Cognitive neuroscience of creativity: EEG based approaches

Cognitive neuroscience of creativity has been extensively studied using non-invasive electrical recordings from the scalp called electroencephalograms (EEGs) and event related potentials (ERPs). The paper discusses major aspects of performing research using EEG/ERP based experiments including the recording of the signals, removing noise, estimating ERP signals, and signal analysis for better understanding of the neural correlates of processes involved in creativity. Important factors to be kept in mind to record clean EEG signal in creativity research are discussed. The recorded EEG signal can be corrupted by various sources of noise and methodologies to handle the presence of unwanted artifacts and filtering noise are presented followed by methods to estimate ERPs from the EEG signals from multiple trials. The EEG and ERP signals are further analyzed using various techniques including spectral analysis, coherence analysis, and non-linear signal analysis. These analysis techniques provide a way to understand the spatial activations and temporal development of large scale electrical activity in the brain during creative tasks. The use of this methodology will further enhance our understanding the processes neural and cognitive processes involved in creativity.     

Complex, multifocal, individual-specific attention-related cortical functional circuits

Recent studies focusing on the analysis of individual patterns of non-sensory-motor CNS activity may significantly alter our view of CNS functional mapping. We have recently provided evidence for highly variable attention-related Slow Potential (SP) generating cortical areas across individuals (Basile et al., 2003, 2006). In this work, we present new evidence, searching for other physiological indexes of attention by a new use of a well established method, for individual-specific sets of cortical areas active during expecting attention. We applied latency corrected peak averaging to oscillatory bursts, from 124-channel EEG recordings, and modeled their generators by current density reconstruction. We first computed event-related total power, and averaging was based on individual patterns of narrow task-induced band-power. This method is sensitive to activity out of synchrony with stimuli, and may detect task-related changes missed by regular Event-Related Potential (ERP) averaging. We additionally analyzed overall inter-electrode phase-coherence. The main results were (1) the detection of two bands of attention-induced beta range oscillations (around 25 and 21 Hz), whose scalp topography and current density cortical distribution were complex multi-focal, and highly variable across subjects, including prefrontal and posterior cortical areas. Most important, however, was the observation that (2) the generators of task-induced oscillations are largely the same individual-specific sets of cortical areas active during the resting, baseline state. We concluded that attention-related electrical cortical activity is highly individual-specific (significantly different from sensory-related visual evoked potentials or delta and theta induced band-power), and to a great extent already established during mere wakefulness. We discuss the critical implications of those results, in combination with other studies presenting individual data, to functional mapping: the need to abandon group averaging of task-related cortical activity and to revise studies on group averaged data, since the assumption of universal function to each cortical area appears deeply challenged. Clinical implications regard the interpretation of focal lesion consequences, functional reorganization, and neurosurgical planning.     

Real-time change detection of steady-state evoked potentials

Steady-state evoked potentials (SSEP) are the electrical activity recorded from the scalp in response to high-rate sensory stimulation. SSEP consist of a constituent frequency component matching the stimulation rate, whose amplitude and phase remain constant with time and are sensitive to functional changes in the stimulated sensory system. Monitoring SSEP during neurosurgical procedures allows identification of an emerging impairment early enough before the damage becomes permanent. In routine practice, SSEP are extracted by averaging of the EEG recordings, allowing detection of neurological changes within approximately a minute. As an alternative to the relatively slow-responding empirical averaging, we present an algorithm that detects changes in the SSEP within seconds. Our system alerts when changes in the SSEP are detected by applying a two-step Generalized Likelihood Ratio Test (GLRT) on the unaveraged EEG recordings. This approach outperforms conventional detection and provides the monitor with a statistical measure of the likelihood that a change occurred, thus enhancing its sensitivity and reliability. The system’s performance is analyzed using Monte Carlo simulations and tested on real EEG data recorded under coma.     

