Distal Endarterectomy Combined With Endovascular Proximal Treatment: The Hybrid DEEP Retrograde Technique for High-Complexity Infrainguinal Disease.

Purpose: We present a hybrid technique for the treatment of chronic limb-threatening ischemia (CLTI) due to complex, multilevel infrainguinal disease. It consists of an open distal endarterectomy combined with endovascular proximal treatment (the DEEP technique). Materials and Methods: This was a prospective cohort study. Thirty-three limbs (30 patients) were treated. Main inclusion criteria were absence of significant disease in femoral bifurcation associated with a complex infrainguinal pattern. This approach was specially considered in absence of suitable vein for bypass, obesity, hostile groin, and overall high surgical risk. Results: Mean age was 72.8 ± 10 years (ranging 50-93). Most cases presented with severe limb threatening onset (90.9% Rutherford >4 and 81.8% WIfi >3) due to high-complexity infrainguinal disease pattern (Global Limb Anatomic Staging System [GLASS] stage III) in 31/33 (93.9%), chronic total occlusions (CTOs) in 24/33 (72.7%), and severe calcification (Peripheral Arterial Calcium Scoring System [PACSS] grade 4) in 22/33 (66.6%). Mean lesion length was 228.2 mm ± 83 (ranging 40-340 mm). In all procedures, a covered-stent (25 cm length Viabahn) was implanted in a retrograde fashion as the endovascular component. Effective revascularization was achieved in all cases, showing significant clinical and hemodynamic improvement (median pre- and postprocedure ankle-brachial index [ABI]: 0.3 and 0.9, respectively). Results at 12 months follow-up were as follows: 93.9% limb salvage ratio, 75.7% primary patency, 84.6% assisted primary patency, and 90.9% secondary patency. Major adverse limb events (MALE) and cardiovascular events (MACE) occurred in 8/33 (24.2%) and 2/33 (6%), respectively. Mean length of postoperative stay was 7.5 ± 6.92 days (3-27). Conclusion: This less invasive hybrid technique has promising short-term results for limb salvage and it is worth to be included in vascular armamentarium for CLTI revascularization in selected patients.

Beamforming Seizures from the Temporal Lobe Using Magnetoencephalography.

BACKGROUND: Surgical treatment of drug-resistant temporal lobe epilepsy (TLE) depends on proper identification of the seizure onset zone (SOZ) and differentiation of mesial, temporolimbic seizure onsets from temporal neocortical seizure onsets. Noninvasive source imaging using electroencephalography (EEG) and magnetoencephalography (MEG) can provide accurate information on interictal spike localization; however, EEG and MEG have low sensitivity for epileptiform activity restricted to deep temporolimbic structures. Moreover, in mesial temporal lobe epilepsy (MTLE), interictal spikes frequently arise in neocortical foci distant from the SOZ, rendering interictal spike localization potentially misleading for presurgical planning. METHODS: In this study, we used two different beamformer techniques applied to the MEG signal of ictal events acquired during EEG-MEG recordings in six patients with TLE (three neocortical, three MTLE) in whom the ictal source localization results could be compared to ground truth SOZ localizations determined from intracranial EEG and/or clinical, neuroimaging, and postsurgical outcome evidence. RESULTS: Beamformer analysis proved to be highly accurate in all cases and was able to identify focal SOZs in mesial, temporolimbic structures. In three patients, interictal spikes were absent, too complex for dipole modeling, or localized to anterolateral temporal neocortex distant to a mesial temporal SOZ, and thus unhelpful in presurgical investigation. CONCLUSIONS: MEG beamformer source reconstruction is suitable for analysis of ictal events in TLE and can complement or supersede the traditional analysis of interictal spikes. The method outlined is applicable to any type of epileptiform event, expanding the information value of MEG and broadening its utility for presurgical recording in epilepsy.

Trans-popliteal hybrid retrograde technique for revascularization of chronic total occlusions of the superficial femoral artery.

