Recurrence quantification analysis during a mental calculation task.

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 computer interfaces. In both cases, there are no reported features that could describe intersubject and intra subject dynamics behavior accurately enough to be applied on a daily basis. The present work proposes the use of three nonlinear features (recurrence rate, determinism, and recurrence times) extracted from recurrence quantification analysis (RQA) to describe central and parietal EEG power series complexity in continuous alternating episodes of mental calculation and rest state. Our results demonstrate a consistent mean directional change of determinism, recurrence rate, and recurrence times between conditions. Increasing values of determinism and recurrence rate were present from the rest state to mental calculation, whereas recurrence times showed the opposite pattern. The analyzed features in the present study showed statistically significant changes between rest and mental calculation states in both individual and population analysis. In general, our study described mental calculation EEG power series as less complex systems in comparison to the rest state. Moreover, ANOVA showed stability of RQA features along time.

Devices and Technology in Transcranial Magnetic Stimulation: A Systematic Review.

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 technology is presented and analyzed to assess the limitations to overcome. This SLR was carried out following the PRISMA 2020 statement. Published articles of TMS were searched for in four databases (Web of Science, PubMed, Scopus, IEEE). Conference papers and other reviews were excluded. Records were filtered using terms about TMS technology with a semi-automatic software; articles that did not present new technology developments were excluded manually. After this screening, 101 records were included, with 19 articles proposing new stimulator designs (18.8%), 46 presenting or adapting coils (45.5%), 18 proposing systems for coil placement (17.8%), and 43 implementing algorithms for coil optimization (42.6%). The articles were blindly classified by the authors to reduce the risk of bias. However, our results could have been influenced by our research interests, which would affect conclusions for applications in psychiatric and neurological diseases. Our analysis indicates that more emphasis should be placed on optimizing the current technology with a special focus on the experimental validation of models. With this review, we expect to establish the base for future TMS technological developments.

Disruption of the Cortical-Vagal Communication Network in Parkinson's Disease.

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 bidirectional communication pathways between cortex and autonomic control. This work presents a primer analysis on study brain ↔ heart interaction on a databse of PD patients under two conditions: without and after levadopa (L-dopa) intake. Additionally a healthy control population was also analyzed, and used as comparison level between both conditions. Results show PD affects pathways by reducing the number of connections, specially association of beta and power and the second faster component of HRV seems to be more sensitive to L-dopa administration.

Spectral Electroencephalographic and Heart Rate Variability features enhance identification of medicated/non-medicated Parkinson's disease patients.

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), medicated and non medicated subjects diagnosed with Parkinson's disease. Classification performance was measured using accuracy over these classes and a cross validation scheme was used to assess repeatability for the classification process. Results tend to prove that inclusion of an autonomic index derived from HRV analysis enhances classification, suggesting that Parkinson's disease could be related with unperceptible to mild alterations of the Autonomic Nervous System.

Bidirectional intrinsic modulation of EEG band power time series and spectral components of heart rate variability.

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) and the proposed EEG band power time series (BPts). To verify the existence of directional causal relationships, using Granger Causality (GC) test between HRV and BPts. Analyses were performed using two databases, of 9 and 14 subjects respectively. Experiments consisted of spontaneous breathing and a controlled breathing task (CBT). GC was tested over Intrinsinc Mode Functions of HRV derived from Empirical Mode Decomposition and BPts computed over α, ß and γ bands. Positive GC tests were observed through each experimental task, channels, IMFs, EEG band, and direction. The largest number of positive GC relationships were found from BPts to HRV when testing, higher EEG band and IMF with lower spectral content. Opposite direction achieves lower total counts, but more related with IMFs of higher spectral content. Its presence also suggests that some homeostatic condition alters the BPts course given its increment under the CBT. It is important to notice that in both cases γ band achieves larger values for almost all of the studied conditions. Suggesting that such band has an important influence over HRV, but alterations on breathing condition also produce changes on BPts evolution, suggesting that the closed loop for homeostatic control alters neural dynamics at cortical level.

