Mu rhythm separation from the mix with alpha rhythm: Principal component analyses and factor topography

BACKGROUND

EEG mu rhythm suppression is assessed in experiments on the execution, observation and imagination of movements. It is utilised for studying of actions, language, empathy in healthy individuals and preservation of sensorimotor system functions in patients with schizophrenia and autism spectrum disorders. While EEG alpha and mu rhythms are recorded in the same frequency range (8-13 Hz), their specification becomes a serious issue. THE NEW METHOD: is based on the spatial and functional characteristics of the mu wave, which are: (1) the mu rhythm is located over the sensorimotor cortex; (2) it desynchronises during movement processing and does not respond on the eyes opening. In EEG recordings, we analysed the mu rhythm under conditions with eyes opened and eyes closed (baseline), and during a motor imagery task with eyes closed. EEG recordings were processed by principal component analysis (PCA).

RESULTS

The analysis of EEG data with the proposed approach revealed the maximum spectral power of mu rhythm localised in the sensorimotor areas. During motor imagery, mu rhythm was suppressed more in frontal and central sites than in occipital sites, whereas alpha rhythm was suppressed more in parietal and occipital sites. Mu rhythm desynchronization in sensorimotor sites during motor imagery was greater than alpha rhythm desynchronization. The proposed method enabled EEG mu rhythm separation from its mix with alpha rhythm.

CONCLUSIONS

EEG mu rhythm separation with the proposed method satisfies its classical definition.

Frequency Effects on Spelling Error Recognition: An ERP Study

Spelling errors are ubiquitous in all writing systems. Most studies exploring spelling errors focused on the phonological plausibility of errors. However, unlike typical pseudohomophones, spelling errors occur in naturally produced written language. We investigated the time course of recognition of the most frequent orthographic errors in Russian (error in an unstressed vowel in the root) and the effect of word frequency on this process. During event-related potentials (ERP) recording, 26 native Russian speakers silently read high-frequency correctly spelled words, low-frequency correctly spelled words, high-frequency words with errors, and low-frequency words with errors. The amplitude of P200 was more positive for correctly spelled words than for misspelled words and did not depend on the frequency of the words. In addition, in the 350–500-ms time window, we found a more negative response for misspelled words than for correctly spelled words in parietal–temporal-occipital regions regardless of word frequency. Considering our results in the context of a dual-route model, we concluded that recognizing misspelled high-frequency and low-frequency words involves common orthographic and phonological processes associated with P200 and N400 components such as whole word orthography processing and activation of phonological representations correspondingly. However, at the 500–700 ms stage (associated with lexical-semantic access in our study), error recognition depends on the word frequency. One possible explanation for these differences could be that at the 500–700 ms stage recognition of high-frequency misspelled and correctly spelled words shifts from phonological to orthographic processes, while low-frequency misspelled words are accompanied by more prolonged phonological activation. We believe these processes may be associated with different ERP components P300 and N400, reflecting a temporal overlap between categorization processes based on orthographic properties for high-frequency words and phonological processes for low-frequency words. Therefore, our results complement existing reading models and demonstrate that the neuronal underpinnings of spelling error recognition during reading may depend on word frequency.

Top-down modulation of brain responses in spelling error recognition

The task being undertaken can influence orthographic, phonological and semantic processes. In linguistic research, two tasks are most often used: a task requiring a decision in relation to the presented word and a passive reading task which does not require a decision regarding the presented word. The results of studies using these different tasks are not always consistent. This study aimed to explore brain responses associated with the process of recognition of spelling errors, as well as the influence of the task on this process. Event-related potentials (ERPs) were recorded in 40 adults during an orthographic decision task to determine correctly spelled words and words written with errors that did not change the phonology and during the passive reading. During spelling recognition, the early stages up to 100 ms after the stimulus were automatic and did not depend on the requirements of the task. The amplitude of the N1 component (90-160 ms) was greater in the orthographic decision task, but did not depend on the correct spelling of the word. Late word recognition after 350-500 ms was task dependent, but spelling effects were similar across the two tasks: misspelled words evoked an increase in the amplitude of the N400 component related to lexical and semantic processing regardless of the task. In addition, the orthographic decision task modulated spelling effects, this was reflected in an increase in the amplitude of the P2 component (180-260 ms) for correctly spelled words compared with misspelled words. Thus, our results show that spelling recognition involves general lexico-semantic processes independent of the task. Simultaneously, the orthographic decision task modulates the spelling-specific processes necessary to quickly detect conflicts between orthographic and phonological representations of words in memory.