OBJECTIVES: We present the technical description and preliminary results of a hybrid approach for the treatment of chronic total occlusions of superficial femoral artery in the setting of critical limb-threatening ischemia (CLTI). METHODS: A retrospective analysis of selected case series was performed. A trans-popliteal hybrid technique was carried out in seven limbs (six patients). Open exposure of above-the-knee popliteal artery was performed over its maximum calcification zone. After retrograde recanalization and graft-stenting of the entire superficial femoral artery, endarterectomy of the popliteal artery was performed for debulking and widening of the distal landing zone of the endoprosthesis. The latter is included in the bovine patch suture to avoid leaving a segment untreated. RESULTS: Technical success, haemodynamic and clinical improvement were achieved in all procedures. Median length of treated occlusion was 19.8 cm. After a mean follow-up of 12 months (range 6-26 months), the primary patency was 85.7% (only one asymptomatic occlusion occurred). There were no major cardiovascular or limb adverse events. No re-interventions were required. CONCLUSION: This less-invasive, one-incision technique is safe and effective for the restoration of in-line flow from groin to ankle, currently recommended in CLTI revascularization. It could be especially useful in highly calcified popliteal artery lesions, hostile groins or those at high risk of infection and in cases of vein absence for bypass surgery.

A Distinct EEG Marker of Celiac Disease-Related Cortical Myoclonus.

BACKGROUND: Celiac disease is associated with motor cortex hyperexcitability and neurological manifestations including cortical myoclonus. Electroencephalography abnormalities have been described, but no distinct pattern has been reported. METHODS: We describe the neurophysiological characteristics of 3 patients with celiac-associated cortical myoclonus using electroencephalography, magnetoencephalography, and transcranial magnetic stimulation. RESULTS: Electroencephalography in all cases demonstrated lateralized low-amplitude, electropositive beta-frequency polyspike activity over the central head region, corresponding to motor cortex contralateral to the myoclonic limb. Jerk-locked back-averaging demonstrated a preceding cortical potential; magnetoencephalography source localization revealed a cortical generator in the posterior wall of the precentral gyrus for the back-averaged potential and oscillatory abnormality. In 1 patient, cerebellar inhibition of the motor cortex was physiologically normal. CONCLUSIONS: Central head oscillatory, low-amplitude, electropositive electroencephalography polyspike activity may be a distinct marker of celiac-related cortical myoclonus and is consistent with celiac-related motor cortex hyperexcitability, which may not necessarily result from cerebellar disinhibition. © 2020 International Parkinson and Movement Disorder Society.

Electromagnetic evidence that benign epileptiform transients of sleep are traveling, rotating hippocampal spikes.

OBJECTIVE: Benign epileptiform transients of sleep (BETS) have a unique voltage topography and a posteriorly propagating, inferiorly rotating diphasic EEG pattern. The source generators of BETS have not been definitively identified. We aimed to clarify the cerebral localization of BETS using MEG and electromagnetic source imaging (EMSI). METHODS: We analyzed BETS recorded with simultaneous MEG and EEG in four patients with epilepsy. Magnetic source imaging (MSI) and EMSI using equivalent current, single moving and rotating dipole inverse models was performed on averaged BETS potentials. MEG beamforming was performed in one case with abundant BETS. RESULTS: MSI and EMSI revealed hippocampal dipole source maxima in all cases, with current flow direction rotating from inferomedial to superomedial or superolateral between the first and second BETS peaks. Moving dipole analyses revealed spatiotemporal propagation along the anterior-posterior hippocampal axis and concomitant electromagnetic field rotation. Beamformer source reconstruction revealed an identical hippocampal localization. CONCLUSIONS: Converging evidence from different electromagnetic inverse modeling methods indicates that BETS are traveling, rotating hippocampal spikes, whose diphasic waveform is due to back and forth propagation along the anterior-posterior axis of the hippocampus. SIGNIFICANCE: The hippocampal localization and longitudinal, rotating propagation pattern of BETS raises the possibility of a sleep-related functional role for these hippocampal spikes.

Pilomotor seizures marked by infraslow activity and acetazolamide responsiveness.

A patient with pilomotor seizures post anti-LGI1 limbic encephalitis, refractory to immunotherapy and anti-epileptic drugs, was investigated with electroencephalography and magnetoencephalography. Seizures occurred daily (14.9 ± 4.9/day), with catamenial exacerbation, inducible by hyperventilation. Anterior temporal ictal onsets were heralded (by ~15 sec) by high amplitude ipsilateral electromagnetic infraslow activity. The catamenial/ventilatory sensitivity and the infraslow activity (reflecting glial depolarization) suggested an ionic, CO 2/pH-related glioneuronal mechanism. Furosemide decreased seizure frequency by ~33%. Acetazolamide led to immediate seizure freedom, but lost efficacy with daily treatment. A cycling acetazolamide regimen (2 days on, 4 days off) plus low-dose topiramate maintained >95% reduction (0.5 ± 0.9/day) in seizures.

