Jitter of corticospinal neurons during repetitive transcranial magnetic stimulation. Method and possible clinical implications.
BACKGROUND: Repetitive transcranial magnetic stimulation (rTMS) of the motor cortex activates corticospinal neurons mainly through the depolarization of cortico-cortical axons belonging to interneurons of superficial layers. OBJECTIVE: We used single-fiber electromyography (SFEMG) to estimate the "central jitter" of activation latency of interneural pools from one pulse of TMS to another. METHODS: We evaluated 10 healthy subjects and one patient with multiple sclerosis. By recording SFEMG evoked activity from the left first dorsal interosseous (FDI), we first used a standard repetitive electrical 3 Hz stimulation of the ulnar nerve at the wrist to calculate the mean consecutive difference from at least 10 different potentials. The same procedure was applied during 3 Hz repetitive TMS of the contralateral motor cortex. The corticospinal monosynaptic connection of the FDI and the selectivity of SFEMG recording physiologically justified the subtraction of the "peripheral jitter" from the whole cortico-muscular jitter, obtaining an estimation of the actual "central jitter." RESULTS: All subjects completed the study. The peripheral jitter was 28 mus +/- 6 and the cortico-muscular jitter was 344 mus +/- 97. The estimated central jitter was 343 +/- 97 mus. In the patient the central jitter was 846 mus, a value more than twice the central jitter in healthy subjects. CONCLUSION: Current results demonstrate that the evaluation of the central component of the cumulative cortico-muscular latency variability in healthy subjects is feasible with a minimally invasive approach. We present and discuss this methodology and provide a "proof of concept" of its potential clinical applicability in a patient with multiple sclerosis.
The results of cross-cultural research of implicit theories of innovativeness among students and teachers, representatives of three ethnocultural groups: Russians, the people of the North Caucasus (Chechens and Ingushs) and Tuvinians (N=804) are presented. Intergroup differences in implicit theories of innovativeness are revealed: the ‘individual’ theories of innovativeness prevail among Russians and among the students, the ‘social’ theories of innovativeness are more expressed among respondents from the North Caucasus, Tuva and among the teachers. Using the structural equations modeling the universal model of values impact on implicit theories of innovativeness and attitudes towards innovations is constructed. Values of the Openness to changes and individual theories of innovativeness promote the positive relation to innovations. Results of research have shown that implicit theories of innovativeness differ in different cultures, and values make different impact on the attitudes towards innovations and innovative experience in different cultures.
Transcranial magnetic stimulation (TMS) is a modern non-invasive approach to study brain organization in humans. In TMS a time-varying magnetic fields generate induced electrical currents in the targeted brain regions with focal location of its maximum. Using of MRI navigation systems allows to fully realizing the advantages of TMS focality for brain mapping purposes. Due to this development, nowadays motor and speech nTMS mapping is becoming a routinely used procedure in neurosurgery. However, nTMS mapping for dynamic cortical assessment, for example, to study neuroplastic changes is still limited. An important reason for that is a lack of a standardized methodology for nTMS mapping results assessment. Here we propose TMSmap – a standalone graphical interface software for quantative analysis of the results of motor nTMS mapping (http://tmsmap.ru/), which allows considering both standard parameters like the size of the cortical muscle representation, the hotspot and the center of gravity location, as well as the additional ones such as the volume of the representation, the profile of the muscle cortical area and the overlap between the cortical representations and other user-defined parameters. The input data includes coordinates of the coil position and the response in each point of stimulation and individual structural MRI data.
Despite being a routine technique for presurgical motor assessment, transcranial magnetic stimulation (TMS) mapping is underused for probing of neuroplastic brain changes. We investigated the test-retest reproducibility of the TMS cortical maps of several hand muscles using both standard and alternative parameters of the cortical representation.Pilot study results for four healthy right-handed male volunteers (19-33y.o.) are presented. Two TMS mapping sessions with the stimulation of the left motor cortex were performed within 5-10 days (Day1 and Day2). Day2 points repeated an exact order of the Day1. For quantative comparison of 3D profiles similarities earth mover's distance metrics was used. Analysis of nTMS maps was performed using custom-made software TMSmap (http://tmsmap.ru).The between-days difference in the area of cortical representation for four analyzed subjects was 14.5-30.4% for one and 3.9-11.2% for five repetitions of each cortical point. Considering 3D profiles of cortical representation, higher similarity was shown for the same muscles’ representations and their overlaps compared to the representations of the different muscles. The study is ongoing, further analyzed results will be present.
TMSmap software was developed for quantative analysis of the results of motor nTMS mapping, which allows to consider not only standard parameters like the size of the cortical muscle representation and hotspot and center of gravity location, but as well the volume of the representation considering the amplitude of MEPs in each stimulation spot, the shape of the area, the profile/landscape of the muscle cortical representation and the overlap between representations.
