Effect of time windows in LSTM networks for EEG-based BCIs.

People with impaired motor function could be helped by an effective brain-computer interface (BCI) based on a real-time electroencephalogram (EEG) and artificial intelligence algorithms. However, current methodologies for interpreting patient instructions from an EEG are not accurate enough to be completely safe in a real-world situation , where a poor decision would place their physical integrity at risk, such as when traveling in an electric wheelchair in a city. For various reasons, such as the low signal-to-noise ratio of portable EEGs or the effects of signal contamination (disturbances due to user movement, temporal variation of the features of EEG signals, etc.), a long short-term memory network (LSTM) (a type of recurrent neural network) that is able to learn data flow patterns from EEG signals could improve the classification of the actions taken by the user. In this paper, the effectiveness of using an LSTM with a low-cost wireless EEG device in real time is tested, and the time window that maximizes its classification accuracy is studied. The goal is to be able to implement it in the BCI of a smart wheelchair with a simple coded command protocol, such as opening or closing the eyes, which could be executed by patients with reduced mobility. Results show a higher resolution of the LSTM with an accuracy range between 77.61 and 92.14% compared to traditional classifiers (59.71%), and an optimal time window of around 7 s for the task done by users in this work. In addition, tests in real-life contexts show that a trade-off between accuracy and response times is necessary to ensure detection.

Mediterranean dietary pattern in pregnant women and offspring risk of overweight and abdominal obesity in early childhood: the INMA birth cohort study.

BACKGROUND: Animal models have suggested that maternal diet quality may reduce offspring obesity risk regardless of maternal body weight; however, evidence from human studies is scarce. OBJECTIVE: The aim of this study was to evaluate associations between adherence to the Mediterranean diet (MD) during pregnancy and childhood overweight and abdominal obesity risk at 4 years of age. METHODS: We analysed 1827 mother-child pairs from the Spanish 'Infancia y Medio Ambiente' cohort study, recruited between 2003 and 2008. Diet was assessed during pregnancy using a food frequency questionnaire and MD adherence by the relative Mediterranean diet score (rMED). Overweight (including obesity) was defined as an age-specific and sex-specific body mass index ≥85th percentile (World Health Organization referent), and abdominal obesity as a waist circumference (WC) >90th percentile. Multivariate adjusted linear and logistic regression models were used to evaluate associations between pregnancy rMED and offspring overweight and abdominal obesity. RESULT: There was no association between rMED and body mass index z-score, whereas there was a significant association between higher adherence to MD and lower WC (ß of high vs. low rMED: -0.62 cm; 95% confidence interval: -1.10, -0.14 cm, P for trend = 0.009). CONCLUSION: Pregnancy adherence to the MD was not associated with childhood overweight risk, but it was associated with lower WC, a marker of abdominal obesity.

Scopolamine effects on functional brain connectivity: a pharmacological model of Alzheimer's disease.

Scopolamine administration may be considered as a psychopharmacological model of Alzheimer's disease (AD). Here, we studied a group of healthy elderly under scopolamine to test whether it elicits similar changes in brain connectivity as those observed in AD, thereby verifying a possible model of AD impairment. We did it by testing healthy elderly subjects in two experimental conditions: glycopyrrolate (placebo) and scopolamine administration. We then analyzed magnetoencephalographic (MEG) data corresponding to both conditions in resting-state with eyes closed. This analysis was performed in source space by combining a nonlinear frequency band-specific measure of functional connectivity (phase locking value, PLV) with network analysis methods. Under scopolamine, functional connectivity between several brain areas was significantly reduced as compared to placebo, in most frequency bands analyzed. Besides, regarding the two complex network indices studied (clustering and shortest path length), clustering significantly decreased in the alpha band while shortest path length significantly increased also in alpha band both after scopolamine administration. Overall our findings indicate that both PLV and graph analysis are suitable tools to measure brain connectivity changes induced by scopolamine, which causes alterations in brain connectivity apparently similar to those reported in AD.

Nonlinear dynamical analysis of the interdependence between central and autonomic nervous systems in neonates during sleep.

We present in this paper the results of a study of the interdependence between signal characteristic of the central nervous system (electroencephalography) and the autonomic nervous system (heart rate and respiration) in human neonates during sleep. By using methods from nonlinear dynamical systems theory, we show that there exist significant differences in this interdependence with the sleep stage and the electrodes considered. This paves the way for the application of this methodology in clinical practice to study pathologies where this interdependence is altered, such as the sudden infant death syndrome.

