Learning and self-regulation of slow cortical potentials in older adults

The efficacy of electroencephalography neurofeedback for enhancing episodic memory in healthy and clinical participants: A systematic qualitative review and meta-analysis

Several studies have examined whether electroencephalography neurofeedback (EEG-NF), a self-regulatory technique where an individual receives real-time feedback on a pattern of brain activity that is theoretically linked to a target behaviour, can enhance episodic memory. The aim of this research was to i) provide a qualitative overview of the literature, and ii) conduct a meta-analysis of appropriately controlled studies to determine whether EEG-NF can enhance episodic memory. The literature search returned 46 studies, with 21 studies (44 effect sizes) meeting the inclusion criteria for the meta-analysis. The qualitative overview revealed that, across EEG-NF studies on both healthy and clinical populations, procedures and protocols vary considerably and many studies were insufficiently powered with inadequate design features. The meta-analysis, conducted on studies with an active control, revealed a small-size, significant positive effect of EEG-NF on episodic memory performance (g = 0.31, p = 0.003), moderated by memory modality and EEG-NF self-regulation success. These results are discussed with a view towards optimising EEG-NF training and subsequent benefits to episodic memory.

How standardized are “standard protocols”? Variations in protocol and performance evaluation for slow cortical potential neurofeedback: A systematic review

Neurofeedback (NF) aims to alter neural activity by enhancing self-regulation skills. Over the past decade NF has received considerable attention as a potential intervention option for many somatic and mental conditions and ADHD in particular. However, placebo-controlled trials have demonstrated insufficient superiority of NF compared to treatment as usual and sham conditions. It has been argued that the reason for limited NF effects may be attributable to participants' challenges to self-regulate the targeted neural activity. Still, there is support of NF efficacy when only considering so-called “standard protocols,” such as Slow Cortical Potential NF training (SCP-NF). This PROSPERO registered systematic review following PRISMA criteria searched literature databases for studies applying SCP-NF protocols. Our review focus concerned the operationalization of self-regulatory success, and protocol-details that could influence the evaluation of self-regulation. Such details included; electrode placement, number of trials, length per trial, proportions of training modalities, handling of artifacts and skill-transfer into daily-life. We identified a total of 63 eligible reports published in the year 2000 or later. SCP-NF protocol-details varied considerably on most variables, except for electrode placement. However, due to the increased availability of commercial systems, there was a trend to more uniform protocol-details. Although, token-systems are popular in SCP-NF for ADHD, only half reported a performance-based component. Also, transfer exercises have become a staple part of SCP-NF. Furthermore, multiple operationalizations of regulatory success were identified, limiting comparability between studies, and perhaps usefulness of so-called transfer-exercises, which purpose is to facilitate the transfer of the self-regulatory skills into every-day life. While studies utilizing SCP as Brain-Computer-Interface mainly focused on the acquisition of successful self-regulation, clinically oriented studies often neglected this. Congruently, rates of successful regulators in clinical studies were mostly low (<50%). The relation between SCP self-regulation and behavior, and how symptoms in different disorders are affected, is complex and not fully understood. Future studies need to report self-regulation based on standardized measures, in order to facilitate both comparability and understanding of the effects on symptoms. When applied as treatment, future SCP-NF studies also need to put greater emphasis on the acquisition of self-regulation (before evaluating symptom outcomes).

Shutting Down Sensorimotor Interferences after Stroke: A Proof-of-Principle SMR Neurofeedback Study

Introduction: Neurofeedback training aims at learning self-regulation of brain activity underlying cognitive, emotional or physiological functions. Despite of promising investigations on neurofeedback as a tool for cognitive rehabilitation in neurological diseases, such as after stroke, there is still a lack of research on feasibility and efficiency of neurofeedback in this field.

