A Bootstrapping Method for Improving the Classification Performance of the P300 Speller

Abstract In this paper, we present a novel approach to training classifiers in a speller based on P300 potentials. The method, based on bootstrapping, is a known strategy for generating new samples, but it is rarely used in neurosciences. The study first demonstrates how the performance of the classification task (detecting P300 and Non-P300 classes) could be sub-optimal in the traditional approach. Then, a new method for taking new samples from the training data is proposed. Each classifier is re-trained using balanced sub-groups of individual P300 and non-P300 samples. Data were collected from 14 healthy subjects, using 16 electroencephalography channels. These were filtered in bandpass and decimated. Subsequently, four linear classifiers were trained using the traditional method followed by the proposed one, with 1000, 2000 and 3000 samples per class. Results indicate an improvement in the accuracy and discrimination capacity of discriminative classifiers with the proposed method, maintaining the same statistical properties between the training and test data. By contrast, for generative classifiers, there is no significant difference in the results. Therefore, the proposed method is highly recommended for training discriminative classifiers in spell-based P300 potentials.

Resumen Este artículo presenta un método novedoso para entrenar clasificadores en un deletreador basado en potenciales P300. El método, basado en bootstrapping, es una estrategia conocida para generar nuevas muestras pero escasamente implementado en neurociencias. El estudio muestra cómo el rendimiento de la detección de P300 (frente a No-P300) puede resultar sub-óptimo usando el método tradicional. Luego, se propone un nuevo método donde se toman nuevas muestras a partir de los datos de entrenamiento. Con ellas, se re-entrena al clasificador usando sub-grupos equilibrados de muestras individuales P300 y No-P300. Los datos se recolectaron de 14 sujetos sanos, usando 16 canales de electroencefalografía. Estos fueron filtrados en pasa-banda y diezmados. Posteriormente, cuatro clasificadores lineales fueron entrenados, usando primero el método tradicional y después el método propuesto, con 1000, 2000 y 3000 muestras por clase. Los resultados muestran una mejoría en la precisión y la capacidad de discriminación de clasificadores discriminativos con el método propuesto, manteniendo las mismas propiedades estadísticas entre los datos de entrenamiento y los de prueba. En contraste, para los clasificadores generativos, no existe una diferencia significativa en los resultados. Por consiguiente, el método propuesto es altamente recomendado para entrenar clasificadores discriminativos en deletreadores basados en potenciales P300.

[Neonatal intussusception]. / Invaginación intestinal neonatal.

Intussusception in infants and young children is a relatively common entity with a well defined clinical picture and a favorable outcome in most cases.The neonatal intussusceptions is extremely rare and does not have a well-defined clinical picture since its clinical manifestations vary according to the gestational time it occurs, the response of the injured intestine and the gestational age of the child concerned. Two new cases of neonatal intussusceptions are presented and a review of the world literature is performed. Given the stage of intussusceptions (pre- or postnatal) occurs and gestational age of the affected infant (preterm or term), there are three entities with clinical characteristics, topography and evolution rather different: prenatal or intrauterine intussusception, postnatal intussusception in the preterm and postnatal intussusception in the term infant.

La invaginación intestinal en el lactante y niño pequeño es una entidad relativamente frecuente, con un cuadro clínico definido y una evolución favorable en la mayoría de los casos. La invaginación intestinal neonatal es sumamente rara y no tiene un cuadro bien definido, ya que sus manifestaciones clínicas varían de acuerdo con el momento gestacional en que se produce, con la respuesta del intestino lesionado y con la edad gestacional del niño afectado. Se presentan dos nuevos casos de invaginación intestinal neonatal y se realiza una revisión de la bibliografía mundial. Teniendo en cuenta la etapa en que se produce la invaginación (pre o postnatal) y la edad gestacional del neonato afectado (prematuro o a término), se pueden distinguir tres entidades con características clínicas, topográficas y evolutivas bien diferentes: la invaginación intestinal prenatal o intraútero, la invaginación intestinal postnatal en el prematuro y la invaginación intestinal postnatal en el neonato a término.

[Splenic epidermoid cyst: laparoscopic partial decapsulation]. / Quiste esplénico epidermoide: decapsulación parcial por vía laparoscópica.

