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PubMedDate not supplied

[A comparison of the spike train activity of the cortical neurons and of the spatial synchronization of the EEG].

In chronic experiments EEG coherence and conjugation of impulse activity were compared of neurones of the visual and sensorimotor areas of rabbits neocortex simultaneously recorded with the same electrodes. Connection was revealed between the presence and properties of conjugated neurones activity and EEG coherence at various frequencies. At correlated neurones activity a greater EEG coherence was observed on frequencies of 3-4,5 Hz than at the independent activity. At the highest level of the EEG coherence the neurones discharged with less delay of one after the other in pairs, and in their synchronization a common source participated more often than at the lowest level of the EEG coherence.

Animals↗
PubMed1999

Origin and propagation of spontaneous electrographic sharp waves in the in vitro turtle brain: a model of neuronal synchronization.

OBJECTIVES: Neuronal synchronization is a basic feature in the generation of epileptiform discharges. Spontaneous large sharp waves (LSWs) can be recorded in the turtle brain in vitro, indicating the synchronous activation of large neuronal populations. The aim of this study was to analyze the spatial and temporal distribution of LSWs within the brain; the participation of glutamate in LSWs generation was also investigated. METHODS: Extracellular field potentials were recorded in vivo (n = 4) and in vitro (n = 36). LSWs were recorded from cerebral cortex, optic tectum, and thalamus. RESULTS: LSWs were recorded from cerebral cortex, optic tectum and thalamus. No LSWs were observed in cerebellum and brain stem. In some experiments, LSWs could be recorded only from medial cortex. Latency studies demonstrated that, within each hemisphere, medial cortex led the generation of LSWs; in addition, isolated medial cortex could sustain LSWs. Intracortical laminar field potentials in medial cortex indicated that LSWs generate mainly in the molecular layer, probably at pyramidal cell dendrites. Pharmacological experiments demonstrated that NMDA and non-NMDA glutamate receptors are involved in LWSs generation. CONCLUSIONS: These results suggest that turtle medial cortex is the pacemaker area for LSWs generation and it can be a useful model to study cellular and circuital mechanisms of neuronal synchronization.

Animals↗
PubMed2006

Variability of EEG synchronization prior to and during observation and execution of a sequential finger movement.

The aim of this study was to test the validity of mirror neuron activity in humans through analysis of electroencephalographic (EEG) functional connectivity during an action not directed towards an object. We investigated changes in EEG interchannel synchronization prior to and during action execution and also prior to and during observation of the same action. Twelve participants observed a simple finger movement sequence. In a second testing session they physically executed the movement. EEGs were recorded from 19 active sites across the cortex. Activity was considered in four frequency bands (7-10 Hz, 10-13 Hz, 13-20 Hz, and 20-30 Hz) using a new measure: synchronization likelihood. This technique considers rapid changes in signal synchronization and spatiotemporal patterns of coherence. The results revealed no statistically significant difference in synchronization likelihood between the observation and execution data. We found an increase in synchronization over a broad frequency range during task processing and suggest that this may reflect interregional cortical coupling of intricately and hierarchically interconnected networks that are active in a similar way during both observation and execution of a movement. While EEG may be insensitive to differences present during the observation and execution of a movement, the results of the present study shed some light on the general mechanisms of cognitive integration.

Adult↗
PubMed2003

Early onset of post-movement beta electroencephalogram synchronization in the supplementary motor area during self-paced finger movement in man.

A voluntary finger movement is accompanied by an event-related desynchronization followed by a short burst of beta oscillations or event-related synchronization. These beta bursts are dominant over the contralateral hand representation area, but also appear over the midcentral area overlaying the supplementary motor area (SMA) and the foot representation area. We show that the induced midcentral beta oscillations following movement-offset display not only slightly higher frequency components, but have also a significantly earlier onset. These beta oscillations arise likely from the SMA. Assuming that the short-lasting beta synchronizations at frequencies below 35 Hz after termination of a movement reflect a state of localized cortical inhibition, we propose that the induced midcentral oscillations reflect the inhibition of networks within the SMA. This assumed resetting or inhibitory process within the SMA precedes that of the networks within the primary motor hand area.

Beta Rhythm↗
PubMed1976

[Pathogenesis of central mechanisms of speech function disorders in children with alalia].

A study of special synchronization of brain biopotentials in EEG registrations by a correlational analysis permitted to establish that in children with alalia there was a complex defect in intercentral relations of the associative infraparietal areas with auditory, visual and motor analyzers in the left hemisphere. In children with alalia the intercentral correlations of biopotentials of the parieto-temporal areas were 10 times less, in the parieto-occipital ares 3 times less and almost twice less in the parieto-motor areas in the left hemisphere in comparison with norman children. Consequently disturbed speech development in children with alalia is connected with a defect in the functions of the higher sensory analysis and synthesis in the associative infraparietal areas with disturbed activity in the synchronizing, activating brain systems with disorders in the organization of spacial-time relations in different cortical areas.

Brain Mapping↗
PubMed2004

Interhemispheric functional synchronization at the first step of visual information processing in humans.

