CRUSE), which required participants to integrate dynamically changing information over time. We demonstrated that the relationship between IAF and cognitive performance extends from simple cognitive tasks (e.g., digit span) to complex, dynamic measures of information processing. Further, our results showed that individual 1/ƒ parameters (slope and intercept) differentially predicted performance across practice and testing sessions, whereby flatter slopes and higher intercepts were associated with improved performance during learning. In addition to the EEG predictors, we demonstrate a link between cognitive skills most closely related to the TMA task (i.e., spatial imagery) and subsequent performance. Overall, the current study highlights (1) how resting-state metrics - both oscillatory and aperiodic - have the potential to index higher-order cognitive capacity, while (2) emphasising the importance of examining these electrophysiological components within more dynamic settings and over time.

You Eat How You Think: A Review on the Impact of Cognitive Styles on Food Perception and Behavior

Sensory perception is understood to be a complex area of research that requires investigations from a variety of different perspectives. Although researchers have tried to better understand consumers’ perception of food, one area that has been minimally explored is how psychological cognitive theories can help them explain consumer perceptions, behaviors, and decisions in food-related experiences. The concept of cognitive styles has existed for nearly a century, with the majority of cognitive style theories existing along a continuum with two bookends. Some of the more common theories such as individualist-collectivist, left-brain-right-brain, and convergent-divergent theories each offered their own unique insight into better understanding consumer behavior. However, these theories often focused only on niche applications or on specific aspects of cognition. More recently, the analytic-holistic cognitive style theory was developed to encompass many of these prior theoretical components and apply them to more general cognitive tendencies of individuals. Through applying the analytic-holistic theory and focusing on modern cultural psychology work, this review may allow researchers to be able to answer one of the paramount questions of sensory and consumer sciences: how and why do consumers perceive and respond to food stimuli the way that they do?

Design Meets Neuroscience: An Electroencephalogram Study of Design Thinking in Concept Generation Phase

Extant research on design thinking is subjective and limited. This manuscript combines protocol analysis and electroencephalogram (EEG) to read design thoughts in the core design activities of concept generation phase. The results suggest that alpha band power had event related synchronization (ERS) in the scenario task and divergent thinking occupies a dominant position. However, it had event related desynchronization (ERD) in analogy and inference activities, etc., and it is stronger for mental pressure and exercised cognitive processing. In addition, the parietooccipital area differs significantly from other brain areas in most design activities. This study explores the relationship of different design thinking and EEG data, which is innovative and professional in the field of design, providing a more objective data basis and evaluation method for future applied research and diverse educational practices.

More than off-task: Increased freely-moving thought in ADHD

Off-task thought has been found to occur at high rates and is related to impairment in ADHD. However, off-task thought is heterogenous and it remains unclear which specific dimensions of off-task thought are more prevalent in this disorder. It is therefore important to dissociate different aspects of off-task thought in order to better understand the mechanisms underlying impairment. The current study focused on the dimension of constrained (focused) to freely moving off-task thought. Self-report and neurophysiological measures during a computerized attention tasks provided convergent evidence that individuals with ADHD not only have more off-task thought than those without, but also engaged in a greater proportion of freely moving off-task thought than non-ADHD controls. Overall, this work demonstrated differences in both the quantity and type of off-task thought in adults with ADHD. It provides novel insight into both the phenomenology of off-task thought, as well as potential mechanisms underlying impairment in ADHD.

Associations of brain entropy (BEN) to cerebral blood flow and fractional amplitude of low-frequency fluctuations in the resting brain

Entropy is a fundamental trait of human brain. Using fMRI-based brain entropy (BEN) mapping, interesting findings have been increasingly revealed in normal brain and neuropsychiatric disorders. As BEN is still relatively new, an often-raised question is how much new information can this measure tell about the brain compared to other more established brain activity measures. The study aimed to address that question by examining the relationship between BEN and cerebral blood flow (CBF) and the fractional amplitude of low-frequency fluctuations (fALFF), two widely used resting state brain state measures. fMRI data acquired from a large cohort of normal subjects were used to calculate the three metrics; inter-modality associations were assessed at each voxel through the Pearson correlation analysis. A moderate to high positive BEN-CBF and BEN-fALFF correlations were found in orbito-frontal cortex (OFC) and posterior inferior temporal cortex (ITC); Strong negative BEN-fALFF correlations were found in visual cortex (VC), anterior ITC, striatum, motor network, precuneus, and lateral parietal cortex. Positive CBF-fALFF correlations were found in medial OFC (MOFC), medial prefrontal cortex (MPFC), left angular gyrus, and left precuneus. Significant gender effects were observed for all three metrics and their correlations. Our data clearly demonstrated that BEN provides unique information that cannot be revealed by CBF and fALFF.

