Evoked responses to rhythmic visual stimulation vary across sources of intrinsic alpha activity in humans

Rhythmic flickering visual stimulation produces steady-state visually evoked potentials (SSVEPs) in electroencephalogram (EEG) recordings. Based on electrode-level analyses, two dichotomous models of the underpinning mechanisms leading to SSVEP generation have been proposed: entrainment or superposition, i.e., phase-alignment or independence of endogenous brain oscillations from flicker-induced oscillations, respectively. Electrode-level analyses, however, represent an averaged view of underlying ‘source-level’ activity, at which variability in SSVEPs may lie, possibly suggesting the co-existence of multiple mechanisms. To probe this idea, we investigated the variability of SSVEPs derived from the sources underpinning scalp EEG responses during presentation of a flickering radial checkerboard. Flicker was presented between 6 and 12 Hz in 1 Hz steps, and at individual alpha frequency (IAF i.e., the dominant frequency of endogenous alpha oscillatory activity). We tested whether sources of endogenous alpha activity could be dissociated according to evoked responses to different flicker frequencies relative to IAF. Occipitoparietal sources were identified by temporal independent component analysis, maximal resting-state alpha power at IAF and source localisation. The pattern of SSVEPs to rhythmic flicker relative to IAF was estimated by correlation coefficients, describing the correlation between the peak-to-peak amplitude of the SSVEP and the absolute distance of the flicker frequency from IAF across flicker conditions. We observed extreme variability in correlation coefficients across sources, ranging from −0.84 to 0.93, with sources showing largely different coefficients co-existing within subjects. This result demonstrates variation in evoked responses to flicker across sources of endogenous alpha oscillatory activity. Data support the idea of multiple SSVEP mechanisms

Combining gamma with Alpha and Beta power modulation for enhanced cortical mapping in patients with focal epilepsy

About one third of patients with epilepsy have seizures refractory to the medical treatment. Electrical stimulation mapping (ESM) is the gold standard for the identification of "eloquent" areas prior to resection of epileptogenic tissue. However, it is time-consuming and may cause undesired side effects. Broadband gamma activity (55-200 Hz) recorded with extraoperative electrocorticography (ECoG) during cognitive tasks may be an alternative to ESM but until now has not proven of definitive clinical value. Considering their role in cognition, the alpha (8-12 Hz) and beta (15-25 Hz) bands could further improve the identification of eloquent cortex. We compared gamma, alpha and beta activity, and their combinations for the identification of eloquent cortical areas defined by ESM. Ten patients with intractable focal epilepsy (age: 35.9 ± 9.1 years, range: 22-48, 8 females, 9 right handed) participated in a delayed-match-to-sample task, where syllable sounds were compared to visually presented letters. We used a generalized linear model (GLM) approach to find the optimal weighting of each band for predicting ESM-defined categories and estimated the diagnostic ability by calculating the area under the receiver operating characteristic (ROC) curve. Gamma activity increased more in eloquent than in non-eloquent areas, whereas alpha and beta power decreased more in eloquent areas. Diagnostic ability of each band was close to 0.7 for all bands but depended on multiple factors including the time period of the cognitive task, the location of the electrodes and the patient's degree of attention to the stimulus. We show that diagnostic ability can be increased by 3-5% by combining gamma and alpha and by 7.5-11% when gamma and beta were combined. We then show how ECoG power modulation from cognitive testing can be used to map the probability of eloquence in individual patients and how this probability map can be used in clinical settings to optimize ESM planning. We conclude that the combination of gamma and beta power modulation during cognitive testing can contribute to the identification of eloquent areas prior to ESM in patients with refractory focal epilepsy.info:eu-repo/semantics/publishedVersio

Preservice Elementary Science Teachers' Argumentation Competence: Impact of a Training Programme

The recent literature has shown the importance of Preservice Elementary Science Teachers (PESTs) having a deep understanding of argumentation, as this factor may affect the nature of the class activities that are taught and what students learn. A lack of understanding of this factor may represent an obstacle in the development of science education programmes in line with the development of scientific competences. This paper presents the results of the design and implementation of a training programme of 6 sessions (12 hours of class participation plus 8 hours of personal homework) on argumentation. The programme was carried out by 57 Spanish PESTs from Malaga, Spain. The training programme incorporates the innovative use of certain strategies to improve competence in argumentation, such as teaching PESTs to identify the elements of arguments in order to design assessment rubrics or by including peer assessment during evaluation with and without rubrics. The results obtained on implementing the training programme were evaluated based on the development of PESTs’ argumentation competence using Toulmin’s argumentative model. Data collection methods involved two tasks carried out at the beginning and the end of the programme, i.e., pre-test and post-test, respectively. The conclusion of the study is that students made significant progress in their argumentation competence on completing the course. In addition, PESTs who followed the training programme achieved statistically better results at the end than those in the control group (n = 41), who followed a traditional teaching programme. A 6-month transfer task showed a slight improvement for the PESTs of the experimental group in relation to the control group in their ability to transfer argumentation to practice, especially to the extent to which they mentioned argumentation in their practice portfolios.This work is part of the “I+D Excelencia” project “Development and evaluation of scientific competences through context based and modelling teaching approaches” case studies (EDU2013-41952-P), funded by the Spanish Ministry of Economy and Finance through its 2013 research call