Cognitive and spectral coherence of EEG alterations in resting state in children with chronic TBI / Alteraciones cognitivas y en la coherencia espectral del EEG en estado de reposo en niños con TCE crónico

Abstract 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. Method Cross-sectional study of 15 children with chronic TBI and 17 healthy children. The Neuropsychological Assessment of Children (Evaluación Neuropsicológica Infantil, ENI) was used and the resting activity of the EEG with eyes-closed was recorded. Offline, two-second epochs of the EEG of each participant were chosen and the spectral coherence was estimated in a range of 1.6 to 30 Hz. The cognitive performance between groups was compared with T-test/Mann-Whitney U Test and MANOVA for the coherence values. Results The TBI group showed a lower performance (p ≤ 0.05) in metalinguistic, visuospatial skills, attention, memory, non-verbal flexibility, planning, and organization. Differences (p ≤ 0.000) were found both inter and intrahemispherically in the spectral coherence between the groups, particularly on F1-F3 (95% CI: 0.543 - 0.557) over the whole frequency range and F3-C3 (95% CI: 0.503 - 0.515) in delta, theta, alpha2, and beta frequencies. Discussion and conclusión Our findings suggest alterations of hypo and hyper functional connectivity, particularly on the frontal and parietal lobes of both hemispheres, even after several years of a TBI. It is possible that a subtle difference in the degree of connectivity is crucial in the genesis or successful development of attentional, mnesic, executive, and visuospatial processes.

Resumen Introducción El TCE se asocia con alteraciones en la conectividad cortico-subcortical. Sin embargo, se ha prestado poca atención a las características clínicas y de conectividad funcional en pacientes pediátricos con TCE crónico. Objetivo Evaluar el desempeño cognitivo y la coherencia espectral de un grupo de niños con TCE en fase no aguda. Método Estudio transversal de 15 niños con TCE y 17 niños controles. Se empleó la Evaluación Neuropsicológica Infantil (ENI) y se registró la actividad en reposo del EEG con ojos cerrados. Fuera de línea, se eligieron épocas de 2 s del trazo de cada participante y se estimó la coherencia espectral en un rango de 1.6 a 30 Hz. Se comparó el rendimiento cognitivo entre los grupos con la prueba T/U-Mann de Whitney y MANOVA para los valores de coherencia. Resultados El grupo con TCE mostró un menor rendimiento (p ≤ 0.05) en habilidades metalingüísticas, visuoespaciales, atención, memoria, flexibilidad no verbal, planeación y organización. Se encontraron diferencias (p ≤ 0.000) en la coherencia espectral tanto inter como intrahemisférica entre los grupos. Particularmente, en F1-F3 (95%IC: 0.543 - 0.557) en todo el rango de frecuencias y F3-C3 (95%IC: 0.503 - 0.515) en delta, theta, alfa2 y beta. Discusión y conclusión Los resultados sugieren que distintas redes en estado de reposo muestran alteraciones de hipo e hiperconectividad funcional aun después de varios años de un TCE. Es probable que una sutil diferencia en el grado de conectividad sea determinante en la génesis o desarrollo exitoso de procesos atencionales, mnésicos, ejecutivos y visoespaciales.

Latency and amplitude changes in cognitive event related potentials due to hemodialysis.

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 $( \sim 50$ ms) and with larger amplitude $( \sim 0.128\mathrm {a}$.u.) after the treatment session. While only a limited sample of five patients is reported herein, the observed changes immediately after hemodialysis could be a sign of central nervous system alterations that are not clinically evaluated. Signs like these could entail an early indicator of possible evolution into some neuropathology.

Scenario Screen: A Dynamic and Context Dependent P300 Stimulator Screen Aimed at Wheelchair Navigation Control.