Electric reactive potentials to events of a positive and negative emotional nature

The event-related potentials (ERP) in the frontal and posterior associative cortex in the right and left hemispheres were studied in two different outcomes of tennis television game. These outcomes were "win" and "loss" of the ball, the first serving as a model of positive, the second--of negative emotional reactions. The averaging procedure was synchronized with the moment of ball crossing the racket line. The ERP consisted of four waves: P300, N600, P800, N1000. The most characteristic interhemispheric difference for the win was an increase of N600 wave in the left posterior associative cortex and for the loss--a decrease of P800 wave in the right frontal area. Thus the positive and negative emotional reactions have specific spatiotemporal organization and are based on complicated interaction of cortical areas.     

Intercentral EEG relationships in regressive and chronic post-traumatic Korsakoff syndrome.]

Dynamic EEG study of patients with posttraumatic Korsakoff's syndrome (KS) with the application of complex analysis methods revealed a complicated pathological structure of the intercentral relations of cortical electrical activity. The interhemispheric EEG coherence between symmetrical frontal cortical areas are sharply reduced, while the intrahemispheric coherence are increased in comparison with the normal values. The proposed technique of segregation of statistically homogeneous spectro-coherent characteristics made it possible to reveal the earlier intercentral EEG relations formed by stable and variable coherence spectra. The structure formed by the stable and variable coherence spectra in KS differs from that reflected in the mean coherence levels. During the KS regression, the EEG coherence between the right and left frontal areas increased to the normal level, and the variable spectra are revealed. In the chronic KS syndrome, the pathological intercentral relations persist, while the variable relations in the frontal areas are absent. A reduction of pathologically decreased intrahemispheric coherence selectively revealed in the right hemisphere during the KS regression and formation of variable relations in this hemisphere point to a leading role of the right hemisphere in development of compensatory processes in KS. The reciprocal relations between the intra- and interhemispheric coherence and coherence dynamics in the theta rhythm suggest that pathological activity in the basal diencephalic structures plays an important role in formation of the pathological EEG pattern in KS.     

The effect of the level of consciousness on the spatial organization of cortical activity in mental processes

In the present study the influence of the level of consciousness on spatial organization of the cortical functional activity in human psychic processes was investigated. For regulation of the level of consciousness models were used of hypnotic analgesia, automatization of intellectual actions and mental activity in hypnotic state. Evaluation of the mosaic of the cortical activity was made by parameters of spatial synchronization of the potentials with topographic mapping of crosscorrelation, spectral and coherent-phasic EEG characteristics. The obtained data allow to conclude about special role of the frontal areas of the left hemisphere in the process of realization of information. It has been shown that one of the main functions in neurophysiological structure of consciousness is the selection of signals according to dominating motivation. The frontal areas of the left hemisphere control the degree of inclusion of foci of increased activity, specific and non-specific for each type of activity, and possibly, regulate the way of transformation of the information.     

Differential effects of normal aging on sources of standard N1, target N1 and target P300 auditory event-related brain potentials revealed by low resolution electromagnetic tomography (LORETA)

The P300 event-related potential (ERP) is considered to be closely related to cognitive processes. In normal aging, P300 scalp latencies increase, parietal P300 scalp amplitudes decrease and the scalp potential field shifts to a relatively more frontal distribution. Based on ERPs recorded in 172 normal healthy subjects aged between 20 and 88 years in an auditory oddball paradigm, the effects of age on the electrical activity in the brain corresponding to N1 and P300 components were estimated by means of low resolution electromagnetic tomography (LORETA). This distributed approach directly computes a unique 3-dimensional electrical source distribution by assuming that neighbouring neurons are simultaneously and synchronously active. N1 LORETA generators, located predominantly in both auditory cortices and also symmetrically in prefrontal areas, increased with advancing age for standards but remained stable for targets. P300 LORETA generators, located symmetrically in the prefrontal cortex, in the parieto-occipital junction and in the inferior parietal cortex (supramarginal gyrus) and medially in the superior parietal cortex, were differentially affected by age. While age did not affect parieto-occipital sources, superior parietal and right prefrontal sources decreased pronouncedly. Thus, in normal aging, P300 current density decreased in regions were a fronto-parietal network for sustained attention was localized.     

