Basic and Clinical Neuroscience
Volume:15 Issue: 2, Mar-Apr 2024

In January 2020, a novel coronavirus was identified by the Chinese Center for Disease Control and Prevention (CDC) and was subsequently named 2019 nCoV (Li et al., 2020). Coronavirus disease 2019 (COVID-19) has spread to many countries in 2020.

Binaural beat (BB), as a non-invasive auditory beat stimulation type, has found its potential applications in cognitive domains. This review presents a proper summary to deepen our understanding of the soundness of the BB technique by looking into its applications, possible mechanisms of action, effectiveness, limitations, and potential side effects. BB has been claimed to improve cognitive and psychological functions such as memory, attention, stress, anxiety, motivation, and confidence. We have also looked into preclinical and clinical research studies that have been performed using BB and proposed changes in the brain following the application of BB stimulations, including EEG changes. This review also presents applications outside the cognitive domain and evaluates BB as a possible treatment method.

Abnormal brain structure and function have been reported in individuals with attention deficit hyperactivity disorder (ADHD). This study investigated the parietal lobe structure and function alteration in individuals with ADHD.

In this systematic review, we searched English papers in accordance with the PRISMA (the preferred reporting items for systematic reviews and meta-analyses) approach. Studies were published between January 2010 and May 2021. Our search was conducted in two parts. Our first search was in July 2020, and our final search was in June 2021. A literature search identified 20 empirical experiments.

Functional magnetic resonance imaging (MRI) studies generally reported low activity and poor connectivity; structural MRI studies reported less gray matter in this lobe, and an echo study reported atrophy. In addition, electroencephalographic studies reported less connectivity of the parietal lobes in ADHD. Furthermore, the transcranial direct current stimulation intervention has shown that activation of this lobe improves attention and executive functions in children with ADHD. Finally, a deep transcranial magnetic stimulation study has demonstrated that activation of this lobe improves working memory.

Functional and structural alteration of the parietal cortex has been reported in ADHD, which has a causal relationship with cognitive impairments. In sum, all included studies reported abnormal structure, function, or connectivity of the parietal lobe or improvement of cognitive functions with parietal lobe stimulation.

Patients in the early stages of Parkinson disease (PD) may have subtle cognitive deficits, while overt cognitive deficits are usually manifestations of late-stage PD. There is still a debate on the outcome of deep brain stimulation (DBS) on the cognitive function of PD patients. This study aimed to investigate the effect of subthalamic nucleus (STN)-DBS on the dementia of PD patients after surgery compared to medical therapy and other procedures. 

We searched PubMed, Scopus, Cochrane Library, and Web of Science database on October 2020, with keywords: “Deep brain stimulation,” “Parkinson disease,” “dementia,” and “memory.” Reviews, abstracts, case presentations, and letters were excluded. 

In total, 491 studies were screened after removing the duplicates. The screening results yielded 81 articles to be screened for eligibility. Finally, 6 studies were included in this meta-analysis for synthesis. Overall, 800 patients were included in this meta-analysis, using the Mattis dementia rating scale (MDRS) and descriptive data from the articles extracted to assess global dementia.

Our results suggest that the STN-DBS group showed a larger cognitive decline than the patients receiving the best medical treatment (BMT). However, comparing STN-DBS with globus pallidus interna stimulation and pallidotomy could not demonstrate a significant statistical effect on the global dementia of patients. More long-term studies with larger sample sizes are needed to validate current findings.

Parkinson disease is the world’s second most prevalent neurological disease. In this disease, intracytoplasmic neuronal inclusions are observed in enteric neurons in the gastrointestinal tract, and the composition of the intestinal microbiome is altered. These changes correlate with the motor phenotype. A systematic review was conducted to determine the effect of using probiotics in Parkinson disease.

Scopus, PubMed, Web of Science, the Cochrane Library, ScienceDirect, and Ovıd-LWW were searched until April 2021. A total of 27395 records were found according to inclusion and exclusion criteria with the following outcomes: Parkinson disease rating, oxidative stress, and gastrointestinal system markers. Data search, article selection, and data extraction assessments were performed according to the PRISMA (preferred reporting items for systematic reviews and meta-analyses) guidelines. The Jadad scale was used to rate the evidence’s quality.

Our study information was gathered from 5 randomized controlled trials involving 350 individuals with Parkinson disease receiving probiotic supplements. Parkinson disease rating and non-motor symptoms test were performed in the samples. Also, oxidative stress (glutathione, malondialdehyde) and gastrointestinal system symptoms (bowel opening frequency, gut transit time, complete bowel movement, spontaneous bowel movements) were evaluated during 4-12 weeks of using probiotics in these patients. 

While all high-quality studies demonstrate improvement in disease symptoms of the patients, currently sufficient data are not available to recommend the use of probiotics for people with Parkinson disease in clinical practice.