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 relevant landmarks, such as suitable paths, doors, windows, and wall signs. Other scenario stimulation screen features were green/blue stimulation marker color scheme, variable Interstimulus Interval, single marker stimulus mode, and optimized stimulus sequence generator. Eighteen able-bodied subjects participated in the experiment; 78% had no experience in BCI usage. A waveform feature analysis and a Mann-Whitney U test performed over the pairs of target and nontarget coherent averages confirmed that 94% of the subjects elicit P300 (p < .005) on this modified stimulator. Least Absolute Shrinkage and Selection Operator optimization and Linear Discriminant Analysis were utilized for the automatic detection of P300. For evaluation with unseen data, target detection was computed (median sensitivity = 1.00 (0.78-1.00)), together with nontarget discrimination (median specificity = 1.00 (0.98-1.00)). The scenario screen adequately elicits P300 and seems suitable for commanding a wheelchair even when users have no previous experience on the BCI spelling task.

Electroencephalographic Indicators in Default Mode, Habituation, and Visual-motor Association in Female College Students.

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 support diagnostic and rehabilitation processes. However, important differences seem to exist between men and women. Therefore, we aim to analyze EEG characteristics in a female sample. SUBJECTS AND METHODS: In the current study, EEG was recorded at rest with closed eyes before and during repeated photostimulations (RPh) and before (pre) and during association of RPh with switch pressing (VM-asso) in 70 female adults. EEG was analyzed using UAM/INR software, which removes artifacts, identifies corresponding signals, selects 20 samples (2-s) from each condition, applies Welch's periodogram to calculate and average the absolute power (AP; AAPs) of áµ¹, θ, α, and ß, before and during learning, and emits data to a spreadsheet. Differences in each condition were evaluated using non-parametric tests. RESULTS: The AAPs were different; in habituation, áµ¹ and θ increased significantly in fronto-frontal (FF) and frontocentral and decreased in the other leads. During association, they increased in FF and decreased in the other three regions. α AAP decreased in all leads except in FF during habituation, and the decrement was lower in the association. ß AAP increased in all leads during both learning conditions. CONCLUSION: The SP and the topographic distribution are descriptive parameters of habituation and VM-asso; we propose them as EEG indicators.

Correlación del funcionamiento ejecutivo y la potencia absoluta del EEG en niños / Correlation of excutive functioning and the absolute power of the EEG in children

RESUMEN: 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: Investigación transversal correlacional en 30 niños (8.6 ± 1 años). Se realizó el EEG con ojos cerrados y análisis de derivaciones bipolares. Con la transformada de Fourier se calculó la PA en el espectro de 1.6-30 Hz. Se aplicó la batería NEUROPSI Atención y Memoria y se calculó el Indice de Atención y Funciones Ejecutivas (IAFE). En función de éste, se comparó la PA con Kruskal-Wallis y valor Z, coeficiente de Spearman para la correlación con las subpruebas. Resultados: Los niños con alteraciones severas ( x - = 63 ± 8 IC 95% [57.2, 68.5]) tuvieron mayor PA delta en F1F7, P301 y P402, así como valores Z cercanos a 2 DE en F7T3, F3C3 y F8T4 en frecuencias lentas. Las correlaciones fueron significativas (rho, p ≤ .05) entre el IAFE con la PA delta en P301 (-.57), P402 (-.43) y T5O1 (-.37); con PA alfa principalmente en zonas fronto-temporo-parieto-occipitales izquierdas. La puntuación en Detección Visual y Fluidez Semántica se relacionó con la PA alfa. Discusión y conclusión: El rendimiento en actividades de FE es diferente en relación con la PA delta frontal y parietal. Existe una relación inversa entre la PA delta y alfa en reposo con la atención y fluidez (245/250).

ABSTRACT: Introduction: The resting EEG power is considered as a robust marker of brain function; however, a few studies have associated it to a specific function. Objective: To analyze the relationship between EEG absolute power (AP) with performance on tasks of executive functioning in children. Method: Correlational cross-sectional study of 30 children (8.6 ± 1 year). EEG was performed with eyes closed and bipolar leads. With the Fourier transform AP was calculated in the spectrum of 1.6, 30 Hz. NEUROPSI Attention and Memory was applied and the Index of Attention and Executive functions (IAFE) was calculated. Based on this, the AP was compared with Kruskal-Wallis and the Z value, Spearman coefficient for correlation with the subtests. Results: Children with severe impairment ( x - = 63 ± 8 CI 95% [57.2, 68.5]) had higher delta AP (α ≤ .05) in F1F7, P301 and P402, and Z values near 2 SD in F7T3, F3C3 and F8T4 at slow frequencies. Correlations were significant between the IAFE and delta AP P301 (-.57), P402 (-.43) and T5O1 (-.37); with AP alpha mainly on left fronto- temporo - parietal- occipital areas. The score in Visual Detection and Semantic Fluency inversely related to AP alpha frequency. Discussion and conclusion: Performance on tasks of executive functioning is different in relation to the frontal and parietal AP delta. There is an inverse relationship between AP delta and alpha at rest with attention and verbal fluency.