Changes in the spatial organization of the cortical electrical activity during formation and actualization of a cognitive set to facial expression

Coherence function of the EEG in the bands of 8-13 (alpha rhythm) and 14-25 Hz (beta rhythm) was analyzed in 35 healthy adult subjects during formation and testing of a visual cognitive set to pictures of faces with different emotional expressions. The intra- and interhemispheric coherences of the potentials in the frontal area and coherence between the right frontal and temporal derivation were shown to increase at the stage of set actualization. The results of the analysis confirm the suggestion that the frontal cortical areas are predominantly involved in formation and actualization of the set to facial emotional expression. The conclusion is based on the idea that the spatial synchronization of the brain electrical potentials is an index of the functional relations between the corresponding cortical areas and their cooperative involvement in a certain kind of activity (their simultaneous activation).     

Event-related potentials associated with a shift in the strategy of visual perception during recognition of a hierarchical stimulus

Recording of event-related potentials (ERPs) was used to study the brain mechanisms of shifting the strategy of recognition of the global and local levels of a hierarchical image by adult subjects. A shift in the strategy of visual recognition results in substantial changes in ERP parameters in the caudal and frontocentral cortical areas. The activation effect of the switchover from one recognition strategy to another is associated with an increase in the amplitude of early ERP components (C1, P100, and N150) of the caudal cortical areas. Changes in the late ERP components associated with processing of significant information features during the shift in the recognition strategy are observed in the frontal areas within the interval 388–579 ms, with the amplitude of components N300 and N400 increasing.     

The nature of the relationships between the dynamics of local interneuronal connections and of the total bioelectrical activity of the frontal cortex in the dog]

Temporal patterns of correlated firings were studied in small groups of neurons simultaneously recorded in the frontal cortex of a behaving dog. To identify the character of relations between the patterns of interneuronal connections in local ensembles and event-related potentials (ERP), the following procedure was applied. At the first step, single trials of behavioral task were classified by clustering temporal distribution of correlated firings in pairs of units. Then the surface ERP were averaged separately for each cluster and parameters of the ERP components were compared between the clusters. The analysis revealed 3 of 7 recording sites, where significant differences were observed between the ERP sampled from the clusters with different structures of the local interneuronal connections. The results suggest that temporal modulation of interactions between neurons in local ensembles reflects a large-scale reorganization of cortical networks.     

A latent state space model for estimating brain dynamics from electroencephalogram (EEG) data

Modern neuroimaging technologies have substantially advanced the measurement of brain activity. Electroencephalogram (EEG) as a noninvasive neuroimaging technique measures changes in electrical voltage on the scalp induced by brain cortical activity. With its high temporal resolution, EEG has emerged as an increasingly useful tool to study brain connectivity. Challenges with modeling EEG signals of complex brain activity include interactions among unknown sources, low signal-to-noise ratio, and substantial between-subject heterogeneity. In this work, we propose a state space model that jointly analyzes multichannel EEG signals and learns dynamics of different sources corresponding to brain cortical activity. Our model borrows strength from spatially correlated measurements and uses low-dimensional latent states to explain all observed channels. The model can account for patient heterogeneity and quantify the effect of a subject's covariates on the latent space. The EM algorithm, Kalman filtering, and bootstrap resampling are used to fit the state space model and provide comparisons between patient diagnostic groups. We apply the developed approach to a case-control study of alcoholism and reveal significant attenuation of brain activity in response to visual stimuli in alcoholic subjects compared to healthy controls.     