OBJECTIVE: We examined the interhemispheric functional synchronization of the visual cortex using coherence (Coh) analysis. METHODS: Achromatic or isoluminant chromatic sinusoidal grating stimuli were presented to each hemifield at a rate of 8 reversals/s to record steady-state visual-evoked potentials (S-VEPs) in 10 healthy subjects. Four recording electrodes were placed at O1, O2, P3 and P4, referred to an electrode at Cz. A total of 50 responses of 1 s epoch were averaged, and were subjected to discrete fast Fourier transforms to yield the amplitude and phase of the 8 Hz component. Ordinary and partial Coh values were also calculated. RESULTS: For both achromatic and chromatic stimuli, the 8 Hz amplitudes of O1 and O2 were significantly larger than those of P3 and P4 without any significant difference between O1 and O2. The phase lag between O1 and O2 was approximately 30 degrees (latency shift 10.4 ms). Partial Coh between O1 and O2 at 8 Hz was significantly greater than that of the unstimulated condition, and this was only observed at 8 Hz. CONCLUSIONS: These results suggest that interhemispheric synchronization in the occipital area occurs despite the nature of the visual stimuli. Therefore, the activation of interhemispheric connection is important for the early stage of the visual information processing. SIGNIFICANCE: Our results indicate that the first step of the visual information processing requires interhemispheric functional synchronization.

Adult↗
PubMedDate not supplied

Structural bases of intracortical processes underlying the synchronization of epileptic potentials in the sensorimotor areas of the neocortex in rats.

Studies in long-term isolated areas of the rat neocortex were performed to investigate the dynamics of the numbers and areas of nerve cell bodies in layer V and to compare these data with the degree of synchronization of epileptic discharges evoked by application of penicillin. Decreases in the number of pyramidal neurons with body areas of 200-350 microm2 in isolated strips after maintenance for 30 and 90 days led to decreases in the degree of synchronization of epileptiform potentials. Large pyramidal neurons are known to have long horizontal axon collaterals, spreading into layers V and VI of the neocortex. It is suggested that the neural networks formed by large pyramidal neurons by means of their long horizontal collaterals mediate the process of intracortical synchronization.

Animals↗
PubMed2003

Task-dependent modulation of multi-digit force coordination patterns.

When grasping and holding an object with five digits under a variety of task constraints, subjects use well-defined force coordination patterns, i.e., consistent force covariations and in-phase synchronization among all digit pairs. The question arises as to whether these force coordination patterns are default mechanisms for controlling multi-digit force production or whether they are specific to lifting and holding an object. To address this question, we asked subjects to grasp a manipulandum and exert forces with five digits simultaneously so as to match a force template measured from an actual object grasp, lift, and hold task (GLH). Unlike GLH, the force production task (FP) lacked the constraint of having to maintain object stability against gravity. The amplitude of individual finger forces and force covariations were similar for both tasks (with the exception of the little finger, which tended to produce less force in FP). Nonetheless, when multiple grip forces were not required to hold the manipulandum against gravity (FP), there was a significantly lower tendency for forces to be synchronized with higher intertrial variability of phase differences between forces exerted by all digit-pairs. Furthermore, the tendency for force phase differences to cluster at 0 degrees was lower for FP than GLH. These results suggest that some aspects of the control of multi-digit grasping, i.e., force synchronization, are specific to object lift and hold rather than to the production of multi-digit forces. Modeling work suggests that motor unit synchronization might play an important role in the modulation of force synchronization patterns.

Cerebral Cortex↗
PubMed2006

Analysis of synchronization between two modules of pulse neural networks with excitatory and inhibitory connections.

To study the synchronized oscillations among distant neurons in the visual cortex, we analyzed the synchronization between two modules of pulse neural networks using the phase response function. It was found that the intermodule connections from excitatory to excitatory ensembles tend to stabilize the antiphase synchronization and that the intermodule connections from excitatory to inhibitory ensembles tend to stabilize the in-phase synchronization. It was also found that the intermodule synchronization was more noticeable when the inner-module synchronization was weak.

Action Potentials↗
PubMedDate not supplied

[Electrographic activity in rats during elaboration of fine distinctions].

A definite correlation has been found between the background EEG, the sensory afterdischarge (SAD) of the visual cortex and the nature of the animals' behaviour. Calmer rats with a well pronounced SAD exhibited activation of a certain type of hygienic movements, as fine differentiations were presented. As a rule, the movements were accompanied by EEG synchronization. At the same time positive conditioned reflexes persisted, in spite of an increased number of collisions. In restless animals, as the stress situation became stronger, forced movements appeared against the background of EEG desynchronization with a slightly pronounced SAD, alternating with numbness and stupor. Conditioned reflexes disappeared for several weeks. It has been assumed that relative retention of temporary connections in stress situations in animals with a well pronounced SAD is linked with the defensive-stabilizing nature of the inhibitory synchronized EEG rhythms.

Action Potentials↗
PubMed2003

Age-dependent appearance of an insulo-parietal cortical signal propagation that elicits a synchronized population oscillation in the parietal cortex in rats.

We investigated postnatal development of a functional connectivity from the gustatory insular cortex to the parietal cortex, which is known to contain many more neurons responding to oral somesthetic stimulation than the insular cortex, in slices obtained from 9-35-day-old rats. Field potentials were evoked by stimulation to the insular cortex. In the mature cortex, insular stimulation elicited a solitary field potential in both the insular and parietal cortices and, as the simulation continued, the initial solitary potential came to be followed by a population oscillation of field potential in the parietal cortex, but not in the insular cortex. In the immature cortex, by contrast, insular stimulation failed to evoke both the initial solitary potential and the subsequent population oscillation in the parietal cortex. In the mature cortex, application of neither thapsigargin nor AP5 prevented elicitation of the initial solitary potential in the parietal cortex, but either of them abolished the parietal oscillation. In immature cortex bathed with low Mg(2+) medium, insular stimulation elicited both the initial solitary potential and the subsequent parietal oscillation, which were both prevented by thapsigargin or AP5. Theses results suggest that the insular and parietal cortices are anatomically connected but functionally unlinked at an early postnatal stage, and that a functional linkage, dependent both on NMDA and ryanodine receptors, is formed during the first postnatal month.

2-Amino-5-phosphonovalerate↗