Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 35
Filtrar
1.
BMC Neurol ; 22(1): 246, 2022 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-35794522

RESUMO

BACKGROUND: Children with cerebral palsy (CP) often have communication impairments, including speech altered intelligibility. Multiple levels of disrupted speech have been reported in CP, which negatively impact on participation and quality of life, with increase of care needs. Augmentative Alternative Communication (AAC) is an option, with debated benefits and limitations, in particular for its functional use. This is supported by a substantial lack of defined evidences in favor of direct speech articulation intervention in CP. Motor learning-based interventions are effective in CP and are the basis of speech motor interventions such as PROMPT (Prompts for Restructuring Oral Muscular Phonetic Targets). The PROMPT speech motor treatment provides tactile-kinesthetic inputs to facilitate articulatory movements by dynamic modelling, resulting in more efficient motor patterns that can be integrated into speech and communication. In CP, exploratory evidences support the feasibility and preliminarily advantages on intelligibility of motor speech treatments, such as PROMPT, with increased speech motor control, also documented by kinematic analyses. METHODS: A randomized waitlist-control trial will be conducted in children aged between 3- and 10-years having CP and dysarthria (estimated sample size = 60 children). Children will be allocated in the immediate intervention or in the waitlist control group. The intervention consists of an intensive 3 weeks period of twice-a-day administration of PROMPT. Standard care will be administered in the control (waitlist) group. After repeated baseline assessments (T0), the PROMPT treated group will undergo the experimental 3-week intervention period, with T1 assessment at the end. A further T2 assessment will be provided at medium term (3 months after the end of the intervention) for evaluating the stability of intervention. Primary and secondary speech clinical and kinematics outcome measures will be collected at T0, T1 and T2. DISCUSSION: This paper describes the study protocol consisting of a RCT with two main objectives: (1) to evaluate the or short-term benefits of an intensive speech motor intervention on speech and intelligibility in children with CP and the stability of the intervention at medium term; (2) to describe the kinematic correlates of speech motor control modifications. TRIAL REGISTRATION: Trial registration date 06/12/2019; ClinicalTrials.gov Identifier: NCT04189159 .


Assuntos
Paralisia Cerebral , Fala , Paralisia Cerebral/complicações , Criança , Pré-Escolar , Grupos Controle , Disartria/etiologia , Disartria/terapia , Humanos , Qualidade de Vida , Ensaios Clínicos Controlados Aleatórios como Assunto
2.
BMC Pediatr ; 22(1): 360, 2022 06 23.
Artigo em Inglês | MEDLINE | ID: mdl-35739502

RESUMO

BACKGROUND: Children with neurological impairment may have dysphagia and/or gastro-esophageal reflux disease (GERD), which predispose to complications affecting the airways, increasing risk for aspiration-induced acute and chronic lung disease, or secondarily malnutrition, further neurodevelopmental disturbances, stressful interactions with their caregivers and chronic pain. Only multidisciplinary clinical feeding evaluation and empirical trials are applied to provide support to the management of feeding difficulties related to dysphagia or GERD, but no standardized feeding or behavioral measure exists at any age to assess aspiration risk and support the indication to perform a videofluoroscopic swallowing study (VFSS) or a fibre-optic endoscopic examination of swallowing (FEES), in particular in newborns and infants with neurological impairments. Lung ultrasound (LUS) has been proposed as a non-invasive, radiation-free tool for the diagnosis of pulmonary conditions in infants, with high sensitivity and specificity. METHODS: A RCT will be conducted in infants aged between 0 and 6 years having, or being at risk for, cerebral palsy, or other neurodevelopmental disease that determines abnormal muscular tone or motor developmental delay assessed by a quantitative scale for infants or if there is the suspicion of GERD or dysphagia based on clinical symptoms. Infants will be allocated in one of 2 groups: 1) LUS-monitored management (LUS-m); 2) Standard care management (SC-m) and after baseline assessment (T0), both groups will undergo an experimental 6-months follow-up. In the first 3 months, infants will be evaluated a minimum of 1 time per month, in-hospital, for a total of 3 LUS-monitored meal evaluations. Primary and secondary endpoint measures will be collected at 3 and 6 months. DISCUSSION: This paper describes the study protocol consisting of a RCT with two main objectives: (1) to evaluate the benefits of the use of LUS for monitoring silent and apparent aspiration in the management of dysphagia and its impact on pulmonary illness and growth and (2) to investigate the impact of the LUS management on blood sample and bone metabolism, pain and interaction with caregivers. TRIAL REGISTRATION: Trial registration date 02/05/2020; ClinicalTrials.gov Identifier: NCT04253951 .