Methods: The present study aimed at investigating behavioral and electrophysiological effects of 10 sessions of sensorimotor rhythm (SMR) neurofeedback in a 74-years-old stroke patient (UG20). Based on previous results in healthy young participants, we hypothesized that SMR neurofeedback leads to a decrease in sensorimotor interferences and improved stimulus processing, reflected by changes in event-related potentials (ERPs) and electrophysiological coherence. To assess whether UG20 benefited from the training as much as healthy persons of a similar age, a healthy control group of N = 10 elderly persons was trained as well. Before and after neurofeedback training, participants took part in a multichannel electroencephalography measurement conducted during a non-verbal and a verbal learning task.

Results: Both UG20 and the healthy controls were able to regulate their SMR activity during neurofeedback training. Moreover, in a non-verbal learning task, changes in ERPs and coherence were observed after training: UG20 showed a better performance in the non-verbal learning task and a higher P3 amplitude after training than before, and coherence between central and parietal electrodes decreased after training. The control group also showed a behavioral improvement in the non-verbal learning task and tendencies for higher P3 amplitudes and decreased central-parietal coherence after training. Single-case analyses indicated that the changes observed in UG20 were not smaller than the changes in healthy controls.

Conclusion: Neurofeedback can be successfully applied in a stroke patient and in healthy elderly persons. We suggest that SMR neurofeedback leads to a shutting-down of sensorimotor interferences which benefits semantic encoding and retrieval.

Slow Cortical Potential Neurofeedback in Chronic Tinnitus Therapy: A Case Report

This study is the first to demonstrate outcomes of slow cortical potential (SCP) Neurofeedback training in chronic tinnitus. A 50-year old male patient with tinnitus participated in three SCP training blocks, separated with 1-month breaks. After the training the patient reported decreased tinnitus loudness and pitch, as well as improved quality of daily life. A quantitative electroencephalography analysis revealed close to normal changes of resting state bioelectrical activity in cortical areas considered to be involved in tinnitus generation. The present case study indicates that SCP Neurofeedback training can be considered a promising method for tinnitus treatment.

The predictive role of pre-cue EEG rhythms on MI-based BCI classification performance

BACKGROUND

One of the main issues in motor imagery-based (MI-based) brain-computer interface (BCI) systems is a large variation in the classification performance of BCI users. However, the exact reason of low performance of some users is still under investigation. Having some prior knowledge about the performance of users may be helpful in understanding possible reasons of performance variations.

NEW METHOD

In this study a novel coefficient from pre-cue EEG rhythms is proposed. The proposed coefficient is computed from the spectral power of pre-cue EEG data for specific rhythms over different regions of the brain. The feasibility of predicting the classification performance of the MI-based BCI users from the proposed coefficient is investigated.

RESULTS

Group level analysis on N=17 healthy subjects showed that there is a significant correlation r=0.53 (p=0.02) between the proposed coefficient and the cross-validation accuracies of the subjects in performing MI. The results showed that subjects with higher cross-validation accuracies have yielded significantly higher values of the proposed coefficient and vice versa.

COMPARISON WITH EXISTING METHODS

In comparison with other previous predictors, this coefficient captures spatial information from the brain in addition to spectral information.

CONCLUSION

The result of using the proposed coefficient suggests that having higher frontal theta and lower posterior alpha prior to performing MI may enhance the BCI classification performance. This finding reveals prospect of designing a novel experiment to prepare the user towards improved motor imagery performance.

Neurocognitive mechanisms of statistical-sequential learning: what do event-related potentials tell us?

Statistical-sequential learning (SL) is the ability to process patterns of environmental stimuli, such as spoken language, music, or one's motor actions, that unfold in time. The underlying neurocognitive mechanisms of SL and the associated cognitive representations are still not well understood as reflected by the heterogeneity of the reviewed cognitive models. The purpose of this review is: (1) to provide a general overview of the primary models and theories of SL, (2) to describe the empirical research - with a focus on the event-related potential (ERP) literature - in support of these models while also highlighting the current limitations of this research, and (3) to present a set of new lines of ERP research to overcome these limitations. The review is articulated around three descriptive dimensions in relation to SL: the level of abstractness of the representations learned through SL, the effect of the level of attention and consciousness on SL, and the developmental trajectory of SL across the life-span. We conclude with a new tentative model that takes into account these three dimensions and also point to several promising new lines of SL research.