P300 Detection Based on EEG Shape Features.

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 accurately detect P300s; we also define a method to find a template that best represents, for a given electrode, the subject's P300 based on his/her own acquired signals. Our experiments with 21 subjects showed that the SWLDA's performance using our shape-feature vector was 93%, that is, 10% higher than the one obtained with BCI2000-feature's vector. The shape-feature vector is 34-dimensional for every electrode; however, it is possible to significantly reduce its dimensionality while keeping a high sensitivity. The validation of the calibration algorithm showed an averaged area under the ROC (AUROC) curve of 0.88. Also, most of the subjects needed less than 15 trials to have an AUROC superior to 0.8. Finally, we found that the electrode C4 also leads to better classification.

Evolución de la potencia absoluta, relativa e índices de ritmos electroencefalográficos en estudiantes de primaria, licenciatura y maestría / Evolution of absolute and relative power and indices of electroencephalographic rhythms in elementary, college, and graduate students

Resumen: 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 en delta (δ), theta (θ), alfa 1 (α1), alfa 2 (α2), beta 1 (β1) y beta 2 (β2) y su topografía en los hemisferios cerebrales de niños, jóvenes y adultos para establecer indicadores EEGc. MÉTODO: Se estudiaron tres grupos de 16 participantes: niños en primaria (GN), estudiantes de licenciatura (GL) y de maestría (GM). Los padres y los participantes otorgaron su consentimiento. En el aparato Nicolet se registró el EEG utilizando el sistema 10/20. Se analizaron muestras bipolares, con T Fourier se obtuvo la potencia absoluta (PA), se calculó su promedio (PPA), la potencia relativa (PR) y los índices de frecuencias lentas/rápidas. Las diferencias se evaluaron con Kruskal Wallis y la comparación de Dunnet para sub-grupos. RESULTADOS: El PPA de seis frecuencias fue mayor en GN que en GL y GM. En éstos fue similar con excepciones, relacionadas con la distribución topográfica. El índice δ/α fue mayor en GN con particular distribución topográfica y θ/α fue más variable. La PR de α fue mayor en GL y GM comparados con GN, la de θ y de δ en algunas derivaciones, fueron mayores en el GN. DISCUSIÓN Y CONCLUSIÓN: En la maduración cerebral disminuye la PA debido a la integración de más ensambles glío-neuronales, que presentan mayor asimetría en determinada frecuencia. Estos perfiles establecen indicadores para compararlos con futuros registros EEG.

Abstract: ANTECEDENTS: Cerebral function results from the electrical activity in glial-neuronal networks, integrated proactively through sensory, motor, and regulating interactions. These networks oscillate since early life and are modulated by diverse maturation factors, including educational processes. OBJECTIVE: To identify the power spectrum separated in delta (δ), theta (θ), alfa 1 (α1), alfa 2 (α2), beta 1 (β1) y beta 2 (β2), and their topography in cerebral hemispheres of children, youngsters, and adults to establish qEEG indicators. METHOD: We studied three groups of 16 participants each: elementary school children (CG), undergraduate students (UG), and graduate students (GG). Parents and participants granted their consent. The EEG was recorded (Nicolet) following the 10/20 system. Bipolar samples were analyzed. Absolute power (AP) was obtained with Fourier transform; its average (AAP) relative power (RP), and slow/fast frequencies and indices were calculated. Differences were assessed with Kruskal Wallis and Dunnet's comparison for subgroups. RESULTS: The AAP of six frequencies was higher in CG than in UG and GG. Frequencies were similar with exceptions correlating with topographic distribution. The δ/α index was higher in CG with a particular topographic distribution, θ/α varied more. RP of α was higher in UG and GG than in CG; that of θ and δ were higher in some leads of CG. DISCUSSION AND CONCLUSION: During cerebral maturation, AP diminishes due to integration of more glial-neuronal ensembles, presenting greater asymmetry in a giving frequency. These profiles establish indicators for comparison with future EEG recordings.

