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EEG oscillatory states: Temporal and spatial microstructure
150
Symposium abstracts / International Journal of Psychophysiology 69 (2008) 139–205
conceal the item enhances the late positive potential elicited by it. This effect, however, is not due to a deception-specific process, but due to the increased significance or meaning of the item by an additional processing, either concealing or revealing the item. The intention to conceal the selected card paradoxically makes the card more significant, and this process was reflected in a larger ERP response.
doi:10.1016/j.ijpsycho.2008.05.369
(2) Different types of EEG segments have different importance to the brain — their occurrence is less or more probable for particular functional brain state. (3) EEG segments of the same type have the tendency to be stabilized in time. (4) There is functional synchronization among segments found in different EEG channels. (5) The inter-channel segmental EEG synchrony reflects the metastable principle of brain functioning.
Combining P300 and SCR in the detection of concealed information E.H. Meijer, F.T.Y. Smulders, H.L.G.J. Merckelbach Maastricht University, Faculty of Psychology, Maastricht, The Netherlands The P300 component of the ERP has often been suggested as a viable alternative to skin conductance response (SCR) in a concealed information test (CIT). Little is known, however, about the association between these two measures. In a mock crime study we simultaneously recorded skin conductance response (SCR) and midline EEG, while stimuli were presented with a short inter stimulus interval. Overlap between SCRs to successive stimuli was handled by presenting stimuli in a specially balanced order using M-sequences (Buracas and Boynton, 2002). SCRs were smaller than typical, but differed between crime relevant and crime irrelevant stimuli, as did P300. Most importantly, SCR and P300 were uncorrelated, indicating that different mechanisms underlie these measures in a CIT.
doi:10.1016/j.ijpsycho.2008.05.370 SYMPOSIUM 7: Differentiation of Mentally-Specific and Non-Specific Brain Activations: Temporal and Spatial Scales Symposium Chair: Sergey Danko (Russia) EEG oscillatory states: Temporal and spatial microstructure Al.A. Fingelkurts, An.A. Fingelkurts BM-Science — Brain & Mind Technologies Research Centre, Espoo, Finland Majority of EEG characteristics are usually derived from averaged parameters. However, the averaging of the EEG-signal might not only mask its dynamics, but also may lead to ambiguous data interpretation. Research has established several important facts. (1) The ongoing EEG has unstationary structure and is characterized by natural inherent dynamics. (2) The average spectral characteristics of a broad frequency band predominantly reflect an influence of high-amplitude synchronized segments of the signal and the low-amplitude desynchronized ones are totally obscured. (3) In terms of the EEG variability, not only the stochastic fluctuations of the EEG parameters, but also a temporal structure of the signal can be observed. Therefore, averaging of EEG estimates masks an actual — “principal” — processes over total signal. Hence, when examining the average brain EEG activity, it is not clear whether the observed effect is real (not the “virtual” result of averaging procedure), stable and typical for the whole analyzed signal. Thus, regardless of how statistically significant the different estimations of averaged EEG phenomena may be, there might be difficulties in the meaningful interpretation of these if they are not matched to the EEG unstationary structure. A new promising area of the study of EEG transformations during cognitive processing is based on the reduction of the signal to the sequence of elementary EEG-oscillatory-states. It has been suggested that operational elements of behavioral/mental activity are originated in the periods of short-term metastable states of the whole brain and its subsystems. From this viewpoint, it is possible to obtain an entire set of individual short-term stationary EEG segments. It was demonstrated that the parameters of the relative presence of the individual EEG segments of each type, peculiarities of their alternation and synchronization in the analyzed multichannel-EEG are adequate characteristics of brain operational activity. Our research indicated the indubitable functional significance of the segmental EEG architectonics: (1) EEG signal consists of a restricted number of typical quasi-stationary segments (not more than 10–35 types for different EEGs), which do not exceed 1–2 s, but usually has duration of 10–300 ms.
doi:10.1016/j.ijpsycho.2008.05.371 What we can(not) learn from studies combining electrophysiological recordings and functional magnetic resonance imaging H. Laufs Johann Wolfgang Goethe University, Frankfurt am Main, Department of Neurology and Brain Imaging Center, Frankfurt am Main, Germany Multimodal imaging with electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) can be used to study dynamics of brain activity by visualising different brain states. Despite their spontaneous occurrence, the related fMRI “signatures” can be meaningful if associated with interpretable EEG phenomena, such as interictal epileptic discharges, sleep phenomena and state of vigilance-defining EEG patterns including so-called EEG background activity. Vice versa, if fMRI-activation maps are functionally well characterized, the associated EEG can be assigned a meaning. On the one hand, examples will be given of EEG/fMRI experiments with on first sight very similar designs yielding different EEG (e.g. spectral band)associated fMRI-signal maps. On the other hand it will be shown that fMRI signal changes can occur in very similar brain regions (e.g. in those constituting the so called “default mode network” of the brain) under a variety of dissimilar conditions including both healthy and pathological brain states. A concept of the interpretation of EEG/fMRI multimodal studies will be presented leading to a reconciliation of the seeming discrepancy of the above studies. It will be highlighted where multimodal studies can serve to make valuable inferences on healthy and pathological brain function.