Prediction of auditory and visual p300 brain-computer interface aptitude

OBJECTIVE

Brain-computer interfaces (BCIs) provide a non-muscular communication channel for patients with late-stage motoneuron disease (e.g., amyotrophic lateral sclerosis (ALS)) or otherwise motor impaired people and are also used for motor rehabilitation in chronic stroke. Differences in the ability to use a BCI vary from person to person and from session to session. A reliable predictor of aptitude would allow for the selection of suitable BCI paradigms. For this reason, we investigated whether P300 BCI aptitude could be predicted from a short experiment with a standard auditory oddball.

METHODS

Forty healthy participants performed an electroencephalography (EEG) based visual and auditory P300-BCI spelling task in a single session. In addition, prior to each session an auditory oddball was presented. Features extracted from the auditory oddball were analyzed with respect to predictive power for BCI aptitude.

RESULTS

Correlation between auditory oddball response and P300 BCI accuracy revealed a strong relationship between accuracy and N2 amplitude and the amplitude of a late ERP component between 400 and 600 ms. Interestingly, the P3 amplitude of the auditory oddball response was not correlated with accuracy.

CONCLUSIONS

Event-related potentials recorded during a standard auditory oddball session moderately predict aptitude in an audiory and highly in a visual P300 BCI. The predictor will allow for faster paradigm selection.

SIGNIFICANCE

Our method will reduce strain on patients because unsuccessful training may be avoided, provided the results can be generalized to the patient population.

Neuroanatomical and cognitive mediators of age-related differences in perceptual priming and learning

Our objectives were to assess age differences in perceptual repetition priming and perceptual skill learning and to determine whether they are mediated by cognitive resources and regional cerebral volume differences. Fragmented picture identification paradigm allows the study of both priming and learning within the same task. The authors presented this task to 169 adults (ages 18-80), assessed working memory and fluid intelligence, and measured brain volumes of regions that were deemed relevant to those cognitive skills. The data were analyzed within a hierarchical path modeling framework. In addition to finding age-related decrease in both perceptual priming and learning, the authors observed several dissociations with regards to their neural and cognitive mediators. Larger visual cortex volume was associated with greater repetition priming, but not perceptual skill learning, and neither process depended upon hippocampal volume. In contrast, the volumes of the prefrontal gray and white matter were differentially related to both processes via direct and indirect effects of cognitive resources. The results indicate that age-related differences in perceptual priming and skill learning have dissociable cognitive and neural correlates.

Complementary and alternative medicine use for treatment and prevention of late-life mood and cognitive disorders

Late-life mood disorders and cognitive aging are the most common reasons for using complementary and alternative therapies. The amount of rigorous scientific data to support the efficacy of complementary therapies in the treatment of depression or cognitive impairment is extremely limited. The areas with the most evidence for beneficial effects are exercise, herbal therapy (Hypericum perforatum), the use of fish oil, and, to a lesser extent, acupuncture and relaxation therapies. There is a need for further research involving randomized, controlled trials to investigate the efficacy of complementary and alternative therapies in the treatment of depression and cognitive impairment in late-life. This research may lead to the development of effective treatment and preventive approaches for these serious conditions.

gSRT-Soft: a generic software application and some methodological guidelines to investigate implicit learning through visual-motor sequential tasks

Serial reaction time tasks and, more generally, the visual-motor sequential paradigms are increasingly popular tools in a variety of research domains, from studies on implicit learning in laboratory contexts to the assessment of residual learning capabilities of patients in clinical settings. A consequence of this success, however, is the increased variability in paradigms and the difficulty inherent in respecting the methodological principles that two decades of experimental investigations have made more and more stringent. The purpose of the present article is to address those problems. We present a user-friendly application that simplifies running classical experiments, but is flexible enough to permit a broad range of nonstandard manipulations for more specific objectives. Basic methodological guidelines are also provided, as are suggestions for using the software to explore unconventional directions of research. The most recent version of gSRT-Soft may be obtained for free by contacting the authors.