The splenic cysts are rare among all age groups and there are a few reports in the world literature. The splenic epidermoid cyst is a true congenital one, that can cause signs and symptoms, or suffer complications. For these reasons, some form of treatment is recommended. The management of splenic cysts continues to evolve. The standard treatment was splenectomy, but the knowledge about the immunologic function of the spleen and the existence of postesplenectomy mortal sepsis, have conduced most of pediatric surgeons to adopt techniques that preserves splenic tissue. The treatment by percutaneous drainage with injection of a sclerosing agent has complications and a significant recurrence rate. During the last two decades, preservation procedures such as partial splenectomy or partial cyst excision and omental packing have gained the preference of most pediatric surgeons. The second technique has advantages over the partial splenectomy. The possibility to perform the procedure by a laparoscopic approach add the advantages of this last technique. We present two patients with splenic epidermoid cyst treated by laparoscopic partial cyst decapsulation and review the literature.

Malformaciones anorrectales: evaluación de aspectos clínicos, táctica y resultados funcionales / Anorrectal malformations; analysis of the clinical aspects, tactics and functional results

El objetivo del trabajo es analizar en forma retrospectiva en una serie consecutiva de niños con malformación anorrectal(MAR)los aspectos clínicos,la táctica y resultados funcionales obtenidos.Entre junio de 1989 y Junio de 1999 fueron evaluados y tratados quirúrgicamente en forma primaria 115 pacientes con MAR(55 mujeres y 60 varones)Tipos de defecto;41 malformaciones bajas,30 fistulas vestibulares,11 sin fistula,10 fístulas recto-vesicales,8 fístulas recto-bulbares,2 atresias rectales,1 estenosis rectal,1 cloaca y 2 malformaciones asociadas.Hubo buena correlación entre el desarrollo perineal y lesiones de sacro.Se realizaron 80 colostomías(68 sigmoideas,10 transversas derechas,2 transversas izquierdas)Once pacientes fueron reoperados para modificar el tipo de ostomia previa al descenso,3 presentaron complicaciones inherentes a su ostomía que obligaron a cirugía y 3 fueron colostomizados sin que fuera necesario por el tipo de malformación anorrectal.Todos los pacientes fueron corregidos mediante anorrectoplastia sagital posterio.Presentaron complicaciomes 16 pacientes que requirieron algún tipo de solución quirúrgica.Doce pacientes presentaron complicaciones en el cierre de la colostomía.Los pacientes fueron divididos en 3 grupos(sin alteracion sacra,con alteración sacra mínima y con alteración sacra severa.En el primer grupo(85 pacientes)77 presentaron defecación voluntaria(90.58 por ciento)en el segundo grupo(5 pacientes)3 presentan defecación voluntaria y en el tercer grupo(8 pacientes)solo 3 presentan defecación voluntaria.Sobre 98 pacientes evaluados,83 presentan defecación voluntaria y 15 son incontinentes

Malformaciones anorrectales: evaluación de aspectos clínicos, táctica y resultados funcionales / Anorrectal malformations; analysis of the clinical aspects, tactics and functional results

El objetivo del trabajo es analizar en forma retrospectiva en una serie consecutiva de niños con malformación anorrectal(MAR)los aspectos clínicos,la táctica y resultados funcionales obtenidos.Entre junio de 1989 y Junio de 1999 fueron evaluados y tratados quirúrgicamente en forma primaria 115 pacientes con MAR(55 mujeres y 60 varones)Tipos de defecto;41 malformaciones bajas,30 fistulas vestibulares,11 sin fistula,10 fístulas recto-vesicales,8 fístulas recto-bulbares,2 atresias rectales,1 estenosis rectal,1 cloaca y 2 malformaciones asociadas.Hubo buena correlación entre el desarrollo perineal y lesiones de sacro.Se realizaron 80 colostomías(68 sigmoideas,10 transversas derechas,2 transversas izquierdas)Once pacientes fueron reoperados para modificar el tipo de ostomia previa al descenso,3 presentaron complicaciones inherentes a su ostomía que obligaron a cirugía y 3 fueron colostomizados sin que fuera necesario por el tipo de malformación anorrectal.Todos los pacientes fueron corregidos mediante anorrectoplastia sagital posterio.Presentaron complicaciomes 16 pacientes que requirieron algún tipo de solución quirúrgica.Doce pacientes presentaron complicaciones en el cierre de la colostomía.Los pacientes fueron divididos en 3 grupos(sin alteracion sacra,con alteración sacra mínima y con alteración sacra severa.En el primer grupo(85 pacientes)77 presentaron defecación voluntaria(90.58 por ciento)en el segundo grupo(5 pacientes)3 presentan defecación voluntaria y en el tercer grupo(8 pacientes)solo 3 presentan defecación voluntaria.Sobre 98 pacientes evaluados,83 presentan defecación voluntaria y 15 son incontinentes

Long-term treatment with recombinant interferon alpha-2b prolongs survival of asymptomatic HIV-infected individuals.

