Oscar Yanez-Suarez

Metropolitan Autonomous University | UAM · Departamento de Ingeniería Eléctrica

Functional electrical stimulation (FES) is a rehabilitation and assistive technique used for stroke survivors. FES systems mainly consist of sensors, a control algorithm, and a stimulation unit. However, there is a critical need to reassess sensing and control techniques in FES systems to enhance their efficiency. This SLR was carried out following...

There is a substantial corpus of evidence about the shared brain mechanism between imagery and perception. However, the psychophysiological exploration concerning possible mechanisms underlying modality-independent mental imagery and how much it involves or depends on other cognitive processes, such as attention and memory, is still scant. To addre...

The identification of brain dynamical changes under different cognitive conditions with noninvasive techniques such as electroencephalography (EEG) is relevant for the understanding of their underlying neural mechanisms. The comprehension of these mechanisms has applications in the early diagnosis of neurological disorders and asynchronous brain co...

The technology for transcranial magnetic stimulation (TMS) has significantly changed over the years, with important improvements in the signal generators, the coils, the positioning systems, and the software for modeling, optimization, and therapy planning. In this systematic literature review (SLR), the evolution of each component of TMS technolog...

Parkinson's disease (PD) is a neuropathy characterized by motor disorders, but it has also been associated with the presence of autonomic alterations as a result of degradation of the dopaminergic system. Studying the relation between Band Power time series (BPts) and Heart Rate Variability (HRV), has been proposed as a tool to explore the bidirect...

Parkinson's Disease is a neuropathy that produces changes in several biomarkers, these changes could be used to evaluate even sub-clinical conditions. This paper presents an evaluation of indices extracted from electroencephalography and Heart Rate Variability (HRV), when used to classify a sample of subjects from three groups: control (healthy), m...

Some hypotheses relate oscillations of EEG band power with autonomic processes derived from homeostatic control modulated by structures like the Central Autonomic Network and the Autonomic Nervous System. This research project studies the causal relationships between fluctuations of an autonomic process marker like the Heart Rate Variability (HRV)...

Autonomic control evidenced in both heart rate variability (HRV) and electroencephalographic (EEG) oscillations, reflect the behaviour of the underlying physiological non-stationary dynamical systems. In order to assess the influence of autonomic changes in the performance of an asynchronous brain-computer interface, recurrence analysis of EEG spec...

Introduction. TBI is associated with alterations in cortico-subcortical connectivity. However, little attention has been paid to its clinical characteristics and functional connectivity in pediatric patients with chronic TBI. Objective. To evaluate the cognitive performance and spectral coherence of a group of children with TBI in non-acute phase....

1. Introducción La enfermedad de Alzheimer (EA) es un trastorno neurodegenerativo que conduce a un deterioro de las capacidades cognitivas e intelectuales de forma irreversible, limitando el desempeño de las actividades cotidianas [1]. Esta patología afecta la morfología cerebral, ya sea globalmente o en regiones específicas. Para cuantificar el pr...

Chronic kidney disease impacts the cognitive abilities of patients, and yet few works have analyzed functional electroencephalographic changes on event-related potentials before and after an hemodialysis session. This work shows that, as a consequence of hemodialysis, cognitive potential waveforms suffer changes, occurring with reduced latency $( \...

Most EEG phase synchrony measures are of bivariate nature. Those that are multivariate focus on producing global indices of the synchronization state of the system. Thus, better descriptions of spatial and temporal local interactions are still in demand. A framework for characterization of phase synchrony relationships between multivariate neural t...

P300 spellers have been widely modified to implement nonspelling tasks. In this work, we propose a “scenario” stimulation screen that is a P300 speller variation to command a wheelchair. Our approach utilized a stimulation screen with an image background (scenario snapshot for a wheelchair) and stimulation markers arranged asymmetrically over relev...

Objective: Event Related Potentials (ERP) are phenomena that produces alterations on the spectral power of different bands synced with stimuli presentation. Such perspective overlooks that the spectral power time series present spontaneous oscillations, whose dynamics has been associated with health state and could be also linked with superior proc...

Background: Oscillations, action, and postsynaptic potentials in glial-neuronal ensembles integrate the spectral power (SP) of electroencephalographic (EEG). Our objective is to propose SP indicators of healthy brains (control groups) based on the default mode and their modifications by habituation and visual-motor association (VM-asso), to suppor...