[Possibility of application Mexidol for the treatment of patients suffering from sensorineural hearing loss and cerebrovascular insufficiency]

Sensorineural hearing loss can develop as a consequence of vascular pathology. The etiology and pathogenesis of chronic sensorineural hearing loss allow us to consider promising the use of neuroprotective drugs in the treatment regimen that can activate the function of the neural structures of the auditory pathway. Ethylmethylhydroxypyridine succinate, having complex pharmacological capabilities and a wide range of effects realized at the neural and vascular levels can be used in the treatment of hearing impairment and speech intelligibility.

[Labyrinth hydrops and its diagnosis]

The article deals with the basic theories of maze and labyrinth hydrops, which are often used in clinical practice for its diagnosis according to the world literature. Tonal threshold, suprathreshold audiometry, broadband thympanometry, ultrasound tests, test for determination of lateralization of loud sounds, dehydration test, extra-timbanical electrocochleography, method of registration of evoked vestibular myogenic potentials, study of vestibular function (video pulse test, caloric sample), CT of temporal bones with gadolinium, MRI, and other methods are considered. None of these study methods gives an accurate confirmation of the presence of maze hydrops. Only taking into account the history, complaints of the patient, clinical manifestations of the disease and a comprehensive evaluation of the results of all the above methods of study can we speak with confidence about hydropse.

[Clinical and diagnostic criteria and differential diagnosis in the first and second stages of the development of Ménière's disease - A modern view of the problem]

The results of a comprehensive examination of 82 patients with clinical signs of definite Ménière's disease, unilateral lesion and confirmed by extratympanic electrocochleography endolymphatic hydrops are presented. The results of the study showed that only 38% of patients had cochleovestibular syndrome due to Ménière's disease. In 45% of patients, Ménière's disease was combined with other diseases: benign paroxysmal positional vertigo, vestibular migraine, persistent postural-perceptual dizziness, superior semicircular canal dehiscence. In 17% of patients cochleovestibular syndrome was due to other reasons: vestibular migraine, tumor of the posterior cranial fossa, superior canal dehiscence syndrome, Cogan's syndrome, enlarged vestibular aqueduct, otosclerosis. Complaints, medical history of the disease and life, brain MRI, temporal bone CT and pure tone audiometry in dynamics are important in suspected Ménière's disease. For 1 and 2 Ménière's disease stages the most important characteristic are: progressive unilateral sensorineural hearing loss and reduced slow faze velocity values of caloric nystagmus in dynamics, mainly in warm response if attacks of vertigo is maintain; normal head impulse test between vertigo attacks and pathological result of this test in attack of vertigo with the normalization of gain during the first day.

Spelling principles matter: An ERP study investigating the processing of different types of pseudohomophones

Spelling in any writing system is governed by fundamental principles. We examined the processing of two types of pseudohomophones constructed from words whose spellings are based on different principles - on the traditional principle of writing, requiring memorization of their spelling, and on the morphological principle, allowing the determination of their spelling from another word with the same morpheme (root) to examine the dependence of the occurrence of orthography-phonology conflict on spelling principles. Event-related potentials were recorded from 22 volunteers during silent reading. Pseudohomophones based on the morphological principle increased the N400 amplitude, emphasizing semantic and morphological processing importance. The P600 component showed significant effects for differentiating words and pseudohomophones based on the traditional principle, predominantly indicating the involvement of memory and reanalysis processes. Source reconstruction demonstrates that both pseudohomophones activate the left inferior frontal gyrus. However, pseudohomophones based on the traditional principle additionally activate the right and left postcentral gyrus, indicating the involvement of additional areas in the differentiation process. The earlier differences for stimuli based on the morphological principle indicate access to smaller units (morphemes), whereas stimuli based on the traditional principle require whole word processing. Our findings underscore the significant role of spelling principles in orthographic processing.