Feasibility of magnetoencephalographic source imaging in patients with thalamic deep brain stimulation for epilepsy.

Source localization of interictal spikes in patients with medically refractory epilepsy is the most common clinical application of magnetoencephalography (MEG). In recent decades, many patients with intractable epilepsy have been treated with various forms of neurostimulation, including thalamic deep brain stimulation (DBS). Patients with suboptimal seizure control after DBS might in some cases benefit from further investigations for resective epilepsy surgery, including MEG source imaging (MSI). We sought to determine the feasibility and accuracy of MSI in the setting of active thalamic DBS. Simultaneous EEG/MEG was obtained in a patient using an Elekta 306-channel MEG system, with high-frequency (100 Hz) DBS of the thalamic anterior nuclei cycling between on and off states. Magnetic artifacts associated with the DBS apparatus were successfully suppressed using the spatiotemporal signal space separation (tSSS) method. Electrical stimulation artifact was removed by standard digital low-pass filtering. Dipole source modeling results for spike foci in frontal and posterior temporal regions were comparable between stimulation on and stimulation off states, and the source solutions corresponded well to the localization of spikes documented by intracranial EEG. MSI is thus feasible and source solutions can be accurate when performed in patients with active thalamic DBS for epilepsy.

TMSEEG: A MATLAB-Based Graphical User Interface for Processing Electrophysiological Signals during Transcranial Magnetic Stimulation.

Concurrent recording of electroencephalography (EEG) during transcranial magnetic stimulation (TMS) is an emerging and powerful tool for studying brain health and function. Despite a growing interest in adaptation of TMS-EEG across neuroscience disciplines, its widespread utility is limited by signal processing challenges. These challenges arise due to the nature of TMS and the sensitivity of EEG to artifacts that often mask TMS-evoked potentials (TEP)s. With an increase in the complexity of data processing methods and a growing interest in multi-site data integration, analysis of TMS-EEG data requires the development of a standardized method to recover TEPs from various sources of artifacts. This article introduces TMSEEG, an open-source MATLAB application comprised of multiple algorithms organized to facilitate a step-by-step procedure for TMS-EEG signal processing. Using a modular design and interactive graphical user interface (GUI), this toolbox aims to streamline TMS-EEG signal processing for both novice and experienced users. Specifically, TMSEEG provides: (i) targeted removal of TMS-induced and general EEG artifacts; (ii) a step-by-step modular workflow with flexibility to modify existing algorithms and add customized algorithms; (iii) a comprehensive display and quantification of artifacts; (iv) quality control check points with visual feedback of TEPs throughout the data processing workflow; and (v) capability to label and store a database of artifacts. In addition to these features, the software architecture of TMSEEG ensures minimal user effort in initial setup and configuration of parameters for each processing step. This is partly accomplished through a close integration with EEGLAB, a widely used open-source toolbox for EEG signal processing. In this article, we introduce TMSEEG, validate its features and demonstrate its application in extracting TEPs across several single- and multi-pulse TMS protocols. As the first open-source GUI-based pipeline for TMS-EEG signal processing, this toolbox intends to promote the widespread utility and standardization of an emerging technology in brain research.

Evidence for inhibitory deficits in the prefrontal cortex in schizophrenia.

Abnormal gamma-aminobutyric acid inhibitory neurotransmission is a key pathophysiological mechanism underlying schizophrenia. Transcranial magnetic stimulation can be combined with electroencephalography to index long-interval cortical inhibition, a measure of GABAergic receptor-mediated inhibitory neurotransmission from the frontal and motor cortex. In previous studies we have reported that schizophrenia is associated with inhibitory deficits in the dorsolateral prefrontal cortex compared to healthy subjects and patients with bipolar disorder. The main objective of the current study was to replicate and extend these initial findings by evaluating long-interval cortical inhibition from the dorsolateral prefrontal cortex in patients with schizophrenia compared to patients with obsessive-compulsive disorder. A total of 111 participants were assessed: 38 patients with schizophrenia (average age: 35.71 years, 25 males, 13 females), 27 patients with obsessive-compulsive disorder (average age: 36.15 years, 11 males, 16 females) and 46 healthy subjects (average age: 33.63 years, 23 females, 23 males). Long-interval cortical inhibition was measured from the dorsolateral prefrontal cortex and motor cortex through combined transcranial magnetic stimulation and electroencephalography. In the dorsolateral prefrontal cortex, long-interval cortical inhibition was significantly reduced in patients with schizophrenia compared to healthy subjects (P = 0.004) and not significantly different between patients with obsessive-compulsive disorder and healthy subjects (P = 0.5445). Long-interval cortical inhibition deficits in the dorsolateral prefrontal cortex were also significantly greater in patients with schizophrenia compared to patients with obsessive-compulsive disorder (P = 0.0465). There were no significant differences in long-interval cortical inhibition across all three groups in the motor cortex. These results demonstrate that long-interval cortical inhibition deficits in the dorsolateral prefrontal cortex are specific to patients with schizophrenia and are not a generalized deficit that is shared by disorders of severe psychopathology.

