Biomedical subjects

Alexander A Fingelkurts

Publications and source records attributed to Alexander A Fingelkurts.

At least 19 recordsLinked to original sources

PubMed2007

Cortex functional connectivity as a neurophysiological correlate of hypnosis: an EEG case study.

Cortex functional connectivity associated with hypnosis was investigated in a single highly hypnotizable subject in a normal baseline condition and under neutral hypnosis during two sessions separated by a year. After the hypnotic induction, but without further suggestions as compared to the baseline condition, all studied parameters of local and remote functional connectivity were significantly changed. The significant differences between hypnosis and the baseline condition were observable (to different extent) in five studied independent frequency bands (delta, theta, alpha, beta, and gamma). The results were consistent and stable after 1 year. Based on these findings we conclude that alteration in functional connectivity of the brain may be regarded as a neuronal correlate of hypnosis (at least in very highly hypnotizable subjects) in which separate cognitive modules and subsystems may be temporarily incapable of communicating with each other normally.

Adult↗

PubMed2007

Impaired functional connectivity at EEG alpha and theta frequency bands in major depression.

Recent reports on functional brain imaging in major depression have lead to an assumption that observed psychopathology might be related to an altered brain functional connectivity. Our hypothesis was that an increase in brain functional connectivity occurs in major depression. As a measure of functional connectivity, the electroencephalogram (EEG) structural synchrony approach was used in 12 medication-free depressive outpatients and 10 control subjects. Differences in the number and strength of structurally synchronized EEG patterns were compared between groups. In depressive patients the number and strength of short cortex functional connections were significantly larger for the left than for the right hemisphere, while the number and strength of long functional connections were significantly larger for the right than for the left hemisphere. Some of the functional connections were positively correlated with the severity of depression, thus being predictive. These were short-range anterior, posterior, and left hemisphere functional connections for the alpha frequency band and short-range anterior functional connections for the theta frequency band. The topology of the most representative functional connections among all patients with major depression indicated that the right anterior and left posterior brain parts may discriminate depressive patients from healthy controls. The obtained data support our hypothesis that there is an increase in brain functional connectivity in major depression. This finding was interpreted within the semantic framework, where different specialization of left (monosemantic context) and right (polysemantic context) hemispheres is functionally insufficient in patients with depression.

Adult↗

PubMed2006

Reorganization of the composition of brain oscillations and their temporal characteristics in opioid dependent patients.

In the present study, we examined the composition of electroencephalographic (EEG) brain oscillations in broad frequency band (0.5-30 Hz) in 22 opioid-dependent patients and 14 healthy subjects during resting condition (closed eyes). The exact compositions of brain oscillations and their temporal behavior were assessed by the probability-classification analysis of short-term EEG spectral patterns. It was demonstrated that EEG of patients with opioid dependence was characterized by (a) significant reorganization of brain oscillations with increase in the percentage of beta- and mostly fast-alpha-rhythmic segments, (b) longer periods of temporal stabilization for alpha and beta brain oscillations and by shorter periods of temporal stabilization for theta and polyrhythmic activity when compared with control subjects, and (c) right-sided dominance (significantly larger relative presence of particular spectral patterns in EEG channels of the right hemisphere). These effects were widely distributed across the cortex with the maximum magnitude in the occipital, right parietal, temporal, and frontal areas. Taken together the present study suggested (a) an allostatic state with neuronal activation, and (b) high sensitivity of the right hemisphere to adverse opioid effects.

Adult↗

PubMed2006

Composition of brain oscillations in ongoing EEG during major depression disorder.

In the present study, we examined the composition of electroencephalographic (EEG) brain oscillations in 12 unmedicated major depressive outpatients and 10 healthy subjects during resting conditions (closed eyes). The exact composition of brain oscillations was assessed by the probability-classification analysis of short-term EEG spectral patterns. In contrast to previous studies of depression, the current study found that major depression affects brain activity in nearly the whole cortex and manifests itself in considerable reorganization of the composition of brain oscillations in a broad frequency range: 0.5-30 Hz. At the same time, the magnitude of the effect of depression was maximal in the posterior cortex of the brain. Interhemisphere asymmetry during major depression was also observed in the whole cortex with right hyperactivity in frontal, parietal and occipital brain areas. It is suggested that depressive brain is manifested in the superposition of distributed multiple oscillations. Our findings provide new insight on the relationship between major depressive disorder and cortical oscillatory activity.

Adult↗

PubMed2006

Increased local and decreased remote functional connectivity at EEG alpha and beta frequency bands in opioid-dependent patients.