Patients with myasthenia gravis (MG), an autoimmune disease affecting the neuromuscular junction, exhibits varying rates of COVID-19 infection across different studies. This systematic review and meta-analysis aim to estimate the pooled prevalence of COVID-19 infection in individuals with MG. 

We systematically searched PubMed, Scopus, EMBASE, Web of Science, Google Scholar, and gray literature, including references to the research published before October 2021. The total number of participants, the first author, the publication year, the country of origin, the number of MG patients, their symptoms, hospitalization rates, and deaths were all extracted as study data. 

Our literature search yielded 253 articles, of which 75 remained after removing duplicates. Finally, 18 articles were included in the meta-analysis. The pooled prevalence of COVID-19 infection in MG cases was found to be 2% (95% CI, 1%, 3%; I2=85%, P<0.001). Additionally, the pooled prevalence of hospitalization among those with COVID-19 infection was 43% (95% CI, 26%, 60%; I2=97.6%; P<0.001), and the pooled prevalence of MG exacerbation was 33% (95% CI, 20%, 46%; I2=92.6%; P<0.001). 

In summary, this systematic review and meta-analysis reveal that the pooled prevalence of COVID-19 infection in individuals with MG is 2%.

Today, high-voltage (HV) lines create a pernicious environment for humans living or working in the vicinity and even under these lines. The male rhesus monkey is used to investigate the effects of fields produced by HV towers. This study examines the function and level of impact in rhesus monkeys’ brains from the cerebellum’s cognitive, biological, and structural perspective. 

Two monkeys have been used, one as a control and the second as a test. The monkey under test was subjected to a simulated HV electrical field of 3 kV/m, 4 hours a day, for 1 month. Behavioral tests were performed using a device designed and built for this purpose. Concentration analysis of adrenocorticotropic hormones (ACTH) and inspection of glucocorticoid receptor gene’s (GR) expression were performed by the reverse transcription polymerase chain reaction method. Changes in cerebellar anatomy were examined with magnetic resonance imaging (MRI). All tests were performed before and after the study period and compared with the control monkey. 

Cognitive tests showed a significant reduction for the monkey exposed to the HV electrical field in the first week after imposition compared with the same time before. Also, the expression of the GR gene decreased, and the concentration of ACTH hormone in plasma increased. Surveying the level of cerebral MRI images did not show any difference, but hemorrhage was evident in a part of the cerebellum. 

The tested monkey’s cognitive, biological, and MRI results showed a decrease in visual learning and memory indices.

Repetitive transcranial magnetic stimulation (rTMS) is a non-pharmacological treatment for drug-resistant major depressive disorder (MDD) patients. Since the success rate of rTMS treatment is about 50%-55%, it is essential to predict the treatment outcome before starting based on electroencephalogram (EEG) signals, leading to identifying effective biomarkers and reducing the burden of health care centers. 

To this end, pretreatment EEG data with 19 channels in the resting state from 34 drug-resistant MDD patients were recorded. Then, all patients received 20 sessions of rTMS treatment, and a reduction of at least 50% in the total beck depression inventory (BDI-II) score before and after the rTMS treatment was defined as a reference. In the current study, effective brain connectivity features were determined by the direct directed transfer function (dDTF) method from patients’ pretreatment EEG data in all frequency bands separately. Then, the brain functional connectivity patterns were modeled as graphs by the dDTF method and examined with the local graph theory indices, including degree, out-degree, in-degree, strength, out-strength, in-strength, and betweenness centrality. 

The results indicated that the betweenness centrality index in the Fp2 node and the δ frequency band are the best biomarkers, with the highest area under the receiver operating characteristic curve value of 0.85 for predicting the rTMS treatment outcome in drug-resistant MDD patients. 

The proposed method investigated the significant biomarkers that can be used to predict the rTMS treatment outcome in drug-resistant MDD patients and help clinical decisions.

Olfactory ensheathing cells (OECs) are widely used in transplantation studies. The high purification of this unique cell type is valuable for medical applications. Although recent improvements in OECs isolation procedures opened a new era in this field, the high purification efficacy and viability rate are still of concern. The most widely used OECs isolation techniques can be broadly classified based on adherence properties, particularly in olfactory bulb-derived OEC isolation. Considering the invasive nature of harvesting OECs from human olfactory bulbs, a highly efficient purification of these cells from olfactory mucosa can benefit clinical trials. In this study, we isolated OECs from rats’ olfactory bulbs and mucosa due to their differential adherence properties and compared them. 

Cell preparations were characterized by NGFR p75 and S100β antibodies, the specific markers for OECs, using immunocytochemistry and western blot analysis, respectively. OECs morphology and viability were monitored over time by microscopy and MTT (3-[4,5-dimethylthiazol2-yl]-2,5-diphenyltetrazolium bromide) assay. 

