S. G. Danko

Study of the Brain Organization of Creativity: III. Brain Activation Assessed by the Local Cerebral Blood Flow and EEG

In this article, a polymethodological approach was applied to the analysis of the brain organization of creative thinking. The electroencephalographic studies and the investigation of the local cerebral blood flow by means of positron-emission tomography in the same testing conditions substantially validate and supplement each other. The physiological indices of subjects were recorded during the composition of stories with the given words belonging to the same or different semantic fields. The reconstruction of correct grammatical forms in a presented text and memorizing of a set of words were used as control tasks. The fundamental importance of the processes taking place in both frontal lobes (Brodmanns areas (BA) 8–11 and 44–47) and the interhemispheric interaction was demonstrated.

EEG differences between resting states with eyes open and closed in darkness

Transition from a resting state with eyes closed (REC) to a resting state with eyes open (REO) is associated with visible changes in EEG, which are traditionally considered to be a sign of reorganization of the brain’s activity in response to visual stimuli. The EEGs recorded in the REC and REO states in complete darkness, when the stimulatory effect of light to the eye’s retina was absent, were compared. Thirty healthy subjects participated in the study. EEG in the range of 1.5–50 Hz was recorded from nineteen zones of the head monopolarly. It was found that, under conditions of complete darkness, the REC and REO states significantly differed in their EEG spectral power and coherence in the Δ, θ, α1, α2, β1, β2 and γ frequency bands. Under experimental conditions, these changes in the EEG could not be induced by external influence to the visual system. Therefore, we suppose that they are correlates of the switching of involuntary preliminary attention from internally directed attention specific for the REC state to externally directed attention specific for the REO state.

Influence of the Emotional Perception of a Signal on the Electroencephalographic Correlates of Creative Activity

Subjects were asked to invent as many definitions (ideas of a definition) of emotionally positive, emotionally negative, or neutral notions as possible using notions of other semantic fields. In the control task, the notions to be defined and to be used in definition were of the same or close semantic fields. The EEG was recorded during task performance. Significant differences in EEG local power (LS) and spatial synchronization (SS) were established in comparison of EEGs recorded during performance of creative tasks differing in complexity, complex creative tasks differing in emotional background (positive and negative), and tasks performed with or without emotional induction. Differences in LS and SS were most distinct in the medio- and posterotemporal areas of both hemispheres. Positive emotions increased LS and differently affected SS. Negative emotions predominantly increased SS. Analysis of self-reports of the subjects showed that both positive and negative induced emotions increased the fluency of association of notions from different semantic fields but decreased the originality of the ideas produced by a subject to define a notion.

[The reflection of different aspects of brain activation in the electroencephalogram: quantitative electroencephalography of the states of rest with the eyes open and closed].

The rest states with the eyes open (RSEO) and closed (RSEC) were subjected to quantitative EEG study as states similar in the pattern of mental activity and subjective assessments but different in the EEG pattern. The mean values of the spectral power and EEG coherence function were compared in 74 subjects for the following bands: Δ, ϑ, α1, α2, β1, β2, and γ. Upon the transition from the RSEC to the RSEO, the EEG local power significantly decreased over the whole cortex for the α, ϑ, and β bands. A simultaneous decrease in the EEG power in all the bands (including β and γ) was most pronounced (as judged by relative changes and tests of significance of difference) in the parietooccipital derivations immediately related to the cortical zones where an increase in the neuronal activity upon opening the eyes is most probable. A significant increase in the EEG power was observed only for the γ band in frontal derivations F3 and F4. Significant differences in the mean EEG coherence in the RSEO-RSEC comparison were present in many derivation pairs, especially in the α2, β1, β2, and γ bands. For each of these bands, the number of differences determined on the basis of Fisher test was more than 70% of the maximum possible number. In the overwhelming majority of cases, the coherence was lower in the RSEO; however, in the caudal cortical zones, a higher coherence in the α1, ϑ, and Δ bands in the RSEO was rather typical. The results confirmed that the two states under study differ in a number of averaged EEG parameters with high statistical significance and may be used as reference states during performance of tasks with the eyes open and closed, respectively. The differences between the RSEC and the RSEO may be caused by the fact that the RSEC is a functional state oriented predominantly to the analysis of internal information (internally oriented), and the RSEO, predominantly to the analysis of information coming from the outside (externally oriented). The pattern of the observed EEG differences points to a combination of effects both localized in the visual zone and reflecting changes in the network cortical activity, i.e., simultaneous, although nonuniform, changes over all the main zones of the cortex. Comparison of the results with published estimations of differences in the local cerebral blood flow (ICBF) between the RSEO and the RSEC shows that increase in the ICBF may be associated with a local decrease in the EEG spectral power in any frequency band, including the high-frequency β and γ bands, or several frequency bands simultaneously.

Comparison of the effects of the subjective complexity and verbal creativity on EEG spectral power parameters

The EEG recording was made when the subjects performed tasks that involved overcoming the stereotype (creative) and retrieving information from memory (noncreative) with the usual and complicated presentation of the initial material (incomplete proverbs and sayings without concluding words). The subjective complexity of the task performance under different conditions was assessed. The EEG power from 19 EEG derivations was compared in the β2 and γ frequency bands. The creative task performance was associated with a marked increase in the EEG power; significantly more complicated noncreative tasks were not accompanied by marked changes in the EEG power in these bands.

