Effects of Near-Infrared Pulsed Light on the Attention of Human Beings Using Electroencephalography.

In our previous studies, photobiomodulation (PBM) stimulation can induce significant brain activation in normal subjects. In an open-eye study, the PBM stimulation was able to increase the power of alpha rhythms and theta waves, as well as decrease the beta activities after PBM stimulation. However, in the closed eyes study, the alpha rhythms in the laser group were reduced. This means the PBM stimulation can induce specific brainwaves under different conditions. Thus, to investigate the effects of PBM stimulation on human's attention, forty students were recruited in this single-blind randomized trial. A PBM stimulator, with seven pcs laser diodes (LDs), frequency 10 Hz, 30 mW/each LD, and wavelength 830 nm, was used to radiate the palm of the subject. PBM stimulation was found to induce significant variation in beta activity in most of the regions of the brain in the laser group. Compared to the placebo group, the PBM stimulation has a significant change in beta activity on electroencephalography (EEG). Three types of tests, the random number test, the Stroop color-word test, and the Multiple-Dimension Attention Test (MDAT), were used to evaluate the effects of the PBM stimulation. The scores of MDAT in the laser group increased more significantly than those in the placebo group after PBM stimulation (p < 0.01). An improvement in attention was observed in this study.

Cross-Domain Transfer of EEG to EEG or ECG Learning for CNN Classification Models.

Electroencephalography (EEG) is often used to evaluate several types of neurological brain disorders because of its noninvasive and high temporal resolution. In contrast to electrocardiography (ECG), EEG can be uncomfortable and inconvenient for patients. Moreover, deep-learning techniques require a large dataset and a long time for training from scratch. Therefore, in this study, EEG-EEG or EEG-ECG transfer learning strategies were applied to explore their effectiveness for the training of simple cross-domain convolutional neural networks (CNNs) used in seizure prediction and sleep staging systems, respectively. The seizure model detected interictal and preictal periods, whereas the sleep staging model classified signals into five stages. The patient-specific seizure prediction model with six frozen layers achieved 100% accuracy for seven out of nine patients and required only 40 s of training time for personalization. Moreover, the cross-signal transfer learning EEG-ECG model for sleep staging achieved an accuracy approximately 2.5% higher than that of the ECG model; additionally, the training time was reduced by >50%. In summary, transfer learning from an EEG model to produce personalized models for a more convenient signal can both reduce the training time and increase the accuracy; moreover, challenges such as data insufficiency, variability, and inefficiency can be effectively overcome.

Movement pattern and upper extremity muscle activation during fast and slow continuous steering movement.

Continuous steering movement (CSM) is an essential component of the upper extremity (UE) task during vehicle driving, and could be a suitable candidate for multi-joint rehabilitation programs for patients with UE disabilities. This study aims to evaluate the UE muscle activation during CSM and how the rotating speed and direction affect CSM's kinematic and kinetic performance. Surface electromyography (EMG), hand contact information, and steering torque were measured under fast (180°/s) and slow (60°/s) constant-velocity CSM to reveal the activation of shoulder and elbow muscles, temporal characteristics, and force exertion during the stance and swing phases of a CSM cycle. Data from 24 normal young adults showed that shorter contact duration but higher force exertion occurred in the hand moving in an outward steering direction during only fast CSM in either the clockwise (CW) or counterclockwise (CCW) direction. During a steering cycle (either fast or slow speed), the triceps brachii, sternal part of the pectoralis major (PS), and posterior deltoid play major roles in generating steering torque in the CW direction of the CSM. In contrast, the PS, clavicular part of the pectoralis major (PC), and anterior deltoid (AD) largely contribute to torque generation during the CCW CSM. During the swing phase of CSM, AD, PC, and PS are the major muscles that move the hand for the next grasping of the steering wheel in all four conditions. Using the mean activation profiles of the major contributing muscles, the functional roles of these elbow and shoulder muscles were analyzed and are discussed herein. These findings help us to further understand the activation patterns of UE muscles and the kinematic and kinetic changes during two rotating directions and two speeds of CSM, and suggest important implications for future practice in clinical training.