To search for possible interactions between the autonomic heart control and the brain activity we have evaluatedthe relation between heart rate variability (HRV) and the alpha and beta EEG band power dynamics. Theexperiments consisted in the alteration of HRV induced by respiratory rhythm changes. Modi cations in thetime series of the spectral dens...

Introducción: La potencia espectral en reposo a menudo se considera como un marcador robusto de la función cerebral; sin embargo, pocos estudios la han asociado con una función específica. Objetivo: Analizar la relación entre la potencia absoluta (PA) del EEG con el desempeño en las tareas de funcionamiento ejecutivo en niños. Método: Investigaci...

ANTECEDENTES: La función cerebral resulta de la actividad eléctrica en redes glío-neuronales, integradas de forma activa por interacciones sensoriales, motoras y reguladores. Redes que oscilan desde la infancia y se modulan por diversos factores de maduración, incluyendo procesos educativos. OBJETIVO: Identificar el espectro de potencia separado e...

We present a novel approach to describe a P300 by a shape-feature vector, which offers several advantages over the feature vector used by the BCI2000 system. Additionally, we present a calibration algorithm that reduces the dimensionality of the shape-feature vector, the number of trials, and the electrodes needed by a Brain Computer Interface to a...

This paper presents an evaluation of the continuous detection of mental calculation episodes, which may be useful for users who strive to operate current BCI paradigms or even for augmenting degrees of freedom. The experimentation consisted in the alternated realization of basic arithmetic mental calculations and resting periods. EEG data were anal...

Near-infrared spectroscopy (NIRS) is a noninvasive and portable technique to quantify changes of oxy- and deoxy-hemoglobin concentration in tissue. In this paper the development of a continuous wave NIRS instrument is presented. The instrument was designed using a LED emitting light at 750 and 850 nm, that are wavelengths at which the oxy- and deox...

This paper presents the development of a visual stimulation screen prototype for P300 BCI based on the native OpenViBE Donchin speller where an RGB snapshot of the navigation scenario for an electric wheelchair was embedded on the background instead of the usual solid color. The letters which are the stimulation markers were appropriately replaced...

We present a discrete compactness (DC) index, together with a classification scheme, based both on the size and shape features extracted from brain volumes, to determine different aging stages: healthy controls (HC), mild cognitive impairment (MCI), and Alzheimer's disease (AD). A set of 30 brain magnetic resonance imaging (MRI) volumes for each gr...

In this paper a binary BCI control based on mental computation of arithmetic operations is evaluated. Data analysis was performed using information derived from five EEG channels, estimating the detrended fluctuation analysis scaling exponent and the power on beta band. The strategy (task and data analysis) was validated on fifteen subjects realizi...

Berger related the EEG with cognition; we are attempting to identify which rhythms and circuits participate in habituation, a learning that decreases responses to meaningless stimuli which, changed the absolute power (AP) of EEG oscillations. To characterize habituation, analyzing the AP of four rhythms in lateral regions of both hemispheres (BH),...

Reported studies describing normal and abnormal aging based on anatomical MRI analysis do not consider morphological brain changes, but only volumetric measures to distinguish among these processes. This work presents a classification scheme, based both on size and shape features extracted from brain volumes, to determine different aging stages: he...

The EEG records neuronal membrane potential oscillations that depend on the morpho-functional characteristics of the membrane and of modifications by postsynaptic excitatory (PSEP) and inhibitory (PSIP) potentials. The quantitative EEG (qEEG) measures the absolute power (AP) of oscillations separated in frequencies, resulting from the interaction a...

This paper presents an application developed on the BCI2000 platform which reduces the average spelling time per symbol on the Donchin speller. The motivation was to reduce the compromise between spelling rate and spelling accuracy due to the large amount of responses required in order to perform coherent average techniques. The methodology was mad...

This paper presents an application developed on the BCI2000 platform which reduces the average spelling time per symbol on the Donchin speller. The motivation was to reduce the compromise between spelling rate and spelling accuracy due to the large amount of responses required in order to perform coherent average techniques. The methodology was mad...

Resumen— Se implementó el uso de clasificadores por árbol de decisión (ID3) y k-vecinos más cercanos (K-NN) para evaluar el comportamiento del parámetro α 1(SIGN) en las fluctuaciones de la frecuencia cardiaca , que refleja aspectos de la regulación autonómica. Resultados previos sugieren que existen cambios en dicho parámetro en grupos de mujeres...