Evaluation of the continuous detection of mental calculation episodes as a BCI control input.

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 analyzed using sliding windows of 2s length. The experimental population was comprised of fifteen healthy subjects who participated in three sessions on different days. The features used for the classification process were the power spectral density over the beta band ([14-35] Hz) and the scaling exponent obtained via detrended fluctuation analysis. Both indices were estimated over four channels, specifically selected for each subject. The performance was evaluated using the Area Under the ROC Curve (AUC) by measuring the overall classification performance of each experimental session with a cross-validation procedure, and by transferring the model obtained from one session to the others called inter Session Validation (iSV). The best AUC values computed in each cross-validation session were: 0.87±0.067, 0.89±0.056 and 0.88±0.040 respectively; and the iSV provided a value of 0.67±0.122. These high values indicate that a mental calculation paradigm and a combination of features can efficiently control a BCI system. Notwithstanding that several days passed between sessions, the AUC mean value estimated for the iSV is similar to the performance of a motor imagery-BCI calibrated on the same day.

Description and classification of normal and pathological aging processes based on brain magnetic resonance imaging morphology measures.

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 group was segmented and two indices were measured for several structures: three-dimensional DC and normalized volumes (NVs). The discrimination power of these indices was determined by means of the area under the curve (AUC) of the receiver operating characteristic, where the proposed compactness index showed an average AUC of 0.7 for HC versus MCI comparison, 0.9 for HC versus AD separation, and 0.75 for MCI versus AD groups. In all cases, this index outperformed the discrimination capability of the NV. Using selected features from the set of DC and NV measures, three support vector machines were optimized and validated for the pairwise separation of the three classes. Our analysis shows classification rates of up to 98.3% between HC and AD, 85% between HC and MCI, and 93.3% for MCI and AD separation. These results outperform those reported in the literature and demonstrate the viability of the proposed morphological indices to classify different aging stages.

Automatic error detection in the clinical measurement of gastric impedance spectra.

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 be incorporated to potentially avoid the loss of measurements. This paper presents an algorithm developed to detect errors due to bad connection, bad location or bad contact of the electrode probe. A labeled database with 20,908 sets of 92 spectral measurements each, obtained from critically ill patients was used as training/testing data. To reduce the dimensionality, the database was resized by dividing the spectral range into four bands, and then by computing mean and standard deviation in magnitude, phase, resistance and reactance for each band and measurement. Initial exploration into the data space was performed by k-means clustering, establishing the number of classes. Sequential Forward Selection was performed to determine best features from the reduced data set. Finally, Support Vector Machine classifiers were designed in a one-vs-rest hierarchical scheme to classify the quality of the spectra. Each classifier gave a hit rate greater than 95% and an area under the relative operating characteristic curve of 0.99. In a validation run with cardiac surgery and intensive care unit patient spectra, the error rates were 2.3% and 8.4% respectively.

Assisted diagnosis of attention-deficit hyperactivity disorder through EEG bandpower clustering with self-organizing maps.

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, among other brain disorders. This paper focuses in the design and implementation of a computer-aided diagnostic tool for establishing the likelihood of presence of Attention-Deficit Hyperactivity Disorder in children, out of routine electroencephalographic recordings obtained during a specific visual stimulation protocol. Classical bandpower features from multiple differential recordings are computed and used as features in a classifier built from a cooperative ensemble of labeled self-organizing maps. Classification accuracy of the proposed system is 0,7 ± 0,11, as estimated from unseen data, a result that points to the idea that such a quantitative diagnostic aid could adequately support the diagnostic task of a clinical expert.