[Cognitive disorders and some particularly of brain electrical activity in the use of cannabinoids]

In the current work we review the research on the effects of exogenous cannabinoids. Exogenous cannabinoids probably disrupt the normal functioning of cannabinoid receptors and area of the brain in which they are located, and this disruption is reflected in the change of related functions. Particular attention is drawn to the research of brain electrical activity in cannabis users. These studies can be divided into two directions--the study of acute and of long-term effects. Principal acute effects of cannabis are: reduction in the power of the theta oscillations, and the decrease in the amplitude of P300. The results of studies of long-term effects are contradictory: some studies indicate a reduction of adverse effects during disuse. Other studies give reason to believe that cognitive disorders associated with chronic use of cannabinoids are stable and long-term.

EEG activity for semantic task in paranoid schizophrenia

We identified a potential neurophysiological marker for processing of verbal cues in paranoid schizophrenia: high desynchronization in the beta-2 band in the right parietal area for meaningless cues, and no synchronization differences in the beta-2 and gamma bands in the left prefrontal area pointing to deficient categorization of the stimuli.

Electrophysiological signatures of spelling sensitivity development from primary school age to adulthood

Recognizing spelling errors is important for correct writing and reading, and develops over an extended period. The neural bases of the development of orthographic sensitivity remain poorly understood. We investigated event-related potentials (ERPs) associated with spelling error recognition when performing the orthographic decision task with correctly spelled and misspelled words in children aged 8-10 years old, early adolescents aged 11-14 years old, and adults. Spelling processing in adults included an early stage associated with the initial recognition of conflict between orthography and phonology (reflected in the N400 time window) and a later stage (reflected in the P600 time window) related to re-checking the spelling. In children 8-10 years old, there were no differences in ERPs to correct and misspelled words; in addition, their behavioral scores were worse than those of early adolescents, implying that the ability to quickly recognize the correct spelling is just beginning to develop at this age. In early adolescents, spelling recognition was reflected only at the later stage, corresponding to the P600 component. At the behavioral level, they were worse than adults at recognizing misspelled words. Our data suggest that orthographic sensitivity can develop beyond 14 years.

[Neuroimaging of the endolymphatic hydrops of the labyrinth in severe and moderately severe Meniere's disease]

The results of magnetic resonance imaging (MRI) of the inner ear 24 hours after intratympanic administration of 1 ml of diluted (1:7) contrast substance for gadolinium-based MRI in 43 patients with moderate and severe Meniere's disease course are presented. It has been revealed that in case of severe and moderate course of Meniere's disease endolymphatic hydrops is presented in all departments of labyrinth: cochlea, vestibule, semicircular canals, but is most pronounced in vestibular department of labyrinth: horizontal semicircular canal and vestibule. The neuroimaging method according to the presented protocol is safe and can be applied in a wide practice both to assess the presence and localization, and the degree of expression of the endolymphatic hydrops.

EEG alpha reactivity on eyes opening discriminates patients with schizophrenia and schizoaffective disorder

OBJECTIVE

Alpha activity in the electroencephalogram (EEG) is typically dominant during rest with closed eyes but suppressed by visual stimulation. Previous research has shown that alpha-blockade is less pronounced in schizophrenia patients compared to healthy individuals, but no studies have examined it in schizoaffective disorder.

METHODS

A resting state EEG was used for the analysis of the alpha-reactivity between the eyes closed and the eyes opened conditions in overall (8 - 13 Hz), low (8 - 10 Hz) and high (10 - 13 Hz) alpha bands in three groups: schizophrenia patients (SC, n = 30), schizoaffective disorder (SA, n = 30), and healthy controls (HC, n = 36). All patients had their first psychotic episode and were receiving antipsychotic therapy.