A novel method for removal of deep brain stimulation artifact from electroencephalography.

BACKGROUND: Deep brain stimulation (DBS) has treatment efficacy in neurological and psychiatric disorders such as Parkinson's disease and major depression. Electroencephalography (EEG) is a versatile neurophysiological tool that can be used to better understand DBS treatment mechanisms. DBS causes artifacts in EEG recordings that preclude meaningful neurophysiological activity from being quantified during stimulation. NEW METHOD: In this study, we modeled the DBS stimulation artifact and illustrated a technique for removing the artifact using matched filters. The approach was validated using a synthetically generated DBS artifact superimposed on EEG data. Mean squared error (MSE) between the recovered signal and the artifact-free signal was used to quantify the effectiveness of the approach. RESULTS: The DBS artifact was characterized by a series of narrow band components at the harmonic frequencies of DBS stimulation. The filtering approach successfully removed the DBS artifact with MSE value being less than 2% of base signal power for the typical stimulation and recording setups. General guidelines on how to setup DBS EEG studies and configure the subsequent artifact removal process are described. COMPARISON WITH PREVIOUS METHOD: To avoid stimulus artifacts, a number of EEG studies with DBS subjects have resorted to turning the stimulator off during recording, while other studies have used low pass filters to remove artifacts and look at frequencies well below 50 Hz. CONCLUSIONS: This study establishes a method through which DBS artifact in EEG recordings can be reliably eliminated, thereby preserving a meaningful neurophysiological signal through which to better understand DBS treatment mechanisms.

Characterizing long interval cortical inhibition over the time-frequency domain.

OBJECTIVE: Long-interval cortical inhibition (LICI) can be recorded from motor and non-motor regions of the cortex through combined transcranial magnetic stimulation (TMS) with electroencephalography (EEG). This study aimed to evaluate additional dimensions of LICI characteristics over an extended time-frequency and spatial domain. This was done by introducing two alternative measures of LICI signal amplitude: the Discrete Fourier Transform (DFT) and the Hilbert transform (HT). Both approaches estimate signal amplitude not taking into account the phase. In both cases LICI was measured as the difference between the unconditioned and conditioned activity evoked by the test pulse. Finally, we evaluated whether the topographical patterns of single and paired responses differed beyond the expected variations in amplitude. MATERIALS AND METHODS: LICI was delivered as single and paired pulses to the motor cortex (MC) and dorsolateral prefrontal cortex (DLPFC) in 33 healthy subjects with TMS-EEG. RESULTS: Significant differences (p<0.0001) between the unconditioned and conditioned evoked activity were found for both the DLPFC and MC using both methods (i.e., DFT and HT) after correcting for multiple comparisons in the time-frequency domain. The influence of inhibition was found to be significantly larger in space and time than previously considered. Single and paired conditions differ in intensity, but also in their topographic pattern (i.e., the specific spatiotemporal configuration of active sources). CONCLUSION: Similar results were found by both DFT and HT. The effect of inhibition across the cortex was also found to be complex and extended. In particular, it was found that LICI may be measured with high sensitivity in areas that were relatively distant from the stimulation site, which may have important practical applications. The analysis presented in this study overcomes some limitations of previous studies and could serve as a key reference for future studies examining TMS-indices of inhibition/excitation in healthy and diseased states.

The imaginary part of coherency in autism: differences in cortical functional connectivity in preschool children.