Fragmented pictures revisited: long-term changes in repetition priming, relation to skill learning, and the role of cognitive resources

BACKGROUND

Whereas age-related declines in declarative memory have been demonstrated in multiple cross-sectional and longitudinal studies, the effect of age on non-declarative manifestations of memory, such as repetition priming and perceptual skill learning, are less clear. The common assumption, based on cross-sectional studies, is that these processes are only mildly (if at all) affected by age.

OBJECTIVE

To investigate long-term changes in repetition priming and age-related differences in identification of fragmented pictures in a 5-year longitudinal design.

METHOD

Healthy adults (age 28-82 years) viewed drawings of objects presented in descending order of fragmentation. The identification threshold (IT) was the highest fragmentation level at which the object was correctly named. After a short interval, old pictures were presented again along with a set of similar but novel pictures. Five years later the participants repeated the experiment.

RESULTS

At baseline and 5-year follow-up alike, one repeated exposure improved IT for old (priming) and new (skill acquisition) pictures. However, long-term retention of priming gains was observed only in young adults. Working memory explained a significant proportion of variance in within-occasion priming, long-term priming, and skill learning.

CONCLUSION

Contrary to cross-sectional results, this longitudinal study suggests perceptual repetition priming is not an age-invariant phenomenon and advanced age and reduced availability of cognitive resources may contribute to its decline.

Self-regulation of slow cortical potentials: a new treatment for children with attention-deficit/hyperactivity disorder

OBJECTIVE

We investigated the effects of self-regulation of slow cortical potentials for children with attention-deficit/hyperactivity disorder. Slow cortical potentials are slow event-related direct-current shifts of the electroencephalogram. Slow cortical potential shifts in the electrical negative direction reflect the depolarization of large cortical cell assemblies, reducing their excitation threshold. This training aims at regulation of cortical excitation thresholds considered to be impaired in children with attention-deficit/hyperactivity disorder. Electroencephalographic data from the training and the 6-month follow-up are reported, as are changes in behavior and cognition.

METHOD

Twenty-three children with attention-deficit/hyperactivity disorder aged between 8 and 13 years received 30 sessions of self-regulation training of slow cortical potentials in 3 phases of 10 sessions each. Increasing and decreasing slow cortical potentials at central brain regions was fed back visually and auditorily. Transfer trials without feedback were intermixed with feedback trials to allow generalization to everyday-life situations. In addition to the neurofeedback sessions, children exercised during the third training phase to apply the self-regulation strategy while doing their homework.

RESULTS

For the first time, electroencephalographic data during the course of slow cortical potential neurofeedback are reported. Measurement before and after the trials showed that children with attention-deficit/hyperactivity disorder learn to regulate negative slow cortical potentials. After training, significant improvement in behavior, attention, and IQ score was observed. The behavior ratings included Diagnostic and Statistical Manual of Mental Disorders criteria, number of problems, and social behavior at school and were conducted by parents and teachers. The cognitive variables were assessed with the Wechsler Intelligence Scale for Children and with a computerized test battery that measures several components of attention. All changes proved to be stable at 6 months' follow-up after the end of training. Clinical outcome was predicted by the ability to produce negative potential shifts in transfer sessions without feedback.

CONCLUSIONS

According to the guidelines of the efficacy of treatments, the evidence of the efficacy of slow cortical potential feedback found in this study reaches level 2: "possibly efficacious." In the absence of a control group, no causal relationship between observed improvements and the ability to regulate brain activity can be made. However, it could be shown for the first time that good performance in self-regulation predicts clinical outcome. "Good performance" was defined as the ability to produce negative potential shifts in trials without feedback, because it is known that the ability to self-regulate without feedback is impaired in children and adults with attention problems. Additional research should focus on the control of unspecific effects, medication, and subtypes to confirm the assumption that slow cortical potential feedback is a viable treatment option for attention-deficit/hyperactivity disorder. Regulation of slow cortical potentials may involve similar neurobiological pathways as medical treatment. It is suggested that regulation of frontocentral negative slow cortical potentials affects the cholinergic-dopaminergic balance and allows children to adapt to task requirements more flexibly.