Effects of transcranial direct current stimulation on improving performance of delayed- reinforcement attentional set-shifting tasks in attention-deficit/hyperactivity disorder rat model.

Behavioral flexibility (or set-shifting), which is regulated by the prefrontal cortex (PFC), is often impaired in patients with attention-deficit/hyperactivity disorder (ADHD), which is characterized by poor inhibitory control and reinforcement learning. Transcranial direct current stimulation (tDCS) has been proposed as a means of noninvasive brain stimulation and a potential therapeutic tool for modulating behavioral flexibility. Animal studies can pave the way to know if tDCS application can potentially benefit rule- and goal-based activities in ADHD. Spontaneously hypertensive rats (SHRs) and inbred Wistar-Kyoto (WKY) rats were used as an animal model of ADHD and controls, respectively, and their strategy set-shifting abilities, including initial discrimination, set-shifting, and reversal learning tasks under 0-s or 15-s reinforcer delivery delay conditions, were evaluated. The tDCS treatment had a limited effect on the performance of the SHRs and WKY rats in initial discrimination task under 0-s delay condition. Under the 15-s delay condition, the SHRs had longer lever-press reaction times and/or more trial omissions than the WKY rats did when completing set-shifting and reversal-learning tasks. Among the SHRs, tDCS treatment improved the rats' reaction times and/or reduced their trial omissions in the set-shifting and reversal-learning tasks. Although tDCS may improve delayed reinforcement learning set-shifting performance in SHRs, further studies are required to clarify the responsible mechanism.

Classification of cognitive reserve in healthy older adults based on brain activity using support vector machine.

OBJECTIVE: Cognitive reserve (CR) refers to the capacity of the brain to actively cope with damage via the implementation of remedial cognitive processes. Traditional CR measurements focus on static proxies, which may not be able to appropriately estimate dynamic changes in CR. This study therefore investigated the cognitive performance and characteristics of brain activity of low- and high-CR healthy adults during resting and n-back task states and categorized subjects according to magnetoencephalographic (MEG) information using a support vector machine (SVM) classifier. APPROACH: Forty-one volunteers were divided into groups with low and high CR indexes based on their education, occupational attainment, leisure and social activities. MAIN RESULTS: The results can be summarized as follows. First, subjects with a higher CR had higher accuracies and faster reaction times in the task. Second, subjects with a lower CR had a higher M300 intensity but a constant M300 latency. Third, subjects with a higher CR had a higher beta intensity in the parietal and occipital regions during the task, whereas subjects with a higher CR had a higher gamma intensity in the right temporal region in the resting state. Finally, subjects with a higher CR had negative gamma asymmetry between the right and left occipital regions, whereas subjects with a lower CR had positive values in the resting state. SIGNIFICANCE: These MEG results were subsequently used to classify subjects into high-/low-CR subjects using an SVM classifier, and a mean accuracy of 88.89% was obtained. This objective and nonstatic method for determining CR level warrants further research for a wider variety of future clinical applications.

Analysis and Discrimination of Surface Electromyographic Features for Parkinson's Disease during Elbow Flexion Movements.

Parkinson's disease (PD) is the second most common neurodegenerative disorder. Early intervention/treatment relies on early diagnosis of PD. There is increasing interest in methods based on electromyography measurements of PD patients because of its noninvasiveness. Thus, this study was to investigate electromyographic (EMG) characteristics of the upper limb between PD patients and healthy control subjects using EMG, and to distinguish PD patients from healthy control subjects according to the EMG information using a support vector machine (SVM) classifier. Sixteen right-handed PD patients and 25 right-handed healthy subjects participated in experiments involving elbow flexion movement. The frequency power, duration, skewness, recurrence rate, and correlation dimension of EMG signals and success rate for the right hand and the skewness of EMG signals for the left hand were found to be significantly different between the two groups. This information was subsequently used to distinguish PD patients from healthy control subjects using the SVM classifier to obtain a mean accuracy of 87.02%. Although the results may not be immediately available to use in clinical applications, the safety, simplicity and speed of the system still merits further consideration. Enhancing performance accuracy and examining PD patients in different stages of disease are anticipated in future investigations.