Mechanisms of Creativity Differences Between Art and Non-art Majors: A Voxel-Based Morphometry Study

Creativity is considered the ability to generate new ideas or behaviors, an ability that have diverse expressions in different human groups, such as painters and non-painters. Art major students require more creative activities than non-art students do. In this study, we plan to explore the figural creativity abilities of art major students and whether these students exhibited higher figural creativity scores and why their brain structure of gray matter are lower which may benefit from their professional training relative to non-art majors. Therefore, in this study, we use voxel-based morphometry (VBM) to identify different behavioral and brain mechanisms between art major students and non-art major students by using the figural Torrance Test of Creative Thinking. Our results showed that the TTCT-figural (TTCT-F) scores of art majors were higher than those of non-art majors. The TTCT-F score of art major students and practicing and study time have positive correlations which means art major's figural creativity score benefit from there art professional training in some degree. Subsequently, the interaction analysis revealed that the TTCT-figural scores of art majors and non-majors exhibited significant correlations with the gray matter volumes (GMV) of the left anterior cingulate cortex (ACC) and the left medial frontal gyrus (MFG). While the simple slope analysis showed that art majors, compared with non-art majors, exhibited a marginal significantly positive association with the left ACC and MFG, non-art majors exhibited a significantly negative association with the left ACC and MFG. Overall, our study revealed that people who major in artistic work are more likely to possess enhanced figural creative skills relative to non-artistic people. These results indicated that professional artistic programs or training may increase creativity skills via reorganized intercortical connections.

Fractal dimension of EEG signals and heart dynamics in discrete emotional states

In this study, we explored the fractal dimension (FD; a measure of signal complexity) of 28 EEG channels with positive and negative emotional states. The EEG of participants and their ECG were registered while watching short video clips that induced fear, disgust, humour, or neutral emotions. In order to better understand the nature of these emotions, the Higuchi FD of EEG segments and the heart rate variability (HRV) of the ECG associated with each emotion were obtained. Our results exhibited similar patterns of results with both measures. Humour elicited the highest FD scores in most EEG channels and the highest HRV, while fear, among all emotions, produced the lowest scores in both measures. These results may contribute to the understanding of the relationship between cortical and heart dynamics and their role on emotion perception.

Nonlinear Dynamic Complexity and Sources of Resting-state EEG in Abstinent Heroin Addicts

It has been reported that chronic heroin intake induces both structural and functional changes in human brain; however, few studies have investigated the carry-over adverse effects on brain after heroin withdrawal. In this paper, we examined the neurophysiological differences between the abstinent heroin addicts (AHAs) and healthy controls (HCs) using nonlinear dynamic analysis and source localization analysis in resting-state electroencephalogram (EEG) data; 5 min resting EEG data from 20 AHAs and twenty age-, education-, and gender-matched HCs were recorded using 64 electrodes. The results of nonlinear characteristics (e.g., the correlation dimension, Kolmogorov entropy, and Lempel-Ziv complexity) showed that the EEG signals in alpha band from AHAs were significantly more irregular. Moreover, the source localization results confirmed the neuronal activities in alpha band in AHAs were significantly weaker in parietal lobe (BA3 and BA7), frontal lobe (BA4 and BA6), and limbic lobe (BA24). Together, our analysis at both the sensor level and source level suggested the functional abnormalities in the brain during heroin abstinence, in particular for the neuronal oscillations in alpha band.

Dissociation, Epileptiform Discharges and Chaos in the Brain: Toward a Neuroscientific Theory of Dissociation

Dissociated states represent pathological conditions when psychological trauma may emerge in a variety of forms such as psychic dissociative symptoms or, on the contrary, as paroxysms or other somatoform symptoms. There is evidence that epileptic activity plays an important role in the generation of dissociative states and it is able to generate various psychopathological processes as well as a wide spectrum of somatic symptoms or seizures. For the explanation of these connections between dissociative states and epileptic discharges the author proposes a neuroscientific model of dissociation based on the theory of competitive neural assemblies which can lead to chaotic self-organization in brain neural networks. This model is suggested as an integrative view interconnecting the various psychopathological and somatoform manifestations of dissociative states and suggests further possibilities for future research regarding common pathogenic mechanisms among epilepsy and mental disorders.