Assuntos
Paralisia Cerebral , Transtornos de Deglutição , Deficiências do Desenvolvimento , Refluxo Gastroesofágico , Paralisia Cerebral/complicações , Criança , Pré-Escolar , Transtornos de Deglutição/diagnóstico por imagem , Deficiências do Desenvolvimento/complicações , Refluxo Gastroesofágico/diagnóstico por imagem , Humanos , Lactente , Recém-Nascido , Pulmão/diagnóstico por imagem , Ensaios Clínicos Controlados Aleatórios como Assunto , Ultrassonografia
3.
AJNR Am J Neuroradiol ; 42(10): 1870-1877, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34413061

RESUMO

BACKGROUND AND PURPOSE: Conventional MR imaging scoring is a valuable tool for risk stratification and prognostication of outcomes, but manual scoring is time-consuming, operator-dependent, and requires high-level expertise. This study aimed to automate the regional measurements of an established brain MR imaging scoring system for preterm neonates scanned between 29 and 47 weeks' postmenstrual age. MATERIALS AND METHODS: This study used T2WI from the longitudinal Prediction of PREterm Motor Outcomes cohort study and the developing Human Connectome Project. Measures of biparietal width, interhemispheric distance, callosal thickness, transcerebellar diameter, lateral ventricular diameter, and deep gray matter area were extracted manually (Prediction of PREterm Motor Outcomes study only) and automatically. Scans with poor quality, failure of automated analysis, or severe pathology were excluded. Agreement, reliability, and associations between manual and automated measures were assessed and compared against statistics for manual measures. Associations between measures with postmenstrual age, gestational age at birth, and birth weight were examined (Pearson correlation) in both cohorts. RESULTS: A total of 652 MRIs (86%) were suitable for analysis. Automated measures showed good-to-excellent agreement and good reliability with manual measures, except for interhemispheric distance at early MR imaging (scanned between 29 and 35 weeks, postmenstrual age; in line with poor manual reliability) and callosal thickness measures. All measures were positively associated with postmenstrual age (r = 0.11-0.94; R2 = 0.01-0.89). Negative and positive associations were found with gestational age at birth (r = -0.26-0.71; R2 = 0.05-0.52) and birth weight (r = -0.25-0.75; R2 = 0.06-0.56). Automated measures were successfully extracted for 80%-99% of suitable scans. CONCLUSIONS: Measures of brain injury and impaired brain growth can be automatically extracted from neonatal MR imaging, which could assist with clinical reporting.


Assuntos
Recém-Nascido Prematuro , Imageamento por Ressonância Magnética , Encéfalo/diagnóstico por imagem , Estudos de Coortes , Humanos , Lactente , Recém-Nascido , Reprodutibilidade dos Testes
5.
Ann Oncol ; 29(12): 2363-2370, 2018 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-30307529

RESUMO

Background: Gene expression profiling (GEP) studies recognized a prognostic role for tumor microenvironment (TME) in diffuse large B-cell lymphoma (DLBCL), but the routinely adoption of prognostic stromal signatures remains limited. Patients and methods: Here, we applied the computational method CIBERSORT to generate a 1028-gene matrix incorporating signatures of 17 immune and stromal cytotypes. Then, we carried out a deconvolution on publicly available GEP data of 482 untreated DLBCLs to reveal associations between clinical outcomes and proportions of putative tumor-infiltrating cell types. Forty-five genes related to peculiar prognostic cytotypes were selected and their expression digitally quantified by NanoString technology on a validation set of 175 formalin-fixed, paraffin-embedded DLBCLs from two randomized trials. Data from an unsupervised clustering analysis were used to build a model of clustering assignment, whose prognostic value was also assessed on an independent cohort of 40 cases. All tissue samples consisted of pretreatment biopsies of advanced-stage DLBCLs treated by comparable R-CHOP/R-CHOP-like regimens. Results: In silico analysis demonstrated that higher proportion of myofibroblasts (MFs), dendritic cells, and CD4+ T cells correlated with better outcomes and the expression of genes in our panel is associated with a risk of overall and progression-free survival. In a multivariate Cox model, the microenvironment genes retained high prognostic performance independently of the cell-of-origin (COO), and integration of the two prognosticators (COO + TME) improved survival prediction in both validation set and independent cohort. Moreover, the major contribution of MF-related genes to the panel and Gene Set Enrichment Analysis suggested a strong influence of extracellular matrix determinants in DLBCL biology. Conclusions: Our study identified new prognostic categories of DLBCL, providing an easy-to-apply gene panel that powerfully predicts patients' survival. Moreover, owing to its relationship with specific stromal and immune components, the panel may acquire a predictive relevance in clinical trials exploring new drugs with known impact on TME.