RATIONALE AND OBJECTIVE: Early long-term treatment with recombinant interferon (IFN) alpha-2b delayed disease progression in asymptomatic Human Immunodeficiency Virus (HIV) carriers in a randomized trial that lasted from October 1987 to February 1992 (14). The aim of the work reported in this paper was to observe if there was also an effect on survival when the same patients were followed-up further. DESIGN AND INTERVENTIONS: IFN alpha-2b was given 3 x 10(6) IU, 3 times weekly. The control group did not receive any treatment. The main end-point for this evaluation was death due to any cause. The deadline was August 1995. POPULATION: Subjects were anti-HIV-1 seropositive, Western blot-confirmed, asymptomatic (CDC group II), or with generalized lymphadenopathies (CDC group III). The groups had 79 (control) and 83 (IFN) patients. MAIN RESULTS: Mean survival was longer in the IFN group (95% CI: 127-152 vs. 101-120 months since infection or 80-90 vs. 70-82 months since the start of treatment). Survival rates were higher in IFN-treated individuals (61-77% vs. 24-54% at 10 years of infection or 53-69% vs. 34-52% at 7 years of treatment or follow-up). It was also confirmed that disease progression is significantly slower in IFN-treated patients. There were 23.4 vs. 3.2% long-term survivors in the IFN and control groups, respectively (p = 0.005). IFN-treated patients had fewer AIDS-related malignancies (5 vs. 11), mainly Kaposi's sarcomas (1 vs. 5). This difference was not statistically significant, but clinically interesting. There was no difference in survival if measured since the onset of AIDS. CONCLUSION: IFN alpha treatment given from the early stages of infection, but not after the appearance of AIDS symptoms, can prolong survival.

[Interactive morphometry and densitometry for the study of epidermoid carcinoma of the larynx. Preliminary results]. / Aplicación de la morfometría y densitometría interactivas al estudio del carcinoma epidermoide laríngeo. Resultado preliminar.

At present the utilization of quantitative techniques in anatomopathological studies is becoming more and more frequent, so adding the possibility of gaining measures and numerical assessments in front of conventional quantitative evaluations. In the paper the AA. report their first attempt with conventional slides of epidermoid carcinomas of the larynx, taken from the files. The aim has been to check out the contribution of this procedure compared with other traditional pathological techniques.

[Calcified embolism of the coronary artery due to the degeneration of a bioprosthesis in the aortic position]. / Embolia calcificada a la arteria coronaria por degeneración de bioprótesis en posición aórtica.

We present a case of arterial coronary embolism by calcified material of a bioprosthesis of bovine pericardium of the INC in aortic position 8 years after its implantation. Echocardiogram and catheterization with coronarography demonstrated prosthetic aortic dysfunction and normal coronaries. The patient complained of stable angor and dyspnea. During coronarography there was an increase of symptoms together with ECG changes and after a few hours with enzymatic increase. The patient was brought urgently to surgery where mitroaortic prosthesis was changed with mechanic prosthesis. As surgical findings: absence of a leaflet of prosthesis in aortic position with free fragmented calcium in periannular region and two remaining leaflet completely calcified, prosthesis in mitral position of normal appearance. We conclude that ischemia or myocardial infarction in presence of normal coronaries in patients with bovine pericardial bioprosthesis in aortic position can be secondary to calcium embolism, originated by mineralization process of a degenerated bioprosthesis several years after its implantation.

[Prognostic value of the degree of differentiation and the peri-tumor lymphoid infiltration in epidermoid carcinoma of the larynx]. / Valor pronóstico del grado de diferenciación y el infiltrado linfoide peritumoral en el carcinoma epidermoide de laringe.

By multiple linear regression the authors show a closed relationship between survival and conventional anatomopathologic data as grade of differentiation and of lymphoid infiltration of the primary tumor. This retrospective pathological study showed that various degrees of squamous cell differentiation may be recognized for malignant laryngeal lesions and that such distinction may be of prognostic significance.

[Vascular microinvasion in laryngeal epidermoid carcinoma]. / Microinvasión vascular en el carcinoma epidermoide laríngeo.