Neuronal activity in the substantia nigra in the anaesthetized rat has fractal characteristics. Evidence for firing-code patterns in the basal ganglia.

Current models of the basal ganglia assume a firing-rate code for information processing. We have applied five complementary computing methods to assess firing patterns in 188 cells of the substantia nigra in the anaesthetized rat. Fractal firing activity was found in 100% of nigral cells projecting to the superior colliculus, in 51% of cells projecting to the thalamus and in 33% of cells projecting to the pedunculopontine nucleus, but was practically absent in dopaminergic nigrostriatal neurons (3%). The finding of fractal firing patterns may lead to a better understanding of the normal operational mode and pathological manifestations of the basal ganglia.

Effective detection of coupling in short and noisy bivariate data.

In the study of complex systems, one of the primary concerns is the characterization and quantification of interdependencies between different subsystems. In real-life systems, the nature of dependencies or coupling can be nonlinear and asymmetric, rendering the classical linear methods unsuitable for this purpose. Furthermore, experimental signals are noisy and short, which pose additional constraints for the measurement of underlying coupling. We discuss an index based on nonlinear dynamical system theory to measure the degree of coupling which can be asymmetric. The usefulness of this index has been demonstrated by several examples including simulated and real-life signals. This index is found to effectively disclose the nature and the degree of interactions even when the coupling is very weak and data are noisy and of limited length; by this way, new insight into the functioning of the underlying complex system is possible.

Long-range synchrony in the gamma band: role in music perception.

Synchronization seems to be a central mechanism for neuronal information processing within and between multiple brain areas. Furthermore, synchronization in the gamma band has been shown to play an important role in higher cognitive functions, especially by binding the necessary spatial and temporal information in different cortical areas to build a coherent perception. Specific task-induced (evoked) gamma oscillations have often been taken as an indication of synchrony, but the presence of long-range synchrony cannot be inferred from spectral power in the gamma range. We studied the usefulness of a relatively new measure, called similarity index to detect asymmetric interdependency between two brain regions. Spontaneous EEG from two groups-musicians and non-musicians-were recorded during several states: listening to music, listening to text, and at rest (eyes closed and eyes open). While listening to music, degrees of the gamma band synchrony over distributed cortical areas were found to be significantly higher in musicians than non-musicians. Yet no differences between these two groups were found at resting conditions and while listening to a neutral text. In contrast to the degree of long-range synchrony, spectral power in the gamma band was higher in non-musicians. The degree of spatial synchrony, a measure of signal complexity based on eigen-decomposition method, was also significantly increased in musicians while listening to music. As compared with non-musicians, the finding of increased long-range synchrony in musicians independent of spectral power is interpreted as a manifestation of a more advanced musical memory of musicians in binding together several features of the intrinsic complexity of music in a dynamical way.

Interdependencies in the spontaneous EEG while listening to music.

We studied the patterns of interdependency between different brain regions during the performance of higher cognitive functions. Our goal was to check the existence in these patterns of both task-related differences (e.g. listening to music vs. rest) and training-related differences (musicians vs. non-musicians). For this purpose, a non-linear measure, called similarity index (S.I.), was used to detect asymmetric interdependencies between different brain regions by means of EEG signals. Relatively active and passive regions of the brain were found where the degree of activity was represented by excited degrees of freedom. The S.I. obtained during listening to different kinds of music was compared statistically with the S.I. with eyes closed, and significant changes (P< or = 0.05) were entered into schematic brain maps. A topographical representation of the S.I. yielded differences in the interdependency while performing different cognitive tasks. The results demonstrate the occurrence of task-related differences in both groups of subjects. Furthermore, subjects with musical training possessed significantly higher degrees of interdependencies than such without musical training while listening to music but not to text. We conclude that the new measure can be successfully applied for studying the dynamical co-operation between cortical areas during higher cognitive functioning.

Detection and sources of nonlinearity in the variability of cardiac R-R intervals and blood pressure in rats.