Spontaneous Decoding of the Timing and Content of Human Object Perception from Cortical Surface Recordings Reveals Complementary Information in the Event-Related Potential and Broadband Spectral Change

The link between object perception and neural activity in visual cortical areas is a problem of fundamental importance in neuroscience. Here we show that electrical potentials from the ventral temporal cortical surface in humans contain sufficient information for spontaneous and near-instantaneous identification of a subject’s perceptual state. Electrocorticographic (ECoG) arrays were placed on the subtemporal cortical surface of seven epilepsy patients. Grayscale images of faces and houses were displayed rapidly in random sequence. We developed a template projection approach to decode the continuous ECoG data stream spontaneously, predicting the occurrence, timing and type of visual stimulus. In this setting, we evaluated the independent and joint use of two well-studied features of brain signals, broadband changes in the frequency power spectrum of the potential and deflections in the raw potential trace (event-related potential; ERP). Our ability to predict both the timing of stimulus onset and the type of image was best when we used a combination of both the broadband response and ERP, suggesting that they capture different and complementary aspects of the subject’s perceptual state. Specifically, we were able to predict the timing and type of 96% of all stimuli, with less than 5% false positive rate and a ~20ms error in timing.     

Hemispheric asymmetry of visual evoked potentials during human recognition of facial emotional expressions

Visual evoked potentials (VEP) in standard 16 EEG derivations were recorded in 26 young men and 20 women during recognition of facial emotional expressions and geometric figures. The stimuli were presented on a computer screen in the center of the visual field or randomly in the right or left vision hemifields. Peak VEP latency and mean amplitude in 50-ms epochs were measured; spatiotemporal VEP dynamics was analyzed in a series of topographic maps. The right hemisphere was shown to be more important in processing emotional faces. The character of the asymmetry was dynamic: at earlier stages of emotion processing the electrical activity was higher in the right inferior temporal region compared to the left symmetrical site. Later on the activity was higher in the right frontal and central areas. The dynamic mapping of "face-selective" component N180 of VEPs revealed the onset of activation over the right frontal areas that was followed by the fast activation of symmetrical left zones. Notably, this dynamics didn't correlate with the hemifield of stimuli exposition. The degree of asymmetry was lower during presentation of figures, especially in the inferior temporal and frontal regions. The prominent asymmetry of information processes in the inferior temporal and frontal areas was suggested to be specific for recognition of facial expression.     

Developmental and Individual Differences in the Neural Processing of Dynamic Expressions of Pain and Anger

We examined the processing of facial expressions of pain and anger in 8-month-old infants and adults by measuring event-related brain potentials (ERPs) and frontal EEG alpha asymmetry. The ERP results revealed that while adults showed a late positive potential (LPP) to emotional expressions that was enhanced to pain expressions, reflecting increased evaluation and emotional arousal to pain expressions, infants showed a negative component (Nc) to emotional expressions that was enhanced to angry expressions, reflecting increased allocation of attention to angry faces. Moreover, infants and adults showed opposite patterns in their frontal asymmetry responses to pain and anger, suggesting developmental differences in the motivational processes engendered by these facial expressions. These findings are discussed in the light of associated individual differences in infant temperament and adult dispositional empathy.     

Extracting Visual Evoked Potentials from EEG Data Recorded During fMRI-guided Transcranial Magnetic Stimulation

Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological effects. Specifically, by creating a transient interference with the normal activity of a target region and measuring changes in an electrophysiological signal, we can establish a causal link between the stimulated brain area or network and the electrophysiological signal that we record. If target brain areas are functionally defined with prior fMRI scan, TMS could be used to link the fMRI activations with evoked potentials recorded. However, conducting such experiments presents significant technical challenges given the high amplitude artifacts introduced into the EEG signal by the magnetic pulse, and the difficulty to successfully target areas that were functionally defined by fMRI. Here we describe a methodology for combining these three common tools: TMS, EEG, and fMRI. We explain how to guide the stimulator''s coil to the desired target area using anatomical or functional MRI data, how to record EEG during concurrent TMS, how to design an ERP study suitable for EEG-TMS combination and how to extract reliable ERP from the recorded data. We will provide representative results from a previously published study, in which fMRI-guided TMS was used concurrently with EEG to show that the face-selective N1 and the body-selective N1 component of the ERP are associated with distinct neural networks in extrastriate cortex. This method allows us to combine the high spatial resolution of fMRI with the high temporal resolution of TMS and EEG and therefore obtain a comprehensive understanding of the neural basis of various cognitive processes.     