Working-memory evaluation based on EEG signals during n-back tasks.

Working memory is the cognitive process of receiving, processing, and communicating information. Early evaluation and training may help to prevent a marked decline in working-memory ability. The aim of this study was to establish an n-back task system for objectively evaluating the working-memory ability based on the θ power, the γ power, and the degree of θ-γ synchronization. Our experiments were divided into four memory loads (1-back to 4-back) and further divided into digital and matrix stimulation modes. The γ band was divided into three components (γ1: 30-50 Hz, γ2: 50-70 Hz, and γ3: 70-90 Hz). The study recruited 23 healthy young subjects. The obtained results indicate that accuracy rates might be inappropriate for assessing the working memory. The θ power relates to working-memory recognition while the γ power varied with the memory load. Besides, a higher load level should be more appropriate for assessing the working-memory ability. Finally, the number of θ-γ3 couplings was highest between the frontal area and Pz and O2. In summary, the results of this study may be useful in multiple evaluations of working memory, and may lead to a wider variety of clinical applications in the future.

Magnetoencephalography study of different relationships among low- and high-frequency-band neural activities during the induction of peaceful and fearful audiovisual modalities among males and females.

Our previous study estimated the bias from the match attributes of the auditory and visual modalities related to a peaceful mood in the male brain. However, the interactions among the four main frequency bands of neural activity remain unknown. Therefore, this study uses magnetoencephalography to explore gender differences in the perceptions of auditory and visual modalities related to peaceful and fearful moods. Instead of analyzing single frequencies, this study analyzes interactions between low-frequency phase and high-frequency amplitude to reflect neural communication. The top four values in each of the 10 brain regions were averaged to give a representative value for further analysis with repeated-measures ANOVA. The results from the cross-frequency analyses suggest that delta-theta, delta-alpha, delta-beta, and delta-gamma couplings are associated with interactions between emotion and modality; theta-alpha, theta-beta, and theta-gamma couplings are associated with interactions between gender and emotion/time; alpha-beta and alpha-gamma couplings are associated with time; and beta-gamma coupling is associated with interactions between gender and modality. Although no obvious hemispheric lateralization of emotion in the macroscopic neural activity was found, these results reveal that males have stronger couplings (e.g., beta-gamma coupling) in the visual modality related to peaceful mood, whereas females have stronger couplings (e.g., beta-gamma coupling) in the audiovisual modality related to fearful mood. Gender differences become much more apparent when analysis is based on cross-frequency coupling. © 2016 Wiley Periodicals, Inc.

The High-efficiency LED Driver for Visible Light Communication Applications.

This paper presents a LED driver for VLC. The main purpose is to solve the low data rate problem used to be in switching type LED driver. The GaN power device is proposed to replace the traditional silicon power device of switching LED driver for the purpose of increasing switching frequency of converter, thereby increasing the bandwidth of data transmission. To achieve high efficiency, the diode-connected GaN power transistor is utilized to replace the traditional ultrafast recovery diode used to be in switching type LED driver. This work has been experimentally evaluated on 350-mA output current. The results demonstrate that it supports the data of PWM dimming level encoded in the PPM scheme for VLC application. The experimental results also show that system's efficiency of 80.8% can be achieved at 1-Mb/s data rate.

Effect of deep pressure input on parasympathetic system in patients with wisdom tooth surgery.

BACKGROUND/PURPOSE: Deep pressure input is used to normalize physiological arousal due to stress. Wisdom tooth surgery is an invasive dental procedure with high stress levels, and an alleviation strategy is rarely applied during extraction. In this study, we investigated the effects of deep pressure input on autonomic responses to wisdom tooth extraction in healthy adults. METHODS: A randomized, controlled, crossover design was used for dental patients who were allocated to experimental and control groups that received treatment with or without deep pressure input, respectively. Autonomic indicators, namely the heart rate (HR), percentage of low-frequency (LF) HR variability (LF-HRV), percentage of high-frequency (HF) HRV (HF-HRV), and LF/HF HRV ratio (LF/HF-HRV), were assessed at the baseline, during wisdom tooth extraction, and in the posttreatment phase. RESULTS: Wisdom tooth extraction caused significant autonomic parameter changes in both groups; however, differential response patterns were observed between the two groups. In particular, deep pressure input in the experimental group was associated with higher HF-HRV and lower LF/HF-HRV during extraction compared with those in the control group. CONCLUSION: LF/HF-HRV measurement revealed balanced sympathovagal activation in response to deep pressure application. The results suggest that the application of deep pressure alters the response of HF-HRV and facilitates maintaining sympathovagal balance during wisdom tooth extraction.