Microvascular invasion by carcinoma cells is one of the first steps for the potential development of metástasis. The presence of squamous cell carcinoma within capillaries and/or venules in the immediate vicinity of primary lesions of the oral cavity and oropharynx may be related to regional lymph node metastasis. To evaluate this possibility in laryngeal carcinomas we have reviewed the histopathologic features of 48 cases of this type of tumor with simultaneous surgical treatment of the primary neoplasms and the neck. In our opinion the histologic finding of such invasion is not pathognomonic for establishment of regional metástasis in epidermoid carcinoma of the larynx.

[The importance of laryngeal compartmentation in the limitation of tumor extension]. / Importancia de la compartimentación laríngea en la limitación de la extensión tumoral.

Histologic specimens from 75 patients with squamous cell carcinoma of the larynx treated exclusively by surgery were studied with special attention paid to the growth of the tumor in relation with the different laryngeal compartments. Some aspects traditionally admitted are discussed. The result show a not very close relation between the classic anatomic descriptions and the tumoral growing.

[Prognostic value of lymph node histologic pattern in epidermoid carcinoma of the larynx]. / Interés pronóstico del patrón histológico ganglionar en el carcinoma epidermoide de laringe.

Histologic specimens from 48 patients with squamous cell carcinoma of the larynx treated exclusively by surgery were studied with special attention paid to the reactivity of regional lymph nodes. The lymph nodes were classified into four microscopic patterns of immune response: lymphocytic predominance, sinus histiocytosis, germinal center predominance and unstimulated or lymphocytic depletion. As a result no correlation were then made between the patterns and survival rate at 5 year follow-up.

[A morpho-photometric study of laryngeal epidermoid carcinoma]. / Estudio morfofotométrico del carcinoma epidermoide de laringe.

At the moment the use of quantitative techniques in anatomopathology is more and more frequent. In this study the authors use for the first time the morpho-photometry approach in epidermoid carcinomas of the larynx coming from filed material. In this way they are checking if this method adds anything to conventional anatomopathology.

[A comparative study of the prognostic value of morphometric data and of conventional pathological anatomy in laryngeal epidermoid carcinoma]. / Estudio comparativo del valor pronóstico de los datos morfofotométricos y de la anatomía patológica convencional en el carcinoma epidermoide de laringe.

At the moment the use of quantitative techniques is not very frequent in standard anatomopathologic studies of epidermoid carcinoma of the larynx. By "multiple linear regression" the authors show a closed relationship between survival and conventional anatomopathologic data as grade of differentiation and of lymphoid infiltration of the primary tumor.

[Study of histological preparations of laryngeal epidermoid carcinoma using image analysis]. / Estudio de preparaciones histológicas de carcinoma epidermoide laríngeo mediante análisis de imagen.

At the present application of quantitative techniques in anatomopathologic studies is becoming more and more frequent, adding the possibility of numeric and quantitative evaluation. In this study the authors make a first attempt with one of these methods, the image analysis using conventional slides of epidermoid carcinomas from larynx.

[Prognostic value of the grade of malignancy in epidermoid carcinoma of the larynx]. / Valor pronóstico del grado de malignidad en el carcinoma epidermoide de la laringe.

At the moment the use of quantitative techniques in anatomopathology are becoming more and more frequent. In this study, with the mathematical transformation of morphometric data obtained from cell populations of epidermoid carcinoma of the larynx, the authors arrive at the "grade of malignancy" for every patient which has in itself prognostic value without taking into account the other anatomopathologic or clinical parameters.

[Use of morphophotometry in the study of the kinetics of cell populations in laryngeal epidermoid carcinoma]. / Aplicación de la morfofotometría al estudio de la cinética de poblaciones celulares en el carcinoma epidermoide laríngeo.

The use of morpho-photometric techniques in anatomopathology is, on the whole, not very frequent at the moment. In this study the authors show the possible applications of these quantitative methods for the evaluation of kinetics characteristics of cell population in epidermoid carcinomas of the larynx.

[The prognostic value of conventional pathological anatomy in laryngeal epidermoid carcinoma]. / Valor pronóstico de la anatomía patológica convencional en el carcinoma epidermoide laríngeo.

The anatomopathologic study of epidermoid carcinoma of the larynx is a reason for many publications in the international scientific community in spite of the apparent histologic similarity of this type of tumor. After a careful review from wide material the authors make reference to the prognostic value of certain anatomopathologic finding.

[Granulomatous lymphadenitis in cancer of the larynx]. / Linfadenitis granulomatosa en el cáncer de laringe.

Epithelioid granuloma is not the typical antitumors reaction of the lymph nodes in head and neck area. In this study the authors look at and consider this subject in relation with tumors in the larynx.