Variability of EEG synchronization prior to and during observation and execution of a sequential finger movement

Therapeutic Role of Additional Mirror Therapy on the Recovery of Upper Extremity Motor Function after Stroke: A Single-Blind, Randomized Controlled Trial

Background

Rehabilitation of upper extremity hemiplegia after stroke remains a great clinical challenge, with only 20% of patients achieving a basic return to normal hand function. How to promote the recovery of motor function at an early stage is crucial to the life of the patient.

Objectives

To invest the effects of additional mirror therapy in improving upper limb motor function and activities of daily living in acute and subacute stroke patients, and further explore the effects of other factors on the efficacy of MT.

Methods

Participants who presented with unilateral upper extremity paralysis due to a first ischemic or hemorrhagic stroke were included in the study. They were randomly allocated to the experimental or control group. Patients in the control group received occupational therapy for 30 minutes each session, six times a week, for three weeks, while patients in the experimental group received 30 minutes of additional mirror therapy based on occupational therapy. The primary outcome measures were Fugl-Meyer Assessment-upper extremity (FMA-UE), Action Research Arm Test (ARAT), and Instrumental Activity of Daily Living (IADL) which were evaluated by two independent occupational therapists before treatment and after 3-week treatment. A paired t-test was used to compare the values between pretreatment and posttreatment within an individual group. Two-sample t-test was utilized to compare the changes (baseline to postintervention) between the two groups.

Results

A total of 52 stroke patients with unilateral upper extremity motor dysfunction who were able to actively cooperate with the training were included in this study. At baseline, no significant differences were found between groups regarding demographic and clinical characteristics (P > 0.05 for all). Upper limb motor function and ability to perform activities of daily living of the patients were statistically improved in both groups towards the third week (P < 0.05). In addition, statistical analyses showed more significant improvements in the score changes of FMA-UE and IADL in the experimental group compared to the control group after treatment (P < 0.05), but no significant difference was observed in the ARAT score changes between the two groups (P > 0.05). The subgroup analysis showed that no significant heterogeneity was observed in age, stroke type, lesion side, and clinical stage (P > 0.05).

Conclusion

In conclusion, some positive changes in aspects of upper limb motor function and the ability to perform instrumental activities of daily living compared with routine occupational therapy were observed in additional mirror therapy. Therefore, the application of additional mirror therapy training should be reconsidered to improve upper extremity motor in stroke patients.

Emerging Limb Rehabilitation Therapy After Post-stroke Motor Recovery

Stroke, including hemorrhagic and ischemic stroke, refers to the blood supply disorder in the local brain tissue for various reasons (aneurysm, occlusion, etc.). It leads to regional brain circulation imbalance, neurological complications, limb motor dysfunction, aphasia, and depression. As the second-leading cause of death worldwide, stroke poses a significant threat to human life characterized by high mortality, disability, and recurrence. Therefore, the clinician has to care about the symptoms of stroke patients in the acute stage and formulate an effective postoperative rehabilitation plan to facilitate the recovery in patients. We summarize a novel application and update of the rehabilitation therapy in limb motor rehabilitation of stroke patients to provide a potential future stroke rehabilitation strategy.

Unimanual sensorimotor learning-A simultaneous EEG-fMRI aging study

Sensorimotor coordination requires orchestrated network activity in the brain, mediated by inter‐ and intra‐hemispheric interactions that may be affected by aging‐related changes. We adopted a theoretical model, according to which intra‐hemispheric inhibition from premotor to primary motor cortex is mandatory to compensate for inter‐hemispheric excitation through the corpus callosum. To test this as a function of age we acquired electroencephalography (EEG) simultaneously with functional magnetic resonance imaging (fMRI) in two groups of healthy adults (younger N = 13: 20–25 year and older N = 14: 59–70 year) while learning a unimanual motor task. On average, quality of performance of older participants stayed significantly below that of the younger ones. Accompanying decreases in motor‐event‐related EEG β‐activity were lateralized toward contralateral motor regions, albeit more so in younger participants. In this younger group, the mean β‐power during motor task execution was significantly higher in bilateral premotor areas compared to the older adults. In both groups, fMRI blood oxygen level dependent (BOLD) signals were positively correlated with source‐reconstructed β‐amplitudes: positive in primary motor and negative in premotor cortex. This suggests that β‐amplitude modulation is associated with primary motor cortex “activation” (positive BOLD response) and premotor “deactivation” (negative BOLD response). Although the latter results did not discriminate between age groups, they underscore that enhanced modulation in primary motor cortex may be explained by a β‐associated excitatory crosstalk between hemispheres.

An action-observation/motor-imagery based approach to differentiate disorders of consciousness: what is beneath the tip of the iceberg?