Assuntos
Linfoma Difuso de Grandes Células B/mortalidade , Transcriptoma/genética , Microambiente Tumoral/genética , Adulto , Idoso , Algoritmos , Biópsia , Análise por Conglomerados , Estudos de Coortes , Biologia Computacional , Conjuntos de Dados como Assunto , Feminino , Perfilação da Expressão Gênica/métodos , Humanos , Linfoma Difuso de Grandes Células B/genética , Linfoma Difuso de Grandes Células B/patologia , Masculino , Pessoa de Meia-Idade , Inclusão em Parafina , Valor Preditivo dos Testes , Prognóstico , Intervalo Livre de Progressão , Ensaios Clínicos Controlados Aleatórios como Assunto , Reprodutibilidade dos Testes , Análise de Sobrevida , Adulto Jovem
7.
AJNR Am J Neuroradiol ; 38(7): 1435-1442, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28522659

RESUMO

BACKGROUND AND PURPOSE: The diagnostic and prognostic potential of brain MR imaging before term-equivalent age is limited until valid MR imaging scoring systems are available. This study aimed to validate an MR imaging scoring system of brain injury and impaired growth for use at 29 to 35 weeks postmenstrual age in infants born at <31 weeks gestational age. MATERIALS AND METHODS: Eighty-three infants in a prospective cohort study underwent early 3T MR imaging between 29 and 35 weeks' postmenstrual age (mean, 32+2 ± 1+3 weeks; 49 males, born at median gestation of 28+4 weeks; range, 23+6-30+6 weeks; mean birthweight, 1068 ± 312 g). Seventy-seven infants had a second MR scan at term-equivalent age (mean, 40+6 ± 1+3 weeks). Structural images were scored using a modified scoring system which generated WM, cortical gray matter, deep gray matter, cerebellar, and global scores. Outcome at 12-months corrected age (mean, 12 months 4 days ± 1+2 weeks) consisted of the Bayley Scales of Infant and Toddler Development, 3rd ed. (Bayley III), and the Neuro-Sensory Motor Developmental Assessment. RESULTS: Early MR imaging global, WM, and deep gray matter scores were negatively associated with Bayley III motor (regression coefficient for global score ß = -1.31; 95% CI, -2.39 to -0.23; P = .02), cognitive (ß = -1.52; 95% CI, -2.39 to -0.65; P < .01) and the Neuro-Sensory Motor Developmental Assessment outcomes (ß = -1.73; 95% CI, -3.19 to -0.28; P = .02). Early MR imaging cerebellar scores were negatively associated with the Neuro-Sensory Motor Developmental Assessment (ß = -5.99; 95% CI, -11.82 to -0.16; P = .04). Results were reconfirmed at term-equivalent-age MR imaging. CONCLUSIONS: This clinically accessible MR imaging scoring system is valid for use at 29 to 35 weeks postmenstrual age in infants born very preterm. It enables identification of infants at risk of adverse outcomes before the current standard of term-equivalent age.


Assuntos
Lesões Encefálicas/congênito , Lesões Encefálicas/diagnóstico por imagem , Encéfalo/diagnóstico por imagem , Encéfalo/crescimento & desenvolvimento , Desenvolvimento Infantil , Imageamento por Ressonância Magnética/métodos , Adulto , Cerebelo/diagnóstico por imagem , Cerebelo/crescimento & desenvolvimento , Estudos de Coortes , Feminino , Substância Cinzenta/diagnóstico por imagem , Substância Cinzenta/crescimento & desenvolvimento , Humanos , Lactente , Lactente Extremamente Prematuro , Recém-Nascido , Variações Dependentes do Observador , Gravidez , Estudos Prospectivos , Reprodutibilidade dos Testes , Fatores de Risco , Substância Branca/diagnóstico por imagem , Substância Branca/crescimento & desenvolvimento
8.
Am J Transplant ; 17(9): 2312-2325, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28276660

