Electrophysiological markers of skill-related neuroplasticity

Long-Duration Response to Levodopa, Motor Learning, and Neuroplasticity in Early Parkinson's Disease

BACKGROUND

Long-duration response (LDR) to levodopa and motor learning could be involved in changes in neuroplasticity of cortical excitability in Parkinson's disease (PD). P300, motor evoked potentials (MEPs), and Bereitschaftspotential (BP) are neurophysiological surrogate markers of neuroplasticity.

OBJECTIVE

We aimed to define in PD the effects of LDR and motor learning on neurophysiological parameters involved in neuroplasticity.

METHODS

Drug-naive PD patients underwent a 15-day treatment with levodopa/carbidopa 250/25 mg daily. Achievement of LDR was assessed on the 15th day of treatment (T15). Patients were grouped based on the achievement of a sustained LDR (LDR+) or no LDR (LDR-) and to the assignment of a learning motor exercise (LME) or no motor exercise (NME). Patients underwent clinical and neurophysiological (P300, MEPs, and BP) assessments at baseline (T0) and on T15.

RESULTS

Forty-one PD patients and 24 age- and sex-matched normal controls (NCs) were enrolled. Neurophysiological parameters differed between untreated PD patients and NCs. Four groups of patients were obtained at the end of treatments: trained patients with a sustained LDR (LDR + LME group), untrained patients with a sustained LDR (LDR + NME group), trained patients without LDR (LDR-LME group), and untrained patients without LDR (LDR-NME group). At baseline, no differences in clinical and neurophysiological parameters were evident among the groups. After the treatments, significant improvements in neurophysiological parameters were observed in the LDR + LME group. No modifications were found in the groups without LDR.

CONCLUSIONS

The achievement of a sustained LDR may act synergistically with motor learning to induce adaptive changes in neuroplasticity in basal ganglia and cortical networks. Our findings support LDR as a pharmacological outcome possibly facilitating the action of motor learning on neuroplasticity in early PD. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Study on the diversity of mental states and neuroplasticity of the brain during human-machine interaction

Introduction

With the increasing demand for human-machine collaboration systems, more and more attention has been paid to the influence of human factors on the performance and security of the entire system. Especially in high-risk, high-precision, and difficult special tasks (such as space station maintenance tasks, anti-terrorist EOD tasks, surgical robot teleoperation tasks, etc.), there are higher requirements for the operator's perception and cognitive level. However, as the human brain is a complex and open giant system, the perception ability and cognitive level of the human are dynamically variable, so that it will seriously affect the performance and security of the whole system.

Methods

The method proposed in this paper innovatively explained this phenomenon from two dimensions of brain space and time and attributed the dynamic changes of perception, cognitive level, and operational skills to the mental state diversity and the brain neuroplasticity. In terms of the mental state diversity, the mental states evoked paradigm and the functional brain network analysis method during work were proposed. In terms of neuroplasticity, the cognitive training intervention paradigm and the functional brain network analysis method were proposed. Twenty-six subjects participated in the mental state evoked experiment and the cognitive training intervention experiment.

Results

The results showed that (1) the mental state of the subjects during work had the characteristics of dynamic change, and due to the influence of stimulus conditions and task patterns, the mental state showed diversity. There were significant differences between functional brain networks in different mental states, the information processing efficiency and the mechanism of brain area response had changed significantly. (2) The small-world attributes of the functional brain network of the subjects before and after the cognitive training experiment were significantly different. The brain had adjusted the distribution of information flow and resources, reducing costs and increasing efficiency as a whole. It was demonstrated that the global topology of the cortical connectivity network was reconfigured and neuroplasticity was altered through cognitive training intervention.

Discussion

In summary, this paper revealed that mental state and neuroplasticity could change the information processing efficiency and the response mechanism of brain area, thus causing the change of perception, cognitive level and operational skills, which provided a theoretical basis for studying the relationship between neural information processing and behavior.

