Quality and denoising in real‐time functional magnetic resonance imaging neurofeedback: A methods review

Neurofeedback training using real‐time functional magnetic resonance imaging (rtfMRI‐NF) allows subjects voluntary control of localised and distributed brain activity. It has sparked increased interest as a promising non‐invasive treatment option in neuropsychiatric and neurocognitive disorders, although its efficacy and clinical significance are yet to be determined. In this work, we present the first extensive review of acquisition, processing and quality control methods available to improve the quality of the neurofeedback signal. Furthermore, we investigate the state of denoising and quality control practices in 128 recently published rtfMRI‐NF studies. We found: (a) that less than a third of the studies reported implementing standard real‐time fMRI denoising steps, (b) significant room for improvement with regards to methods reporting and (c) the need for methodological studies quantifying and comparing the contribution of denoising steps to the neurofeedback signal quality. Advances in rtfMRI‐NF research depend on reproducibility of methods and results. Notably, a systematic effort is needed to build up evidence that disentangles the various mechanisms influencing neurofeedback effects. To this end, we recommend that future rtfMRI‐NF studies: (a) report implementation of a set of standard real‐time fMRI denoising steps according to a proposed COBIDAS‐style checklist ( https://osf.io/kjwhf/ ), (b) ensure the quality of the neurofeedback signal by calculating and reporting community‐informed quality metrics and applying offline control checks and (c) strive to adopt transparent principles in the form of methods and data sharing and support of open‐source rtfMRI‐NF software. Code and data for reproducibility, as well as an interactive environment to explore the study data, can be accessed at https://github.com/jsheunis/quality‐and‐denoising‐in‐rtfmri‐nf.     

神经反馈调节健康个体注意力的研究进展

神经反馈是指通过脑机交互方式,将大脑活动转换成声音、图像、游戏等形式反馈给个体,以实现自主调节脑功能的目的。注意力是认知功能的重要方面,不仅是儿童发展成长的影响因素,也是成人日常生活中不可替代的重要心理品质。越来越多的实证研究已经发现神经反馈对健康个体的注意力具有调节作用,但缺乏对相关研究进展的总结和综述。综述基于大脑节律活动的神经反馈对于健康个体注意力调节作用的研究进展,分析注意力测量范式、学习者和非学习者的划分以及实验设计类型对神经反馈训练效果的影响,指出了追踪实验对研究的必要性。同时提及可用于健康个体注意力调节的其他几种神经反馈技术。期望为神经反馈提高注意能力的研究和实践提供参考。     

BOOK REVIEW

SUMMARY

Background. Hemoencephalography (HEG) is cortical circulatory biofeedback using refracted light tuned to oxygenated hemoglobin, emitted into the skull and detected at the scalp using a photoelectric cell. Red light at 660 nm is used as the probe, with changes in the returning refracted light representing changes in cortical circulation.

Method. A single-subject design case study was employed. TL, at age twelve, had a well-established diagnosis of ADHD given by pediatric neurologists, and required significant stimulant medication that was clinically effective. He was performing well in school on Concerta 36 mg at 7 a.m. and Ritalin 5 mg at 4 p.m. Off medication, he had significant abnormalities on IVA testing (Attention Quotient or AQ = 78) and in the quantitative electroencephalogram (QEEG). Using HEG, the patient engaged the system to exercise increases in signals corresponding to cortical circulation in the prefrontal cortex. QEEG, Continuous Performance Testing (CPT) and clinical status measurements were made before and after 10 sessions of HEG therapy. HEG exercise was typically given in weekly to bi-weekly sessions for 10 minutes in each of three standard prefrontal EEG locations: FP₁, FP₂ and FPz.

Results. During the 10 therapy sessions TL's HEG data showed positive gain indicating success at raising the biofeedback signal. Following the 10 sessions, TL showed a normal QEEG with improved Z scores for relative power and normal IVA testing off medication (mean AQ 99.75 ± 7.85 on three dates), which persisted in the 18-month follow-up. His medication was lowered to Focalin 2.5 mg twice daily.

Conclusion. This work documents a patient who showed clinically significant improvement after only 10 sessions using a new form of neurobiofeedback, hemoencephalography. If confirmed in controlled studies, this represents a breakthrough in treatment options for ADHD. Future studies should explore synergies between HEG and EEG neurofeedback therapies.     

The Low Energy Neurofeedback System (LENS): Theory,Background, and Introduction

SUMMARY

This article presents the concepts, operations, and history of the Low Energy Neurofeedback System (LENS) approach as they are now known and as it has evolved over the past 16 years. The conceptual bases and practical operating principles as described are quite different from those in traditional neurofeedback. The LENS, as a behavioral neurofeedback application, often provides the same qualitative outcome as that in traditional neurofeedback, with reduced treatment time.     