Cambios del EEG por habituación y condicionamiento en niños de tres a 15 años que acuden al Instituto Nacional de Rehabilitación (INR) / EEG changes induced by habituation and conditioning in 3- to 15-year-old children attending the Instituto Nacional de Rehabilitación

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 event-related synchronization or event-related desynchronization, ERD or ERS) propagated in the specific and unspecific cortex are added to the changes elicited by the responses and to the new signals originated by those same responses, bringing about perception. Diverse factors can alter these glialneuronal circuits, producing alterations in attention processes (ADD) and in the integration with their meaning. The inability to identify signals and integrate correct coordinated responses leads to deficiencies in responding to the environment and to associated morbidities that are added to ADD. ADD and its associated morbidities cause high social and economic impacts and, even more so, because of their persistence into adolescence and adulthood. Therefore, highly accurate diagnostic procedures are needed for these diseases. According to the CIE-10, in the clinical setting symptoms are analyzed without studying the neuro-developmental and neuro-degenerative signs that identify alterations in neuronal circuits. As is known, behavior (including motivation, memory, thoughts) results from the Central Nervous System (CNS) activity, and the EEG records the electrical activity of neurons and synapses of the cerebral cortex, where cognitive processes are most likely to take place. To establish more accurate diagnostic procedures for ADD, we are integrating an electronic database, considering the intensity and cerebral distribution of theta (θ), alpha (α), and beta (β) rhythms. We propose that the ERD of α and β reflects a cortical activation that gives rise to sensory-motor coordination processes. The first stimulations induce ERD, and their repetitions produce its decrement (ERS): ERD habituation. In addition, this ERD to ERS change might be reversed when giving meaning to the stimulation. We present herein the changes in θ, α, and β rhythms induced by repeated photostimulation (RPS), with the same characteristics, that, when presented, requires the subject to press a knob. Hundred-twenty-four children were studied at the Instituto Nacional de Rehabilitación (INR, for its initials in Spanish) in Mexico City. Children were of either gender and aged from 3 to 15 years, separated in four groups of 3-year intervals. During clinical exploration, we searched for possible delays in physical-emotional-intellectual development, epilepsy, and medical or psychological treatments during the last six months, which were considered exclusion factors. Parents were briefed on the study, explaining them that the procedure had a low-risk nature and allowed for the analyzis of the electrical activity of the brain. Once having understood and accepted the procedure, they signed the informed consent form prepared by the institution. Children were explained <> work and that the procedure caused no pain at all. They were asked to close their eyelids during the recordings, and to remain as motionless as possible. The exclusion factors left a sample of 94 children for the habituation analysis and of 47 for the simple conditioning procedures. The EEG was recorded in dorsal decubitus position, with a digital 24-channel electroencephalograph, according to the 10/20 international system. In addition, we recorded eye movements and the EKG. After 5-min recordings with closed eyelids, photo-stimulation was started at 5 flashes per second during 2s, repeated 20 times (RPS), at 21 to 25 sec. intervals. After finishing the series, 5 min rest were provided, and then a round device with a knob was placed in the children's hands, telling them to press the knob at the start of the RPS and to release it at the end. Analyses were performed with 1.6 to 40 Hz bandwidth filters. From the bipolar leads, samples recorded 2 sec. before, during, and after the 1st, 5th, 10th, 20th associations (PS-knob pressing) were manually chosen. For conditioning analyses, we also measured the response latency. The Fourier's FT was applied to the samples and the absolute potency (AP) was calculated for θ (4.0 to 7.5 Hz), α (8.0 to 12.5 Hz), and β (13 to 20 Hz). The average of these frequencies was obtained for each hemisphere (Right, RH; Left, LH) and for both (BH). Wilcoxon's test for related samples was used with (α > 0.05 as significant. Analyses of the AP of the three frequencies in all children revealed a background activity below 10 µV². The first RPS produced a decrease in the AP of θ and α, with an increase in β in BH. At the 5th RPS, θ and α continued to decrease along with an increase in β. At the 10th RPS, θ and α decreased less but the increase in β persisted. At the 15th RPS, θ continued to decrease but α increased in the LH and decreased somewhat in the RH, whereas β continued its increase in BH. At the 20th RPS, the AP of θ and a decreased in BH, but the difference was smaller than that recorded during the previous RPS. The AP of β continued to increase in BH. The most relevant aspects are: a) in G-1 (children aged 3 to 6 years), the AP of the three frequencies is higher, predominating θ, which is twice the magnitude of that of the whole group; b) the 1st PS produced an increase in the AP of all three frequencies, which was not recorded in the other groups (children aged 6.5 to 15 years); c) in G-4 (children 12.5 to 15 years of age), the 1st and 5th PS produced a clear diminution in the AP of θ and a (ERD), which was smaller at the 10th RPS and reversed at the 15th and 20th RPS (ERS). After indicating to the children that with each RPS they would have to press a knob, the background activity increased to 12 µV². During the 1st association (assoc), the AP of θ and α decreased with a slight decrease in β; the response latency was 930 ms. At the 5th assoc, θ decreased together with a small increase in a and β, and the response latency decreased to 750 ms. On the 10th and 15th assoc, the three frequencies increased and the latency decreased to 650 and 640 ms, respectively. On the 20th assoc, the AP increase of each rhythm was smaller, and the latency increased to 750 ms. The EEG analysis per group revealed a higher AP for 0 in the smaller children that decreased along increasing age together with a relative increase in a, which reached its maximal value in G-4. In the four groups, the RPS induced an undulating tendency towards a decrease in the EEG desynchronization that represents habituation, being more noticeable in G-4. Although the reached synchronization level did not reflect a better inhibition, as described in adults, it suggested that, in these children, the inhibitory activity on sensory control has not yet developed completely. Another important finding is that in G-1, the 1st RPS induced and increase in θ and α that was not observed in the other groups.