We found that OECs could be purified from the olfactory mucosa using our suggested method as efficiently as the olfactory bulb. Both derived OECs showed high levels of NGFR p75 and S100β expression, although the S100β expression was higher in olfactory mucosa-derived OECs preparations (P<0.05). Moreover, there was no significant difference between the two sources in cell viability in our suggested protocol. 

Due to the non-invasive harvesting method, olfactory mucosa-derived OECs are preferred from a clinical point of view in transplantation studies.

The pia-arachnoid is a critical component of cerebrospinal fluid removal. It covers and invaginates into the brain parenchyma, and physiologic failure results in hydrocephalus and cerebral edema. The purpose of this study was to characterize the role of arachnoid within brain parenchyma and determine if water flux and solute transport are affected by these intra-parenchymal cells.

An immortalized arachnoid rat cell line was used to seed 300-µm organotypic rat brain slices of 4-week-old rats. Fluid and tracer transport analyses were conducted following a 7-10 day intraparenchymal growth period. The development of an arachnoid brain slice model was characterized using diffusion chamber experiments to calculate permeability, diffusion coefficient, and flux. 

Labeled rat arachnoid cells readily penetrated organotypic cultures for up to 10 days. A significant reduction of dye and water flux across arachnoid-impregnated brain slices was observed after 3 hours in the diffusion chamber. Permeability decreased in whole brain slices containing arachnoid cells compared to slices without arachnoid cells. In comparison, a significant reduction of dextran across all slices occurred when molecular weights increased from 40 to 70 kDa. 

Tracer and small molecule studies show that arachnoid cells’ presence significantly impacts water’s movement through brain parenchyma. Size differential experiments indicate that the permeability of solute changed substantially between 40 and 70 kDa, an essential marker of blood-CSF barrier definition. We have developed an arachnoid organotypic model that reveals their ability to alter permeability and transport.

Binaural beats are one of the new methods of brainwave synchronization. However, there is little knowledge about its clinical applications. The positive effect of this method on executive functions, such as attention and working memory, in the γ band has been mainly confirmed in healthy individuals. Still, its effectiveness on disorders such as obsessive-compulsive disorder (OCD), with a prominent cognitive profile, has not been established. Therefore, the present study was conducted to examine the effect of binaural beats on working memory and the severity of OCD symptoms in the γ band in the affected women.a

Twenty-nine OCD women aged 25-40 years referring to psychological clinics in Tehran City, Iran, were selected by convenience sampling. After completing the symptom checklist 90 (SCL90) and the Yale-Brown severity scale (SS), the participants were given the Wechsler memory scale (WMS) digit repetition subtests. Then, they were randomly assigned to the experimental (n=15) and control (n=14) groups. The audio file of the binaural beats in the γ band was provided to the experimental group. The participants in the control group listened to the normal (no-wave) audio file. Both groups listened to the audio files for two weeks, three times a week, for 30 minutes each time. The Yale-Brown SS and digit repetition in post-test and one-month follow-up periods were obtained from both groups.

According to the results, the severity of OCD symptoms was significantly reduced in the post-test and follow-up stages by the γ binaural beats (P<0.05). Also, the working memory function was improved, although it was not statistically significant (P>0.05).

The results of this study show that binaural beats can be used as a complementary treatment to reduce the severity of OCD symptoms. Also, it seems that the patients’ working memory is strengthened with this method.

Valproic acid (VPA) is the most widely used chemical to develop the preclinical model of autism spectrum disorder (ASD). However, in addition to inducing autism, it causes different teratogenic effects like teeth malformation, tail kink, and abnormal body growth in offspring. So far, no study has explored VPA-induced maternal misbehavior, miscarriage, and maternal cannibalism. We aimed to determine the cannibalistic effects of VPA in pregnant female Wistar rats and VPA’s influence on causing miscarriage frequency.

Our study was conducted on pregnant Wistar rats. On gestation day (GD) 12.5, they were treated with VPA (600 mg/kg intraperitoneal) dissolved in saline at 250 mg/mL concentration. The observations were mean litter size, mean male/female pups, mean mortality, maternal cannibalism, mean number of pups alive, cannibalism of malformed pups, miscarriage, survival analysis of pups, and odds and risk ratio were calculated for deaths observed in both study (control and VPA-treated) groups. The study was conducted till the weaning period. 

VPA-exposed pregnant females portrayed significantly decreased litter size (P<0.0001), significantly higher cannibalistic behavior (P=0.0023), and significantly higher cannibalism of malformed pups (P=0.0484) than the control group. VPA had caused complete pregnancy loss (miscarriage) in 5 pregnant females. Moreover, the VPA group’s mortality percentage (P=0.0019) was significantly higher than the control group.

Overall, VPA has marked teratogenic effects (anatomical and morphological changes in offspring) with maternal behavior disruption, which causes cannibalism in Wistar female rats. The current manuscript findings can aid in investigating the novel mechanisms involved in maternal behavior disruption during the development of the VPA autism model.