Gender difference in the theta/alpha ratio during the induction of peaceful audiovisual modalities.

Gender differences in emotional perception have been found in numerous psychological and psychophysiological studies. The conducting modalities in diverse characteristics of different sensory systems make it interesting to determine how cooperation and competition contribute to emotional experiences. We have previously estimated the bias from the match attributes of auditory and visual modalities and revealed specific brain activity frequency patterns related to a peaceful mood. In that multimodality experiment, we focused on how inner-quiet information is processed in the human brain, and found evidence of auditory domination from the theta-band activity. However, a simple quantitative description of these three frequency bands is lacking, and no studies have assessed the effects of peacefulness on the emotional state. Therefore, the aim of this study was to use magnetoencephalography to determine if gender differences exist (and when and where) in the frequency interactions underpinning the perception of peacefulness. This study provides evidence of auditory and visual domination in perceptual bias during multimodality processing of peaceful consciousness. The results of power ratio analyses suggest that the values of the theta/alpha ratio are associated with a modality as well as hemispheric asymmetries in the anterior-to-posterior direction, which shift from right to left with the auditory to visual stimulations in a peaceful mood. This means that the theta/alpha ratio might be useful for evaluating emotion. Moreover, the difference was found to be most pronounced for auditory domination and visual sensitivity in the female group.

A programmable high-voltage compliance neural stimulator for deep brain stimulation in vivo.

Deep brain stimulation (DBS) is one of the most effective therapies for movement and other disorders. The DBS neurosurgical procedure involves the implantation of a DBS device and a battery-operated neurotransmitter, which delivers electrical impulses to treatment targets through implanted electrodes. The DBS modulates the neuronal activities in the brain nucleus for improving physiological responses as long as an electric discharge above the stimulation threshold can be achieved. In an effort to improve the performance of an implanted DBS device, the device size, implementation cost, and power efficiency are among the most important DBS device design aspects. This study aims to present preliminary research results of an efficient stimulator, with emphasis on conversion efficiency. The prototype stimulator features high-voltage compliance, implemented with only a standard semiconductor process, without the use of extra masks in the foundry through our proposed circuit structure. The results of animal experiments, including evaluation of evoked responses induced by thalamic electrical stimuli with our fabricated chip, were shown to demonstrate the proof of concept of our design.

Time-Varying Network Measures in Resting and Task States Using Graph Theoretical Analysis.

Recent studies have shown the importance of graph theory in analyzing characteristic features of functional networks of the human brain. However, many of these explorations have focused on static patterns of a representative graph that describe the relatively long-term brain activity. Therefore, this study established and characterized functional networks based on the synchronization likelihood and graph theory. Quasidynamic graphs were constructed simply by dividing a long-term static graph into a sequence of subgraphs that each had a timescale of 1 s. Irregular changes were then used to investigate differences in human brain networks between resting and math-operation states using magnetoencephalography, which may provide insights into the functional substrates underlying logical reasoning. We found that graph properties could differ from brain frequency rhythms, with a higher frequency indicating a lower small-worldness, while changes in human brain state altered the functional networks into more-centralized and segregated distributions according to the task requirements. Time-varying connectivity maps could provide detailed information about the structure distribution. The frontal theta activity represents the essential foundation and may subsequently interact with high-frequency activity in cognitive processing.

Utilizing the extent of theta-gamma synchronization to estimate visuospatial memory ability.

