Frontiers in neurology and neuroscience research最新文献

Objective: To estimate the prevalence of depression among stroke survivors in India.

Participants: Stroke survivors diagnosed with depression.

Outcomes: Prevalence of Depression.

Methods: Cochrane systematic review methods were followed. The literature search was from 1960-2019. We searched the following electronic databases Medline, ERIC, Embase, IndMED, PsycEXTRA, Global Health, Cochrane, CENTRAL Register, Econ Lit, and conference abstracts to identify studies for inclusion. A search strategy was appropriately developed and performed from May 2019 to December 2019. All included studies were assessed for their content and methodological quality using JBI Critical Appraisal Checklist.

Results: A total of 15 studies were included in this study. Prevalence of post-stroke depression in the studies varied from 24% to 90%. The pooled prevalence was 55% (95% CI 43%, 65%) with high heterogeneity (I²=94.83%). Prevalence also varied between the tools (HAMD -60%, GDS -70%, HADS -40%). The overall methodological quality of the included studies was very poor.

Conclusion: It is evident from the meta-analysis that about half of those who survive a stroke experience post-stroke depression. The methods and tools used to investigate this was not rigorous and homogeneous. Hence results of this review imply the need to rigorously assess and effectively address post-stroke depression in India. Also, this review recommends future research to ensure methodological quality and generalizability of the study findings. This would help develop scalable, innovative public health intervention for post-stroke depression in the future.

Troxler Fading (TF) is a complex visual phenomenon with uncertain mechanisms. This study was performed to test hypotheses concerning the contributions of parvocellular and magnocelluar processing in extrastriate pathways to TF. The study used low-frequency, repetitive Transcranial Magnetic Stimulation (rTMS) delivered at target sites in the parietal, temporal and dorsolateral frontal cortex to alter performance on a TF paradigm and on tests sensitive to parvocellular and magnocellular processing. Nine, right-handed, healthy subjects completed 3 tasks, TF, Texture Detection (TD), and Motion Detection (MD), at baseline and after undergoing 15 minutes of low-frequency rTMS at each cortical site on separate occasions. Results revealed lateralized effects of rTMS on each test. Left temporal stimulation slowed the parvocellular, TD task and it accelerated TF. Right parietal stimulation markedly accelerated TF whereas left parietal stimulation slowed TF. Right frontal stimulation accelerated performance on the magnocellular, MD task. Taken together and in the context of other research studies, the findings suggest hemispheric specialization both for TF and for the parvocellular and magnocellular processing tasks.

The intracarotid sodium amobarbital procedure (ISAP or Wada test) lateralizes cerebral functions to the cerebral hemispheres preoperatively. Functional magnetic resonance imaging (fMRI) is increasingly used to characterize preoperative language and memory lateralization. In this study, concordance of fMRI with Wada was examined in patients with medically intractable seizures. The relationship of the distance between the epileptogenic focus to functional activation area with patients' post-operative deficits in language was also analyzed. 27 epilepsy patients with preoperative fMRI and Wada data were analyzed using established fMRI paradigms for language and memory. Activation of Broca's and Wernicke's areas were measured in three dimensions. Language and memory lateralization were determined, and standard neuropsychiatry Wada test procedures were used for comparison. The shortest distance between a language area to the border of surgical focus (LAD) was also measured and compared with postoperative language deficits. Our study found that concordance between fMRI and Wada testing was 0.41 (Kappa's 'fair to good' concordance) for language dominance and 0.1 (Kappa's 'poor' concordance) for memory. No significant correlation was found between LAD and post-op language deficit (p=0.439). A correlation was found between LAD and post-op memory deficit (p=0.049; the further distance from surgical lesion to language area is associated with less post-operative memory loss). Females demonstrated significantly increased postoperative seizure improvement (Fisher's p-value=0.0296; female=8; male=6). A significant association between handedness (right-handed subjects) and postoperative seizure improvement was found (p=0.02) as well as a significant trend for interaction of gender and handedness on postoperative seizure improvement (p=0.09). Overall, our results demonstrate fMRI as a useful preoperative adjunct to Wada testing for language lateralization in patients with medically intractable seizures.