Xylobium papillosum : une nouvelle esp\ue8ce de la sous-tribu Xylobiinae (Orchidaceae) du Guatemala

Volume: 14Start Page: 117End Page: 12

Paracoccidioidomicosis ganglionar juvenil: reporte de un caso.

La paracoccidioidomicosis es una micosis sistémica profunda, producida por elhongo dimorfo Paracoccidioides brasiliensis, de carácter progresivo y granulomatoso.Se describen dos presentaciones de la enfermedad: la forma crónica, que ocurretradicionalmente en personas adultas dedicadas a la agricultura, y la forma aguda, subagudao juvenil, que corresponde a tan solo el 3-10% de los casos, caracterizándose por ser mássevera y contar con un peor pronóstico. Se presenta el caso de un paciente masculinode 11 años de edad, quien acude a centro hospitalario por presentar fiebre prolongada yadenopatías cervicales. Las serologías para enfermedad de Chagas, histoplasmosis, HTLV-1 y 2, citomegalovirus y Epstein-Barr resultaron negativas. La tomografía computarizadamuestra un plastrón ganglionar paraaórtico en retroperitoneo, así como ganglios decaracterísticas inflamatorios en ambas regiones prevasculares cervicales. Se decide la tomade biopsia de ganglio intra-abdominal, la cual reportó linfadenitis crónica granulomatosanecrotizante con presencia de estructuras micóticas intra y extracelulares compatiblescon P. brasiliensis. A pesar del resultado de la biopsia, la serología para el agente etiológicoresultó negativa. Se le diagnostica paracoccidioidomicosis ganglionar y se indicaanfotericina B por 14 días e itraconazol, el cual es sustituido debido a reacciones adversaspor trimetoprim-sulfametoxazol. Por mejoría del cuadro es egresado luego de 61 días dehospitalización. Las paracoccidioidomicosis por fuera de la descripción epidemiológicaclásica y en sus formas atípicas representan un verdadero reto para el diagnóstico médico,por lo que se deben tener en cuenta para asegurar un manejo adecuado de estos pacientes

Paracoccidioidomicosis ganglionar juvenil: reporte de un caso.

La paracoccidioidomicosis es una micosis sistémica profunda, producida por elhongo dimorfo Paracoccidioides brasiliensis, de carácter progresivo y granulomatoso.Se describen dos presentaciones de la enfermedad: la forma crónica, que ocurretradicionalmente en personas adultas dedicadas a la agricultura, y la forma aguda, subagudao juvenil, que corresponde a tan solo el 3-10% de los casos, caracterizándose por ser mássevera y contar con un peor pronóstico. Se presenta el caso de un paciente masculinode 11 años de edad, quien acude a centro hospitalario por presentar fiebre prolongada yadenopatías cervicales. Las serologías para enfermedad de Chagas, histoplasmosis, HTLV-1 y 2, citomegalovirus y Epstein-Barr resultaron negativas. La tomografía computarizadamuestra un plastrón ganglionar paraaórtico en retroperitoneo, así como ganglios decaracterísticas inflamatorios en ambas regiones prevasculares cervicales. Se decide la tomade biopsia de ganglio intra-abdominal, la cual reportó linfadenitis crónica granulomatosanecrotizante con presencia de estructuras micóticas intra y extracelulares compatiblescon P. brasiliensis. A pesar del resultado de la biopsia, la serología para el agente etiológicoresultó negativa. Se le diagnostica paracoccidioidomicosis ganglionar y se indicaanfotericina B por 14 días e itraconazol, el cual es sustituido debido a reacciones adversaspor trimetoprim-sulfametoxazol. Por mejoría del cuadro es egresado luego de 61 días dehospitalización. Las paracoccidioidomicosis por fuera de la descripción epidemiológicaclásica y en sus formas atípicas representan un verdadero reto para el diagnóstico médico,por lo que se deben tener en cuenta para asegurar un manejo adecuado de estos pacientes

Notes sur le genre Stanhopea (Orchidaceae). I

Volume: 15Start Page: 96End Page: 10