The ability of human memory declines due to normal aging and cognitive diseases, which means that everyone will eventually be affected by this problem. Fortunately, memory ability can be improved by training, and early detection and treatment can even actively prevent serious memory loss. Based on this principle, we aimed to identify a method for estimating the memory ability in order to slow the progression of memory loss. Numerous studies have found that coupling between the theta and gamma bands (also referred to as theta-gamma synchronization) reflect memory processes, with this being more pronounced when maintaining working memory. This study measured the extent of theta-gamma synchronization, and used a wavelet transform to observe the activity in the theta and gamma bands during a visuospatial memory task. The findings showed that there was a pronounced change during the encoding and retrieval phases of a working-memory task, and a significant correlation between the rate of correct responses and the synchronization index in the parietal brain area. We propose that the extent of theta-gamma synchronization can be used to estimate the working-memory ability. The further application of theta-gamma synchronization in both clinical and home situations may be expected in the future.

Coherent activity between auditory and visual modalities during the induction of peacefulness.

Multisensory integration involves combining information from different senses to create a perception. The diverse characteristics of different sensory systems make it interesting to determine how cooperation and competition contribute to emotional experiences. Therefore, the aim of this study were to estimate the bias from the match attributes of the auditory and visual modalities and to depict specific brain activity frequency (theta, alpha, beta, and gamma) patterns related to a peaceful mood by using magnetoencephalography. The present study provides evidence of auditory domination in perceptual bias during multimodality processing of peaceful consciousness. Coherence analysis suggested that the theta oscillations are a transmitter of emotion signals, with the left and right brains being active in peaceful and fearful moods, respectively. Notably, hemispheric lateralization was also apparent in the alpha and beta oscillations, which might govern simple or pure information (e.g. from single modality) in the right brain but complex or mixed information (e.g. from multiple modalities) in the left brain.

Sensorimotor resonance is an outcome but not a platform to anticipating harm to others.

When perceiving imminent harm to others, quickly detecting potential hazards to oneself should be vital. In this case, mirroring the outcome of observed actions appears paradoxical. This study measured electroencephalographic/event-related potentials and mu suppression that were induced by dynamic animations; each animation was composed of three consecutive pictures depicting an individual being accidentally injured. The results indicated that the first picture evoked frontal N260 and central N360, the possible brain source of which is estimated in the dorsolateral prefrontal cortex, and the third picture elicited late positive potentials, the possible sources of which might be generated from the insular and mid-cingulate cortex. Differential mu suppression, in relation to the sensorimotor resonance of empathy for pain, is associated with the third picture containing the crucial affective valence, but not with the first picture. The masking procedure on the third picture attenuated this mu suppression. Mediation analysis further confirmed that sensorimotor resonance is not a significant mediator in predicting subjective unpleasantness for observed actions. The findings suggest that sensorimotor resonance is not a platform, but rather an outcome when anticipating harm to others.

Differences in early dynamic connectivity between visual expansion and contraction stimulations revealed by an fMRI-directed MEG approach.

BACKGROUND AND PURPOSE: The human visual system responds asymmetrically to visual motion stimuli in opposite directions due to the involvement of the same brain areas but different operating processes. The expansion mode is thought to invoke a vigilance mechanism, whereas the contraction mode does not. METHODS: To investigate discrepancies between these modes, we produced dynamic connectivity maps based on mutual information between visual-evoked dipole sources of magnetoencephalography, which were steered by visual activity patterns in functional magnetic resonance imaging under two motion-stimulus modes. RESULTS: In the expansion mode, information was conveyed from V1 at 50-75 ms after motion onset, fed forward to V3A and then V5. Top-down connectivity paths were evident after a latency of 100 ms. Many of these interactions occurred within 200 ms. However, in the contraction mode, information was conveyed from V3A to V5, followed by feedback, but regained from V1 after a latency of 250 ms. Although these interactions were delayed by about 250 ms, they were completed within 500 ms. CONCLUSIONS: These findings show that detect spatiotemporal differences between expansion and contraction modes can be readily detected using time-flow charts. Moreover, delay interactions could be insensitive to object motion away from the observer.

An SSVEP-based BCI using high duty-cycle visual flicker.