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 alterar la organización de esos circuitos glioneuronales produciendo trastornos de la atención (TDA), de su integración con su significado, lo que regula el tipo e intensidad de respuestas adecuadas al contexto social. La discapacidad de estas funciones genera comorbilidades que se suman al TDA. Estas enfermedades son de alto impacto socio-económico y cultural y lo son más cuando persisten en la adolescencia y la adultez. Por esto es necesario desarrollar metodologías diagnósticas de alta precisión. Actualmente se acepta que la conducta integral resulta de la actividad del Sistema Nervioso (SN). El EEG registra la actividad eléctrica de las neuronas de la corteza cerebral donde se realizan procesos cognitivos. Para caracterizar el EEG estamos integrando, en una base de datos electrónica, la intensidad y distribución cerebral de los ritmos delta (Δ), theta (θ), alfa (α) y beta (β). Proponemos que la desincronización (DRE) refleja la activación cortical, base de los procesos de coordinación sensoriomotora. Las primeras estimulaciones producen DRE que, al repetirse, disminuyen la habituación de la DRE. Además, es posible que se invierta este cambio DRE a sincronización (SRE) al darle significado a la misma estimulación. En este trabajo se presentan los cambios de θ, α y β ante la fotoestimulación repetida y cuando el sujeto tiene que presionar un botón al inicio de dicha estimulación. Sujetos y método Se atendieron 124 niños, de tres a 15 años, separados en cuatro grupos con intervalos de tres años. En el interrogatorio clínico se indagó el posible retraso del desarrollo físico-emocional-intelectual, de epilepsia o tratamientos médicos o psicológicos convirtiéndose en factores de exclusión. A los niños, delante de los padres, se les explicó cómo funciona su cerebro, que el estudio no produce dolor, que estarán acostados con los párpados cerrados (OC), permaneciendo lo más inmóviles posible, los padres al comprenderlo y aceptar firmaron la autorización. Los factores de exclusión dejaron 94 niños para análisis de habituación y 47 para condicionamiento. El EEG se registró utilizando los montajes bipolares A-P parasagitales del sistema internacional 10/20, además se registraron los movimientos oculares y el EKG. El sujeto con OC se fotoestimulaba 20 veces (FR a 5/s X 2s). Después de 5 min de terminada la serie se les ponía en la mano dominante un aditamento con un botón, indicándoles que lo apretaran al inicio de cada FR y lo liberaran al terminarse (asociaciones). El análisis se efectuó con filtro de 1.6 y 40 Hz. Seleccionando manualmente, de la 1era, 5ª, 10ª 15ª y 20ª FR muestras de registros bipolares de 2s antes, durante y después. Para el condicionamiento se agregó la medición de la latencia de la respuesta. Se aplicó la TRF y se calculó la Potencia Absoluta (PA) de θ (4.0-7.5 Hz), α (8.0-1 2.5 Hz) y β (1 3-20 Hz), se obtuvo el promedio en cada hemisferio (HI, HD) y de ambos (AH). Se utilizó la prueba de Wilcoxon con α >0.05. Resultados El promedio de la PA de la actividad de fondo, de todos los niños, está por debajo de 10 µV². La 1era FR disminuye la PA de θ y de α con incremento de β en AH. En la 5ª FR disminuye θ y α con incremento de β. En la 10° disminuye menos θ y α, persistiendo el incremento de β. En la 15ª continúa la disminución de θ, pero aumenta α en el HI y disminuye en el HD. En AH se incrementa β. En la 20° se vuelve a disminuir θ y α en AH; sin embargo, el rango de la diferencia es menor que el registrado en anteriores FR. La PA de β sigue aumentando en AH. El análisis por grupo muestra que en el G-1, la PA de los tres ritmos es mayor, con predominio de θ, siendo del doble del grupo total. En la 1era FR incrementa la PA de los 3 ritmos, lo cual no se registró en los otros grupos. En el G-4, la 1era y 5ª FR disminuyen la PA de θ y de α (DRE), siendo menor la disminución en la 10ª y se invierte en la 1 5ª y 20ª (SER). Consecutivamente a la explicación de que con la FR deben presionar el botón, se incrementa el promedio de la PA a 12 µV² en promedio de la muestra. En la 1era Aso disminuye la PA de 6 y de θ incluyendo una discreta disminución de β, la latencia es de 930 ms. En la 5ª Aso disminuye θ con pequeño incremento de θ y α y la latencia es de 750 ms. En la 10ª y 15ª continúa el incremento de los tres ritmos y la latencia disminuye a 650 y 640 ms, respectivamente. Mientras que en la 20ª el incremento de la PA de cada ritmo es menor y la latencia se incrementa a 750 ms.