Steady state visual evoked potentials represent the least training-dependent brain computer interface paradigm, a condition that significantly improves the user experience with this kind of interfaces. On the other hand, the open- source DASHER writing system is an unconventional machine interface paradigm on its own, for which their developers enc...

Middle Latency Auditory Evoked Potentials are bioelectrical signals that constitute a key technique for the assessment and diagnosis of various clinical conditions, nonethe- less background electrical activity and artifacts prevent clini- cally relevant information to be revealed. Many state of the art techniques allow physicians to remove noise an...

The electroencephalogram is an attractive clinical tool given its non-invasive nature, its ability to reflect real-time changes in local cortical activity, and the load of objective bioelectrical measurements that can be derived from it. For decades, the electroencephalogram has been successfully used for diagnosing epilepsy and schizophrenia, amon...

Gastric impedance spectroscopy has been proposed as a method of monitoring mucosal injury due to hypoperfusion and ischemia in the critically ill. During validation tests for this procedure, it was found that 60% of the measurements had errors by factors inherent to the clinical setting, indicating that some kind of automatic error detection should...

An LMS-based algorithm to monitor fetal and maternal heart rate in real time was implemented and evaluated on a development platform. Hardware has three modules: dsPIC30F digital signal controller, a low-noise analog front end and a storage stage. They were evaluated using on-chip debugging tools and a patient simulator. Algorithm performance was t...

GOAL: The P300 Speller is probably the best known application in BCI [1]. Over the years, many improvements over the pioneering systems have been made and some performance comparisons exist [2]. To contribute to the improvement process, we propose an open access to a large database obtained from first-time users of the P300 speller application impl...

This is an open database of P300 Speller experimentation. It comprises 30 healthy naive subjects, performing Donchin Speller paradigm. The database is divided in three sessions, the first was directed (3 words, 16 characters), in the second a classification was performed (1word, 5 characters), and the third was a free-spelling paradigm changing the...

During waking, stimuli activate the sensory pathways giving rise to sensation and the response to such stimulation. The electrobiochemical changes and modifications in EEG rhythms eventrelated synchronization or event-related desynchronization, ERD or ERS) propagated in the specific and unspecific cortex are added to the changes elicited by the res...

Objective. - The goal of this research was to design, set up, use and evaluate a realistic simulation platform that could host real-time simulated robotics applications controlled with a brain-computer interface based on an event-related potential paradigm. Materials and methods. - The platform is composed of the following modules: (i) six band-lim...

Algunos cambios del ambiente activan las vías sensoriales generando la sensación y la respuesta a dicha estimulación. Los cambios electrobioquímicos modifican el EEG que al propagarse en la corteza cerebral se suman a los potenciales que generan las respuestas y éstas producen nuevas señales que dan lugar a la percepción. Diversos factores pueden a...

Character identification on a P300 Speller is treated as a pattern recognition problem. SVM were used to detect ERP when character to spell were intensified. The input char- acteristics to SVM were the projections on an estimated signal subspace. This Subspace was estimated via eigendecomposition of correlation matrix, from a set of epochs containi...

In this work, a meshless (free Galerkin) method is used to define a realistic head conductor model to solve the EEG inverse problem. The aim is to find sources responsible for scalp potentials with precision and low computation time. In order to assess the proper method's performance, it was evaluated with simulated EEG signals, obtained from diffe...

In this work we evaluated a method for detection of steady-state visual evoked potentials in one-second EEG recordings, based on the multisignal classification (MUSIC) algorithm and support vector machine classification. Three experiments were carried out to test the performance of the method and its applicability for BCI related tasks. The first e...

Magnetic Resonance Imaging (MRI) is increasingly used for the diagnosis and monitoring of neurological disorders. In particular Diffusion-Weighted MRI (DWI) is highly sensitive in detecting early cerebral ischemic changes in acute stroke. Cerebral infarction lesion segmentation from DWI is accomplished in this work by applying nonparametric density...

We present the first results of four projects of a second phase of a Mexican Project Computer Assisted Surgery and Medical Robotics, supported by the Mexican Science and Technology National Council (Consejo Nacional de Ciencia y Tecnología) under grant SALUD-2002-C01-8181. The projects are being developed by three universities (UNAM, UAM, ITESM) an...