Right frontal gamma and beta band enhancement while solving a spatial puzzle with insight

Solving a problem with an "a-ha" effect is known as insight. Unlike incremental problem solving, insight is sudden and unique, and the question about its distinct brain activity, intrigues many researchers. In this study, electroencephalogram signals were recorded from 12 right handed, human participants before (baseline) and while they solved a spatial puzzle known as the '10 coin puzzle' that could be solved incrementally or by insight. Participants responded as soon as they reached a solution and reported whether the process was incremental or by sudden insight. EEG activity was recorded from 19 scalp locations. We found significant differences between insight and incremental solvers in the Gamma and Beta 2 bands in frontal areas (F8) and in the alpha band in right temporal areas (T6). The right-frontal gamma indicates a process of restructuring which leads to an insight solution, in spatial problems, further suggesting a universal role of gamma in restructuring. These results further suggest that solving a spatial puzzle via insight requires exclusive brain areas and neurological-cognitive processes which may be important for meta-cognitive components of insight solutions, including attention and monitoring of the solution.

Dissociative states in dreams and brain chaos: implications for creative awareness

This article reviews recent findings indicating some common brain processes during dissociative states and dreaming with the aim to outline a perspective that neural chaotic states during dreaming can be closely related to dissociative states that may manifest in dreams scenery. These data are in agreement with various clinical findings that dissociated states can be projected into the "dream scenery" in REM sleep periods and dreams may represent their specific interactions that may uncover unusual psychological potential of creativity in psychotherapy, art, and scientific discoveries.

Memory load effect in auditory-verbal short-term memory task: EEG fractal and spectral analysis

The objective of this preliminary study was to quantify changes in complexity of EEG using fractal dimension (FD) alongside linear methods of spectral power, event-related spectral perturbations, coherence, and source localization of EEG generators for theta (4-7 Hz), alpha (8-12 Hz), and beta (13-23 Hz) frequency bands due to a memory load effect in an auditory-verbal short-term memory (AVSTM) task for words. We examined 20 healthy individuals using the Sternberg's paradigm with increasing memory load (three, five, and seven words). The stimuli were four-letter words. Artifact-free 5-s EEG segments during retention period were analyzed. The most significant finding was the increase in FD with the increase in memory load in temporal regions T3 and T4, and in parietal region Pz, while decrease in FD with increase in memory load was registered in frontal midline region Fz. Results point to increase in frontal midline (Fz) theta spectral power, decrease in alpha spectral power in parietal region-Pz, and increase in beta spectral power in T3 and T4 region with increase in memory load. Decrease in theta coherence within right hemisphere due to memory load was obtained. Alpha coherence increased in posterior regions with anterior decrease. Beta coherence increased in fronto-temporal regions. Source localization delineated theta activity increase in frontal midline region, alpha decrease in superior parietal region, and beta increase in superior temporal gyrus with increase in memory load. In conclusion, FD as a nonlinear measure may serve as a sensitive index for quantifying dynamical changes in EEG signals during AVSTM tasks.

Neurophysiological basis of creativity in healthy elderly people: a multiscale entropy approach

OBJECTIVES

Creativity, which presumably involves various connections within and across different neural networks, reportedly underpins the mental well-being of older adults. Multiscale entropy (MSE) can characterize the complexity inherent in EEG dynamics with multiple temporal scales. It can therefore provide useful insight into neural networks. Given that background, we sought to clarify the neurophysiological bases of creativity in healthy elderly subjects by assessing EEG complexity with MSE, with emphasis on assessment of neural networks.

METHODS

We recorded resting state EEG of 20 healthy elderly subjects. MSE was calculated for each subject for continuous 20-s epochs. Their relevance to individual creativity was examined concurrently with intellectual function.

RESULTS

Higher individual creativity was linked closely to increased EEG complexity across higher temporal scales, but no significant relation was found with intellectual function (IQ score).

CONCLUSIONS

Considering the general "loss of complexity" theory of aging, our finding of increased EEG complexity in elderly people with heightened creativity supports the idea that creativity is associated with activated neural networks.

SIGNIFICANCE

Results reported here underscore the potential usefulness of MSE analysis for characterizing the neurophysiological bases of elderly people with heightened creativity.

Nonlinear measures and dynamics in psychophysiology of consciousness

According to recent findings nonlinear dynamic processes related to neural chaos and complexity likely play a crucial role in neural synchronization of distributed neural activities that enable information integration and conscious experience. Disturbances in these interactions produce patterns of temporal and spatial disorganization with decreased or increased functional connectivity and complexity that underlie specific changes of perceptual and cognitive states. These perceptual and cognitive changes may be characterized by neural chaos with significantly increased brain sensitivity that may underlie sensitization and kindling, and cognitive hypersensitivity in some mental disorders. Together these findings suggest that processes related to more irregular neural states with higher complexity that may lead to neural chaos, negatively affect information integration and processing in the brain, and may influence disintegrated conscious experience.