RATIONALE: Although researchers now have a working knowledge of key brain structures involved in realization of actions of substance abuse and addiction, deeper understanding will require examination of network interactions between cortical neuronal assemblies and their subcortical tails in the effects of opioid dependence. OBJECTIVES: Given that repeated exposure to opiates initiates a widespread reorganization of cortical regions, we predict that opioid dependence would result in a considerable reorganization of local and remote functional connectivity in the neocortex. METHODS: We applied the novel operational architectonics approach that enables us to estimate two local and remote functional cortex connectivities by means of electroencephalogram structural synchrony measure. RESULTS: In 22 opioid-dependent patients, we found the evidence that brain functional connectivity was indeed disrupted by chronic opioid abuse (i.e., the local functional connectivity increased and remote functional connectivity decreased in opioid abusers). This significant difference between "opioid" and "control" populations was the same for alpha and beta frequency bands. Additionally, significant negative relations between duration (years) of daily opioid abuse and the number/strength of functional connections in the posterior section of the cortex were found.

Adult↗

PubMed2006

Timing in cognition and EEG brain dynamics: discreteness versus continuity.

This article provides an overview of recent developments in solving the timing problem (discreteness vs. continuity) in cognitive neuroscience. Both theoretical and empirical studies have been considered, with an emphasis on the framework of operational architectonics (OA) of brain functioning (Fingelkurts and Fingelkurts in Brain Mind 2:291-29, 2001; Neurosci Biobehav Rev 28:827-836, 2005). This framework explores the temporal structure of information flow and interarea interactions within the network of functional neuronal populations by examining topographic sharp transition processes in the scalp EEG, on the millisecond scale. We conclude, based on the OA framework, that brain functioning is best conceptualized in terms of continuity-discreteness unity which is also the characteristic property of cognition. At the end we emphasize where one might productively proceed for the future research.

Brain↗

PubMed2006

Interictal EEG as a physiological adaptation. Part II. Topographic variability of composition of brain oscillations in interictal EEG.

OBJECTIVE: In the present experimental study, we examined topographic variability of composition of brain oscillations and their temporal behavior in frequencies from 0.5 to 30 Hz of interictal EEG without epileptiform abnormalities and healthy EEG. METHODS: Spatio-temporal variability of brain oscillations (indexed by short-term EEG spectral patterns (SPs)) was assessed by the probability-classification analysis of SPs. As a result, multi-dimensional SP-vector for each analysis EEG epoch was obtained. RESULTS: It was demonstrated that interictal EEG was characterized (a) by a significant decrease of spatio-temporal variability of brain oscillations, (b) by longer periods of temporal stabilization for operational modules which comprise larger number of cortical areas, and (c) by significantly more intermittent recurrence when compared with EEG of control subjects. Generally it was shown that EEG channels display different states of coordination independently on their correlation and coherence using brain oscillations at multiple frequencies. CONCLUSIONS: Results of this study suggested that EEG correlate of chronic epileptogenesis in the brain is a particular metastable state of biopotential field, which can be estimated by SP-vector. The fact that all results were significantly different from surrogate EEGs reflects a nonoccasional and thus, most likely, an adaptive nature of spatio-temporal reorganization in interictal EEG. SIGNIFICANCE: Parameters of spatio-temporal organization of interictal EEG without the signs of epileptiform activity can be considered as additional information in premorbid diagnostics of status epilepticus, and may also provide insights into basic laws that govern brain oscillations in general.

Action Potentials↗

PubMed2005

Interictal EEG as a physiological adaptation. Part I. Composition of brain oscillations in interictal EEG.

OBJECTIVE: In the present experimental study, we examined the compositions of brain oscillations and their temporal behavior in broad frequency band (0.5-30 Hz) in interictal EEG without epileptiform abnormalities during generalized epilepsy in resting conditions. METHODS: The exact compositions of brain oscillations and their percent ratio were assessed by a probability-classification analysis of short-term EEG spectral patterns (SPs), which reveals temporal dynamics of these SPs and results in the probability-classification profile. RESULTS: It has been demonstrated that the interictal EEG was characterized by (a) a shift towards higher frequencies in all observed brain oscillations, (b) an increased amount of polyrhythmic activity, (c) a decrease in SP types diversity, (d) a decreased relative incidence of the SP type change in the transition between neighboring EEG epochs of the same EEG, and (e) an increased temporal stabilization periods of polyrhythmic activity. All these were observed in distributed brain areas. CONCLUSIONS: It was suggested that these findings reflect a disorganization of neurodynamics in the epileptic brain. At the same time, the fact that all these indices were significantly different from surrogate EEG reflects a non-occasional and thus, most likely, an adaptive nature of the microstructural reorganization of interictal EEG. SIGNIFICANCE: Parameters of interictal EEG without the signs of epileptiform activity can be considered as additional information in premorbid diagnostics of epistatus.