General principles of brain electromagnetic rhythmic oscillations and implications for neuroplasticity

Neuro-plasticity describes the ability of the brain in achieving novel functions, either by transforming its internal connectivity, or by changing the elements of which it is made, meaning that, only those changes, that affect both structural and functional aspects of the system, can be defined as "plastic." The concept of plasticity can be applied to molecular as well as to environmental events that can be recognized as the basic mechanism by which our brain reacts to the internal and external stimuli. When considering brain plasticity within a clinical context-that is the process linked with changes of brain functions following a lesion- the term "reorganization" is somewhat synonymous, referring to the specific types of structural/functional modifications observed as axonal sprouting, long-term synaptic potentiation/inhibition or to the plasticity related genomic responses. Furthermore, brain rewires during maturation, and aging thus maintaining a remarkable learning capacity, allowing it to acquire a wide range of skills, from motor actions to complex abstract reasoning, in a lifelong expression. In this review, the contribution on the "neuroplasticity" topic coming from advanced analysis of EEG rhythms is put forward.

Test-Retest Reliability of Electroencephalographic Measures of Performance Monitoring in Children and Adults

This study examined the test-retest reliability of the error-related negativity (ERN) and error positivity (Pe) amplitudes using a Flanker task in 118 neurotypical children and 53 adults before and after latency jitter adjustments. The reliability of the ERN and Pe amplitudes was moderate for children and moderate to strong for adults. The latency variability adjustment did not improve the reliability of the ERN and Pe amplitudes for either group, suggesting that latency variability may be a trait-like measure. For comparison purposes, the reliability of the stimulus-locked ERPs was strong for correct trials, yet the reliability was weak for incorrect trials.

Towards a unified model of event-related potentials as phases of stimulus-to-response processing

This study demonstrates the utility of combining principles of connectionist theory with a sophisticated statistical approach, structural equation modeling (SEM), to better understand brain-behavior relationships in studies using event-related potentials (ERPs). The models show how sequential phases of neural processing measured by averaged ERP waveform components can successfully predict task behavior (response time; RT) while accounting for individual differences in maturation and sex. The models assume that all ERP measures are affected by individual differences in physical and mental state that inflate measurement error. ERP data were collected from 154 neurotypical children (7-13 years, M = 10.22, SD = 1.48; 74 males) performing a cued Go/No-Go task during two separate sessions. Using SEM, we show a latent variable path model with good fit (e.g., χ²(51) = 56.20, p = .25; RMSEA = .03; CFI = .99; SRMR = .06) yielding moderate-to-large predictive coefficients from N1 through the E-wave latent variables (N1 β = -.29 → P2 β = -.44 → N2 β = .28 → P3 β =.64→ E-wave), which in turn significantly predicted RT (β =.34, p = .02). Age significantly related to N1 and P3 latent variables as well as RT (β =.31, -.58, & -.40 respectively), and Sex significantly related to the E-wave latent variable and RT (β =.36 & 0.21 respectively). Additionally, the final model suggested that individual differences in emotional and physical state accounted for a significant proportion of variance in ERP measurements, and that individual states systematically varied across sessions (i.e., the variance was not just random noise). These findings suggest that modeling ERPs as a system of inter-related processes may be a more informative approach to examining brain-behavior relationships in neurotypical and clinical groups than traditional analysis techniques.

Unsuccessful reduction of high-frequency alpha activity during cognitive activation in schizophrenia

AIMS

Electroencephalogram (EEG) alpha activity during resting state reflects the 'readiness' of an individual to respond to the environment; this includes the performance of cognitive processes. Alpha activity is reported to be attenuated in schizophrenia (SCZ). Understanding the interaction between alpha activity during rest and when cognitively engaged may provide insights into the neural circuitry, which is dysfunctional in SCZ. This study investigated the changes of alpha activity between resting state and cognitive engagement in SCZ patients.

METHODS

Thirty-four SCZ patients and 29 healthy controls (HC) were recruited. EEG was performed in the resting state and during an auditory P300 task. All experimental procedures followed the relevant institutional guidelines and regulations.

RESULTS

In SCZ, high-frequency alpha activity was reduced in the resting state. High-frequency alpha source density was decreased in both the resting-state and a P300 task condition in patients, compared to HC. HC, but not SCZ patients, showed a reduction in high-frequency alpha source density during the P300 task compared to the resting state. The negative correlation between high-frequency alpha source density in the resting state and positive symptoms was significant.

CONCLUSIONS

High-frequency alpha activity in SCZ patients and its unsuccessful reduction during cognitive processing may be biological markers of SCZ.