Brain activity of women is more fractal than men

Investigating gender differences of the brain is of both scientific and clinical importance, as understanding such differences may be helpful for improving gender specific treatments of neuropsychiatric disorders. As brain is a highly complex system, it is crucial to investigate its activity in terms of nonlinear dynamics. However, there are few studies that investigated gender differences based on dynamical characteristics of the brain. Fractal dimension (FD) is a key characteristic of the brain dynamics which indicates the level of complexity on which the neuronal regions function or interact and quantifies the associated brain processes on a scale ranging from fully deterministic to fully random. This study investigates the gender differences of brain dynamics, comparing fractal dimension of scalp EEGs (in eyes-closed resting state) of 34 female and 34 male healthy adults. The results showed significantly greater FDs in females compared to males in all brain regions except in lateral and occipital lobes. This indicates a higher complexity of the brain dynamics in females relative to males. The high accuracies of 87.8% and 93.1% obtained by logistic regression and enhanced probabilistic neural network, respectively, in discriminating between the gender groups based on the FDs also confirmed the great gender differences of complexity of brain activities. The results showed that delta, alpha, and beta bands are the frequency bands that contribute most to the gender differences in brain complexity. Furthermore, the lateralization analysis showed the leftward lateralization of complexity in females is greater than in males.

Evaluative and generative modes of thought during the creative process

Psychological theories have suggested that creativity involves a twofold process characterized by a generative component facilitating the production of novel ideas and an evaluative component enabling the assessment of their usefulness. The present study employed a novel fMRI paradigm designed to distinguish between these two components at the neural level. Participants designed book cover illustrations while alternating between the generation and evaluation of ideas. The use of an fMRI-compatible drawing tablet allowed for a more natural drawing and creative environment. Creative generation was associated with preferential recruitment of medial temporal lobe regions, while creative evaluation was associated with joint recruitment of executive and default network regions and activation of the rostrolateral prefrontal cortex, insula, and temporopolar cortex. Executive and default regions showed positive functional connectivity throughout task performance. These findings suggest that the medial temporal lobe may be central to the generation of novel ideas and creative evaluation may extend beyond deliberate analytical processes supported by executive brain regions to include more spontaneous affective and visceroceptive evaluative processes supported by default and limbic regions. Thus, creative thinking appears to recruit a unique configuration of neural processes not typically used together during traditional problem solving tasks.

Global workspace model of consciousness and its electromagnetic correlates

The global workspace of consciousness was proposed in its elementary framework by Baars, in 1982. Since the time of inception, there have been many speculations and modifications of this theory, but the central theme has remained the same, which refers to the global availability of information in the brain. However, the present understanding about the origin of this global workspace or its mechanism of operation is still deficient. One of the less-studied candidates for this global workspace is the electromagnetic field of the brain. The present work is a brief review of the theoretical underpinnings of the Global workspace model, in terms of its theoretical framework and neuroimaging evidences. Subsequently, we turn towards another broad group of theories of consciousness, in the form of electromagnetic field theories. We then proceed to highlight some electromagnetic correlates derived from these theories for this global access phenomenon.

EEG complexity and attentional processes related to dissociative states

Reported findings indicate that attentional narrowing is related to decreased complexity and increased inhibition of neural assemblies. These findings suggest that analysis of electroencephalogram (EEG) complexity could present a useful method for research of attentional changes related to dissociation. To examine this model we used a case study to test the two hypotheses: (1) that successful anticonvulsant medication would result in dissociative symptom alleviation, improvement of inhibitory neural functions, and decreased EEG complexity, and (2) that cognitive conflict, related to aversive events in the patient's past experience, during reliving of a dissociative state would lead to greater allocation of attention and decreased EEG complexity. Three EEG studies recorded in the eyes closed non-drowsy state were performed: (1) at baseline, (2) post-induction of dissociative state, and (3) post-anticonvulsant medication following induction of dissociative state. A dissociative state was achieved following an interview regarding the patient's aversive past experiences through use of the Peritraumatic Dissociative Experiences Questionnaire (PDEQ). The patient's level of dissociation was measured using the Dissociative Experiences Scale-II (DES-II). The PDEQ interview and DES-II assessment were also used one hour following the oral consumption of an anticonvulsant medication (clonazepam 2mg). Analysis of the data revealed that complexity values (PD2) are significantly lower following the oral consumption of clonazepam (2mg) in the majority of EEG channels. Additionally, complexity during the reliving of a dissociative state was statistically significantly lower than both the baseline and post-medication conditions in all but two EEG channels. Results of the case study suggest that changes in attentional processes linked to dissociation are related to: (1) decreased complexity when attention is extremely focused because of attentional narrowing to the disturbing past experience, and (2) increased complexity during ordinary experiences when attention is less narrowly focused.