doi:10.1016/j.ijpsycho.2008.05.372 Berger effect as an example of non-arousal whole-cortex activation J.A. Boytsova, S.G. Danko The Institute of the Human Brain RAS, St-Petersburg, Russia It is well known since Berger (Berger, 1929) that there are visible changes in EEG in transition from an awake resting state with eyes closed (REC) to awake resting state with eyes opened (REO). These changes are known as Berger effect. Berger effect was widely used in clinical neurophysiology as a functional probe and usually treated as an EEG component of generalized non-specific activation (“arousal”). In electrophysiological investigations with quantitative EEG (Danko et al., 2005; Danko, 2006), REO and REC differences were manifested by patterns of EEG power and coherence dynamics in all regions of the cortex and in all frequency bands. Further EEG studies have been undertaken aimed at elucidation of brain mechanisms of the aforementioned states. EEG (1.5–50 Hz) were recorded from 19 scalp zones with reference electrodes on earlobes during 2–4 min intervals of REC or REO either in complete darkness and in dim light room. EEG were recorded also while participants watched video white noise on the screen. Heart rate was recorded too. Spectral power and coherence were calculated for seven EEG frequency bands δ (1,5–4Гц), θ (4–7Гц), α1 (7–10Гц), α2 (10–13Гц), β1 (13–18Гц), β2 (18–30Гц), γ (30–40Гц). No significant changes in heart rate between REO and REC were revealed. Numerous and widespread power and coherence statistically significant differences (SSD) between REO and REC took place both for darkness and light as well as between REO in light and REO in darkness. To the moment two constituents in EEG dynamics can be supposed — attributed to an involuntary shift of attention to visual modality (C1) and to an impact of an illumination factor (C2). C1 can be preliminarily associated with power increases in frontal
Symposium abstracts / International Journal of Psychophysiology 69 (2008) 139–205
conceal the item enhances the late positive potential elicited by it. This effect, however, is not due to a deception-specific process, but due to the increased significance or meaning of the item by an additional processing, either concealing or revealing the item. The intention to conceal the selected card paradoxically makes the card more significant, and this process was reflected in a larger ERP response.
doi:10.1016/j.ijpsycho.2008.05.369
(2) Different types of EEG segments have different importance to the brain — their occurrence is less or more probable for particular functional brain state. (3) EEG segments of the same type have the tendency to be stabilized in time. (4) There is functional synchronization among segments found in different EEG channels. (5) The inter-channel segmental EEG synchrony reflects the metastable principle of brain functioning.
Combining P300 and SCR in the detection of concealed information E.H. Meijer, F.T.Y. Smulders, H.L.G.J. Merckelbach Maastricht University, Faculty of Psychology, Maastricht, The Netherlands The P300 component of the ERP has often been suggested as a viable alternative to skin conductance response (SCR) in a concealed information test (CIT). Little is known, however, about the association between these two measures. In a mock crime study we simultaneously recorded skin conductance response (SCR) and midline EEG, while stimuli were presented with a short inter stimulus interval. Overlap between SCRs to successive stimuli was handled by presenting stimuli in a specially balanced order using M-sequences (Buracas and Boynton, 2002). SCRs were smaller than typical, but differed between crime relevant and crime irrelevant stimuli, as did P300. Most importantly, SCR and P300 were uncorrelated, indicating that different mechanisms underlie these measures in a CIT.
doi:10.1016/j.ijpsycho.2008.05.370 SYMPOSIUM 7: Differentiation of Mentally-Specific and Non-Specific Brain Activations: Temporal and Spatial Scales Symposium Chair: Sergey Danko (Russia) EEG oscillatory states: Temporal and spatial microstructure Al.A. Fingelkurts, An.A. Fingelkurts BM-Science — Brain & Mind Technologies Research Centre, Espoo, Finland Majority of EEG characteristics are usually derived from averaged parameters. However, the averaging of the EEG-signal might not only mask its dynamics, but also may lead to ambiguous data interpretation. Research has established several important facts. (1) The ongoing EEG has unstationary structure and is characterized by natural inherent dynamics. (2) The average spectral characteristics of a broad frequency band predominantly reflect an influence of high-amplitude synchronized segments of the signal and the low-amplitude desynchronized ones are totally obscured. (3) In terms of the EEG variability, not only the stochastic fluctuations of the EEG parameters, but also a temporal structure of the signal can be observed. Therefore, averaging of EEG estimates masks an actual — “principal” — processes over total signal. Hence, when examining the average brain EEG activity, it is not clear whether the observed effect is real (not the “virtual” result of averaging procedure), stable and typical for the whole analyzed signal. Thus, regardless of how statistically significant the different estimations of averaged EEG phenomena may be, there might be difficulties in the meaningful interpretation of these if they are not matched to the EEG unstationary structure. A new promising area of the study of EEG transformations during cognitive processing is based on the reduction of the signal to the sequence of elementary EEG-oscillatory-states. It has been suggested that operational elements of behavioral/mental activity are originated in the periods of short-term metastable states of the whole brain and its subsystems. From this viewpoint, it is possible to obtain an entire set of individual short-term stationary EEG segments. It was demonstrated that the parameters of the relative presence of the individual EEG segments of each type, peculiarities of their alternation and synchronization in the analyzed multichannel-EEG are adequate characteristics of brain operational activity. Our research indicated the indubitable functional significance of the segmental EEG architectonics: (1) EEG signal consists of a restricted number of typical quasi-stationary segments (not more than 10–35 types for different EEGs), which do not exceed 1–2 s, but usually has duration of 10–300 ms.
doi:10.1016/j.ijpsycho.2008.05.371 What we can(not) learn from studies combining electrophysiological recordings and functional magnetic resonance imaging H. Laufs Johann Wolfgang Goethe University, Frankfurt am Main, Department of Neurology and Brain Imaging Center, Frankfurt am Main, Germany Multimodal imaging with electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) can be used to study dynamics of brain activity by visualising different brain states. Despite their spontaneous occurrence, the related fMRI “signatures” can be meaningful if associated with interpretable EEG phenomena, such as interictal epileptic discharges, sleep phenomena and state of vigilance-defining EEG patterns including so-called EEG background activity. Vice versa, if fMRI-activation maps are functionally well characterized, the associated EEG can be assigned a meaning. On the one hand, examples will be given of EEG/fMRI experiments with on first sight very similar designs yielding different EEG (e.g. spectral band)associated fMRI-signal maps. On the other hand it will be shown that fMRI signal changes can occur in very similar brain regions (e.g. in those constituting the so called “default mode network” of the brain) under a variety of dissimilar conditions including both healthy and pathological brain states. A concept of the interpretation of EEG/fMRI multimodal studies will be presented leading to a reconciliation of the seeming discrepancy of the above studies. It will be highlighted where multimodal studies can serve to make valuable inferences on healthy and pathological brain function.
doi:10.1016/j.ijpsycho.2008.05.372 Berger effect as an example of non-arousal whole-cortex activation J.A. Boytsova, S.G. Danko The Institute of the Human Brain RAS, St-Petersburg, Russia It is well known since Berger (Berger, 1929) that there are visible changes in EEG in transition from an awake resting state with eyes closed (REC) to awake resting state with eyes opened (REO). These changes are known as Berger effect. Berger effect was widely used in clinical neurophysiology as a functional probe and usually treated as an EEG component of generalized non-specific activation (“arousal”). In electrophysiological investigations with quantitative EEG (Danko et al., 2005; Danko, 2006), REO and REC differences were manifested by patterns of EEG power and coherence dynamics in all regions of the cortex and in all frequency bands. Further EEG studies have been undertaken aimed at elucidation of brain mechanisms of the aforementioned states. EEG (1.5–50 Hz) were recorded from 19 scalp zones with reference electrodes on earlobes during 2–4 min intervals of REC or REO either in complete darkness and in dim light room. EEG were recorded also while participants watched video white noise on the screen. Heart rate was recorded too. Spectral power and coherence were calculated for seven EEG frequency bands δ (1,5–4Гц), θ (4–7Гц), α1 (7–10Гц), α2 (10–13Гц), β1 (13–18Гц), β2 (18–30Гц), γ (30–40Гц). No significant changes in heart rate between REO and REC were revealed. Numerous and widespread power and coherence statistically significant differences (SSD) between REO and REC took place both for darkness and light as well as between REO in light and REO in darkness. To the moment two constituents in EEG dynamics can be supposed — attributed to an involuntary shift of attention to visual modality (C1) and to an impact of an illumination factor (C2). C1 can be preliminarily associated with power increases in frontal