Cognitive network interactions and beta 2 coherence in processing non-target stimuli in visual oddball task

Spatiotemporal dynamics of event-related potentials (ERP) evoked by non-target stimuli in a visual oddball experiment and the presence of coherent oscillations in beta 2 frequency band of decomposed EEG records from peristimulus period were investigated by means of intracranial electrodes in humans. Twenty-one patients with medically intractable epilepsy participated in the study. The EEG signal was recorded using platinum electrodes implanted in several cortical and subcortical sites. Averaged 2 s EEG records were analyzed. Task-specific EEG changes were found in each patient, ERPs were derived from 92 electrodes used (96 % of possible cases). In the majority of analysed cases, ERPs were composed of several distinct components, and their duration was mostly longer than 1 s. The mean onset of the first ERP component was 158+/-132 ms after the stimulus (median 112 ms, minimum value 42 ms, maximum value 755 ms), and large variability of these onset times was found in all the investigated structures. Possible coherence between neural activities of remote brain sites was investigated by calculating running correlations between pairs of decomposed EEG records (alpha, beta 1, beta 2 frequency bands were used, total number of correlated pairs was 662 in each frequency band). The record pairs exhibiting highly correlated time segments represented 23 % of all the investigated pairs in alpha band, 7 % in beta 1 band, and 59 % in beta 2 band. In investigated 2 s record windows, such segments were distributed evenly, i.e. they were also found before the stimulus onset. In conclusion, the results have implicated the idea that a lot of recorded ERPs was more or less by-products of chance in spreading a signal within the neuronal network, and that their functional relevance was somewhat linked with the phenomenon of activity synchronization.     

Neural synchrony during response production and inhibition

Inhibition of irrelevant information (conflict monitoring) and/or of prepotent actions is an essential component of adaptive self-organized behavior. Neural dynamics underlying these functions has been studied in humans using event-related brain potentials (ERPs) elicited in Go/NoGo tasks that require a speeded motor response to the Go stimuli and withholding a prepotent response when a NoGo stimulus is presented. However, averaged ERP waveforms provide only limited information about the neuronal mechanisms underlying stimulus processing, motor preparation, and response production or inhibition. In this study, we examine the cortical representation of conflict monitoring and response inhibition using time-frequency analysis of electroencephalographic (EEG) recordings during continuous performance Go/NoGo task in 50 young adult females. We hypothesized that response inhibition would be associated with a transient boost in both temporal and spatial synchronization of prefrontal cortical activity, consistent with the role of the anterior cingulate and lateral prefrontal cortices in cognitive control. Overall, phase synchronization across trials measured by Phase Locking Index and phase synchronization between electrode sites measured by Phase Coherence were the highest in the Go and NoGo conditions, intermediate in the Warning condition, and the lowest under Neutral condition. The NoGo condition was characterized by significantly higher fronto-central synchronization in the 300-600 ms window, whereas in the Go condition, delta- and theta-band synchronization was higher in centro-parietal regions in the first 300 ms after the stimulus onset. The present findings suggest that response production and inhibition is supported by dynamic functional networks characterized by distinct patterns of temporal and spatial synchronization of brain oscillations.     

Effects of Correct and Wrong Answers on ERPs Recorded under Conditions of the Continuous Performance Test in ADHD/Normal Participants

Parameters of event-related potentials (ERPs) regarding correct and wrong answers under conditions of the continuous performance test (CPT) were measured in 50 adult subjects characterized by different levels of sustained attention with the absence/presence of attention deficit/hyperactivity disorders (ADHD). For ERP extraction, the average for each group of signals, which were time-locked to the onset of stimuli, was calculated; two ERP groups were considered separately for correct and wrong answers. In both groups, the P300 wave was clearly observed. The time dynamics of ERP components were investigated in six defined time blocks. At the peak of P300, a prominent component of brain activity could be observed. Some ERP morphological features (704 items) were extracted from these potentials. The results indicated that 11 of the obtained features showed a significant (P < 0.01) relation to the level of sustained attention. When comparing correct and wrong answers, 10 features in the normal group and 3 features in the ADHD group demonstrated significant differences (P < 0.05), which means that the participant’s response is reflected in the features of EEG signal. The results reveal a promising relation between CPT results and some parameters of brain signals, which can be used for further evaluations of the sustained attention level.     