Neuroanatomy of creativity

Creativity has long been a construct of interest to philosophers, psychologists and, more recently, neuroscientists. Recent efforts have focused on cognitive processes likely to be important to the manifestation of novelty and usefulness within a given social context. One such cognitive process - divergent thinking - is the process by which one extrapolates many possible answers to an initial stimulus or target data set. We sought to link well established measures of divergent thinking and creative achievement (Creative Achievement Questionnaire - CAQ) to cortical thickness in a cohort of young (23.7 +/- 4.2 years), healthy subjects. Three independent judges ranked the creative products of each subject using the consensual assessment technique (Amabile, 1982) from which a "composite creativity index" (CCI) was derived. Structural magnetic resonance imaging was obtained at 1.5 Tesla Siemens scanner. Cortical reconstruction and volumetric segmentation were performed with the FreeSurfer image analysis suite. A region within the lingual gyrus was negatively correlated with CCI; the right posterior cingulate correlated positively with the CCI. For the CAQ, lower left lateral orbitofrontal volume correlated with higher creative achievement; higher cortical thickness was related to higher scores on the CAQ in the right angular gyrus. This is the first study to link cortical thickness measures to psychometric measures of creativity. The distribution of brain regions, associated with both divergent thinking and creative achievement, suggests that cognitive control of information flow among brain areas may be critical to understanding creative cognition.

Non-linear Analysis of Single Electroencephalography (EEG) for Sleep-Related Healthcare Applications

OBJECTIVES

Soft-computing techniques are commonly used to detect medical phenomena and to help with clinical diagnoses and treatment. The purpose of this paper is to analyze the single electroencephalography (EEG) signal with the chaotic methods in order to identify the sleep stages.

METHODS

Data acquisition (polysomnography) was performed on four healthy young adults (all males with a mean age of 27.5 years). The evaluated algorithm was designed with a correlation dimension and Lyapunov's exponent using a single EEG signal that detects differences in chaotic characteristics.

RESULTS

The change of the correlation dimension and the largest Lyapunov exponent over the whole night sleep EEG was performed. The results show that the correlation dimension and largest Lyapunov exponent decreased from light sleep to deep sleep and they increased during the rapid eye movement stage.

CONCLUSIONS

These results suggest that chaotic analysis may be a useful adjunct to linear (spectral) analysis for identifying sleep stages. The single EEG based nonlinear analysis is suitable for u-healthcare applications for monitoring sleep.

Neural networks involved in artistic creativity

Creativity has been proposed to be either the result of solely right hemisphere processes or of interhemispheric interactions. Little information is available, however, concerning the neuronal foundations of creativity. In this study, we introduced a new artistic task, designing a new tool (a pen), which let us quantitatively evaluate creativity by three indices of originality. These scores were analyzed in combination with brain activities measured by functional magnetic resonance imaging (fMRI). The results were compared between subjects who had been formally trained in design (experts) and novice subjects. In the experts, creativity was quantitatively correlated with the degree of dominance of the right prefrontal cortex over that of the left, but not with that of the right or left prefrontal cortex alone. In contrast, in novice subjects, only a negative correlation with creativity was observed in the bilateral inferior parietal cortex. We introduced structure equation modeling to analyze the interactions among these four brain areas and originality indices. The results predicted that training exerts a direct effect on the left parietal cortex. Additionally, as a result of the indirect effects, the activity of the right prefrontal cortex was facilitated, and the left prefrontal and right parietal cortices were suppressed. Our results supported the hypothesis that training increases creativity via reorganized intercortical interactions.

The effects of the experience of forming visual images on the spatial organization of the EEG

The spatial organization of biopotentials in the cerebral cortex of 23 subjects who were students at the Faculty of Graphic Arts ("professionals") as well as 39 subjects lacking systematic experience of visual images ("non-professionals") was compared with the aim of identifying EEG correlates of the experience of visual images (image formation) in humans. Changes in measures of the spatial organization of biopotentials (spatial synchronization, spatial disordering, coherence, and spectral power) were analyzed as subjects mentally composed visual images consisting of two simple graphic elements - right angles and oblique lines. The total number of image elements increased in each of four sequential tasks, from a number which could be analyzed at the conscious level (4-7 elements) to a number exceeding analysis at the conscious level (8-16). Intergroup differences, particularly increases in the spatial disordering of biopotentials (non-linear processes), were detected when large numbers of elements were used (tasks 3 and 4). This measure increased more markedly in professionals than in non-professionals. Changes were significant in the anterior areas of the right hemisphere. Spatial synchronization of biopotentials (linear processes) increased in non-professionals in the posterior areas of the right hemisphere. Coherence and spectral power increased in professionals in a larger number of narrow-band EEG frequency subranges than in non-professionals. These data show that experience of visual imagery results in a more complex neurodynamic process during the activity, with non-linear dynamics and a multitude of EEG resonance systems at different frequencies.