Beat-to-beat R-R interval (RRV) and systolic blood pressure (SPV) variability signals were obtained from unrestrained rats in baseline and under different pharmacological treatments. The origin and extent of the nonlinearity in both signals, as well as their degree of mutual coupling, was estimated using measurements from the correlation integral (CI) and recurrence quantification analysis (RQA). After the respiratory component of baseline signals was removed, the nonlinearity was lower in the RRV and disappeared in the SPV. This also decreased the RRV-SPV coupling. The nonlinearity of RRV was also reduced after atropine, and the nonlinearity of SPV was strengthened after prazosin and N(omega)-monomethyl-L-arginine (L-NMMA). Atropine and prazosin decreased CI measures of both signals, whereas propranolol, phenylephrine, and L-NMMA decreased only those of SPV. RQA indexes of RRV increased after atropine and decreased after propranolol, whereas the reverse occurred for the RRV-SPV coupling. These results suggest that: 1) the nonlinearity of RRV appears to be very dependent on the parasympathetic activity, whereas that of SPV seems to come from its respiratory component through a nonneural pathway; 2) respiratory component appears to be involved, through the parasympathetic system, in the RRV-SPV coupling; and 3) CI and RQA measures seems to be useful in assessing autonomic mediation of RRV and RRV-SPV coupling.

Relationship between cortical electrical and cardiac autonomic activities in the awake lizard, Gallotia galloti.

ECG and EEG signals were simultaneously recorded in lizards, Gallotia galloti, both in control conditions and under autonomic nervous system (ANS) blockade, in order to evaluate possible relationships between the ANS control of heart rate and the integrated central nervous system activity in reptiles. The ANS blockers used were prazosin, propranolol, and atropine. Time-domain summary statistics were derived from the series of consecutive R-R intervals (RRI) of the ECG to measure beat-to-beat heart rate variability (HRV), and spectral analysis techniques were applied to the EEG activity to assess its frequency content. Both prazosin and atropine did not alter the power spectral density (PSD) of the EEG low frequency (LF: 0.5-7.5 Hz) and high frequency (HF: 7.6-30 Hz) bands, whereas propranolol decreased the PSD in these bands. These findings suggest that central beta-adrenergic receptor mechanisms could mediate the reptilian waking EEG activity without taking part any alpha(1)-adrenergic and/or cholinergic receptor systems. In 55% of the lizards in control conditions, and in approximately 43% of the lizards under prazosin and atropine, a negative correlation between the coefficient of variation of the series of RRI value (CV(RRI)) and the mean power frequency (MPF) of the EEG spectra was found, but not under propranolol. Consequently, the lizards' HRV-EEG-activity relationship appears to be independent of alpha(1)-adrenergic and cholinergic receptor systems and mediated by beta-adrenergic receptor mechanisms.

Nonlinear, fractal, and spectral analysis of the EEG of lizard, Gallotia galloti.

Electroencephalogram (EEG) from dorsal cortex of lizard Gallotia galloti was analyzed at different temperatures to test the presence of fractal or nonlinear structure during open (OE) and closed eyes (CE), with the aim of comparing these results with those reported for human slow-wave sleep (SWS). Two nonlinear parameters characterizing EEG complexity [correlation dimension (D2)] and predictability [largest Lyapunov exponent (lambda(1))] were calculated, and EEG spectrum and fractal exponent beta were determined via coarse graining spectral analysis. At 25 degrees C, evidence of nonlinear structure was obtained by the surrogate data test, with EEG phase space structure suggesting the presence of deterministic chaos (D2 approximately 6, lambda(1) approximately 1. 5). Both nonlinear parameters were greater in OE than in CE and for the right hemisphere in both situations. At 35 degrees C the evidence of nonlinearity was not conclusive and differences between states disappeared, whereas interhemispheric differences remained for lambda(1). Harmonic power always increased with temperature within the band 8-30 Hz, but only with OE within the band 0.3-7.5 Hz. Qualitative similarities found between lizard and human SWS EEG support the hypothesis that reptilian waking could evolve into mammalian SWS.

Interhemispheric differences in awake and sleep human EEG: a comparison between non-linear and spectral measures.

Interhemispheric differences in the EEG of nine healthy right-handed human subjects (C3 vs. C4 derivations) were investigated during resting wake with closed eyes (CE) and sleep stages I, II, III, IV and REM. The harmonic power spectral density within the EEG main spectral bands, the fractal (Dr) and the correlation (D2) dimension as well as the largest Lyapunov exponent (lambda1) of both hemispheres were compared. In addition, the relationships between non-linear and spectral measures were analyzed. Dr, D2, lambda1 and the power in alpha band exhibited interhemispheric differences during waking, the values from the right hemisphere (RH) being higher than those of the left (LH) except for lambda1. During slow wave sleep (SWS), non-linear parameters detected opposite EEG asymmetries (D2 in stage III and lambda1 in stage IV) to those found in the other behavioural stages. In addition, both D2 and lambda1 were correlated (negatively) with the power in the delta band, but lambda1 was also correlated (positively) with the power in the alpha and beta bands. In conclusion, RH appears to be more complex though more predictable than the LH during CE and sleep stages I and II, these characteristics changing to the LH during SWS.