We investigated the time-course of cortical activation during comprehension of literal and idiomatic sentences using MEG and anatomically guided distributed source analysis. Previous fMRI work had shown that the comprehension of sentences including action-related words elicits somatotopic semantic activation along the motor strip, reflecting meaning aspects of constituent words. Furthermore, idioms more strongly activated temporal pole and prefrontal cortex than literal sentences. Here we show that, compared to literal sentences, processing of idioms in a silent reading task modulates anterior fronto-temporal activity very early-on, already 150-250 ms after the sentences' critical disambiguating words ("kick the habit"). In parallel, the meaning of action words embedded in sentences is reflected by somatotopic activation of precentral motor systems. As neural reflections of constituent parts of idiomatic sentences are manifest at the same early latencies as brain indexes of idiomatic vs. literal meaning processing, we suggest that within ¼ of a second, compositional and abstract context-driven semantic processes in parallel contribute to the understanding of idiom meaning.
This training manual contains information about the features of the use of transcranial magnetic stimulation (TMS) in the main mental and neuropsychiatric disorders. The manual discusses in detail the main mechanisms of action of TMS, legal, organizational and sanitary norms of this procedure, indications and contraindications for its implementation, the peculiarities of combining TMS with psychopharmacotherapy and psychotherapy. In separate sections, the features of the use of TMS for affective diseases, anxiety disorders, obsessive-compulsive disorder, schizophrenia, chronic pain, neuropsychiatric diseases, and addictions are highlighted. The textbook "Application of transcranial magnetic stimulation in psychiatric and neuropsychiatric practice" was prepared in the discipline "Psychiatry" in accordance with the Federal State Educational Standard of Higher Professional Education for students of postgraduate and additional professional education of doctors studying in the specialty "Psychiatry" (14.01.06)
We here investigate whether the well-known laterality of spoken language to the dominant left hemisphere could be explained by the learning of sensorimotor links between a word's articulatory program and its corresponding sound structure. Human-specific asymmetry of acoustic-articulatory connectivity is evident structurally, at the neuroanatomical level, in the arcuate fascicle, which connects superior-temporal and frontal cortices and is more developed in the left hemisphere. Because these left-lateralised fronto-temporal fibres provide a substrate for auditory-motor associations, we hypothesised that learning of acoustic-articulatory coincidences produces laterality, whereas perceptual learning does not. Twenty subjects studied a large (n=48) set of novel meaningless syllable combinations, pseudowords, in a perceptual learning condition, where they carefully listened to repeatedly presented novel items, and, crucially, in an articulatory learning condition, where each item had to be repeated immediately, so that articulatory and auditory speech-evoked cortical activations coincided. In the 14 subjects who successfully passed the learning routine and could recognize the learnt items reliably, both perceptual and articulatory learning were found to lead to an increase of pseudoword-elicited event-related potentials (ERPs), thus reflecting the formation of new memory circuits. Importantly, after articulatory learning, pseudoword-elicited ERPs were more strongly left-lateralised than after perceptual learning. Source localisation confirmed that perceptual learning led to increased activation in superior-temporal cortex bilaterally, whereas items learnt in the articulatory condition activated bilateral superior-temporal auditory in combination with left-pre-central motor areas. These results support a new explanation of the laterality of spoken language based on the neuroanatomy of sensorimotor links and Hebbian learning principles.
The neural mechanisms underlying perceptual learning are still under investigation. Eureka effect is a form of rapid, long-lasting perceptual learning by which a degraded image, which appears meaningless when first seen, becomes recognizable after a single exposure to its undegraded version. We used online interference by focal 10-Hz repetitive transcranial magnetic stimulation (rTMS) to evaluate whether the parietal cortex (PC) is involved in Eureka effect, as suggested by neuroimaging data. RTMS of the PC did not affect recognition of degraded pictures when displayed 2s after the presentation of their undegraded version (learning phase). However, rTMS delivered over either right or left intraparietal sulcus simultaneously to the undegraded image presentation, disrupted identification of the degraded version of the same pictures when displayed 30 min after the learning phase. In contrast, recognition of degraded images was unaffected by rTMS over the vertex or by sham rTMS, or when rTMS of either PC was delivered 2s after the presentation of the undegraded image. Findings strongly support the hypothesis that both PC at the level of the intraparietal sulcus play a pivotal role in the Eureka effect particularly in consolidation processes, and contribute to elucidate the neural network underlying rapid perceptual learning
Students' internet usage attracts the attention of many researchers in different countries. Differences in internet penetration in diverse countries lead us to ask about the interaction of medium and culture in this process. In this paper we present an analysis based on a sample of 825 students from 18 Russian universities and discuss findings on particularities of students' ICT usage. On the background of the findings of the study, based on data collected in 2008-2009 year during a project "A сross-cultural study of the new learning culture formation in Germany and Russia", we discuss the problem of plagiarism in Russia, the availability of ICT features in Russian universities and an evaluation of the attractiveness of different categories of ICT usage and gender specifics in the use of ICT.