Brain cognitive-specific functional states studied with quantitative EEG

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Brain cognitive-specific functional states studied with quantitative EEG. Bechtereva N.P., Danko S.G. Institute of the Human Brain, Russian Academy of Sciences, Sankt-Petersburg, Russia. - PowerPoint PPT Presentation

Text of Brain cognitive-specific functional states studied with quantitative EEG

  • Brain cognitive-specific functional states studied with quantitative EEG

    Bechtereva N.P., Danko S.G. Institute of the Human Brain, Russian Academy of Sciences, Sankt-Petersburg, Russia.

  • Initially functional state of the central nervous system was defined and treated as a background to the behavioural activities of humans and animals (e.g. Sokolov, 1975)Functional states regulated by modulating system of the brain are a mandatory component of any activity and behavior (Danilova, 2001 - from Textbook on Psychophysiology, ed Y.Alexandrov ).

  • From: Bechtereva N.P. The neurophysiological aspects of human mental activity. Leningrad:, Meditsina, 1971. (in Russian) Bechtereva N.P. The neurophysiological aspects of human mental activity. NY;Oxford: Univ. Press, 1978

    A well-known difference [with conditioned reflex activity] is the great discontinuity and polimorphism of the changes in the EEG during tests that are strictly psychological. although local changes can be noted during psychological tests, the development of these local changes is always a part of the general modification of bioelectric activity. Thus, EEG changes during mental activity reflect not so much the active state of individual structures as they reflect general changes in the brain, which evidently optimize the conditions for activity.

  • The main ideas feeding the studies in question are:1. Cognitive activities include not only short-term transitions of the information processed but are based also on specific interactions of network brain systems underlying basic psychic functions such as vigilance, attention, memory.2.There are some necessary integrations of the brain systems which result in certain functional states of brain characteristic to certain cognitive activities3. There should be certain manifestations in EEG processes related to a functional state supposed.

  • The term quantitative electroencephalography qEEG should be understood so that both digital processing of EEG raw data and statistical evaluation of observed differences are mandatory. When using term state-related qEEG mean values of EEG parameters are assumed to be constant during certain functional states. The states under considerations here are differed according to cognitive/emotional activities to be controlled. And the states should be durable enough to allow statistical estimations of mean values with acceptable accuracy and they can be discriminated from transitory processes and acts on this base.

  • The volunteers who undergone computer EEG registration presumably in different functional states were of both sexes, aged 17-27, university students and graduates, right-handed, without acute problems with health and without CNS injuries or diseases in their past. EEG was recorded from 19 sites (International 10-20 system), monopolar with reference to earlobes. Mean values of EEG power and coherence for each subject in each state were calculated in frequency bands (1,5-3,5Hz), (4-7Hz), 1 (7,5-9,5Hz), 2 (10-12,5Hz), 1 (13-18Hz), 2 (18,5-30Hz). In the last investigations low (30-40Hz) was added. EEG records were processed on intervals 1-3s duration corresponding to different states under investigation, 20-40 intervals for each state were taken for processing

  • Statistical analysis of the values was conducted not as testing of certain hypotheses but as screening of the all data available using multi-way Anova and within subjects design. Frequency bands, states and zones were considered as effective factors. Greenhouse-Geisser correction was applied for evaluation of main effects and their interactions significance. Statistical significances of differences between means in certain frequency bands, states and zones were tested with post hoc tests (multiple comparisons). Tukey HSD test was used as more conservative and less sensitive, Fisher LSD test as less conservative and more sensitive.

  • Commonly used paradigm of psychophysiological investigation is based on comparisons of test situations as close as possible except for an element being investigated.Thats a very productive paradigm indeed especially if one is sure about physiological interpretation of the parameters controlled. That is the case in rCBF tomography studies but unfortunately not so with EEGIn the situation its desirable to anticipate the results related to cognitive-specific FS with a result of qEEG application to well-known physiological states quiet rest with eyes open and eyes closed

  • DTA1A2B1B2GState-related statistically significant EEG power changesContrast eyes closed eyes openEC-EO**N=57Tukey HSDRed colors - values higher in the first of the compared states, blue lower.