Comparative analysis of changes in short EEG segments during music perception based on event-related synchronization/desynchronization and wavelet synchronicity

The goal of the pilot study was to analyze the characteristics of changes in short EEG segments recorded from 32 sites during perception of musical melodies by healthy subjects depending on logical (recognition) and emotional (pleasant/unpleasant) estimation of the melody. For this purpose, the changes in event-related synchronization/desynchronization and the indices of wavelet synchrony of EEG responses were compared in 31 healthy subjects (18 to 60 years old). It has been shown that melody recognition during logical estimation of music is accompanied by event-related desynchronization in the left frontal-parietal-temporal area. Emotional estimation of a melody is characterized by event-related synchronization in the left frontal-temporal area for pleasant melodies, desynchronization in the temporal area for unpleasant melodies, and desynchronization in the occipital area for melodies inducing no emotional response. The analysis of EEG wavelet synchronization characterizing reactive changes in the interaction between cortical areas shows that the most distinct topographic differences are associated with the type of music processing: logical (familiar/unfamiliar) or emotional (pleasant/unpleasant). The changes in interhemispheric connections between the associative cortical areas (central, frontal, temporal) are greater during emotional estimation, while the changes in inter- and intrahemispheric connections between the projection areas of the acoustic analyzer (temporal area) are greater during logical estimation. It is assumed that the revealed event-related synchronization/desynchronization is most likely to reflect the activation component of musical fragment estimation, whereas wavelet analysis provides insight into the character of musical stimulus processing.     

Time-Dependent Statistical and Correlation Properties of Neural Signals during Handwriting

To elucidate the cortical control of handwriting, we examined time-dependent statistical and correlational properties of simultaneously recorded 64-channel electroencephalograms (EEGs) and electromyograms (EMGs) of intrinsic hand muscles. We introduced a statistical method, which offered advantages compared to conventional coherence methods. In contrast to coherence methods, which operate in the frequency domain, our method enabled us to study the functional association between different neural regions in the time domain. In our experiments, subjects performed about 400 stereotypical trials during which they wrote a single character. These trials provided time-dependent EMG and EEG data capturing different handwriting epochs. The set of trials was treated as a statistical ensemble, and time-dependent correlation functions between neural signals were computed by averaging over that ensemble. We found that trial-to-trial variability of both the EMGs and EEGs was well described by a log-normal distribution with time-dependent parameters, which was clearly distinguished from the normal (Gaussian) distribution. We found strong and long-lasting EMG/EMG correlations, whereas EEG/EEG correlations, which were also quite strong, were short-lived with a characteristic correlation durations on the order of 100 ms or less. Our computations of correlation functions were restricted to the spectral range (13–30 Hz) of EEG signals where we found the strongest effects related to handwriting. Although, all subjects involved in our experiments were right-hand writers, we observed a clear symmetry between left and right motor areas: inter-channel correlations were strong if both channels were located over the left or right hemispheres, and 2–3 times weaker if the EEG channels were located over different hemispheres. Although we observed synchronized changes in the mean energies of EEG and EMG signals, we found that EEG/EMG correlations were much weaker than EEG/EEG and EMG/EMG correlations. The absence of strong correlations between EMG and EEG signals indicates that (i) a large fraction of the EEG signal includes electrical activity unrelated to low-level motor variability; (ii) neural processing of cortically-derived signals by spinal circuitry may reduce the correlation between EEG and EMG signals.