Steady-state visual-evoked potential (SSVEP)-based brain-computer interfaces (BCIs) have generated significant interest due to their high information transfer rate (ITR). Due to the amplitude-frequency characteristic of the SSVEP, the flickering frequency of an SSVEP-based BCI is typically lower than 20 Hz to achieve a high SNR. However, a visual flicker with a flashing frequency below the critical flicker-fusion frequency often makes subjects feel flicker jerky and causes visual discomfort. This study presents a novel technique using high duty-cycle visual flicker to decrease user's visual discomfort. The proposed design uses LEDs flashing at 13.16 Hz, driven by flickering sequences consisting of repetitive stimulus cycles with a duration T (T = 76 ms). Each stimulus cycle included an ON state with a duration T(ON) and an OFF state with a duration T(OFF) (T = T(ON) + T(OFF)), and the duty cycle, defined as T(ON)/T, varied from 10.5% to 89.5%. This study also includes a questionnaire survey and analyzes the SSVEPs induced by different duty-cycle flickers. An 89.5% duty-cycle flicker, reported as a comfortable flicker, was adopted in a phase-tagged SSVEP system. Six subjects were asked to sequentially input a sequence of cursor commands with the 25.08-bits/min ITR.

Frequency recognition in an SSVEP-based brain computer interface using empirical mode decomposition and refined generalized zero-crossing.

This paper presents an empirical mode decomposition (EMD) and refined generalized zero crossing (rGZC) approach to achieve frequency recognition in steady-stated visual evoked potential (SSVEP)-based brain computer interfaces (BCIs). Six light emitting diode (LED) flickers with high flickering rates (30, 31, 32, 33, 34, and 35 Hz) functioned as visual stimulators to induce the subjects' SSVEPs. EEG signals recorded in the Oz channel were segmented into data epochs (0.75 s). Each epoch was then decomposed into a series of oscillation components, representing fine-to-coarse information of the signal, called intrinsic mode functions (IMFs). The instantaneous frequencies in each IMF were calculated by refined generalized zero-crossing (rGZC). IMFs with mean instantaneous frequencies (f(GZC)) within 29.5 Hz and 35.5 Hz (i.e., 29.5≤f(GZC)≤35.5 Hz) were designated as SSVEP-related IMFs. Due to the time-locked and phase-locked characteristics of SSVEP, the induced SSVEPs had the same frequency as the gazing visual stimulator. The LED flicker that contributed the majority of the frequency content in SSVEP-related IMFs was chosen as the gaze target. This study tests the proposed system in five male subjects (mean age=25.4±2.07 y/o). Each subject attempted to activate four virtual commands by inputting a sequence of cursor commands on an LCD screen. The average information transfer rate (ITR) and accuracy were 36.99 bits/min and 84.63%. This study demonstrates that EMD is capable of extracting SSVEP data in SSVEP-based BCI system.

Unbroken mirror neurons in autism spectrum disorders.

BACKGROUND: The 'broken mirror' theory of autism, which proposes that a dysfunction of the human mirror neuron system (MNS) is responsible for the core social and cognitive deficits in individuals with autism spectrum disorders (ASD), has received considerable attention despite weak empirical evidence. METHODS: In this electroencephalographic study, we examined mu suppression, as an indicator of sensorimotor resonance, concurrent with oculomotor performance while individuals (n = 20) with ASD and control participants (n = 20) either executed hand actions or observed hand actions or a moving dot. No difference in visual attention between groups was found as indicated by fixation duration and normalized fixation number on the presented stimuli. RESULTS: The mu suppression over the sensorimotor cortex was significantly affected by experimental conditions, but not by group membership, nor by the interaction between groups and conditions. Individuals with ASD, similar to the controls, exhibited stronger mu suppression when watching hand actions relative to a moving dot. Notably, participants with ASD failed to imitate the observed actions while their mu suppression indicating the MNS activity was intact. In addition, the mu suppression during the observation of hand actions was positively associated with the communication competence of individuals with ASD. CONCLUSION: Our study clearly challenges the broken mirror theory of autism. The functioning of the mirror neuron system might be preserved in individuals with ASD to a certain degree. Less mu suppression to action observation coupled with more communicational severity can reflect the symptom heterogeneity of ASD. Additional research needs to be done, and more caution should be used when reaching out to the media.