Cortex functional connectivity as a neurophysiological correlate of hypnosis: an EEG case study

Cortex functional connectivity associated with hypnosis was investigated in a single highly hypnotizable subject in a normal baseline condition and under neutral hypnosis during two sessions separated by a year. After the hypnotic induction, but without further suggestions as compared to the baseline condition, all studied parameters of local and remote functional connectivity were significantly changed. The significant differences between hypnosis and the baseline condition were observable (to different extent) in five studied independent frequency bands (delta, theta, alpha, beta, and gamma). The results were consistent and stable after 1 year. Based on these findings we conclude that alteration in functional connectivity of the brain may be regarded as a neuronal correlate of hypnosis (at least in very highly hypnotizable subjects) in which separate cognitive modules and subsystems may be temporarily incapable of communicating with each other normally.

Genetic influences on dynamic complexity of brain oscillations

Human electroencephalogram (EEG) consists of complex aperiodic oscillations that are assumed to indicate underlying neural dynamics such as the number and degree of independence of oscillating neuronal networks. EEG complexity can be estimated using measures derived from nonlinear dynamic systems theory. Variations in such measures have been shown to be associated with normal individual differences in cognition and some neuropsychiatric disorders. Despite the increasing use of EEG complexity measures for the study of normal and abnormal brain functioning, little is known about genetic and environmental influences on these measures. Using the pointwise dimension (PD2) algorithm, this study assessed heritability of EEG complexity at rest in a sample of 214 young female twins consisting of 51 monozygotic (MZ) and 56 dizygotic (DZ) pairs. In MZ twins, intrapair correlations were high and statistically significant; in DZ twins, correlations were substantially smaller. Genetic analyses using linear structural equation modeling revealed high and significant heritability of EEG complexity: 62-68% in the eyes-closed condition, and 46-60% in the eyes-open condition. Results suggest that individual differences in the complexity of resting electrocortical dynamics are largely determined by genetic factors. Neurophysiological mechanisms mediating genetic variation in EEG complexity may include the degree of structural connectivity and functional differentiation among cortical neuronal assemblies.

Nonlinear dynamical analysis of EEG and MEG: review of an emerging field

Many complex and interesting phenomena in nature are due to nonlinear phenomena. The theory of nonlinear dynamical systems, also called 'chaos theory', has now progressed to a stage, where it becomes possible to study self-organization and pattern formation in the complex neuronal networks of the brain. One approach to nonlinear time series analysis consists of reconstructing, from time series of EEG or MEG, an attractor of the underlying dynamical system, and characterizing it in terms of its dimension (an estimate of the degrees of freedom of the system), or its Lyapunov exponents and entropy (reflecting unpredictability of the dynamics due to the sensitive dependence on initial conditions). More recently developed nonlinear measures characterize other features of local brain dynamics (forecasting, time asymmetry, determinism) or the nonlinear synchronization between recordings from different brain regions. Nonlinear time series has been applied to EEG and MEG of healthy subjects during no-task resting states, perceptual processing, performance of cognitive tasks and different sleep stages. Many pathologic states have been examined as well, ranging from toxic states, seizures, and psychiatric disorders to Alzheimer's, Parkinson's and Cre1utzfeldt-Jakob's disease. Interpretation of these results in terms of 'functional sources' and 'functional networks' allows the identification of three basic patterns of brain dynamics: (i) normal, ongoing dynamics during a no-task, resting state in healthy subjects; this state is characterized by a high dimensional complexity and a relatively low and fluctuating level of synchronization of the neuronal networks; (ii) hypersynchronous, highly nonlinear dynamics of epileptic seizures; (iii) dynamics of degenerative encephalopathies with an abnormally low level of between area synchronization. Only intermediate levels of rapidly fluctuating synchronization, possibly due to critical dynamics near a phase transition, are associated with normal information processing, whereas both hyper-as well as hyposynchronous states result in impaired information processing and disturbed consciousness.

Changes in artistic style after minor posterior stroke

BACKGROUND

Two professional painters experienced significant changes in their art as the main consequence of minor stroke located in the left occipital lobe or thalamus.

METHODS

The features of this artistic conversion were analysed on the basis of extensive neurological, neuropsychological, and psychiatric evaluations.

RESULTS

Both painters, initially unaware of the artistic changes, exhibited mild signs of executive dysfunction, but no general cognitive decline. The first painter, who showed mild visual-perceptive difficulties (dyschromatopsia and scotoma in his right upper visual field after left occipital stroke), together with increased anxiety and difficulty in emotional control, switched to a more stylised and symbolic art. The second painter, who also presented features of emotionalism related to his left latero-thalamic stroke, switched from an impressionist style to a more joyous and geometric, but more simplistic, abstract art.