Quantitative EEG Findings Among Men Convicted of Murder

Abstract

Quantitative EEG data were collected from 20 men convicted of murder and sentenced to death. Measures of coherence, phase, amplitude asymmetry, and relative power from 19 scalp electrode sites during an eyes closed, resting condition were compared to a normative database. Measures significantly different from normal were tallied to determine electrode site locations with greatest concentrations of abnormalities. There were more right than left hemisphere abnormalities of coherence, phase, and amplitude asymmetry, and more anterior than posterior abnormalities of phase, amplitude asymmetry, and relative power. Bilateral frontal, right temporal, and parietal sites had the greatest concentrations of multiple abnormalities. Increased coherence and longer neural conduction times characterized the majority of coherence and phase abnormalities. The concentrations of frontal and right hemisphere abnormalities are discussed as relating to impairment, in executive functions, modulation of affect, and perception of affect in others. Such impairments perhaps in conjunction with adverse environmental events, are suggested as placing one at risk for violent behaviors. Relevance of these findings for future research, forensic neuropsychological assessments, and neurofeedback treatment is mentioned.     

Real‐time estimation of dynamic functional connectivity networks

Two novel and exciting avenues of neuroscientific research involve the study of task‐driven dynamic reconfigurations of functional connectivity networks and the study of functional connectivity in real‐time. While the former is a well‐established field within neuroscience and has received considerable attention in recent years, the latter remains in its infancy. To date, the vast majority of real‐time fMRI studies have focused on a single brain region at a time. This is due in part to the many challenges faced when estimating dynamic functional connectivity networks in real‐time. In this work, we propose a novel methodology with which to accurately track changes in time‐varying functional connectivity networks in real‐time. The proposed method is shown to perform competitively when compared to state‐of‐the‐art offline algorithms using both synthetic as well as real‐time fMRI data. The proposed method is applied to motor task data from the Human Connectome Project as well as to data obtained from a visuospatial attention task. We demonstrate that the algorithm is able to accurately estimate task‐related changes in network structure in real‐time. Hum Brain Mapp 38:202–220, 2017. © 2016 Wiley Periodicals, Inc.     

Endogenously generated gamma‐band oscillations in early visual cortex: A neurofeedback study

Human subjects were trained with neurofeedback (NFB) to enhance the power of narrow‐band gamma oscillations in circumscribed regions of early visual cortex. To select the region and the oscillation frequency for NFB training, gamma oscillations were induced with locally presented drifting gratings. The source and frequency of these induced oscillations were determined using beamforming methods. During NFB training the power of narrow band gamma oscillations was continuously extracted from this source with online beamforming and converted into the pitch of a tone signal. We found that seven out of ten subjects were able to selectively increase the amplitude of gamma oscillations in the absence of visual stimulation. One subject however failed completely and two subjects succeeded to manipulate the feedback signal by contraction of muscles. In all subjects the attempts to enhance visual gamma oscillations were associated with an increase of beta oscillations over precentral/frontal regions. Only successful subjects exhibited an additional marked increase of theta oscillations over precentral/prefrontal and temporal regions whereas unsuccessful subjects showed an increase of alpha band oscillations over occipital regions. We argue that spatially confined networks in early visual cortex can be entrained to engage in narrow band gamma oscillations not only by visual stimuli but also by top down signals. We interpret the concomitant increase in beta oscillations as indication for an engagement of the fronto‐parietal attention network and the increase of theta oscillations as a correlate of imagery. Our finding support the application of NFB in disease conditions associated with impaired gamma synchronization.     

A Modular Activation/Coherence Approach to Evaluating Clinical/QEEG Correlations and for Guiding Neurofeedback Training: Modular Insufficiencies,Modular Excesses,Disconnections, and Hyperconnections

ABSTRACT

Current approaches to QEEG-guided neurofeedback involve efforts to normalize the abnormalities seen, without reference to the functional localization of the cortical areas involved. Recent advances in cortical neurophysiology indicate that specific brain areas are developed to perform certain functions (cortical modules). Complex brain functions require cooperation between modules, particularly during a learning situation. For example, the left prefrontal “activation module” must cooperate with one or both occipital “visual modules” to attend and see something on a chalkboard. To remember what has been seen, both temporal “memory modules” must cooperate with the visual modules for the image to be retained in short-term memory. If the connections between these modules are not functioning optimally, visual learning will be impaired. Decreased coherence (hypocoherence) indicates a decrease in functional connectivity between these modules, and increased coherence (hypercoherence) indicates an increase in functional connectivity between the modules. Neurofeedback can be used to normalize coherence between these modules, thereby improving the efficiency of their cooperation in the learning process. If coherence is less than normal, it is trained up. If coherence is more than normal, it is trained down. Three cases are presented where this approach has succeeded in remediating the client's symptoms.