BACKGROUND

The evaluation of motor imagery in persons with prolonged Disorders of Consciousness (pDOC) is a practical approach to differentiate between patients with Minimally Conscious State (MCS) and Unresponsive Wakefulness Syndrome (UWS) and to identify residual awareness even in individuals with UWS. Investigating the influence of motor observation on motor imagery could be helpful in this regard.

OBJECTIVE

In order to corroborate the clinical diagnosis and identify misdiagnosed individuals, we used EEG recordings, to assess the influence of the low-level perceptual and motoric mechanisms on motor observation on motor imagery, taking into account the role of the high-level cognitive mechanisms in patients with pDOC.

METHODS

We assessed the influence of motor observation of walking in first-person or third-person view (by a video provision) on motor imagery of walking in the first-person view on the visual N190 (expression of motor observation processing), the readiness potential (RP) (expressing motor preparation), and the P3 component (high-level cognitive processes) in a sample of 10 persons with MCS, 10 with UWS, and 10 healthy controls (CG). Specifically, the video showed a first-view or third-view walk down the street while the participants were asked to imagine a first-view walking down the street.

RESULTS

CG showed greater N190 response (low-level sensorimotor processing) in the non-matching than in the matching condition. Conversely, the P3 and RP responses (high-level sensorimotor processing) were greater in the matching than in the non-matching condition. Remarkably, 6 out of 10 patients with MCS showed the preservation of both high- and low-level sensorimotor processing. One UWS patient showed responses similar to those six patients, suggesting a preservation of cognitively-mediated sensorimotor processing despite a detrimental motor preparation process. The remaining patients with MCS did not show diversified EEG responses, suggesting limited cognitive functioning.

CONCLUSIONS

Our study suggests that identifying the low-level visual and high-level motor preparation processes in response to a simple influence of motor observation of motor imagery tasks potentially supports the clinical differential diagnosis of with MCS and UWS. This might help identify UWS patients which were misdiagnosed and who deserve more sophisticated diagnoses.

Neuroergonomics Applications of Electroencephalography in Physical Activities: A Systematic Review

Recent years have seen increased interest in neuroergonomics, which investigates the brain activities of people engaged in diverse physical and cognitive activities at work and in everyday life. The present work extends upon prior assessments of the state of this art. However, here we narrow our focus specifically to studies that use electroencephalography (EEG) to measure brain activity, correlates, and effects during physical activity. The review uses systematically selected, openly published works derived from a guided search through peer-reviewed journals and conference proceedings. Identified studies were then categorized by the type of physical activity and evaluated considering methodological and chronological aspects via statistical and content-based analyses. From the identified works (n = 110), a specific number (n = 38) focused on less mobile muscular activities, while an additional group (n = 22) featured both physical and cognitive tasks. The remainder (n = 50) investigated various physical exercises and sporting activities and thus were here identified as a miscellaneous grouping. Most of the physical activities were isometric exertions, moving parts of upper and lower limbs, or walking and cycling. These primary categories were sub-categorized based on movement patterns, the use of the event-related potentials (ERP) technique, the use of recording methods along with EEG and considering mental effects. Further information on subjects' gender, EEG recording devices, data processing, and artifact correction methods and citations was extracted. Due to the heterogeneous nature of the findings from various studies, statistical analyses were not performed. These were thus included in a descriptive fashion. Finally, contemporary research gaps were pointed out, and future research prospects to address those gaps were discussed.

Prefrontal transcranial alternating current stimulation improves motor sequence reproduction

Cortical activity in frontal, parietal, and motor regions during sequence observation correlates with performance on sequence reproduction. Increased cortical activity observed during observation has therefore been suggested to represent increased learning. Causal relationships have been demonstrated between M1 and motor sequence reproduction and between parietal cortex and bimanual learning. However, similar effects have not been reported for frontal regions despite a number of reports implicating its involvement in encoding of motor sequences. Investigating causal relations between cortical activity and reproduction of motor sequences in parietal, frontal and primary motor regions can disentangle whether specific regions during simple observation can be selectively ascribed to encoding or reproduction or both. We designed a sensorimotor paradigm that included a strong motor sequence component, and tested the impact of individually adjusted transcranial alternating current stimulation (IAF-tACS) to prefrontal, parietal, and primary motor regions on electroencephalographic motor rhythms (alpha and beta bandwidths) during motor sequence observation and the ability to reproduce the observed sequences. Independently of the stimulated region, IAF-tACS led to a reduction in suppression in the lower beta-range relative to sham. Prefrontal IAF-tACS however, led to significant improvement in motor sequence reproduction, pinpointing the crucial role of prefrontal regions in motor sequence reproduction.