Objective: To examine how 1Hz and 10Hz rTMS temporarily influence ratings of tinnitus loudness, annoyance, and awareness. The thalamocortical dysrhythmia (TCD) model of tinnitus was tested by examining changes in spectral power and coherence of resting state EEGs from baseline to each phase of treatment and correlating these data with change in tinnitus.

Methods: Nineteen participants completed a double-blind, placebo (sham rTMS) controlled, within-subjects study with crossover between the two active rTMS treatment conditions. An imposed order effect, sham rTMS first, eliminated drift of active treatment into the placebo condition. The primary outcome measures were analogue ratings of tinnitus loudness, annoyance, and awareness, assessed repeatedly at baseline and during treatment, and 64 channel, resting state EEGs collected at baseline and the end of each treatment phase. Active rTMS consisted of 1800 pulses at 110% of motor threshold over temporal cortex delivered at 1Hz and 10Hz over four days. The research design also examined the effect of rTMS immediately following stimulation, regression to the mean in tinnitus ratings made over multiple days, and differences between treatment responders and non-responders.

Results: There was no immediate effect of rTMS on tinnitus during a single rTMS session. Regression to the mean in tinnitus ratings occurred over three days of baseline and four days of treatment (both sham and active rTMS). After accounting for regression to the mean in the statistical model, 1Hz rTMS led to a significant decrease in tinnitus awareness from baseline and 10Hz rTMS trended in the same direction, whereas sham rTMS showed little change from baseline other than regression to the mean. Changes from baseline in spectral power of the resting state EEG provided partial support for predictions based on TCD model of tinnitus for active 1 and 10Hz rTMS but not sham rTMS. However, only an increase in beta coherence correlated significantly with a decrease in tinnitus awareness. Changes in the EEG were robust in treatment responders but absent among non-responders and during sham rTMS.

Conclusions: A positive response to rTMS for tinnitus is associated with an rTMS-induced change in beta coherence of the EEG. Increased beta coherence may be a biomarker of the rTMS effect; a "top-down" modulation of the EEG that promotes habituation to tinnitus. Participants whose tinnitus did not improve after rTMS did not show any changes in the EEG.

Background and purpose: Strong experimental neurobehavioral evidence suggests that intensive training improves arm motor disability after stroke. Yet, we still have only limited understanding why some patients recover more completely and others do not. This is in part due to our limited knowledge of the neurobiological principles of recovery from stroke. Mounting evidence suggests that functional and structural remapping of the primary motor cortex (M1) plays a major role in arm recovery after stroke. We used MR Spectroscopy to test the hypothesis that therapy-related arm improvement is associated with changes in levels of a putative marker of neuronal integrity (N-acetylaspartate, NAA) in M1 controlling the paretic arm (ipsilesional M1) in chronic stroke patients (n=5).

Methods: Patients (1 female, age, mean ± SD, 58.4 ± 5.8 years) underwent 4-week arm-focused motor training (1080 repetitions of a reach-to-grasp task) at 13.6 ± 5.3 months after stroke onset. NAA levels in the ipsilesional M1 and arm impairment (Fugl-Meyer, FM, 66=normal; proximal FM, FM_p, 30=normal) were assessed prior to and immediately after training.

Results: At baseline, patients exhibited moderate-to-mild arm impairment (FM, 47.2 ± 18.8, FM_p, 22.2 ± 8.6) and showed lower levels of NAA compared with age/sex-matched healthy controls (10.2 ± 0.9 mM in patients vs. 11.6 ± 1.6 mM in controls, p=0.03). After training, arm impairment improved (FM by 7%, 50.6 ± 17.5, p=0.01; FMp, by 5%, 23.4 ± 8.2, p=0.2) and NAA levels increased by 10.5% (11.2 ± 1.2 mM, p=0.1). Changes in NAA positively correlated with changes in FM (r=0.63, p=0.2) and FM_p (r=0.93, p=0.03), suggesting that patients who show greater neuronal changes have a better chance of recovery.

Conclusions: Our data suggest the potential use of M1 NAA as a biomarker of motor recovery after stroke. However, because of our small sample, these preliminary results should be interpreted cautiously. Further work with larger sample sizes is warranted.

