Assessment of Cortical Plasticity in Schizophrenia by Transcranial Magnetic Stimulation

Neural plasticity refers to the capability of the brain to modify its structure and/or function and organization in response to a changing environment. Evidence shows that disruption of neuronal plasticity and altered functional connectivity between distinct brain networks contribute significantly to the pathophysiological mechanisms of schizophrenia. Transcranial magnetic stimulation has emerged as a noninvasive brain stimulation tool that can be utilized to investigate cortical excitability with the aim of probing neural plasticity mechanisms. In particular, in pathological disorders, such as schizophrenia, cortical dysfunction, such as an aberrant excitatory-inhibitory balance in cortical networks, altered cortical connectivity, and impairment of critical period timing are very important to be studied using different TMS paradigms. Studying such neurophysiological characteristics and plastic changes would help in elucidating different aspects of the pathophysiological mechanisms underlying schizophrenia. This review attempts to summarize the findings of available TMS studies with diagnostic and characterization aims, but not with therapeutic purposes, in schizophrenia. Findings provide further evidence of aberrant excitatory-inhibitory balance in cortical networks, mediated by neurotransmitter pathways such as the glutamate and GABA systems. Future studies with combining techniques, for instance, TMS with brain imaging or molecular genetic typing, would shed light on the characteristics and predictors of schizophrenia.

Noninvasive Brain Stimulation of the Dorsolateral Prefrontal Cortex During Aesthetic Appreciation

Several neuroimaging studies had shown that activity in the left dorsolateral prefrontal cortex (lDLPFC) was associated with aesthetic appreciation. But, was this a causal association? In the article under discussion, the authors used transcranial direct current stimulation (tDCS) to determine whether lDLPFC activity actually caused increased aesthetic appreciation. Their results showed that tDCS over lDLPFC caused liking for artworks and photographs to increase. They therefore concluded that the lDLPFC plays a causal role in visual aesthetic appreciation. The authors suggested that lDLPFC activity contributes to disengaging from a pragmatic orientation to stimuli, consisting mainly in identifying objects, adopting an aesthetic orientation, and focusing on those objects’ aesthetic qualities.

Neuroimaging-Guided Transcranial Magnetic and Direct Current Stimulation in MCI: Toward an Individual, Effective and Disease-Modifying Treatment

The therapeutic approaches currently applied in Alzheimer's disease (AD) and similar neurodegenerative diseases are essentially based on pharmacological strategies. However, despite intensive research, the effectiveness of these treatments is limited to transient symptomatic effects, and they are still far from exhibiting a true therapeutic effect capable of altering prognosis. The lack of success of such pharmacotherapy-based protocols may be derived from the cases in the majority of trials being too advanced to benefit significantly in therapeutic terms at the clinical level. For neurodegenerative diseases, mild cognitive impairment (MCI) may be an early stage of the disease continuum, including Alzheimer's. Noninvasive brain stimulation (NIBS) techniques have been developed to modulate plasticity in the human cortex in the last few decades. NIBS techniques have made it possible to obtain unique findings concerning brain functions, and design novel approaches to treat various neurological and psychiatric conditions. In addition, its synaptic and cellular neurobiological effects, NIBS is an attractive treatment option in the early phases of neurodegenerative diseases, such as MCI, with its beneficial modifying effects on cellular neuroplasticity. However, there is still insufficient evidence about the potential positive clinical effects of NIBS on MCI. Furthermore, the huge variability of the clinical effects of NIBS limits its use. In this article, we reviewed the combinatory approach of NIBS with various neuroimaging and electrophysiological methods. Such methodologies may provide a new horizon to the path for personalized treatment, including a more individualized pathophysiology approach which might even define new specific targets for specific symptoms of neurodegenerations.

Systematic Review and Network Meta-Analysis of Noninvasive Brain Stimulation on Dysphagia after Stroke

Background. Dysphagia is a common sequelae after stroke. Noninvasive brain stimulation (NIBS) is a tool that has been used in the rehabilitation process to modify cortical excitability and improve dysphagia. Objective. To systematically evaluate the effect of NIBS on dysphagia after stroke and compare the effects of two different NIBS. Methods. Randomized controlled trials about the effect of NIBS on dysphagia after stroke were retrieved from databases of PubMed, Embase, Cochrane Library, Web of Science, CNKI, Wanfang Data, VIP, and CBM, from inception to June 2021. The quality of the trials was assessed, and the data were extracted according to the Cochrane Handbook for Systematic Reviews of Interventions. A statistical analysis was carried out using RevMan 5.3 and ADDIS 1.16.8. The effect size was evaluated by using the standardized mean difference (SMD) and a 95% confidence interval (CI). Results. Ultimately, 18 studies involving 738 patients were included. Meta-analysis showed that NIBS could improve the dysphagia outcome and severity scale (DOSS) score (standard mean difference SMD = 1.44 , 95% CI 0.80 to 2.08, P < 0.05 ) and the water swallow test score ( SMD = 6.23 , 95% CI 5.44 to 7.03, P < 0.05 ). NIBS could reduce the standardized swallowing assessment (SSA) score ( SMD = − 1.04 , 95% CI -1.50 to -0.58, P < 0.05 ), the penetration-aspiration scale (PAS) score ( SMD = − 0.85 , 95% CI -1.33 to -0.36, P < 0.05 ), and the functional dysphagia scale score ( SMD = − 1.05 , 95% CI -1.48 to -0.62, P < 0.05 ). Network meta-analysis showed that the best probabilistic ranking of the effects of two different NIBS on the DOSS score is rTMS P = 0.52 > tDCS P = 0.48 , the best probabilistic ranking of the SSA score is rTMS P = 0.72 > tDCS P = 0.28 , and the best probabilistic ranking of the PAS score is rTMS P = 0.68 > tDCS P = 0.32 . Conclusion. Existing evidence showed that NIBS could improve swallowing dysfunction and reduce the occurrence of aspiration after stroke, and that rTMS is better than tDCS. Limited by the number of included studies, more large-sample, multicenter, double-blind, high-quality clinical randomized controlled trials are still needed in the future to further confirm the results of this research.