Neural mirroring systems: exploring the EEG μ rhythm in human infancy

How do human children come to understand the actions of other people? What neural systems are associated with the processing of others' actions and how do these systems develop, starting in infancy? These questions span cognitive psychology and developmental cognitive neuroscience, and addressing them has important implications for the study of social cognition. A large amount of research has used behavioral measures to investigate infants' imitation of the actions of other people; a related but smaller literature has begun to use neurobiological measures to study of infants' action representation. Here we focus on experiments employing electroencephalographic (EEG) techniques for assessing mu rhythm desynchronization in infancy, and analyze how this work illuminates the links between action perception and production prior to the onset of language.

β functional connectivity modulation during the maintenance of motion information in working memory: importance of the familiarity of the visual context

The purpose of this study was to examine whether mechanisms, involved during the maintenance of familiar movement information in memory, were influenced by the degree of familiarity of the display in which the movements were embedded. Twelve gymnasts who possessed high visual and motor familiarity with the movements employed in this study, were recruited. They were invited to retain for a short period of time familiar movements viewed previously and presented under different displays with the aim of recognizing them at a later stage. The first display was a realistic, familiar display which presented videos of movements. The second display was an unfamiliar impoverished display never experienced in every day life which showed point-light movements. Activity during the maintenance period was considered in five frequency bands (4-8 Hz, 8-10 Hz, 10-13 Hz, 13-20 Hz, 20-30 Hz) using a non-linear measure of functional connectivity. The results in the 13-20 Hz frequency band showed that functional connectivity was greater within the frontal and right temporal areas during the unfamiliar display (i.e., point-light maintenance condition) compared to the familiar display (i.e., video maintenance condition). Differences in functional connectivity between the two maintenance conditions in the beta frequency band are mainly discussed in the light of the process of anticipation. Subjects' perception of the expected difficulty of the upcoming recognition task is discussed.

Neural correlates of action observation and execution in 14-month-old infants: an event-related EEG desynchronization study

There is increasing interest in neurobiological methods for investigating the shared representation of action perception and production in early development. We explored the extent and regional specificity of EEG desynchronization in the infant alpha frequency range (6-9 Hz) during action observation and execution in 14-month-old infants. Desynchronization during execution was restricted to central electrode sites, while action observation was associated with a broader desynchronization across frontal, central, and parietal regions. The finding of regional specificity in the overlap between EEG responses to action execution and observation suggests that the rhythm seen in the 6-9 Hz range over central sites in infancy shares certain properties with the adult mu rhythm. The magnitude of EEG desynchronization to action perception and production appears to be smaller for infants than for adults and older children, suggesting developmental change in this measure.

Non-linear EEG synchronization during observation: effects of instructions and expertise

The aim of this study was to examine the effects of instructions and expertise upon neuronal changes during observation of sequential finger movements. Professional pianists and musically naïve subjects observed these movements with the aim of either replicating or recognizing them at a later stage. A non-linear measure of functional coupling was used to investigate EEG activity. In the 10-13 Hz frequency band and in musically naïve subjects, functional coupling during observation for replica was greater within central and neighboring areas than during observation for recognition. An opposite pattern was found in the 4-8 Hz frequency band. In the 10-13 Hz band and in areas including the parietal cortex, functional coupling in musically naïve subjects was greater compared to professional pianists under observation for replica. Results are discussed in the light of recent findings from the cognitive and behavioral neuroscience literature.

Changes in local and distant EEG activities before, during and after the observation and execution of sequential finger movements

AIM OF THE STUDY

To consider cortical oscillations at local and distant/large scale levels during the time course of motor events under both an observation and an execution condition.

METHODS

Local and distant changes in EEG cortical oscillations were respectively assessed by the Event-Related Desynchronization/Synchronization technique and the Synchronization Likelihood technique. Data collected prior to, during, and after observation and execution of complex sequential finger movements were used to investigate these changes. EEGs were recorded from 19 active sites across the cortex of 10 subjects. Sensorimotor activity was examined in alpha frequency bands.

RESULTS

Local power changes and global interregional synchronizations were two distinct phenomena, which occurred simultaneously and displayed different spatiotemporal patterns.

DISCUSSION AND CONCLUSIONS

These findings demonstrate the complementary character of both analysis techniques. Results are discussed in light of the recent findings from the cognitive and behavioural neuroscience literature.

Learning by observation requires an early sleep window

Numerous studies have shown that sleep enhances memory for motor skills learned through practice. Motor skills can, however, also be learned through observation, a process possibly involving the mirror neuron system. We investigated whether motor skill enhancement through prior observation requires sleep to follow the observation, either immediately or after a delay, to consolidate the procedural memory. Sequence-specific fingertapping performance was tested in 64 healthy subjects in a balanced design. Electromyography verified absence of overt or subliminal hand muscle activations during observation. The results show that immediate sleep is necessary for the enhancement of a motor skill through prior observation. Immediate sleep improved the speed of subsequent performance by 22 +/- 11% (mean +/- SEM) (P = 0.04) and reduced the error rate by 42 +/- 19% (P = 0.02). In contrast, no performance gains occurred if sleep was initiated more than 12 h after observation. A second study on 64 subjects ruled out explicit familiarity with the sequence or the spatiotemporal rhythm of the sequence to underlie performance improvements. The sleep-dependent observational motor learning enhancement is at least similar to that previously reported for implicit and declarative memory. The apparent prerequisite of observing real movements indicates that subjects transfer experience obtained through observation of movements to subsequent self-initiated movements, in the absence of practice. Moreover, the consolidation of this transfer requires an early sleep window. These findings could improve learning new motor skills in athletes and children, but also in patients having to remaster skills following stroke or injury.