This paper presents an implementation of an effective synchronization between a registration and a stimulation module that form part of a steady state visual evoked potential (SSVEP)-based Brain Computer Interface (BCI). Each of the synchronized modules were created and designed in two different platforms as well as in two different workstations, s...

A Single-Trial detection for Evoked Potentials is presented, it was tested with Event Related Potentials (oddball) which are used in the Donchin’s Speller. The scheme is based in inner product of registered potentials over signal subspaces, estimated by principal components analysis. Different combinations of projection coefficients were used as ch...

Time-varying autoregressive modeling may consider the driving noise variance as a constant. In this work, the properties of the autoregressive driving noise variance of heart rate variability, with different stationary physiological conditions (resting in supine and sitting; exercise) are obtained. The effect of constant variance consideration for...

This paper describes preliminary performance results of a reconfigurable hardware implementation of a support vector machine classifier, aimed at brain-computer interface applications, which require real-time decision making in a portable device. The main constraint of the design was that it could perform a classification decision within the time s...

We present a new method for single trial detection of P300 evoked responses. The features used to classify are the coefficients of a least-squaress fit of a single EEG epoch to the Intrinsecal Mode Functions of an Empirical Mode Decomposition of the averaged event response from a P300 training set. Support Vector Machines with a linear kernel are u...

This paper describes the outcome of discussions held during the Third International BCI Meeting at a workshop to review and evaluate the current state of BCI-related hardware and software. Technical requirements and current technologies, standardization procedures and future trends are covered. The main conclusion was recognition of the need to foc...

A novel edge-preserving filtering method based on unsupervised clustering within the joint four-dimensional location-intensity space of volume echocardiographic data is presented. A vector codebook, formed by vectors that lie close to the modes of the joint data distribution is derived through an iterative vector quantization procedure. Distributio...

We present a new method for single trial detection of P300 evoked responses. The features used to classify are the coefficients of a least-squares fit of a single EEG epoch to the intrinsical mode functions of an empirical mode decomposition of the averaged event response from a P300 training set. Support vector machines with a linear kernel are us...

To delineate arbitrarily shaped clusters in a complex multimodal feature space, such as the brain MRI intensity space, often requires kernel estimation techniques with locally adaptive bandwidths, such as the adaptive mean shift procedure. Proper selection of the kernel bandwidth is a critical step for a better quality in the clustering. This paper...

This paper presents the novel design of a software phantom for the evaluation of equilibrium radionuclide ventriculography systems. Through singular value decomposition, the data matrix corresponding to an equilibrium image series is decomposed into both spatial and temporal fundamental components that can be parametrized. This parametric model all...

Time-varying autoregressive modeling may consider the driving noise variance as a constant. In this work, the properties of the autoregressive driving noise variance of heart rate variability, with different stationary physiological conditions (resting in supine and sitting; exercise) are obtained. The effect of constant variance consideration for...

Brain magnetic resonance imaging segmentation is accomplished in this work by applying nonparametric density estimation, using the mean shift algorithm in the joint spatial-range domain. The quality of the class boundaries is improved by including an edge confidence map, that represents the confidence of truly being in the presence of a border betw...

The evaluation of the upper respiratory airway obstruction is of significant importance, as its physiological effects on ventilation rapidly evolve to secondary body malfunctions. Given the nature and location of the lesions, the invasive handling of the condition with direct bronchoscopy is undesirable; an imaging approach based on computed tomogr...

In the present study, we examined two baroreflex sensitivity (BRS) issues that remain uncertain: the differences among diverse BRS assessment techniques and the association between BRS and vagal outflow. Accordingly, the electrocardiogram and non-invasive arterial pressure were recorded in 27 healthy subjects, during supine with and without control...

To compare the relationships between heart period and root mean square of successive differences for exercise and recovery, these parameters were obtained in eight subjects during three one-minute successive sub-maximal workloads of cycle exercise and the first three minutes of recovery, using a 25 second sliding window. In most subjects, at recove...

An accurate segmentation of cardiac cavities is necessary to assess cardiac function and to determine quantitative parameters. Several semi-automatic techniques have been tested to achieve this goal. In this work we propose an algorithm to segment cardiac structures, based on a robust pre-processing step that eliminates noise and extracts an initia...

