Epilepsy has been historically seen as a functional brain disorder associated with excessive synchronization of large neuronal populations leading to a hypersynchronous state. Recent evidence showed that epileptiform phenomena, particularly seizures, result from complex interactions between neuronal networks characterized by heterogeneity of neuronal firing and dynamical evolution of synchronization. Desynchronization is often observed preceding seizures or during their early stages; in contrast, high levels of synchronization observed towards the end of seizures may facilitate termination. In this review we discuss cellular and network mechanisms responsible for such complex changes in synchronization. Recent work has identified cell-type-specific inhibitory and excitatory interactions, the dichotomy between neuronal firing and the non-local measurement of local field potentials distant to that firing, and the reflection of the neuronal dark matter problem in non-firing neurons active in seizures. These recent advances have challenged long-established views and are leading to a more rigorous and realistic understanding of the pathophysiology of epilepsy.
Recent findings indicate that changes in synchronization of neural activities underlying sensitization and kindling could be more comprehensively understood using nonlinear methods. With this aim we have examined local synchronization using novel measure of coarse-grained information rate (CIR) in 8 EEG signals recorded at different cortical areas in 44 patients with paranoid schizophrenia. The values of local synchronization that could reflect sensitization related changes in EEG activities of cortical sites were then related to psychometric measures of epileptic-like symptoms and positive and negative schizophrenia symptoms (PANSS). While no significant correlations between CIR and positive and negative symptoms have been found, statistically significant relationships described by Spearman correlation coefficients between CIR indices and results of LSCL-33 have been observed in 7 (of 8) EEG channels (r in the range from 0.307 to 0.374, p<0.05). Results of this study provide first supportive evidence for the relationship between local synchronization measured by CIR and epileptic-like symptoms in schizophrenia.
- MeSH
- Adult MeSH
- Electroencephalography methods MeSH
- Epilepsy etiology MeSH
- Cortical Synchronization * MeSH
- Humans MeSH
- Young Adult MeSH
- Schizophrenia, Paranoid complications MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Young Adult MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Recent findings suggest that specific deficits in neural synchrony and binding may underlie cognitive disturbances in schizophrenia and that key aspects of schizophrenia pathology involve discoordination and disconnection of distributed processes in multiple cortical areas associated with cognitive deficits. In the present study we aimed to investigate the underlying cortical mechanism of disturbed frontal-temporal-central-parietal connectivity in schizophrenia by examination of the synchronization patterns using wavelet phase synchronization index and coherence between all defined couples of 8 EEG signals recorded at different cortical sites in its relationship to positive and negative symptoms of schizophrenia. 31 adult schizophrenic outpatients with diagnosis of paranoid schizophrenia (mean age 27.4) were assessed in the study. The obtained results present the first quantitative evidence indicating direct relationship between wavelet phase synchronization and coherence in pairs of EEG signals recorded from frontal, temporal, central and parietal brain areas and positive and negative symptoms of schizophrenia. The performed analysis demonstrates that the level of phase synchronization and coherence in some pairs of EEG signals is inversely related to positive symptoms, negative symptoms and general psychopathology in temporal scales (frequency ranges) given by wavelet frequencies (WFs) equal to or higher than 7.56 Hz, and positively related to negative symptoms in wavelet frequencies equal to or lower than 5.35 Hz. This finding suggests that higher and lower frequencies may play a specific role in binding and connectivity and may be related to decreased or increased synchrony with specific manifestation in cognitive deficits of schizophrenia.
- MeSH
- Adult MeSH
- Electroencephalography methods MeSH
- Cortical Synchronization * MeSH
- Humans MeSH
- Brain Mapping MeSH
- Young Adult MeSH
- Cerebral Cortex physiopathology MeSH
- Statistics, Nonparametric MeSH
- Schizophrenia, Paranoid pathology physiopathology MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Young Adult MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Event-related desynchronization (ERD) and synchronization (ERS) were studied during the invasive exploration of an epileptic surgery candidate. An electrode that was targeted in the amygdalo-hippocampal complex passed through the putamen with several contacts. During a simple self-paced motor task, we observed in the putamen a power decline (ERD) in both the alpha and beta frequency bands, and a rebound phenomenon (ERS) in the beta frequency band, concurrent with the movement of each hand. This is the first report of ERD/ERS in the basal ganglia.
Using intracerebral EEG recordings in a large cohort of human subjects, we investigate the time course of neural cross-talk during a simple cognitive task. Our results show that human brain dynamics undergo a characteristic sequence of synchronization patterns across different frequency bands following a visual oddball stimulus. In particular, an initial global reorganization in the delta and theta bands (2-8 Hz) is followed by gamma (20-95 Hz) and then beta band (12-20 Hz) synchrony.
- MeSH
- Adult MeSH
- Electroencephalography MeSH
- Cognition physiology MeSH
- Cortical Synchronization physiology MeSH
- Humans MeSH
- Adolescent MeSH
- Young Adult MeSH
- Brain physiology MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Adolescent MeSH
- Young Adult MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
The study investigated whether specific changes in phase synchrony in the beta 2 frequency band of EEG (25-35 Hz) occurred during a recognition task. The level of synchrony was examined between one hundred and eighty loci in the frontal and temporal lobes of eight epileptic patients with intracerebral electrodes; the EEG records were obtained during a visual oddball task. In each pair of records, the correlation curves were created from the sequence of correlation coefficients calculated. These curves consisted of irregular oscillations between the maximal and minimal r-values. Transient highly synchronized activity was observed during the whole time course of the experiment in all record pairs investigated and a significant relationship was found between the number of such episodes and the mean correlation coefficient (Spearman R 0.84; N 3240; p<0.001). On averaged curves, which were calculated using stimulus onsets as the trigger of averaging, a significant increase of the mean correlation coefficient in the post-stimulus epoch was found (p<0.01 after both target and non-target stimuli; t-test for dependent samples). As the cognitive demand significantly increases after stimulus presentation, the results are considered to be the first evidence from intracranial recording of increased synchronization in the beta 2 frequency band related to the cognitive activity.
