Localization of brain electrical activity sources and hemodynamic activity foci during motor imagery

The sources of brain activity that make the maximum contribution to EEG patterns corresponding to motor imagery have been studied. The accuracy of their classification determines the efficiency of brain-computer interface (BCI) for controlling external technical devices directly by brain signals, without the involvement of muscle activity. Brain activity sources are identified by independent component analysis. The independent components providing the maximum BCI classification accuracy are considered relevant for the motor imagery task. The two most relevant sources exhibit clearly marked event-related desynchronization and synchronization of the μ-rhythm during the imagery of contra- and ipsilateral hand movements. These sources were localized by solving the inverse EEG problem with due consideration for individual geometry of the brain and its covers, as determined by magnetic resonance imaging. Each of the sources was shown to be localized in the 3a area of the primary somatosensory cortex corresponding to proprioceptive sensitivity of the contralateral hand. Their positions were close to the foci of BOLD activity obtained by fMRI.     

A CAPS marker set for mapping in linkage group III of pea (Pisum sativum L.)

A set of twelve CAPS markers was mapped for linkage group III of pea (Pisum sativum L.). New primers were designed to use a polymerase chain reaction to amplify fragments of sequenced pea genes containing at least one large intron. Amplification products were tested for polymorphism across three pea lines (Chi115, Flagman and WL1238) using eleven four-base restriction endonucleases. Nine STS markers for linkage group III from the literature were also tested for polymorphism, and five of these were used in this mapping study as anchor points. All polymorphic loci were located by genetic analysis of the F(2)population from the cross Chi115 x WL1238, and a map of linkage group III consisting of one morphological and twelve CAPS markers was created. The map covers the full length of the chromosome and is about 162 cM long. All the CAPS markers in a set were used to test for polymorphism among 10 additional pea DNA samples extracted from different marker lines and cultivars.     

Organization of neural networks for speech recognition in healthy subjects and its reorganization in patients with poststroke aphasia

It has traditionally been accepted that the speech-related brain function is located in some strictly determined areas of the left hemisphere: Broca’s area in the posterior part of the inferior frontal gyrus (Brodmann area 44, BA44) and Wernicke’s area in the posterior part of the superior temporal gyrus (BA22). Modern neuroimaging data including functional magnetic resonance imaging (fMRI) expand our knowledge about speech networks in the brain. Using our own speech tasks (paradigms) with sentence reading and sentence continuation tests, we studied the distribution of the neural speech-related network in healthy subjects and its reorganization in patients with different forms of aphasia. During data processing obtained in the control group we found activation of classic speech areas (Broca’s and Wernicke’s ones) and their right-hemisphere homologues, but the volume of the left-hemispheric activations prevailed. Bilateral activation in the inferior parts of the precentral (BA4) and postcentral (BA1) gyri, in the cerebellar hemispheres, and in the visual cortex (BA17–18) was also revealed. The activation in Broca’s and Wernicke’s speech and speech areas in the group of patients was related to the localization of the brain lesion: in the case of lesion in the corresponding area the activation was shifted towards the stroke area periphery. Additional regions of activation, including the superior parietal lobule (BA7), angular and supramarginal gyri (BA39–40), etc., were recorded in both hemispheres in patients with aphasia. It has been shown that the paradigm used in the current study optimally demonstrates speech-related brain network. The obtained data will help to broaden our comprehension of the brain structures involved in the process of speech and understand their role in the recovery of impaired speech functions.     

Changes in functional connectivity of motor zones in the course of treatment with a regent multimodal complex exoskeleton in neurorehabilitation of post-stroke patients

The effect of a treatment course with a Regent multimodal complex exoskeleton (MCE) on the reorganization of cortical locomotor zones was studied in 14 patients with post-stroke hemiparesis, mainly in the chronic stage of the disease. Specific activation zones were identified prior to treatment in the primary sensorimotor and supplementary motor areas and the inferior parietal lobules of both affected and healthy hemispheres by functional magnetic resonance imaging (fMRI) used in a special passive sensorimotor paradigm. After a treatment course with the MCE, temporal characteristics of walking were found to improve, which was accompanied by a decrease in the activation zones of the inferior parietal lobules, especially in the healthy hemisphere, and a significant increase in the activation zones of the primary sensorimotor and supplementary motor areas. Significant changes in intrahemispheric and interhemispheric interactions were revealed by analyzing the functional connectivity of the zones under study before and after a course of treatment with the MCE.     

Cerebral perfusion changes in patients with internal carotid artery stenoses after surgical revascularization

Changes of cerebral perfusion and the condition of collateral blood supply in patients with internal carotid artery stenoses may have a prognostic value for effective blood flow restoration after revascularization of the internal carotid arteries (ICAs). To determine the patterns of cerebral perfusion changes in patients with ICA stenoses before and after surgical treatment, a clinical CT perfusion study of 41 patients with moderate to severe ICA stenoses was performed. Perfusion CT (PCT) had been conducted in 17 patients with moderate ICA stenoses (50–69%) and in 24 patients with severe ICA stenoses (70–99%) 3 times: before intervention (balloon angioplasty with stenting or carotid endarterectomy), on the 3rd to 7th day, and within 1 to 3 months after surgery. Scanning was performed at the level of the basal ganglia and semioval centers. In patients without ICA stenosis (control group of 39 individuals), PCT was conducted once. We found that surgical recanalization of the ICA leads to normalization of the cerebral blood flow parameters in the perfusion area of the middle cranial artery, as evidenced by a decrease of MTT and CBV and an increase of CBF to values comparable to those in the control group. However, blood flow restoration in the anterior and posterior watershed areas, which are known to be mostly affected under chronic hypoperfusion conditions, was observed only in patients with a complete circle of Willis (CW) and moderate ICA stenosis. Therefore, severe stenosis (>70%) and the incomplete CW are the prognostic factors for inadequate blood flow restoration after revascularization in patients with ICA stenoses.     

Distinctive Features of Lower Hybrid Current Drive in Plasma of the FT-2 Tokamak

Plasma Physics Reports - Experiments on the lower hybrid current drive (LHCD) were performed in plasma of the FT-2 tokamak at the microwave pulse duration of ΔtRF ≤ 20 ms covering the...