  • DTA1A2B1B2GEC-EO**N=57Tukey HSD 1. Occipital and parietal zones are most involved. 2. The changes are unidirectional in all frequency bands considered. 3. So decrease of rCBF in the visual cortex (Gebhardt et al., 2001,2002) corresponds to EEG synchronization in every of the frequency band State-related statistically significant EEG power changesContrast eyes closed eyes open

  • Red colors - values higher in the first of the compared states, blue lower.**N=57State-related statistically significant EEG power changesContrasts: memorizing(MM) eyes open rest(EO); memory retrieval(MR) EO; MM-MR Tukey HSD

  • Red colors - values higher in the first of the compared states, blue lower.**N=57State-related statistically significant EEG power changesContrasts: memorizing(MM) eyes open rest(EO); memory retrieval(MR) EO; MM-MR 1. Both MM-EO and MR-EO patterns are rather similar: desynchronization in alpha and synchronization in beta2 and gamma looks like classical non-specific activation. 2. But in MM-MR no difference in alpha and prominent difference in beta2 and gamma non-specific activation should be omitted. 3. In MM-EO and MR-EO the changes in alpha 2 and gamma are rather widespread.

  • State-related statistically significant EEG power changesContrasts: positive induced emotions(P) time count(C); negative induced emotion(N) C; P-N P-NP-CN-CN=16*Red colors - values higher in the first of the compared states, blue lower.Fisher LSD

  • State-related statistically significant EEG power changesContrasts: positive induced emotions(P) time count(C); negative induced emotion(N) C; P-N N=16*Red colors - values higher in the first of the compared states, blue lower. 1. Both P-C and N-C patterns are unidirectional in all the frequency bands concerned. 2. But in N-C the changes are much less pronounced and that is confirmed in P-N contrast

  • GammaAlfa1Alfa2Beta1Beta2ThetaDeltaTukey HSD test*Red colors - values higher in the first of the compared states, blue lower.State-related statistically significant EEG power changesContrast: complicated verbal task (search for a word changing the proverb sense) non-complicated verbal task (remembering of the certain word missing in the proverb)N=67

  • GammaAlfa1Alfa2Beta1Beta2ThetaDeltaTukey HSD test*Red colors - values higher in the first of the compared states, blue lower.State-related statistically significant EEG power changesContrast: complicated verbal task (search for a word changing the proverb sense) non-complicated verbal task (remembering of the certain word missing in the proverb)N=67 1. Even in a situation when main and control tasks are intentionally close one using srqEEG can reveal significant changes between the states corresponding to the tasks performed 2. Here the changes are unidirectional and concentrated in gamma and beta2 bands.

  • Conclusions:

    Brain functional states cognitive-specific states included can be separated using srqEEG with good statistical reliability.

    In the situations investigated the differences were widespread in space indeed and were present in a variety of frequency bands considered.

    Both unidirectional and bidirectional statistical significant differences could be observed.

    4. So potentially EEG power values in several frequency bands can serve as a tool for multiscale (not only regional and general cortex activation/deactivation) rating of brain functional states.

  • We greatly appreciate contributions of N.V.Shemiakina, M.G.Starchenko, M.L.Solovjeva and Y.A.Boitsova in the studies presentedThank you for your kind attention!

  • Statistically significant EEG differences between states of creative and non-creative thinking with various tests1.Sense changing word2.Storymaking3.Logical chains4.Original definitions5.Drawing pictures from a restricted set of elements *****V e r b a l****

  • Statistically significant EEG differences between states of creative and non-creative thinking with various tests1.Sense changing word2.Storymaking3.Logical chains4.Original definitions5. *****V e r b a l**** Posterior psychological analysis highlighted a number of factors presumably responsible for the scatter of EEG results with the verbal tests: time frames, involvement of remote associations and of mental imagery, emotion-producing tension etc. It looks like the factor of creative load is not so effective in modulating EEG power in the frequency bands - if compared with aforementioned ones.

  • Gr.1 N=22Gr.2 N=25Gr.3 N=20Variants of statistically significant EEG differences between states of creative and non-creative thinking in 3 groups of subjects* * Red colors - values higher in the first of the compared states, blue lower.

  • Emotional components remarkably influence EEG power during creative thinkingC-NC(C+PE)-NC***Alfa1Alfa2Beta1Beta

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