Modeling the interrelationships between brain activity and trait attention measures to predict individual differences in reaction times in children during a Go/No-Go task

Many researchers are utilizing event-related potentials (ERPs) to better understand brain-behavior relationships across development. The present study demonstrates how structural equation modeling (SEM) techniques can be used to refine descriptions of brain-behavior relationships in a sample of neurotypical children. We developed an exploratory latent variable model in which trait measures of maturation and attention are related to neural processing and task behaviors obtained during a cued Go/No-Go task. Model findings are compared to results of traditional analysis techniques such as bivariate correlations. The data suggest that more sophisticated statistical approaches are beneficial to accurately interpreting the nature of brain-behavior relationships.

EEG Source Imaging Guided by Spatiotemporal Specific fMRI: Toward an Understanding of Dynamic Cognitive Processes

Understanding the mechanism of neuroplasticity is the first step in treating neuromuscular system impairments with cognitive rehabilitation approaches. To characterize the dynamics of the neural networks and the underlying neuroplasticity of the central motor system, neuroimaging tools with high spatial and temporal accuracy are desirable. EEG and fMRI stand among the most popular noninvasive neuroimaging modalities with complementary features, yet achieving both high spatial and temporal accuracy remains a challenge. A novel multimodal EEG/fMRI integration method was developed in this study to achieve high spatiotemporal accuracy by employing the most probable fMRI spatial subsets to guide EEG source localization in a time-variant fashion. In comparison with the traditional fMRI constrained EEG source imaging method in a visual/motor activation task study, the proposed method demonstrated superior localization accuracy with lower variation and identified neural activity patterns that agreed well with previous studies. This spatiotemporal fMRI constrained source imaging method was then implemented in a "sequential multievent-related potential" paradigm where motor activation is evoked by emotion-related visual stimuli. Results demonstrate that the proposed method can be used as a powerful neuroimaging tool to unveil the dynamics and neural networks associated with the central motor system, providing insights into neuroplasticity modulation mechanism.

The Test-Retest Reliability of the Visually Evoked Contingent Negative Variation (CNV) in Children and Adults

Establishing the reliability of event-related potentials is critical for future applications to biomarker development and clinical research. Few studies have examined the reliability of the contingent negative variation (CNV), and only in adults. The current study explored test-retest reliability of the visually evoked CNV and its embedded components, the O-wave and the E-wave, in children (7-13 years) and young adults (19-28 years) during a visual Go/No-Go task over 1-2 weeks. Test-retest reliability of the components was moderate for children, and low-to-moderate for adults. These findings were in contrast to previous work with adults showing moderate-to-high reliability of the auditory-evoked CNV.

Pharyngeal electrical stimulation can modulate swallowing in cortical processing and behavior - magnetoencephalographic evidence

BACKGROUND

The act of swallowing is a complex neuromuscular function that is processed in a distributed network involving cortical, subcortical and brainstem structures. Difficulty in swallowing arises from a variety of neurologic diseases for which therapeutic options are currently limited. Pharyngeal electrical stimulation (PES) is a novel intervention designed to promote plastic changes in the pharyngeal motor cortex to aid dysphagia rehabilitation. In the present study we evaluate the effect of PES on cortical swallowing network activity and associated changes in swallowing performance.

METHODS

In a randomized, crossover study design 10min of real (0.2-ms pulses, 5Hz, 280V, stimulation intensity at 75% of maximum tolerated threshold) or sham PES were delivered to 14 healthy volunteers in two separate sessions. Stimulation was delivered via a pair of bipolar ring electrodes mounted on an intraluminal catheter positioned in the pharynx. Before and after each intervention swallowing capacity (ml/s) was tested using a 150ml-water swallowing stress test. Event-related desynchronization (ERD) of cortical oscillatory activity during volitional swallowing was recorded applying whole-head magnetoencephalography before, immediately after and 45min past the intervention.

RESULTS

A prominent reduction of ERD in sensorimotor brain areas occurred in the alpha and beta frequency ranges immediately after real PES but not after sham stimulation (p<0.05) and had faded after 45min. Volume per swallow and swallowing capacity significantly increased following real stimulation only.

CONCLUSION

Attenuation of ERD following PES reflects stimulation-induced increased swallowing processing efficiency, which is associated with subtle changes in swallowing function in healthy subjects. Our data contribute evidence that swallowing network organization and behavior can effectively be modulated by PES.