RESULTS

A significant decrease in alpha power was noted across all subjects from the eyes-closed to eyes-open condition, spanning all regions. Alpha reactivity over the posterior regions was lower in SC compared to HC within overall and high alpha. SA showed a trend towards reduced alpha reactivity compared to HC, especially evident over the left posterior region within the overall alpha. Alpha reactivity was more pronounced over the middle and right posterior regions of SA as compared to SC, particularly in the high alpha. Alpha reactivity in SC and SA patients was associated with various negative symptoms.

CONCLUSIONS

Our findings imply distinct alterations in arousal mechanisms in SC and SA and their relation to negative symptomatology. Arousal is more preserved in SA.

SIGNIFICANCE

This study is the first to compare the EEG features of arousal in SC and SA.

[The use of Gliathiline in patients with sensorineural hearing loss]

The results of treatment of 38 patients suffering from sensorineural hearing loss with the Gliatilin (solution 3 ml intravenously for 10 days, capsules 400 mg 3 times a day or solution for ingestion 600 mg 2 times a day for 3 months) are presented. All patients in dynamics were given a comprehensive audiological, neurological examination, as well as an assessment of psycho-emotional status and cognitive function. Subjective improvement of ear noise tolerance by patients by 40 days of observation and continuation of this trend during the whole period (100 days) outside of the form of the medicinal preparation is noted. A reliable improvement in the 50% speech intelligibility threshold by day 100 of observation was established in patients of both groups, with a tendency towards earlier (on day 70 of the study) onset of this effect when taking the drug inside as a solution. The Gliatilin has been proven to reduce anxiety and depression, as well as reliably improve cognitive function. Thus, Gliatilin (injection solution, ingestion solution, capsules) can be used to improve the subjective tolerance of ear noise, speech intelligibility and quality of life of patients in chronic sensorineural hearing loss.

[The effectiveness of transtympanic use of dexamethasone 4 mg in Meniere's disease, severe and moderate course of the disease]

The results of transtympanic administration of 4 mg dexamethasone in 37 patients with moderate and severe Meniere's disease are presented. The endolymphatic hydrops was detected in all inner ear structures with predominant accumulation in vestibule and semicircular canals by MRI-visualization before therapy. After 1 month of 4 mg dexamethasone transtympanic therapy the hydrops degree decreased. Daily transtympanic administration of 4 mg dexamethasone for a month leads to reduction of vertigo attacks duration and expression in 92% of cases (follow-up period 24 months) and can be considered when conservative therapy is ineffective before destructive surgical interventions.

[Dissociation of the results of caloric and video head impulse tests as a marker of Meniere's disease]

The study of vestibular function in patients with Meniere's disease (MD) is an urgent task, since it influences the choice of treatment tactic. We evaluated the results of caloric and video head impulse (vHIT) tests in 76 patients who met the clinical criteria for significant Meniere's disease (AAO-HNS modified by the Barany Society, 2015). Dissociation of the results of caloric and vHIT tests is observed in the majority (74%) of patients with MD: at normal gain, according to vHIT data, hypofunction of peripheral vestibular structures is recorded according to the caloric test (KASL 47 ± 7.8%). In patients with MD, vestibular dysfunction is observed mainly at low frequencies (0.003 Hz), therefore vHIT, which allows assessing horizontal semicircular canal function at high frequencies (3-5 Hz), is not an optimal study for assessing the degree of vestibular dysfunction in patients with MD.

[P100 and N170 Components of ERPs in Abstinent Cannabinoid Users during the Modified Stroop Task]

In the current work we conducted the comparative analysis of P100 and N170 components of ERPs in abstinent cannabinoid users and in healthy controls during the modified Stroop task. The latency of P100 and N170 components was shorter in the temporal, parietal and occipital areas in abstinent cannabinoid users in comparison with the control subjects. The cannabinoid group showed the decrease of P100 amplitude in the right temporal and parietal areas and the decrease of N170 amplitude in the left temporal and parietal areas. There were no differences in the behavioral indices between these two groups. Thus, cannabinoids influence upon the mechanisms of early selection and these alterations of brain activity are stable and long-term.