RESUMO

Despite the introduction of novel and more targeted immunosuppressive drugs, the long-term survival of kidney transplants has not improved satisfactorily. Early antigen-independent intragraft inflammation plays a critical role in the initiation of the alloimmune response and impacts long-term graft function. Complement activation is a key player both in ischemia/reperfusion injury (IRI) as well as in adaptive antigraft immune response after kidney transplantation. Since the alternative pathway (AP) amplifies complement activation regardless of the initiation pathways and renal IR injured cells undergo uncontrolled complement activation, we speculated whether selective blockade of AP could be a strategy for prolonging kidney graft survival. Here we showed that Balb/c kidneys transplanted in factor b deficient C57 mice underwent reduced IRI and diminished T cell-mediated rejection. In in vitro studies, we found that fb deficiency in T cells and dendritic cells conferred intrinsic impaired alloreactive/allostimulatory functions, respectively, both in direct and indirect pathways of alloantigen presentation. By administering anti-fB antibody to C57 wt recipients in the early post Balb/c kidney transplant phases, we documented that inhibition of AP during both ischemia/reperfusion and early adaptive immune response is necessary for prolonging graft survival. These findings may have implication for the use of AP inhibitors in clinical kidney transplantation.


Assuntos
Ativação do Complemento/imunologia , Fator B do Complemento/deficiência , Rejeição de Enxerto/prevenção & controle , Sobrevivência de Enxerto/imunologia , Transplante de Rim/efeitos adversos , Traumatismo por Reperfusão/prevenção & controle , Linfócitos T/imunologia , Aloenxertos , Animais , Fator B do Complemento/genética , Rejeição de Enxerto/etiologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Traumatismo por Reperfusão/etiologia
9.
AJNR Am J Neuroradiol ; 37(5): 917-23, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26659337

RESUMO

BACKGROUND AND PURPOSE: Advances in MR imaging modeling have improved the feasibility of reconstructing crossing fibers, with increasing benefits in delineating angulated tracts such as cerebellar tracts by using tractography. We hypothesized that constrained spherical deconvolution-based probabilistic tractography could successfully reconstruct cerebellar tracts in children with cerebellar hypoplasia/atrophy and that diffusion scalars of the reconstructed tracts could differentiate pontocerebellar hypoplasia, nonprogressive cerebellar hypoplasia, and progressive cerebellar atrophy. MATERIALS AND METHODS: Fifteen children with cerebellar ataxia and pontocerebellar hypoplasia, nonprogressive cerebellar hypoplasia or progressive cerebellar atrophy and 7 controls were included in this study. Cerebellar and corticospinal tracts were reconstructed by using constrained spherical deconvolution. Scalar measures (fractional anisotropy and mean, axial and radial diffusivity) were calculated. A general linear model was used to determine differences among groups for diffusion MR imaging scalar measures, and post hoc pair-wise comparisons were performed. RESULTS: Cerebellar and corticospinal tracts were successfully reconstructed in all subjects. Significant differences in diffusion MR imaging scalars were found among groups, with fractional anisotropy explaining the highest variability. All groups with cerebellar pathologies showed lower fractional anisotropy compared with controls, with the exception of cerebellar hypoplasia. CONCLUSIONS: This study shows the feasibility of constrained spherical deconvolution to reconstruct cerebellar and corticospinal tracts in children with morphologic cerebellar pathologies. In addition, the preliminary results show the potential utility of quantitative analysis of scalars of the cerebellar white matter tracts in children with cerebellar pathologies such as cerebellar hypoplasia and atrophy. Further studies with larger cohorts of patients are needed to validate the clinical significance of our preliminary results.


Assuntos
Cerebelo/anormalidades , Imagem de Tensor de Difusão/métodos , Interpretação de Imagem Assistida por Computador/métodos , Malformações do Sistema Nervoso/diagnóstico por imagem , Biomarcadores/análise , Cerebelo/diagnóstico por imagem , Cerebelo/patologia , Criança , Deficiências do Desenvolvimento/diagnóstico por imagem , Deficiências do Desenvolvimento/patologia , Feminino , Humanos , Masculino , Malformações do Sistema Nervoso/patologia , Tratos Piramidais/diagnóstico por imagem , Tratos Piramidais/patologia , Substância Branca/diagnóstico por imagem , Substância Branca/patologia
10.
Diagn Ther Endosc ; 2013: 580526, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23983448

