N. P. Bechtereva

EEG local and spatial synchronization during a test on the in site strategy of solving creative verbal tasks

In earlier studies of brain mechanisms of creative activity that were performed at the Institute of the Human Brain, Russian Academy of Sciences, it was found that, during composition of a story including words from different semantic fields, subjects used either a strategy of “uniform” work on the text (a successive, noninsight strategy) or a strategy of deferred, “impulsive” generation of a story immediately before or even during a report (an insight strategy) [1]. At the previous stage, we examined subjects using only the noninsight strategy [2, 3]. In this communication, we present the results of EEG analysis of subjects during their performance of a task requiring the insight strategy. The subjects were presented with two kinds of tasks: (1) in the test task, task D (a variation of Mednick’s remote association test), a subject had to link a “difficult” sequence of 12 words from different semantic fields with associated words (nouns); (2) in the control task, task E (a variation of the generalization test applied in clinical psychology), a subject had to choose five concrete examples (objects or phenomena) belonging to a given word category in response to words of these categories presented in random order (“easy” sequences). Two groups of subjects participated in the study. The first group (15 subjects) comprised first-year students of the Faculty of Acting of the State Academy of Dramatic Art (9 men and 6 women). The second group (15 subjects) comprised students of different St. Petersburg higher educational institutions (7 men and 8 women). The subjects performed each task in silence within a period of 10 s after its administration. The EEG was recorded over the course of this period. They then gave an oral report after a signal. The monopolar EEG was recorded in 19 standard derivations (10/20 system) in reference to linked earlobe electrodes in the frequency band 1.5–30 Hz with a sampling rate of 125 Hz. During the task performance, ten 1-s EEG segments were recorded. The records were analyzed visually, and EEG segments with visible artifacts were excluded from the subsequent analysis. The EEG quantitative characteristics were calculated by means of the WinEEG software package, developed by V.A. Ponomarev. In this communication, we deal with estimations of the EEG absolute spectral power and coherence function (characteristics of the local and spatial EEG synchronization, respectively), summed in the following frequency bands: ∆ (1.5–3.5 Hz), θ (4–7 Hz), α 1 (7.5–9.5 Hz), α 2 (10–12.5 Hz), β 1 (13–18 Hz), and β 2 (18.5–30 Hz). Arrays of the estimations, averaged for each subject during performance of each task, were normalized using the transforms Y =

Electroencephalographic Correlates of Mental Performance of Emotional Personal and Scenic Situations: I. Characteristics of Local Synchronization

An electroencephalogram (EEG) was recorded in 19 standard derivations in two groups of subjects (student actors and nonactors) during emotionally positive and negative mental recalls of personal experiences (test 1) or mental reproduction of scenic situations (test 2), as well as during mental count of time. Statistical comparison of EEG spectral power estimations in the frequency bands Δ, θ, α1, α2, β1, and β2 showed that the induction of emotionally positive and emotionally negative states led to statistically significant changes in the EEG absolute power (local synchronization) simultaneously in many derivations and frequency bands. Analysis of all possible comparisons and changes in frequency bands showed that bilateral prefrontal and temporal cortical areas are most active during the internal induction of emotional states. Emotionally positive states were characterized, predominantly, by higher local EEG power than emotionally negative states. The EEG power changes accompanying internal induction of emotionally negative and positive states were of the same order in the case of reproduction of a presented situation (scenic material), whereas, in the case of recall of personal experience, emotionally negative states were accompanied by substantially weaker EEG spectral changes than emotionally positive states. The internal induction of emotional states on the basis of scenic material was accompanied by a pronounced increase in the power of the EEG Δ range over the whole cortical surface. EEG reactions to induction of emotional states were generally stronger in actors than in nonactors. In case of emotional induction on the basis of scenic material, qualitative differences in the EEG reactions were also revealed between the groups. The findings are discussed in comparison with known data of investigations into regional cerebral blood flow during internal emotional induction and EEG studies of internal and external emotional induction.

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.