Cognition arises from the transient integration and segregation of activity across functionally distinct brain areas. Autism Spectrum Disorders (ASD), which encompass a wide range of developmental disabilities, have been presumed to be associated with a problem in cortical and sub-cortical dynamics of coordinated activity, often involving enhanced local but decreased long range coordination over areas of integration. In this paper we challenge this idea by presenting results from a relatively large population of ASD children and age-matched controls during a face-processing task. Over most of the explored domain, children with ASD exhibited enhanced synchronization, although finer detail reveals specific enhancement/reduction of synchrony depending on time, frequency and brain site. Our results are derived from the use of the imaginary part of coherency, a measure which is not susceptible to volume conduction artifacts and therefore presents a credible picture of coordinated brain activity. We also present evidence that this measure is a good candidate to provide features in building a classifier to be used as a potential biomarker for autism.

Patterns of brain activity distinguishing free and forced actions: contribution from sensory cortices.

The neural basis of decision-making is extremely complex due to the large number of factors that contribute to the outcome of even the most basic actions as well as the range of appropriate responses within many behavioral contexts. To better understand the neural processes underlying basic forms of decision-making, this study utilized an experiment that required a choice about whether to press a button with the right or left hand. These instances of decision-making were compared to identical button presses that were experimentally specified rather than selected by the subject. Magnetoencephalography (MEG) was used to record neural activity during these-what are being termed-free and forced actions and differences in the MEG signal between these two conditions were attributed to the distinct forms of neural activity required to carry out the two types of actions. To produce instances of free and forced behavior, cued button-pressing experiments were performed that use visual, aural, and memorized cues to instruct experimental subjects of the expected outcome of individual trials. Classification analysis of the trials revealed that cortical regions that allowed for the most accurate classification of free and forced actions primarily handle sensory input for the modality used to cue the trials: occipital cortex for visually cued trials, temporal cortex for aurally cued trials, and minor non-localized differences in MEG activity for trials initiated from memory. The differential roles of visual and auditory sensory cortices during free and forced actions provided insight into the neural processing steps that were engaged to initiate cued actions. Specifically, it suggested that detectable differences exist in the activity of sensory cortices and their target sites when subjects performed free and forced actions in response to sensory cues.

Transient coordinated activity within the developing brain's default network.

The concept of a brain default network postulates that specific brain regions are more active when a person is engaged in introspective mental activity. Transient functional coordination between groups of neurons is thought to be necessary for information processing. Since children develop introspection as they mature, regions of the default network may establish increasing functional coordination with age, resulting in fewer fluctuations in synchronization patterns. We investigated the transient coordinated activity in regions of the default network in seventeen children aged 11 months to 17 years of age using EEG recordings while subjects were resting quietly with eyes closed. The temporal and spatial fluctuations in the phase synchrony patterns were estimated across sites associated with the default network pattern and compared to other regions. Lower variability of the spatio-temporal patterns of phase synchronization associated with the default network was observed in the older group as compared to the younger group. This indicates that functional coordination increases among regions of the default network as children develop.

Distinct dynamical patterns that distinguish willed and forced actions.

The neural pathways for generating willed actions have been increasingly investigated since the famous pioneering work by Benjamin Libet on the nature of free will. To better understand what differentiates the brain states underlying willed and forced behaviours, we performed a study of chosen and forced actions over a binary choice scenario. Magnetoencephalography recordings were obtained from six subjects during a simple task in which the subject presses a button with the left or right finger in response to a cue that either (1) specifies the finger with which the button should be pressed or (2) instructs the subject to press a button with a finger of their own choosing. Three independent analyses were performed to investigate the dynamical patterns of neural activity supporting willed and forced behaviours during the preparatory period preceding a button press. Each analysis offered similar findings in the temporal and spatial domains and in particular, a high accuracy in the classification of single trials was obtained around 200 ms after cue presentation with an overall average of 82%. During this period, the majority of the discriminatory power comes from differential neural processes observed bilaterally in the parietal lobes, as well as some differences in occipital and temporal lobes, suggesting a contribution of these regions to willed and forced behaviours.

Enhanced synchrony in epileptiform activity? Local versus distant phase synchronization in generalized seizures.