RESUMO

In celiac disease (CD), the intestinal lesions can be patchy and partial villous atrophy may elude detection at standard endoscopy (SE). Narrow Band Imaging (NBI) system in combination with a magnifying endoscope (ME) is a simple tool able to obtain targeted biopsy specimens. The aim of the study was to assess the correlation between NBI-ME and histology in CD diagnosis and to compare diagnostic accuracy between NBI-ME and SE in detecting villous abnormalities in CD. Forty-four consecutive patients with suspected CD undergoing upper gastrointestinal endoscopy have been prospectively evaluated. Utilizing both SE and NBI-ME, observed surface patterns were compared with histological results obtained from biopsy specimens using the k-Cohen agreement coefficient. NBI-ME identified partial villous atrophy in 12 patients in whom SE was normal, with sensitivity, specificity, and accuracy of 100%, 92.6%, and 95%, respectively. The overall agreement between NBI-ME and histology was significantly higher when compared with SE and histology (kappa score: 0.90 versus 0.46; P = 0.001) in diagnosing CD. NBI-ME could help identify partial mucosal atrophy in the routine endoscopic practice, potentially reducing the need for blind biopsies. NBI-ME was superior to SE and can reliably predict in vivo the villous changes of CD.

11.
Epidemiol Infect ; 141(4): 714-7, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22874073

RESUMO

We describe nine patients (eight aged <1 year) clinically diagnosed with pertussis yet laboratory-confirmed with Bordetella holmesii infections, a human pathogen normally isolated from blood. Most patients reported cough and cold symptoms. No death was reported. We report B. holmesii isolation in infants with respiratory symptoms in Argentina.


Assuntos
Infecções por Bordetella/diagnóstico , Bordetella/isolamento & purificação , DNA Bacteriano/análise , Coqueluche/diagnóstico , Argentina , Bordetella pertussis/isolamento & purificação , Diagnóstico Diferencial , Humanos , Lactente , Reação em Cadeia da Polimerase em Tempo Real
12.
Med. infant ; 17(4): 366-368, Dic 2010. Tab
Artigo em Espanhol | LILACS, UNISALUD, BINACIS | ID: biblio-1281494

RESUMO

Pertussis es una enfermedad particularmente grave en menores de 1 año. No sólo no se ha podido erradicar pese al uso de vacunas por más de cincuenta años, sino que en la actualidad ha reemergido. En junio del 2010 se registró uno de los mayores brotes de coqueluche de los Estados Unidos, con 910 casos confirmados. En la Argentina se ha venido registrando un aumento significativo de casos de pertussis. En este trabajo se presentan datos nacionales y de nuestro hospital confirmados por cultivo y/o métodos moleculares (PCR). Durante el período 2008-2010 se registraron anualmente en nuestro país entre 600 y 1.000 casos con sintomatología compatible y en el Hospital Garrahan entre 110 y 150. La confirmación se concretó en alrededor de 24% de los casos nacionales y entre un 7% y un 36,4% en el hospital. Los datos obtenidos en los laboratorios nacionales de referencia muestran un registro actual que vuelve a alcanzar los valores del 2008, luego de un descenso en el 2009. En el Hospital Garrahan, un aumento relativo en el número de casos sospechosos no confirmados podría estar vinculados a cuadros respiratorios compatibles con pertussis producidos por otros agentes etiológicos. Más allá de las variaciones anuales se puede observar la vigencia de esta enfermedad en la Argentina. Desde el punto de vista de la prevención es importante destacar que muchos de estos niños no habían recibido el esquema de vacunación completo (la mayoría de los casos se registró en menores de 6 meses). (AU)


Pertussis is a especially severe illness in infants. The use of vaccines during more than 50 years could not eradicate this illness, that now it has reemerged. In June 2010 one of the greatest outbreaks of coqueluche was recorded in the United States, with 910 confirmed cases. In Argentina, a significant increase of pertussis cases was recorded. In the present study both national and hospital data is presented, including cases confirmed by culture and/or molecular methods (PCR). During 2008-2010 between 600 and 1,000 cases were recorded in our country, and between 110 and 150 at the Hospital Garrahan. Confirmation was done in almost 24% of national cases and between 7% and 36.4% in the hospital. Data obtained by national reference laboratories showed that cases decreased from 2007 to 2008, to regain similar numbers in 2009. In the Hospital Garrahan a relative increase of non-confirmed suspected cases could be related to respiratory syndromes due to other agents but compatible with pertussis. Beyond annual fluctuations the prevalence of this illness in Argentina can be observed. From the prevention point of view it is very important to highlight that many of these children have not received the complete vaccination scheme (most of cases have been recorded in less than 6-month-old children) (AU)