Adaptation, Physiological↗

PubMed2005

Stability, reliability and consistency of the compositions of brain oscillations.

In the present experimental study, we examined the compositions of electroencephalographic (EEG) brain oscillations and their percent ratio in 12 subjects during resting conditions (closed and open eyes) and during the memory task (waiting, encoding and keeping-in-mind stages). The exact compositions of brain oscillations and their percent ratio were assessed by the probability-classification analysis of short-term EEG spectral patterns, which results in the probability-classification profile (PCP). Within sessions the PCPs are found to be stable, as reflected by a relatively low coefficient of variability, and between sessions the PCPs are highly reproducible. Finally, test-retest reliability of subject's PCPs shows a dependency on task, being higher for the memory task, and in particular for the encoding stage. It was suggested that these findings support and strengthen the superposition principle where integrative brain functions are manifested in the superposition of distributed multiple oscillations.

Adult↗

PubMed2005

Functional connectivity in the brain--is it an elusive concept?

Even though functional brain connectivity is an influential concept in modern cognitive neuroscience, it is a very controversial notion. This is why further theoretical and methodological clarification are needed to help define precisely what is meant by functional connectivity and to help frame-associated issues. In this review we present the neurophysiological concept of functional connectivity, which utilizes in a plausible manner the notion of neural assemblies, as well as local and large-scale levels of description. Here functional connectivity is the mechanism for the coordination of activity between different neural assemblies in order to achieve a complex cognitive task or perceptual process. Our theoretical and empirical findings offer new insights into possible implications of the concept of functional connectivity for cognitive neuroscience.

Animals↗

PubMed2004

New perspectives in pharmaco-electroencephalography.

Recent research emphasizes that majority of brain disorders and psychiatric problems are accompanied by disruption in the temporal structure of brain activity. From this perspective, disruption is viewed as a disorder of the metastable balance between large-scale integration and independent processing in the brain, in favor of either independent or hyper-ordered processing. This paper proposes that the future of psychopharmacology lies in its ability to design the psychotropic drugs which can restore the normal temporal structure and metastable structure of brain activity. Quantitative electroencephalography (QEEG) is one of the key complex technologies utilized in psychopharmacology for this purpose. However, conventional approaches for EEG analysis used in clinical practice are not suitable for studying temporal structure of brain activity. To overcome this limitation, and in order to reveal dynamic and temporal characteristics of brain activity, the advanced analysis of EEG micro-structure should be used.

Animals↗

PubMed2004

Enhancement of GABA-related signalling is associated with increase of functional connectivity in human cortex.

Structural or operational synchrony analysis with EEG was conducted in order to detect functional interaction between cortical areas during an enhanced inhibition induced by the GABAergic agonist lorazepam in a double-blind, randomized, placebo-controlled, cross-over study in eight healthy human subjects. Specifically, we investigated whether a neuronal inhibitory system in the brain mediates functional decoupling of cortical areas. Single-dose lorazepam administration resulted in a widespread increase in the inter-area functional connectivity and an increase in the strength of functional long-range and interhemispheric connections. These results suggest that inhibition can be an efficient mechanism for synchronization of large neuronal populations.

Adult↗

PubMed2004

The interplay of lorazepam-induced brain oscillations: microstructural electromagnetic study.

OBJECTIVE: The effects on cortical rhythms of a single-dose (30 microg/kg) administration of the GABAA agonist lorazepam were examined in a randomized, double-blind, cross-over, placebo-controlled study with 8 healthy volunteers using simultaneous electroencephalography (EEG) and magnetoencephalography (MEG). METHODS: The oscillations were assessed by means of adaptive classification of short-term spectral patterns. RESULTS: Lorazepam (a) decreased the percentage of EEG/MEG segments with fast-theta, delta-alpha, fast-theta-alpha and alpha activity and increased percentage of EEG/MEG segments with delta, delta-slow-theta, delta-beta, slow-theta and polyrhythmic activity; (b) decreased diversity of EEG/MEG signals (in terms of spectral patterns) and increased the general instability of the signal; (c) increased stabilization periods of the spectral patterns (reduced brain information processing); (d) maintained larger maximum periods of temporal stabilization for delta, slow-theta, delta-slow-theta, delta-beta and polyrhythmic activity (in terms of spectral patterns); (e) did not increase power in the independent beta rhythm. CONCLUSIONS: Lorazepam caused significant reorganization of the EEG/MEG microstructure. These results suggest also that adaptive classification analysis of single short-term spectral patterns may provide additional information to conventional spectral analyses.

Adult↗

PubMed2004

Local and remote functional connectivity of neocortex under the inhibition influence.