The phi complex as a neuromarker of human social coordination

Many social interactions rely upon mutual information exchange: one member of a pair changes in response to the other while at the same time producing actions that alter the behavior of the other. However, little is known about how such social processes are integrated in the brain. Here, we used a specially designed dual-electroencephalogram system and the conceptual framework of coordination dynamics to identify neural signatures of effective, real-time coordination between people and its breakdown or absence. High-resolution spectral analysis of electrical brain activity before and during visually mediated social coordination revealed a marked depression in occipital alpha and rolandic mu rhythms during social interaction that was independent of whether behavior was coordinated or not. In contrast, a pair of oscillatory components (phi(1) and phi(2)) located above right centro-parietal cortex distinguished effective from ineffective coordination: increase of phi(1) favored independent behavior and increase of phi(2) favored coordinated behavior. The topography of the phi complex is consistent with neuroanatomical sources within the human mirror neuron system. A plausible mechanism is that the phi complex reflects the influence of the other on a person's ongoing behavior, with phi(1) expressing the inhibition of the human mirror neuron system and phi(2) its enhancement.

EEG spectral cohrence inter and intrahemispheric during catching object fall task

The aim of the present study was to evaluate coherence measures at Theta through qEEG during the accomplishment of a specific motor task. The sample consisted of 23 healthy individuals, both sexes, with ages varying between 25 and 40 years old. All subjects were submmitted to a specific motor task of cacthing sequences of falling balls. A three-way ANOVA was employed for the statistical analysis, which demonstrated main effects for the following factors: time, block and position. However, there was no interection between the factors. A significant and generalized coherence reduction was observed during the task execution time. Coherence was also diminished at the left frontal cortex and contralateral hemisphere of the utilizing limb (comparing to the right frontal cortex). In conclusion, these findings suggest a certain specialization of the neural circuit, also according to previous investigations. The inter-coherence reduction suggests a spatial inter-electrode dependence during the task, rather than a neuronal specialization.

The parent-infant dyad and the construction of the subjective self

Developmental psychology and psychopathology has in the past been more concerned with the quality of self-representation than with the development of the subjective agency which underpins our experience of feeling, thought and action, a key function of mentalisation. This review begins by contrasting a Cartesian view of pre-wired introspective subjectivity with a constructionist model based on the assumption of an innate contingency detector which orients the infant towards aspects of the social world that react congruently and in a specifically cued informative manner that expresses and facilitates the assimilation of cultural knowledge. Research on the neural mechanisms associated with mentalisation and social influences on its development are reviewed. It is suggested that the infant focuses on the attachment figure as a source of reliable information about the world. The construction of the sense of a subjective self is then an aspect of acquiring knowledge about the world through the caregiver's pedagogical communicative displays which in this context focuses on the child's thoughts and feelings. We argue that a number of possible mechanisms, including complementary activation of attachment and mentalisation, the disruptive effect of maltreatment on parent-child communication, the biobehavioural overlap of cues for learning and cues for attachment, may have a role in ensuring that the quality of relationship with the caregiver influences the development of the child's experience of thoughts and feelings.

Cortical Activity Prior to, and During, Observation and Execution of Sequential Finger Movements

The aim of this study was to provide further evidence for the existence of a mirror neuron system in humans using electroencephalography during the observation and execution of non-object-related movements. Event-related desynchronization and synchronization (ERD/ERS) were used to characterize brain activity prior to, and during, observation and execution of a finger movement in four frequency bands (7-10 Hz, 10-13 Hz, 13-20 Hz, and 20-30 Hz). Electroencephalograms (EEGs) were recorded from 19 electrode sites in eight participants. In all the frequency bands and electrode sites, results revealed that there was no significant differences in EEG cortical activity between the observation condition and the execution conditions. Comparison of the two stages of the movement (i.e., pre-movement and movement) in the observation and execution conditions showed, in most cases, that pre-movement ERD values were less than movement ERD values. Whilst there was not an identical match of EEG cortical indices, this study provides further support for the existence of a mirror neuron system in humans. The incomplete congruence may be explained by the different behaviors, the nature of the task and factors in the observed action coded by the mirror system.