CONCLUSIONS

These findings show that mild cognitive and affective modifications due to focal posterior brain lesions can have significant repercussions on artistic expression.

PET study of brain maintenance of verbal creative activity

This paper deals with the investigation of the brain organization of verbal creativity. Psychological tasks were designed in accordance with two main strategies used by volunteers in solving creative tasks. Regional cerebral blood flow (rCBF) was measured with positron emission tomography (PET) when performing two types of creative tasks in two groups of subjects, each type of the task organizing the creativity process in its own way. Valuable brain correlates of creativity were revealed in the left parieto-temporal regions (Brodmann areas 39 and 40).

Psychoses and creativity: is the missing link a biological mechanism related to phospholipids turnover?

Recent evidence suggests that genetic and biochemical factors associated with psychoses may also provide an increased propensity to think creatively. The evolutionary theories linking brain growth and diet to the appearance of creative endeavors have been made recently, but they lack a direct link to research on the biological correlates of divergent and creative thought. Expanding upon Horrobin's theory that changes in brain size and in neural microconnectivity came about as a result of changes in dietary fat and phospholipid incorporation of highly unsaturated fatty acids, we propose a theory relating phospholipase A2 (PLA2) activity to the neuromodulatory effects of the noradrenergic system. This theory offers probable links between attention, divergent thinking, and arousal through a mechanism that emphasizes optimal individual functioning of the PLA2 and NE systems as they interact with structural and biochemical states of the brain. We hope that this theory will stimulate new research in the neural basis of creativity and its connection to psychoses.

Acute influences of estrogen and testosterone on divergent and convergent thinking in postmenopausal women

Previous studies indicated an enhanced capability of divergent creative thinking in young women during the ovulatory phase, which expressed itself also by an increased dimensional complexity of ongoing electroencephalographic (EEG) activity. Considering the enhanced plasma levels of estrogen and testosterone characterizing the ovulatory phase, we tested whether short-term administration of estrogen or testosterone in postmenopausal women with constantly low levels of gonadal steroids induces similar changes in divergent thinking. In two placebo-controlled cross-over studies, healthy postmenopausal women (n=12, in each study, mean age 58 years, range 47-65 years) were treated transdermally over 3 days with estrogen and testosterone, respectively, at doses inducing plasma hormone concentrations comparable with those observed in young women around ovulation. Capabilities of divergent thought and convergent analytical thought, performance on motor perseveration, and verbal memory were examined. EEG activity was recorded while subjects performed on tasks of thinking and during mental relaxation. Estrogen impaired divergent thinking (p <0.01) and enhanced convergent thinking, motor perseveration, and memory for the initial word list (p <0.05 for all tests). In parallel, EEG dimensional complexity was reduced (p <0.05). Overall, these changes indicate an estrogen-induced shift from a "divergent" towards a more "convergent" mode of processing. However, overall less consistent, effects of testosterone were opposite to those of estrogen. It increased performance on some of the divergent thinking tasks (p <0.05), and tended to increase EEG dimensional complexity during divergent thinking. Data indicate a differential sensitivity of modes of thinking to short-term treatment with estrogen and testosterone in postmenopausal women.

Effects of hydration and hyperventilation on cortical complexity

The effects of hydration and hyperventilation on cortical complexity were investigated in a sample of 19 healthy volunteers in a double-blind placebo design using magnetoencephalographic recordings. The subjects were asked to abstain from the intake of liquids 18 h before the study. Spontaneous magnetoencephalograms (MEG) were recorded before and after drinking 750 ml water (WAT group: nine subjects) or saline solution (SAL group: ten subjects) with eyes closed and open and during hyperventilation (HV) with eyes open. The MEG data were analysed using both linear (spectral power) and non-linear (pointwise dimension and largest Lyapunov exponent) algorithms. The prediction that intake of water, because of induced cell swelling, will lead to an increased synchronization and a decreased complexity of the spontaneous MEG during hyperventilation was confirmed. Hyperventilation following the drinking condition produced an increase in all power spectra with a stronger increase of delta and theta power after drinking of water. This synchronization of spontaneous MEG is accompanied by a general significant decrease of cortical complexity, especially after water drinking. Moreover, cortical complexity was inversely related to delta and theta power and partly also to alpha power. The SAL and WAT groups showed different relations between alpha power and dimensional complexity during HV: whereas in the SAL group the correlations between these measures became more negative during HV, they reversed in the WAT group to become positive. The synchronizing effect of hyperventilation, leading to a decrease of cortical complexity, is related in the SAL group to delta, theta and alpha power, whereas in the WAT group only delta and theta activity contribute to a reduction of cortical complexity.