Changes in the power and coherence spectra of the EEG rhythmic components during solution of a verbal creative task of overcoming a stereotype

Changes in EEG power and coherence were analyzed in 117 subjects during the performance of the creative task of finishing well-known proverbs in a new way, so as to change, if possible, their meaning, and the noncreative task of recalling the original (well-known) version of the end of each proverb. A characteristic feature of the creative task was that proverbs and sayings are stereotypes fixed in a memory matrix. During the task performance, the EEG was recorded in 19 derivations according to the international 10–20 system. Performance of the creative task was accompanied by a highly significant and reproducible increase in the power of the γ and β2 EEG frequency bands, as well as a less pronounced decrease in the power of the ϑ band in the central and parietoccipital cortical areas. In addition, the performance of the creative task was also characterized by an increase in the EEG coherence in the α2, β2, and γ bands. No gender-related differences were found in the patterns of EEG changes.

Electroencephalographic Correlates of Brain States during Verbal Learning: II. Characteristics of EEG Spatial Synchronization

Electroencephalograms (EEGs) were recorded by 19 standard derivations in 57 subjects in a resting state with the eyes opened, during memorization of verbal bilingual semantic pairs (Latin and Russian), and during retrieval (monitoring) of the learned information. Statistical comparison of the EEG spectral power in the frequency bands θ, α1, α2, β1, β2, and γ showed that induction of the states of memorization (encoding) and retrieval of the verbal information led to multiple significant changes in the EEG absolute power (local synchronization) as compared to the state of rest. Such changes took place simultaneously in different frequency bands over the entire cortex. The relative values and significance of changes in different cortical regions varied. The main features of the EEG power-difference patterns were an increase in the power of the γ band over the entire cortex, a bilateral increase in the power of the β2 band in the temporal areas, and a decrease in the power of the α2 and α1 bands over a large part of the cortical surface. In the state of retrieval, synchronization in the γ- and β2 bands and desynchronization in the α2 band were significantly stronger than in the state of encoding. In the α1 band, desynchronization was more pronounced in the state of encoding than in the state of retrieval. The results are discussed in combination with the available data of the EEG studies of different types of memory.

Effect of the personality component on the electroencephalographic correlates of induced emotional states

Our previous study [1] showed that similar changes in EEG power are induced by emotionally positive and emotionally negative states when internal induction is based on predetermined circumstances (scenic situations) but, when internal induction is based on autobiographical recollections, EEG changes induced by emotionally negative states are significantly lower than those induced by emotionally positive states. This conclusion was based on visual comparisons of the patterns of significant differences for two groups of subjects who completed different tasks rather than on a direct statistical comparison of the EEG power spectra for different tasks completed by the same subjects. In this study, we tried to reproduce the above effects in a direct comparison involving another group of subjects who performed both tasks in the same EEG session.

Induction of emotional states by reading aloud texts with various emotional valences and changes in the EEG power in the β and γ frequency bands

The EEG power in the β1, β2, and γ frequency bands during reading according to the method of “self-regulatory utterance” was compared in subjects reading aloud emotionally neutral business texts related to an unknown field of activity, fiction texts with clear positive or negative valences or personally important autobiographic texts with similar emotional valences. Two groups of subjects participated in the study: students training to be actors (N = 22) and students with other specializations (N = 23). We observed higher values of the EEG power in the γ (30–40 Hz) and β2 (18.5–29.5 Hz) frequency bands when comparing the states during reading of emotionally positive and emotionally negative fiction texts and personally important texts. These data are similar to our previous studies with the use of techniques that apply internal induction of positive or negative emotions without speech, in different groups of subjects. Internal induction of positive emotions was associated with an increase in the EEG power in these bands compared to the performance of an emotionally neutral task, whereas induction of negative emotions resulted in a decrease in the EEG power.

Electroencephalographic characteristics of cognitive-specific alerting attention in verbal learning: I. Characteristics of EEG local synchronization

The EEG was recorded in 19 standard derivations in 88 students in the following states: rest with the eyes open, memorization (learning) of bilingual verbal semantic pairs (Latin and Russian), and retrieval (check) of the learned information. In order to calculate the mean heart rate (HR) in each state, the electrocardiogram was recorded. The subjective difficulty of task performance was assessed. Statistical comparison of the spectral power estimates in these states for frequency bands θ (4–7 Hz), α1 (7–10 Hz), α2 (10–13 Hz), β1 (13–18 Hz), β2 (18–30 Hz), and γ (30–40 Hz) demonstrated a number of significant differences in the EEG absolute power (local synchronization) between the states reproducible in subgroups. Comparison of the states of memorization and retrieval showed that, in the state of memorization, the EEG power in the γ, β2, and θ bands was significantly lower throughout the cortical surface. Comparison of the active states with the reference state of rest showed that, in both active states, changes in the EEG power were of the same direction in the majority of the frequency bands (an increase in the θ, β2, and γ bands and a decrease in the α2 band) except α1, in which memorization was predominantly accompanied by a decrease in the power, whereas retrieval was associated with an increase. No significant differences were found between the states of memorization and retrieval in the HR or the subjective estimate of task difficulty. The results can be interpreted as a reflection of cognitive-specific forms of general preparatory attention.