Oscillatory responses to semantic and syntactic violations

EEG studies employing time-frequency analysis have revealed changes in theta and alpha power in a variety of language and memory tasks. Semantic and syntactic violations embedded in sentences evoke well-known ERPs, but little is known about the oscillatory responses to these violations. We investigated oscillatory responses to both kinds of violations, while monolingual and bilingual participants performed an acceptability judgment task. Both violations elicited power decreases (event-related desynchronization, ERD) in the 8-30 Hz frequency range, but with different scalp topographies. In addition, semantic anomalies elicited power increases (event-related synchronization, ERS) in the 1-5 Hz frequency band. The 1-5 Hz ERS was strongly phase-locked to stimulus onset and highly correlated with time domain averages, whereas the 8-30 Hz ERD response varied independently of these. In addition, the results showed that language expertise modulated 8-30 Hz ERD for syntactic violations as a function of the executive demands of the task. When the executive function demands were increased using a grammaticality judgment task, bilinguals but not monolinguals demonstrated reduced 8-30 Hz ERD for syntactic violations. These findings suggest a putative role of the 8-30 Hz ERD response as a marker of linguistic processing that likely represents a separate neural process from those underlying ERPs.

Error-related activity and correlates of grammatical plasticity

Cognitive control involves not only the ability to manage competing task demands, but also the ability to adapt task performance during learning. This study investigated how violation-, response-, and feedback-related electrophysiological (EEG) activity changes over time during language learning. Twenty-two Dutch learners of German classified short prepositional phrases presented serially as text. The phrases were initially presented without feedback during a pre-test phase, and then with feedback in a training phase on two separate days spaced 1 week apart. The stimuli included grammatically correct phrases, as well as grammatical violations of gender and declension. Without feedback, participants’ classification was near chance and did not improve over trials. During training with feedback, behavioral classification improved and violation responses appeared to both types of violation in the form of a P600. Feedback-related negative and positive components were also present from the first day of training. The results show changes in the electrophysiological responses in concert with improving behavioral discrimination, suggesting that the activity is related to grammar learning.

Mental training as a tool in the neuroscientific study of brain and cognitive plasticity

Although the adult brain was once seen as a rather static organ, it is now clear that the organization of brain circuitry is constantly changing as a function of experience or learning. Yet, research also shows that learning is often specific to the trained stimuli and task, and does not improve performance on novel tasks, even very similar ones. This perspective examines the idea that systematic mental training, as cultivated by meditation, can induce learning that is not stimulus or task specific, but process specific. Many meditation practices are explicitly designed to enhance specific, well-defined core cognitive processes. We will argue that this focus on enhancing core cognitive processes, as well as several general characteristics of meditation regimens, may specifically foster process-specific learning. To this end, we first define meditation and discuss key findings from recent neuroimaging studies of meditation. We then identify several characteristics of specific meditation training regimes that may determine process-specific learning. These characteristics include ongoing variability in stimulus input, the meta-cognitive nature of the processes trained, task difficulty, the focus on maintaining an optimal level of arousal, and the duration of training. Lastly, we discuss the methodological challenges that researchers face when attempting to control or characterize the multiple factors that may underlie meditation training effects.

Mental training enhances attentional stability: neural and behavioral evidence

The capacity to stabilize the content of attention over time varies among individuals, and its impairment is a hallmark of several mental illnesses. Impairments in sustained attention in patients with attention disorders have been associated with increased trial-to-trial variability in reaction time and event-related potential deficits during attention tasks. At present, it is unclear whether the ability to sustain attention and its underlying brain circuitry are transformable through training. Here, we show, with dichotic listening task performance and electroencephalography, that training attention, as cultivated by meditation, can improve the ability to sustain attention. Three months of intensive meditation training reduced variability in attentional processing of target tones, as indicated by both enhanced theta-band phase consistency of oscillatory neural responses over anterior brain areas and reduced reaction time variability. Furthermore, those individuals who showed the greatest increase in neural response consistency showed the largest decrease in behavioral response variability. Notably, we also observed reduced variability in neural processing, in particular in low-frequency bands, regardless of whether the deviant tone was attended or unattended. Focused attention meditation may thus affect both distracter and target processing, perhaps by enhancing entrainment of neuronal oscillations to sensory input rhythms, a mechanism important for controlling the content of attention. These novel findings highlight the mechanisms underlying focused attention meditation and support the notion that mental training can significantly affect attention and brain function.