- MeSH
- Frontal Lobe physiology MeSH
- Adult MeSH
- Electroencephalography MeSH
- Electrodes, Implanted MeSH
- Cortical Synchronization * MeSH
- Middle Aged MeSH
- Humans MeSH
- Temporal Lobe physiology MeSH
- Visual Perception physiology MeSH
- Check Tag
- Adult MeSH
- Middle Aged MeSH
- Humans MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
A large number of studies document cardiorespiratory changes occurring while listening to music. Less is known, however, about the interaction between cardiorespiratory and cerebral electrical rhythms during listening to music and how cognition and acoustic structural aspects of songs influence that interaction. We focused on tempo as a structural feature of songs, since tempo is a major determinant of physiological responses to music, and on familiarity and randomization of phase of local spectra of known and unknown songs for cognition. Our results indicated an overall increase in the degree of synchronization among cardiorespiratory variables (Heart rate (RR), systolic and diastolic blood pressure (SBP, DBP), respiration) and between cardiorespiratory and cerebral (EEG) oscillations during all songs. We also observed a marked decrease in respiratory frequency bandwidth and increase in respiratory rate while listening to songs, and slow song produced the most periodic breathing. Compared with slow tempo, during fast song, DBP and cerebral oscillations became less synchronized with high frequency components of RR suggesting that the processes causing the previously known reduction in vagal activity with increase in tempo also may have caused the decrease in these synchronizations. Cognition of songs affected the SBP coherencies the most. DBP was synchronized with respiration more than all other measured variables in response to auditory stimuli. Results indicate an overall increase in the degree of synchronization among a variety of cerebral electrical and autonomically driven cardiovascular rhythms. It is possible that this significant increase in synchronizations underlies the widely reported pleasurable and palliative effects of listening to music.
- MeSH
- Autonomic Nervous System physiology MeSH
- Adult MeSH
- Respiration * MeSH
- Music * MeSH
- Cognition physiology MeSH
- Cortical Synchronization * MeSH
- Blood Pressure MeSH
- Humans MeSH
- Adolescent MeSH
- Young Adult MeSH
- Auditory Perception MeSH
- Heart physiology MeSH
- Healthy Volunteers MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Adolescent MeSH
- Young Adult MeSH
- Male MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
The extremophilic unicellular red microalga Galdieria sulphuraria (Cyanidiophyceae) is able to grow autotrophically, or mixo- and heterotrophically with 1% glycerol as a carbon source. The alga divides by multiple fission into more than two cells within one cell cycle. The optimal conditions of light, temperature and pH (500 µmol photons m-2 s-1, 40 °C, and pH 3; respectively) for the strain Galdieria sulphuraria (Galdieri) Merola 002 were determined as a basis for synchronization experiments. For synchronization, the specific light/dark cycle, 16/8 h was identified as the precondition for investigating the cell cycle. The alga was successfully synchronized and the cell cycle was evaluated. G. sulphuraria attained two commitment points with midpoints at 10 and 13 h of the cell cycle, leading to two nuclear divisions, followed subsequently by division into four daughter cells. The daughter cells stayed in the mother cell wall until the beginning of the next light phase, when they were released. Accumulation of glycogen throughout the cell cycle was also described. The findings presented here bring a new contribution to our general understanding of the cell cycle in cyanidialean red algae, and specifically of the biotechnologically important species G. sulphuraria.
- Keywords
- Galdieria, cell cycle, cell division, growth, light intensity, red algae, synchronization, temperature, trophic regimes,
- MeSH
- Cell Cycle physiology MeSH
- Heterotrophic Processes physiology MeSH
- Cells, Cultured MeSH
- Microalgae cytology growth & development MeSH
- Rhodophyta cytology growth & development MeSH
- Temperature MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- MeSH
- Cats MeSH
- Cortical Synchronization MeSH
- Conditioning, Operant physiology MeSH
- Reinforcement, Psychology * MeSH
- Occipital Lobe physiology MeSH
- Animals MeSH
- Check Tag
- Cats MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
Abstract The concept of a temporal integration process in the timing mechanisms in the brain, postulated on the basis of experimental observations from various paradigms (for a review see P$oUppel, 1978), has been explored in a sensorimotor synchronization task. Subjects synchronized their finger taps to sequences of auditory stimuli with interstimulus-onset intervals (ISIs) between 300 and 4800 msec in different trials. Each tonal sequence consisted of 110 stimuli; the tones had a frequency of 500 Hz and a duration of 100 msec. As observed previously, response onsets preceded onsets of the stimuli by some tens of milliseconcls for ISIs in the range from about 600 to 1800 msec. For ISIs longer than or equal to 2400 msec, the ability to time the response sequence in such a way that the response 5 were placed right ahead of the stimuli started to break clown, i.e., the task was fulfilled by reactions to the stimuli rather than by advanced responses. This observation can he understood within the general framework of a temporal integration puce 55 that is supposed to have a maximal capacity (integration interval) of approximately 3 sec. Only if successive stimuli fall within one integration period, can motor programs be initiated properly by a prior stimulus and thus lead to an appropriate synchronization between the stimulus sequence and corresponding motor acts.
- Publication type
- Journal Article MeSH