Assuntos
Humanos , Recém-Nascido , Lactente , Pré-Escolar , Criança , Adolescente , Argentina/epidemiologia , Bordetella pertussis/isolamento & purificação , Coqueluche/prevenção & controle , Coqueluche/epidemiologia , Sistema Nacional de Vigilância em Saúde , Hospitais Pediátricos/estatística & dados numéricos
13.
Neuromuscul Disord ; 17(5): 400-3, 2007 May.
Artigo em Inglês | MEDLINE | ID: mdl-17433677

RESUMO

Previous studies showed that SMN2 copy number correlates inversely with the disease severity. Our aim was to evaluate SMN2 copy numbers and the Hammersmith functional motor scale in 87 patients with SMA II in order to establish whether, within SMAII, the number of copies correlates with the severity of functional impairment. Our results showed a relative variability of functional scores, but a significant correlation between the number of SMN2 genes and the level of function.


Assuntos
Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/genética , Dosagem de Genes/genética , Proteínas do Tecido Nervoso/genética , Proteínas de Ligação a RNA/genética , Índice de Gravidade de Doença , Atrofias Musculares Espinais da Infância/genética , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Proteínas do Complexo SMN , Atrofias Musculares Espinais da Infância/fisiopatologia , Estatística como Assunto , Proteína 2 de Sobrevivência do Neurônio Motor
14.
IEEE Trans Neural Netw ; 14(4): 959-62, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-18238075

RESUMO

We present a generalized adaptive activation function neuron structure which learns through an information-theoretic-based principle, which is able to estimate the probability density function of incoming input. It provides a low-order smooth robust estimate of the input signal probability density function. The presented method has been developed with reference to statistical characterization of polypropylene composites reinforced with vegetal fibers, that the proposed numerical experiments pertain to.

15.
IEEE Trans Neural Netw ; 13(3): 521-31, 2002.
Artigo em Inglês | MEDLINE | ID: mdl-18244453

RESUMO

A new learning theory derived from the study of the dynamics of an abstract system of masses, moving in a multidimensional space under an external force field, is presented. The set of equations describing system's dynamics may be directly interpreted as a learning algorithm for neural layers. Relevant properties of the proposed learning theory are discussed within the paper, along with results of computer simulations performed in order to assess its effectiveness in applied fields.

16.
Int J Neural Syst ; 11(5): 399-417, 2001 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-11709808

RESUMO

In a recent work, we introduced the concept of pseudo-polynomial adaptive activation function neuron (FAN) and presented an unsupervised information-theoretic learning theory for such structure. The learning model is based on entropy optimization and provides a way of learning probability distributions from incomplete data. The aim of the present paper is to illustrate some theoretical features of the FAN neuron, to extend its learning theory to asymmetrical density function approximation, and to provide an analytical and numerical comparison with other known density function estimation methods, with special emphasis to the universal approximation ability. The paper also provides a survey of PDF learning from incomplete data, as well as results of several experiments performed on real-world problems and signals.


Assuntos
Aprendizagem/fisiologia , Neurônios/fisiologia , Aprendizagem por Probabilidade , Algoritmos , Simulação por Computador , Humanos , Teoria da Informação , Modelos Neurológicos , Redes Neurais de Computação , Dinâmica não Linear
17.
Neural Netw ; 13(6): 597-611, 2000 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-10987513

RESUMO

The aim of this paper is to study an Information Theory based learning theory for neural units endowed with adaptive activation functions. The learning theory has the target to force the neuron to approximate the input-output transference that makes it flat (uniform) the probability density function of its output or, equivalently, that maximizes the entropy of the neuron response. Then, a network of adaptive activation function neurons is studied, and the effectiveness of the new structure is tested on Independent Component Analysis (ICA) problems. The new ICA neural algorithm is compared with the closely related 'Mixture of Densities' (MOD) technique by Xu et al.. Both simulation results and structural comparison show the new method is effective and more efficient in computational complexity.


Assuntos
Inteligência Artificial , Aprendizagem/fisiologia , Modelos Neurológicos , Rede Nervosa/fisiologia , Redes Neurais de Computação , Neurônios/fisiologia , Processamento de Sinais Assistido por Computador , Algoritmos , Simulação por Computador , Distribuição Normal
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA