173 research outputs found
Cross-Correlation of Motor Activity Signals from dc-Magnetoencephalography, Near-Infrared Spectroscopy, and Electromyography
Neuronal and vascular responses due to finger movements were synchronously measured using dc-magnetoencephalography (dcMEG) and time-resolved near-infrared spectroscopy (trNIRS). The finger movements were monitored with electromyography (EMG). Cortical responses related to the finger movement sequence were extracted by independent component analysis from both the dcMEG and the trNIRS data. The temporal relations between EMG rate, dcMEG, and trNIRS responses were assessed pairwise using the cross-correlation function (CCF), which does not require epoch averaging. A positive lag on a scale of seconds was found for the maximum of the CCF between dcMEG and trNIRS. A zero lag is observed for the CCF between dcMEG and EMG. Additionally this CCF exhibits oscillations at the frequency of individual finger movements. These findings show that the dcMEG with a bandwidth up to 8 Hz records both slow and faster neuronal responses, whereas the vascular response is confirmed to change on a scale of seconds
Event-Related Desynchronization and Corticomuscular Coherence Observed During Volitional Swallow by Electroencephalography Recordings in Humans
Swallowing in humans involves many cortical areas although it is partly mediated by a series of brainstem reflexes. Cortical motor commands are sent to muscles during swallow. Previous works using magnetoencephalography showed event-related desynchronization (ERD) during swallow and corticomuscular coherence (CMC) during tongue movements in the bilateral sensorimotor and motor-related areas. However, there have been few analogous works that use electroencephalography (EEG). We investigated the ERD and CMC in the bilateral sensorimotor, premotor, and inferior prefrontal areas during volitional swallow by EEG recordings in 18 healthy human subjects. As a result, we found a significant ERD in the beta frequency band and CMC in the theta, alpha, and beta frequency bands during swallow in those cortical areas. These results suggest that EEG can detect the desynchronized activity and oscillatory interaction between the cortex and pharyngeal muscles in the bilateral sensorimotor, premotor, and inferior prefrontal areas during volitional swallow in humans
Concurrent fNIRS and EEG for brain function investigation: A systematic, methodology-focused review
Electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) stand as state-of-the-art techniques for non-invasive functional neuroimaging. On a unimodal basis, EEG has poor spatial resolution while presenting high temporal resolution. In contrast, fNIRS offers better spatial resolution, though it is constrained by its poor temporal resolution. One important merit shared by the EEG and fNIRS is that both modalities have favorable portability and could be integrated into a compatible experimental setup, providing a compelling ground for the development of a multimodal fNIRS-EEG integration analysis approach. Despite a growing number of studies using concurrent fNIRS-EEG designs reported in recent years, the methodological reference of past studies remains unclear. To fill this knowledge gap, this review critically summarizes the status of analysis methods currently used in concurrent fNIRS-EEG studies, providing an up-to-date overview and guideline for future projects to conduct concurrent fNIRS-EEG studies. A literature search was conducted using PubMed and Web of Science through 31 August 2021. After screening and qualification assessment, 92 studies involving concurrent fNIRS-EEG data recordings and analyses were included in the final methodological review. Specifically, three methodological categories of concurrent fNIRS-EEG data analyses, including EEG-informed fNIRS analyses, fNIRS-informed EEG analyses, and parallel fNIRS-EEG analyses, were identified and explained with detailed description. Finally, we highlighted current challenges and potential directions in concurrent fNIRS-EEG data analyses in future research
Early brain activity : Translations between bedside and laboratory
Neural activity is both a driver of brain development and a readout of developmental processes. Changes in neuronal activity are therefore both the cause and consequence of neurodevelopmental compromises. Here, we review the assessment of neuronal activities in both preclinical models and clinical situations. We focus on issues that require urgent translational research, the challenges and bottlenecks preventing translation of biomedical research into new clinical diagnostics or treatments, and possibilities to overcome these barriers. The key questions are (i) what can be measured in clinical settings versus animal experiments, (ii) how do measurements relate to particular stages of development, and (iii) how can we balance practical and ethical realities with methodological compromises in measurements and treatments.Peer reviewe
Brain Signals as a New Biometric Authentication Method Using Brain-Computer Interface
Human biometric techniques are presented as another type of security authentication to cover the problems of password authentication. Brainwave is another human biometric, which recently is one of the popular subjects for scientists and researchers. Brain-computer interface (BCI) is a method of communication based on neural activity’s communication created by the brain
Near-Infrared Spectroscopy for Brain Computer Interfacing
A brain-computer interface (BCI) gives those suffering from neuromuscular
impairments a means to interact and communicate with their surrounding
environment. A BCI translates physiological signals, typically electrical,
detected from the brain to control an output device. A significant problem with
current BCIs is the lengthy training periods involved for proficient usage, which
can often lead to frustration and anxiety on the part of the user and may even lead
to abandonment of the device. A more suitable and usable interface is needed to
measure cognitive function more directly. In order to do this, new measurement
modalities, signal acquisition and processing, and translation algorithms need to
be addressed. This work implements a novel approach to BCI design, using noninvasive
near-infrared spectroscopic (NIRS) techniques to develop a userfriendly
optical BCI. NIRS is a practical non-invasive optical technique that can
detect characteristic haemodynamic responses relating to neural activity. This
thesis describes the use of NIRS to develop an accessible BCI system requiring
very little user training. In harnessing the optical signal for BCI control an
assessment of NIRS signal characteristics is carried out and detectable
physiological effects are identified for BCI development. The investigations into
various mental tasks for controlling the BCI show that motor imagery functions
can be detected using NIRS. The optical BCI (OBCI) system operates in realtime
characterising the occurrence of motor imagery functions, allowing users to
control a switch - a “Mindswitch”. This work demonstrates the great potential of
optical imaging methods for BCI development and brings to light an innovative
approach to this field of research
Slow Potentials of the Sensorimotor Cortex during Rhythmic Movements of the Ankle
The objective of this dissertation was to more fully understand the role of the human brain in the production of lower extremity rhythmic movements. Throughout the last century, evidence from animal models has demonstrated that spinal reflexes and networks alone are sufficient to propagate ambulation. However, observations after neural trauma, such as a spinal cord injury, demonstrate that humans require supraspinal drive to facilitate locomotion. To investigate the unique nature of lower extremity rhythmic movements, electroencephalography was used to record neural signals from the sensorimotor cortex during three cyclic ankle movement experiments. First, we characterized the differences in slow movement-related cortical potentials during rhythmic and discrete movements. During the experiment, motion analysis and electromyography were used characterize lower leg kinematics and muscle activation patterns. Second, a custom robotic device was built to assist in passive and active ankle movements. These movement conditions were used to examine the sensory and motor cortical contributions to rhythmic ankle movement. Lastly, we explored the differences in sensory and motor contributions to bilateral, rhythmic ankle movements. Experimental results from all three studies suggest that the brain is continuously involved in rhythmic movements of the lower extremities. We observed temporal characteristics of the cortical slow potentials that were time-locked to the movement. The amplitude of these potentials, localized over the sensorimotor cortex, revealed a reduction in neural activity during rhythmic movements when compared to discrete movements. Moreover, unilateral ankle movements produced unique sensory potentials that tracked the position of the movement and motor potentials that were only present during active dorsiflexion. In addition, the spatiotemporal patterns of slow potentials during bilateral ankle movements suggest similar cortical mechanisms for both unilateral and bilateral movement. Lastly, beta frequency modulations were correlated to the movement-related slow potentials within medial sensorimotor cortex, which may indicate they are of similar cortical origin. From these results, we concluded that the brain is continuously involved in the production of lower extremity rhythmic movements, and that the sensory and motor cortices provide unique contributions to both unilateral and bilateral movemen
EEG and ECoG features for Brain Computer Interface in Stroke Rehabilitation
The ability of non-invasive Brain-Computer Interface (BCI) to control an exoskeleton was
used for motor rehabilitation in stroke patients or as an assistive device for the paralyzed.
However, there is still a need to create a more reliable BCI that could be used to control
several degrees of Freedom (DoFs) that could improve rehabilitation results. Decoding
different movements from the same limb, high accuracy and reliability are some of the main
difficulties when using conventional EEG-based BCIs and the challenges we tackled in this
thesis.