Non-linear behaviour of human EEG: fractal exponent versus correlation dimension in awake and sleep stages.

The question of whether the finite values of the correlation dimension (D2), used as an index of EEG complexity are due to its chaotic nature or they reflect its behaviour as linearly-correlated noise, remains open. This report aims at clarifying this by measuring D2 and analysing the non-linear nature of EEG through the method of surrogate data as well as by calculating the fractal exponent (beta) via coarse graining spectral analysis (CGSA) in nine adult subjects during waking and sleep states. The results show that even if it is possible to get an estimation of D2 in all states, non-linear structure appears to be present only during slow wave sleep (SWS). EEG exhibits random fractal structure with 1/f(-beta) spectrum (1 < beta < 3) and a negative linear correlation between D2 and beta in all states except during SWS. In consequence, in those states, finite D2 values could be attributed to the fractal nature of EEG and not to the presence of low-dimensional chaos, and therefore, it the use of beta would be more appropriate to describe the complexity of EEG, due to its lower computational cost.

Histological changes mimicking papillary carcinoma following fine needle aspiration of the thyroid gland.

A puzzling artifact caused by previous fine needle aspiration of the thyroid in a 26 year-old woman is reported. The lesion, which mimicked a papillary microcarcinoma, was seen into a follicular adenoma with focal oncocytic changes. The literature concerning histological changes following aspiration cytology in the thyroid and other organs is reviewed. These morphologic changes (notably in the thyroid gland), can be varied and should always be kept in mind in order to avoid misdiagnoses.

Small intestinal stromal tumour with skeinoid fibers. Immunohistochemical study of two cases with CD 34 expression.

The presence of the so-called "skeinoid fibers" in stromal tumours of the gastrointestinal tract is a rare event. The exact origin of this puzzling group of neoplasms still remains controversial. Despite all, the recognition of this histologic feature in routine practice is important for its presence seems to carry histogenetic implications. The authors report the histopathologic findings of two of such cases both occurring in the jejunum of a male aged 48 and a woman, 64. Their positivity with CD 34 antigen is enhanced, for this peculiar immunophenotype help to distinguish them from other stromal tumors in the small bowel. Additionally, the literature is reviewed and commented.

Well differentiated neuroendocrine carcinoma of the breast. A case report.

A neuroendocrine breast carcinoma occurring in a 79 year-old woman is presented. The case presented typically as a single nodule in the upper and outer quadrant of her right breast and showed a pure histology consisting exclusively of organoid nests of well differentiated cells that mimicked those of carcinoid tumors of the lung. The literature is briefly reviewed and commented. In the light of this review, we conclude that the issue of carcinomas with neuroendocrine differentiation in breast pathology is controversial and its terminology somewhat debatable.

Localized fibrous tumor of the pleura. Report of two cases with immunohistochemical study.

The light microscopy and immunohistochemical findings of two new cases of localized fibrous tumor of the pleura are reported. Both cases remained asymptomatic. One of them was incidentally found in a 69 year-old male during a thoracotomy for adenocarcinoma of the lung. The other was discovered in a 51 year-old woman in the course of a routine chest X-ray. Bundles of tightly packed benign fibroblasts within a collagen-rich stroma were the histologic hallmark. Bizarre cells and prominent sclerosis were extensive features in the first case. Only vimentin showed diffuse positive immunostaining in proliferating cells. Our results support the fibroblastic origin proposed for this lesion.

Hemangioma cavernoso del intestino delgado. Presentacion de un caso y revision de la literatura. / Cavernous hemangioma of the small intestine.Report of a case and review of the literature

Se hace una revision de la literatura sobre los hemangiomas del intestino delgado y se presenta un resumen de la historia clinica del primer paciente intervenido con exito en nuestro hospital con este diagnostico (AU)

Hemangioma cavernoso del intestino delgado. Presentacion de un caso y revision de la literatura. / Cavernous hemangioma of the small intestine.Report of a case and review of the literature

Se hace una revision de la literatura sobre los hemangiomas del intestino delgado y se presenta un resumen de la historia clinica del primer paciente intervenido con exito en nuestro hospital con este diagnostico