The current paper focuses on a relatively new and promising area of the study of EEG transformations during brain information processing based on the reduction of the signal to the discrete quasi-stationary segment sequences which may reflect individual brain microstates or discrete operations. In this framework, the complex brain functions require integration of several operations throughout the whole neocortex. However, the role of inhibitory brain systems in such processes is still unsettled. The effects of a single dose (30 microg/kg) of lorazepam on the operational activity of neuronal populations and on the temporal binding between them were examined in a double-blind randomized crossover placebo-controlled study with eight healthy volunteers. EEG measures at 20 channels were evaluated on two occasions: (1) eyes closed, (2) eyes open. In short, we conducted a two-by-two factorial study where one factor manipulated GABAergic neurotransmission (lorazepam vs. placebo), and the other factor was simply brain state (eyes closed vs. eyes opened). We were primarily interested in the main effect of lorazepam. In the present study, a connection between the mesoscopic level, described by the local functional processes (neuronal assemblies or populations) and the macroscopic level, described as a sequence of metastable brain states (remote functionally synchronized neuronal populations) was established. The role of inhibitory brain systems facilitated by lorazepam in the operational dynamics of neuronal populations and in the process of EEG structural synchrony (SS) (topological peculiarities) was addressed for the first time. It was shown that GABA signaling reorganized the dynamics of local neuronal populations and the remote functional connectivity between them.

Adult↗

PubMed2004

Making complexity simpler: multivariability and metastability in the brain.

This article provides a retrospective, current, and prospective overview on developments in brain research and neuroscience. Both theoretical and empirical studies are considered, with emphasis in the concept of multivariability and metastability in the brain. In this new view on the human brain, the potential multivariability of the neuronal networks appears to be far from continuous in time, but confined by the dynamics of short-term local and global metastable brain states. The article closes by suggesting some of the implications of this view in future multidisciplinary brain research.

Animals↗

PubMed2003

Cortical operational synchrony during audio-visual speech integration.

Information from different sensory modalities is processed in different cortical regions. However, our daily perception is based on the overall impression resulting from the integration of information from multiple sensory modalities. At present it is not known how the human brain integrates information from different modalities into a unified percept. Using a robust phenomenon known as the McGurk effect it was shown in the present study that audio-visual synthesis takes place within a distributed and dynamic cortical networks with emergent properties. Various cortical sites within these networks interact with each other by means of so-called operational synchrony (Kaplan, Fingelkurts, Fingelkurts, & Darkhovsky, 1997). The temporal synchronization of cortical operations processing unimodal stimuli at different cortical sites reveals the importance of the temporal features of auditory and visual stimuli for audio-visual speech integration.

Cerebral Cortex↗

PubMed2003

The regularities of the discrete nature of multi-variability of EEG spectral patterns.

The short-term structure of electroencephalogram (EEG) spectral transformations during different brain functional states (closed/opened eyes and memory task) was studied. It was shown that approximately 50% of spectral pattern (SP) types occur not more than 2-3 times per 149 analysis epochs in a 1-min EEG. The remaining 50% of SP types were the same for the different EEG channels, in all subjects and various brain functional states. Additionally, a high incidence of the neighboring SP types in strongly overlapping (by 80%) 2-s analysis epochs of the EEG was shown. The SP identified in a given epoch has only a limited predictive value on the SPs identified in the subsequent epochs. The incidence effect was restricted by the limited SP set and by a 50% reduction in the functionally active SPs, which resulted in a temporary stabilization of SPs in sequential combinations. The parameters of temporary stabilization of SPs were significantly different from 'random' EEG which provides evidence of the non-occasional character of stabilization of the main dynamic parameters of neuronal activity. Thus, the findings suggest that the multi-variability of neuronal nets is discrete in time, and limited by the dynamics of the short quasi-stable brain states.

Adult↗

PubMed2003

Systematic rules underlying spectral pattern variability: experimental results and a review of the evidence.

On the basis of three different experiments: oddball task (visual, auditory, and audio-visual stimuli), modified Sternberg's, and multistage memory tasks, it was shown that: a) there was not a single typical spectral pattern type that would characterize the majority of the trials; b) the total number of the different spectral pattern types was limited; c) different spectral pattern types had different importance to the brain--their occurrence was more or less probable; d) the total number and the number of the most probable spectral pattern types were dependent on the functional brain state; e) actual spectral pattern of variability during rest with closed eyes was relatively high (around 65% from the maximum possible rate), but significantly less than stochastic spectral pattern variability. It is suggested that identical sensory events can potentially trigger a limited number of several different alternative reaction patterns in EEG/MEG, depending on the situational context.

Adult↗