Clinical applications of neurofeedback based on sensorimotor rhythm: a systematic review and meta-analysis.

Background: Among the brain-machine interfaces, neurofeedback is a non-invasive technique that uses sensorimotor rhythm (SMR) as a clinical intervention protocol. This study aimed to investigate the clinical applications of SMR neurofeedback to understand its clinical effectiveness in different pathologies or symptoms. Methods: A systematic review study with meta-analysis of the clinical applications of EEG-based SMR neurofeedback performed using pre-selected publication databases. A qualitative analysis of these studies was performed using the Consensus tool on the Reporting and Experimental Design of Neurofeedback studies (CRED-nf). The Meta-analysis of clinical efficacy was carried out using Review Manager software, version 5.4.1 (RevMan 5; Cochrane Collaboration, Oxford, UK). Results: The qualitative analysis includes 44 studies, of which only 27 studies had some kind of control condition, five studies were double-blinded, and only three reported a blind follow-up throughout the intervention. The meta-analysis included a total sample of 203 individuals between stroke and fibromyalgia. Studies on multiple sclerosis, insomnia, quadriplegia, paraplegia, and mild cognitive impairment were excluded due to the absence of a control group or results based only on post-intervention scales. Statistical analysis indicated that stroke patients did not benefit from neurofeedback interventions when compared to other therapies (Std. mean. dif. 0.31, 95% CI 0.03-0.60, p = 0.03), and there was no significant heterogeneity among stroke studies, classified as moderate I2 = 46% p-value = 0.06. Patients diagnosed with fibromyalgia showed, by means of quantitative analysis, a better benefit for the group that used neurofeedback (Std. mean. dif. -0.73, 95% CI -1.22 to -0.24, p = 0.001). Thus, on performing the pooled analysis between conditions, no significant differences were observed between the neurofeedback intervention and standard therapy (0.05, CI 95%, -0.20 to -0.30, p = 0.69), with the presence of substantial heterogeneity I2 = 92.2%, p-value < 0.001. Conclusion: We conclude that although neurofeedback based on electrophysiological patterns of SMR contemplates the interest of numerous researchers and the existence of research that presents promising results, it is currently not possible to point out the clinical benefits of the technique as a form of clinical intervention. Therefore, it is necessary to develop more robust studies with a greater sample of a more rigorous methodology to understand the benefits that the technique can provide to the population.

Social cognition and psychosocial functioning in schizophrenia and bipolar disorder: Theory of mind as a key to understand schizophrenia dysfunction.

Functional impairment is a common symptom in schizophrenia (SZ) and bipolar disorder (BD). Pharmacological treatments have limited functional recovery in both disorders. Social cognition, a cognitive process, has been associated with functioning in mental disorders. Theory of mind (ToM) is considered a key factor in understanding the social cognitive deficits in SZ and BD. Our study aimed to investigate the relationship between ToM and functioning in SZ, BD, and healthy controls (HC) and compare ToM and functioning impairments between groups. A total of 208 participants (HC n = 69; BD n = 89; SZ n = 50) were evaluated with the Functioning Assessment Short Test (FAST), Reading the Mind in the Eyes Test (RMET), the Vocabulary subtest of the Wechsler Abbreviated Scale for Intelligence (WASI) and the Hopkins Verbal Learning Test - Revised (HVLT-R). Comparisons of RMET between low- and high-functioning individuals and multiple linear regression analyses were conducted for each group. Multiple regression analysis revealed that the association between ToM and psychosocial functioning was observed only in SZ (ß = -1.352, p = 0.008). Low-functioning SZ participants showed a lower ToM performance compared to participants with high-functioning SZ (t = 1.80, p = 0.039, Cohen's d = 0.938). No significant associations were found in the other groups. ToM is essential to understand the functional impairment in SZ, more than in BD. Furthermore, ToM may be a primary target for intervention strategies in improving functioning in SZ.

Retinal layers and symptoms and inflammation in schizophrenia.

Schizophrenia is a neurodevelopmental disorder that affects brain structure and function. The retina, as well as the brain, consists of neuronal and glial cells packed in layers. Cortical volume and brain thickness are associated with inflammatory biomarkers, however, no study has been performed associating inflammatory biomarkers and retina in schizophrenia. our study aims to compare the retinal macular thickness and volume and peripapillary thickness in patients with schizophrenia and controls, and associate it to symptoms of schizophrenia, to interleukin-6 (IL-6) and C Reactive Protein (CRP) levels. Optical coherence tomography was performed to assess retinal layer thickness and volume, and CRP and IL-6 levels were measured in patients with schizophrenia and controls. Positive, negative, and general symptoms of schizophrenia were measured with the Positive and Negative Syndrome Scale (PANSS). A linear regression controlling for confounding factors was performed. 70 subjects were included, 35 patients, and 35 controls matched for sex and age. Patients with schizophrenia presented a significantly lower macular volume (p < 0.05) and thickness (< 0.05) than controls. PANSS positive, general and total scores were associated with retinal nerve fiber layer (RNFL) thickness (p < 0.05). There was no association between inflammatory markers (CRP and IL-6) levels and the retinal layer. A reduction in macular volume and thickness was found in patients with schizophrenia. The severity of schizophrenia symptoms was associated with RNFL thickness. CRP and IL-6 are not associated with retinal thickness/volume in schizophrenia or controls.