Due to limited and contradictory information available, the reproducibility of temporal and spectral measurements of heart rate variability from short-term recordings was evaluated in normal subjects during supine, controlled breathing, standing, exercise and recovery conditions. Five-minute tachograms from 11 individuals were obtained during the s...

Segmentation and extraction of cardiac structures from heart images has been of great importance in the quantification of indicative parameters of cardiac pathologies. In this work we propose an algorithm delineate cardiac cavities, based on a robust extraction of the left ventricle, together with a refined deformable model, that integrates edge co...

The most frequently used imaging procedure for the diagnosis of diverse neurological illnesses is magnetic resonance. Improved benefits have been obtained from multi-spectral information under this imaging modality. Both supervised and unsupervised segmentation procedures have been reported for this kind of images, many of which require a preproces...

A voxel-based measure of discrete compactness for brain structures quantification, is presented. The work proposed here simplifies the measure of discrete compactness, which corresponds to the sum of the contact surface areas of the face-connected voxels of the analyzed brain. A relation between the area of the surface enclosing the cerebral volume...

During the last decade several programs for universal detection of newborn hearing loss (UNHL) have been developed, based on the analysis of either the auditory brainstem response (ABR) and/or otoacoustic emissions (OAEs). At the present time, although there are several systems and algorithms capable of automatically determining the presence of res...

In this paper, a nonparametric statistical segmentation procedure based on the computation of the mean shift within the joint space-range feature representation of brain MR images is presented. The mean shift is a simple, nonparametric estimator, which can be implemented in a data-driven approach. The number of classes and other initialization para...

Signs and symptoms of tracheal stenosis can create confusion about the etiology of the problem. While bronchoscopy is the diagnostic method of choice to evaluate the extension and localization of the lesion, the use of x-ray computed axial tomography (CAT) images has also been considered. Recent works on airway segmentation in CAT images propose th...

A segmentation procedure using a radial basis function network (RBFN), coupled with an active contour (AC) model based on a cubic splines formulation is presented for the detection of the gray-white matter boundary in axial MMRI (T1, T2 and PD). A RBFN classifier has been previously introduced for MMRI segmentation, with good generalization at a ra...

The segmentation of cerebral MRI is approached as a classification problem where the density function is unknown. For MR images, the modes of the intensity distribution are related to cluster centers obtained from anatomical structures of brain images. The modes of the unknown density function can be calculated by applying the mean-shift method. Th...

Acoustic pulse reflectometry has been used in the past for the indirect determination of the cross-section area vs. distance function describing the geometry of solid cylindrical cavities such as the upper airway tract. Excitation pulse bandwidth, noise and system losses are usually the main experimental issues and sources of reconstruction error i...

In order to corroborate the rported performance advantage of Poincaré plot indexes as autonomic activity markers, the correlation among these indexes and those computed from the time and frequency domains were obtained. Starting from the RR series derived from the ECG of 21 healthy volunteers during five manoeuvres, longitudinal (L), transverse (T)...

Spatial quantification of relevant brain structures, is usually carried out through the analysis of a stack of magnetic resonance (MR) images by means of some image segmentation approach. In this paper, multispectral MR imaging segmentation based on a modified radial-basis function network is presented. Multispectral MR image sets are constructed b...

Spatial quantification of relevant brain structures, is usually carried out through the analysis of a stack of magnetic resonance (MR) images by means of some image segmentation approach. In this paper, multispectral MR imaging segmentation based on a modified radial-basis function network is presented. Multispectral MR image sets are constructed b...

Tracheal stenosis is an uncommon pathology that in early stages is often confused with different respiratory affections by its signs and symptoms. An automatic characterization of the tracheal stenosis requires adequate medical images and efficient segmentation algorithms. In CT images, several algorithms of airway segmentation have been used, such...

Segmentation of cardiac structures has a great impact in the quantification of parameters indicative of heart function. The preferred technique for this segmentation is based on edge detection, where deformable models have extensively been used to obtain cardiac cavities contours. This work proposes two alternatives to the traditionally used active...

An automated approach for template-free identification of partially occluded objects is presented. The contour of each relevant object in the analyzed scene is modeled with an approximating polygon whose edges are then projected into the Hough space. A structurally adaptive self-organizing map neural network generates clusters of collinear and/or p...