Changes in EEG coherence during tests for nonverbal (Figurative) creativity

Brain neurodynamics was studied by the EEG method during the performance of a task for figurative (or imaginative) creativity. The EEG was recorded in 19 standard derivations according to the international 10–20 system in 30 subjects. The following creative tasks were presented to subjects to involve them in the creative process: (Crl) thinking up and drawing an original picture; (Cr2) drawing a face, a house, and a clown in an original manner; (C1) drawing a picture from memory; and (C2) drawing geometric figures without any system. All the tasks had to be performed using a given set of geometric figures (a circle, semicircle, triangle, and rectangle). Statistical analysis of the EEG coherence function in these states for the frequency bands Δ, θ, α1, α2, β1, β2, and γ showed that the performance of creative and control tasks was associated with significant coherence changes in all the EEG frequency bands. As compared to the control tasks, performance of creative tasks caused an increase in the coherence of the α1-and α2 bands, more pronounced when creative tasks were compared with the second control task. In addition, the performance of the creative tasks (as compared to the control tasks) was accompanied by a decrease in the interhemispheric coherence of high-frequency rhythms (β2 and γ) and an increase in the intrahemispheric coherence of these rhythms. The findings are compared to the results of previous EEG studies on creative activity.

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.

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.

Electroencephalographic Correlates of Mental Performance of Emotional Autobiographic and Scenic Situations: II. Characteristics of Spatial Synchronization

The EEG spatial synchronization in the frequency bands Δ, θ, α1, α2, β1, and β2 was studied on the basis of estimations of corresponding mean values of the coherence function in two groups of subjects (students actors and nonactors) during internal induction of emotional states by means of recall of autobiographic experience and mental performance of given scenic situations as a known character. Emotion-induced changes in the state of the cortex were reflected in statistically significant heterogeneous changes in the EEG spatial synchronization in many cortical areas and different frequency bands. The results obtained are discussed in combination with data presented earlier on changes in EEG local synchronization obtained in the course of the same experiments. The EEG β bands stand out against the background of extensive changes in the local and spatial EEG synchronization: the EEG changes in these bands are most prominent. Also, the changes in the prefrontal and temporal cortical areas, most involved in actualization of emotional states, are noteworthy. Some of the findings can be interpreted as confirming the hypothesis about neurophysiological mechanisms of brain defense from functionally excessive emotions.

On the Scientific School

At the 33rd International Congress of Physiological Sciences in St. Petersburg in 1997, I had the honor to give the inaugural lecture. There I presented, along with other materials, the main ideas and methodologies that determined the breakthroughs in study of the human brain in the 20th century. The first breakthrough was related to the possibility and reasonability of directly recording the activities of cerebral structures, including the impulse activity of neuronal populations. These studies were performed in two laboratories in the United States (headed by G.A. Ojemann and T.L. Halgren), one laboratory in the United Kingdom (headed by W. Grey Walter), and our laboratory (headed by myself), our studies on the cerebral organization of higher nervous functions being the most large-scale. These studies began in 1962, when the Division of Applied Neurophysiology (later “promoted” to become the Division of Human Neurophysiology) was organized at the Institute of Experimental Medicine of the Academy of Medical Sciences of the USSR. The conditions for organizing the division were favorable: I was summoned to the Central Committee of the Communist Party of the Soviet Union and, after a discussion on some scientific subjects, was asked to organize a research unit for studying the physiology of the human brain in one of the research institutions of Leningrad or Moscow. This plan was implemented at the Institute of Experimental Medicine of the Academy of Medical Sciences of the USSR. The Academy of Medical Sciences initially provided the new unit with 11 vacant positions that I was permitted to staff and afterwards allowed me to hire as many new personnel as required, almost without restrictions. So I staffed the division according to my own criteria; the senior researchers were individuals whom I personally knew as highly creative science enthusiasts but whom circumstances prevented from realizing their full potential at their previous jobs; the junior researchers were also enthusiasts, not spoiled by postgraduate education at other institutions, i.e., those who I felt could be educated (trained) to become human physiologists. By this I meant the absolute priority of the person examined (in our case, especially in the very beginning, a patient); fearlessness in front of the labyrinths of the unknown regarding the human brain; and the willingness to work hard, giving freely of one’s time and energy, both in the laboratory and in the clinic. Funds for pursuing equipment were more limited but still sufficient for the new division to set about working fairly soon.

On the possibility of the correction of emotional disorders under the conditions of the action of a destabilizing factor

The influence of the drug dilantin on the mental state of humans in the presence of objective neuroticizing factors (restriction of freedom and the concomitants) was studied. A positive effect of the drug on the emotional state of prisoners, namely, decreases in the levels of reactive and personal anxiety and depression, as well as in the probability of the development of neurotic disorders, was shown.