Synchronization is a fundamental characteristic of complex systems and a basic mechanism of self-organization. A traditional, accepted perspective on epileptiform activity holds that hypersynchrony covering large brain regions is a hallmark of generalized seizures. However, a few recent reports have described substantial fluctuations in synchrony before and during ictal events, thus raising questions as to the widespread synchronization notion. In this study, we used magnetoencephalographic recordings from epileptic patients with generalized seizures and normal control subjects to address the extent of the phase synchronization (phase locking) in local (neighboring) and distant cortical areas and to explore the ongoing temporal dynamics for particular ranges of frequencies at which synchrony occurs, during interictal and ictal activity. Synchronization patterns were found to differ somewhat depending on the epileptic syndrome, with primary generalized absence seizures displaying more long-range synchrony in all frequency bands studied (3-55 Hz) than generalized tonic motor seizures of secondary (symptomatic) generalized epilepsy or frontal lobe epilepsy. However, all seizures were characterized by enhanced local synchrony compared with distant synchrony. There were fluctuations in the synchrony between specific cortical areas that varied from seizure to seizure in the same patient, but in most of the seizures studied, regardless of semiology, there was a constant pattern in the dynamics of synchronization, indicating that seizures proceed by a recruitment of neighboring neuronal networks. Together, these data indicate that the concept of widespread "hypersynchronous" activity during generalized seizures may be misleading and valid only for very specific neuronal ensembles and circumstances.

Estudio de la Variabilidad de la Frecuencia Cardiaca Mediante el Análisis de recurrencia Visual / I study of the Variability of the Heart Frequency By means of the Analysis of Visual

Se aplicaron varios métodos relacionados con la implementación del análisis de recurrencia visual a un grupo de 10 registros de señales RR obtenidas a partir de una señal de RR de 24 horas de duración de un sujeto sano voluntario del sexo masculino. En particular la utilización de la función de información mutua y del método de los falsos vecinos mostraron que la señal posee una elevada dimensión de inmersión , por esta razón se descarta la posibilidad de que la señal posea una dinámica de caos clásico. Esto está en correspondencia con resultados ya alcanzados en la literatura [14]. En general, en los gráficos de recurrencia se aprecia la presencia de cierta estructura en las señales RR estudiadas, este resultado se confirma con las mediciones de entropía espacio-temporal (aproximadamente 50 por ciento para todas las señales observadas). Conclusiones: i) consideramos que el análisis de recurrencia visual puede ser una herramienta util para explorar la estructura de las señales de variabilidad de la frecuencia cardíaca y su posible alteracion en algunas enfermedades(AU)

Complejidad y codificación en RNAs no codificadores / Complexity and code in RNAs non codifiers

La estructura de la información presente en las regiones genéticas no codificadoras aún está muy poco caracterizada. En este trabajo se plantea como objetivo fundamental hacer una recodificación de estas secuencias y utilizar medidas teórico-informacionales de análisis, como la entropía de Shannon y la complejidad de Lempel-Ziv, para caracterizar estos datos. La complejidad de Lempel-Ziv mostró un patrón similar no aleatorio en secuencias no codificadoras de diferentes organismos; con medidas derivadas de la entropía de Shannon se obtuvieron evidencias de patrones que hacen posible un tipo de codificación diferente al código de tripletes clásico planteado para secuencias codificadoras(AU)

La señal fotopletismográfica procesada con herramientas de análisis de serie de tiempo no lineal / The photoplethismographic signal processed with nonlinear time series analysis tools

Este trabajo aborda el análisis de las señales fotopletismográficas digitales (PPG) con herramientas no-lineales de serie de tiempo. Para esto se aplicaron las siguientes técnicas analíticas: I-Estimación polinomial de alto grado para la corrección de la línea base II-Análisis espectral mediante transformada rápida de Fourier III-Estimación de la dimensión fractal mediante el método propuesto por Higuchi para el dominio del tiempo IV-Estimación no paramétrica por núcleos para la reconstrucción de los atractores libres de ruido y de los componentes estocásticos de las señales. La señal PPG puede ser dividida en los tres componentes siguientes: 1. Una tendencia no-estacionaria, no-lineal dependiente del tiempo que se relaciona con la mayor parte de la no-estacionaridad de la señal PPG 2.Un componente no-lineal de ciclo límite determinístico invariante que corresponde a la generación de ondas pulsátiles que reflejan el punto más relevante de la señal PPG en los estudios clínicos 3.Un componente estocástico que sea, por lo menos, fractal parcialmente. Este componente soporta menos del 5 por ciento de la varianza de la señal corregida básica. La suma de la base (1) más los componentes estocásticos (3) puede explorar las propiedades fractales de la señal PPG original. Se considera que la separación de la señal PPG en tres componentes diferentes posibilita la obtención de nueva información, tanto para las investigaciones básicas, como para propósitos clínicos(AU)