Parkinson's disease (PD) is an incurable neurodegenerative disorder affecting up to 10 million people in the world. Diagnostic motor symptoms of PD appear as a result of progressive degeneration and death of nigrostriatal dopamine neurons. Current PD treatments only relieve symptoms without halting the progression of the disease, and their use is complicated by severe adverse effects emerging as the disease progresses. Therefore, there is an urgent need for new therapies for PD management. We developed a small molecule compound, BT13, targeting receptor tyrosine kinase RET. RET is the signalling receptor for a known survival factor for dopamine neurons called glial cell line-derived neurotrophic factor (GDNF). Previously we showed that BT13 prevents the death of cultured dopamine neurons, stimulates dopamine release and activates pro-survival signalling cascades in naïve rodent brain. In the present study, we evaluate the effects of BT13 on motor imbalance and nigrostriatal dopamine neurons in a unilateral 6-hydroxydopamine rat model of PD. We show that BT13 alleviates motor dysfunction in experimental animals. Further studies are needed to make a conclusion whether BT13 can protect the integrity of the nigrostriatal dopamine system since even the positive control, GDNF protein, was unable to produce a clear neuroprotective effect in the model used in the present work. In contrast to GDNF, BT13 is able to cross the blood-brain barrier, which together with the ability to reduce motor symptoms of the disease makes it a valuable lead for further development as a potential disease-modifying agent to treat PD.

In recent years, the advantages of RNA-sequencing (RNA-Seq) have made it the platform of choice for measuring gene expression over traditional microarrays. However, RNA-Seq comes with bioinformatical challenges and higher computational costs. Therefore, this study set out to assess whether the increased depth of transcriptomic information facilitated by RNA-Seq is worth the increased computation over microarrays, specifically at three levels: absolute expression levels, differentially expressed genes identification, and expression QTL (eQTL) mapping in regions of the human brain. Using the United Kingdom Brain Expression Consortium (UKBEC) dataset, there is high agreement of gene expression levels measured by microarrays and RNA-seq when quantifying absolute expression levels and when identifying differentially expressed genes. These findings suggest that depending on the aims of a study, the relative ease of working with microarray data may outweigh the computational time and costs of RNA-Seq pipelines. On the other, there was low agreement when mapping eQTLs. However, a number of eQTLs associated with genes that play important roles in the brain were found in both platforms. For example, a trans-eQTL was mapped that is associated with the MPZ gene in the substantia nigra. These eQTLs that we have highlighted are extremely promising candidates that merit further investigation.

Objective: Transcranial direct current stimulation (tDCS) has been used to alter cortical excitability of the lower extremity (LE) and to influence performance on LE tasks like ankle tracking accuracy; but no study, to our knowledge, ever reported a significant change in cortical excitability relative to sham-tDCS. Additionally, because several different electrode montages were used in previous studies, it is difficult to know how stimulation should be applied to achieve this effect. Our objective was to determine whether active-tDCS alters cortical excitability of the LE and ankle tracking accuracy relative to sham-tDCS in healthy participants. The efficacy of two electrode montages and two conductance mediums were compared.

Methods: A triple-blind, fully randomized, within-subjects study was conducted with healthy participants (N=18, 24.2 (6.6) years). Cortical recruitment curves and measures of ankle tracking accuracy for the dominant lower extremity were obtained before and after participants received active-tDCS at 2 milliamps for 20 minutes using montage-medium combinations of M₁-SO:Saline, M₁-SO:Gel, C1-C2:Saline, and C1-C2:Gel and a sham-tDCS condition (M1-SO: Saline).

Results: The motor evoked potential maximum of the recruitment curve was significantly lower for active than sham-tDCS, but only for the M₁-SO:Saline combination. No other significant differences in the recruitment curve parameters or in ankle tracking were found.

Conclusions: This is the first study to our knowledge to demonstrate a significant difference in cortical excitability of the LE between active and sham-tDCS conditions. Given the order in which the experimental procedures occurred, the result is consistent with the concept of a homeostatic plasticity response.