Robust nonparametric segmentation of infarct lesion from diffusion-weighted MR images.

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 estimation. The quality of the class boundaries is improved by including an edge confidence map, that is the confidence of truly being in the presence of a border between adjacent regions. The adjacency graph, that is constructed with the label regions, is analyzed and pruned to merge adjacent regions. The method was applied to real images, keeping all parameters constant throughout the process for each data set. The combination of region segmentation and edge detection proved to be a robust automatic technique of segmentation from DWI images of cerebral infarction regions in acute ischemic stroke. In a comparison with the reference infarct lesions segmentation, the automatic segmentation presented a significant correlation (r=0.935), and an average Tanimoto index of 0.538.

BCI meeting 2005--workshop on technology: hardware and software.

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 focus technical requirements on the users' needs and the need for consistent standards in BCI research.

Data-driven brain MRI segmentation supported on edge confidence and a priori tissue information.

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 between adjacent regions; an adjacency graph is then constructed with the labeled regions, and analyzed and pruned to merge adjacent regions. In order to assign image regions to a cerebral tissue type, a spatial normalization between image data and standard probability maps is carried out, so that for each structure a maximum a posteriori probability criterion is applied. The method was applied to synthetic and real images, keeping all parameters constant throughout the process for each type of data. The combination of region segmentation and edge detection proved to be a robust technique, as adequate clusters were automatically identified, regardless of the noise level and bias. In a comparison with reference segmentations, average Tanimoto indexes of 0.90-0.99 were obtained for synthetic data and of 0.59-0.99 for real data, considering gray matter, white matter, and background.