In this PhD thesis, we investigated that the classification of several functional hand reaching
movements from the same limb using EEG is possible with acceptable accuracy. Moreover,
we investigated how the recalibration could affect the classification results. For this reason,
we tested the recalibration in each multi-class decoding for within session, recalibrated
between-sessions, and between sessions.
It was shown the great influence of recalibrating the generated classifier with data from the
current session to improve stability and reliability of the decoding. Moreover, we used a
multiclass extension of the Filter Bank Common Spatial Patterns (FBCSP) to improve the
decoding accuracy based on features and compared it to our previous study using CSP.
Sensorimotor-rhythm-based BCI systems have been used within the same frequency ranges
as a way to influence brain plasticity or controlling external devices. However, neural
oscillations have shown to synchronize activity according to motor and cognitive functions.
For this reason, the existence of cross-frequency interactions produces oscillations with
different frequencies in neural networks. In this PhD, we investigated for the first time the
existence of cross-frequency coupling during rest and movement using ECoG in chronic
stroke patients. We found that there is an exaggerated phase-amplitude coupling between
the phase of alpha frequency and the amplitude of gamma frequency, which can be used as feature or target for neurofeedback interventions using BCIs. This coupling has been also
reported in another neurological disorder affecting motor function (Parkinson and dystonia)
but, to date, it has not been investigated in stroke patients. This finding might change the
future design of assistive or therapeuthic BCI systems for motor restoration in stroke
patients
BioSig: The Free and Open Source Software Library for Biomedical Signal Processing
BioSig is an open source software library for biomedical signal processing. The aim
of the BioSig project is to foster research in biomedical signal processing by providing
free and open source software tools for many different application areas. Some of the
areas where BioSig can be employed are neuroinformatics, brain-computer interfaces,
neurophysiology, psychology, cardiovascular systems, and sleep research. Moreover,
the analysis of biosignals such as the electroencephalogram (EEG), electrocorticogram
(ECoG), electrocardiogram (ECG), electrooculogram (EOG), electromyogram (EMG),
or respiration signals is a very relevant element of the BioSig project. Specifically,
BioSig provides solutions for data acquisition, artifact processing, quality control, feature
extraction, classification, modeling, and data visualization, to name a few. In this
paper, we highlight several methods to help students and researchers to work more efficiently
with biomedical signals
Advancing Brain-Computer Interface System Performance in Hand Trajectory Estimation with NeuroKinect
Brain-computer interface (BCI) technology enables direct communication
between the brain and external devices, allowing individuals to control their
environment using brain signals. However, existing BCI approaches face three
critical challenges that hinder their practicality and effectiveness: a)
time-consuming preprocessing algorithms, b) inappropriate loss function
utilization, and c) less intuitive hyperparameter settings. To address these
limitations, we present \textit{NeuroKinect}, an innovative deep-learning model
for accurate reconstruction of hand kinematics using electroencephalography
(EEG) signals. \textit{NeuroKinect} model is trained on the Grasp and Lift
(GAL) tasks data with minimal preprocessing pipelines, subsequently improving
the computational efficiency. A notable improvement introduced by
\textit{NeuroKinect} is the utilization of a novel loss function, denoted as
. This loss function addresses the discrepancy
between correlation and mean square error in hand kinematics prediction.
Furthermore, our study emphasizes the scientific intuition behind parameter
selection to enhance accuracy. We analyze the spatial and temporal dynamics of
the motor movement task by employing event-related potential and brain source
localization (BSL) results. This approach provides valuable insights into the
optimal parameter selection, improving the overall performance and accuracy of
the \textit{NeuroKinect} model. Our model demonstrates strong correlations
between predicted and actual hand movements, with mean Pearson correlation
coefficients of 0.92 (0.015), 0.93 (0.019), and 0.83 (0.018) for
the X, Y, and Z dimensions. The precision of \textit{NeuroKinect} is evidenced
by low mean squared errors (MSE) of 0.016 (0.001), 0.015 (0.002), and
0.017 (0.005) for the X, Y, and Z dimensions, respectively
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