Dimensional complexity and power spectral measures of the EEG during functional versus predicative problem solving

Electroencephalograms were recorded in 22 men while solving tasks of visual-pattern completion and during mental relaxation. They were primed (by foregoing trials) to solve these tasks either in a predicative or functional mode of thinking. Predicative thinking required that in order to complete the pattern the subject had to get involved with the logic of the static structure of the pattern and therefore had to recognize the recurrence of certain features of the elements (e.g., shape, color, and size). Functional thinking required involvement in a dynamic reading of the logic of the pattern and therefore to search for operations and actions to be performed on the pattern elements (e.g., pushing, mirroring, and rotating). The EEG complexity during predicative thinking decreased in comparison to functional thinking and mental relaxation, with this reduction being most pronounced over the right parietal cortex. A reduction in dimensional complexity during functional thinking as compared to mental relaxation, which was concentrated over the left central cortex, although significant, was less clear. The reduced EEG complexity during predicative thought, dominant over the right hemisphere, could reflect increased competitive inhibition among respective cortical neuron assemblies in association with the visual analysis of static element features, converging upon those predicates relevant for the solution.

Functional organization of different brain areas during convergent and divergent thinking: an EEG investigation

This study examined the task-related changes in EEG patterns during the experimental condition of convergent and divergent thinking in 36 healthy male subjects. EEG was recorded from 16 sites (10/20 system). After FFT a power was calculated for all 16 loci, and a coherence was estimated for all 120 electrode pairs in six frequency bands (4-30 Hz). Different patterns of the significant changes for the obtained EEG parameters were found during the two thinking types. When compared with the rest, both mental experiences produced the significant desynchronization of alpha1,2 rhythms. At the same time, the convergent thinking induced coherence increases in the &theta;1 band that were more caudal and right-sided, whereas divergent thinking showed mainly amplitude decreases in the caudal regions of the cortex in theta1,2 bands and the massive increases of a amplitude and coherence in the beta2 indicating a close interaction between both hemispheres. Distinct task-related discrepancies of EEG pattern in the beta2 band between the subjects divided into groups of good and bad performers of divergent thinking are also found. Good performance is related to the special organization of the cerebral areas in the beta2 band: (i) increased functional connectivity of central-parietal areas of both hemispheres; and (ii) greater ipsilateral connections between the cortex regions of the right hemisphere.

Brain dynamics in theta and alpha frequency bands and working memory performance in humans

In this study non-linear and linear global electroencephalogram (EEG) changes during a visual working memory task were studied using a separate analysis of theta, lower alpha and upper alpha band filtered data. EEGs were recorded in 21 healthy subjects (62.5 year; SD 2.1; 12 females, nine males) during an eyes-closed no-task condition and a working memory condition. Coarse-grained dimension was estimated for both conditions from spatially embedded EEG data filtered in the theta band and both alpha bands. Linear measures of coupling and mean amplitude were also computed. During the working memory condition lower alpha band dimension increased. Linear analysis showed alpha1 band desynchronization. Female subjects had a higher dimension in the theta band as well as more desynchronization in the theta and alpha1 band. Working memory capacity correlated with a lower theta band dimension during the no-task condition in female subjects. The increase in alpha1 band complexity can be interpreted as increased desynchronization corresponding with attentional processes. Higher complexity/desynchronization in females seems to be a more structural phenomenon and may be more intimately related to task performance.

Non-linear time series analysis of intracranial EEG recordings in patients with epilepsy--an overview

Deterministic chaos offers a striking explanation for apparently irregular behavior, a characteristic feature of brain electrical activity. The framework of the theory of non-linear dynamics provides new concepts and powerful algorithms to analyze such time series. However, different influencing factors render the use of non-linear measures in a strict sense problematic. Nevertheless, if interpreted with care, particularly the correlation dimension or the Lyapunov-exponents provide a means to reliably characterize different states of normal and pathological brain function. This overview summarizes recent findings applying this concept in the field of epileptology that promise to be important for clinical practice. Non-linear measures extracted from the intra-cranially recorded EEG allow (a) localization of epileptogenic areas in different cerebral regions even during seizure-free intervals, (b) investigation of the influence of anticonvulsive drugs and (c) detection of features predictive of imminent seizure activity. Moreover, particularly the dimensional complexity proves a valuable parameter reflecting spatially distributed neuronal activity during verbal learning and memory processes. Specific changes in time of this non-linear measure allow the prediction of memory performance and, in addition, represent an estimate of the recruitment potency in the anterior mesial temporal lobes. Thus, the application of non-linear time series analysis to brain electrical activity offers new information about the dynamics of the underlying neuronal networks.