Browsing by Author "Cosmelli Sánchez, Diego José"

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    Clarifying the self: Response to Northoff
    (2011) Christoff, Katalina; Cosmelli Sánchez, Diego José; Legrand, Dorothée; Thompson, Evan
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    Cognitive strategies for mental calculation
    (CLAME-COMITE LATINOAMERICANO MAT EDUC, 2011) Galvez, Grecia; Cosmelli Sánchez, Diego José; Cubillos, Lino; Leger, Paul; Mena, Arturo; Tanter, Eric; Flores, Ximena; Luci, Gina; Montoya, Soledad; Soto Andrade, Jorge
    Abordamos el estudio de la variedad de estrategias cognitivas, idiosincrásicas o aprendidas, empleadas por alumnos del primer ciclo de la enseñanza básica chilena al practicar actividades de cálculo mental. Presentamos un diagnóstico del desempeño en tareas de cálculo mental aditivo (sumas y restas) de una muestra de alumnos de escuelas subvencionadas por el Estado, en estratos socio-económicos medios y medio-bajos en las ciudades de Santiago y Valparaíso, junto con un catastro de las estrategias observadas, así como una primera versión de un programa desarrollado por nosotros disponible en internet, que permite evaluar el desempeño de los alumnos, incluyendo sus tiempos de respuesta. Analizamos además la correlación entre el desempeño en las tareas propuestas (porcentaje de aciertos y tiempos de respuesta) y el rendimiento escolar promedio en matemáticas.
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    Neural Mechanisms of Human Perceptual Learning: Electrophysiological Evidence for a Two-Stage Process
    (2011) Hamamé, Carlos M.; Cosmelli Sánchez, Diego José; Henriquez, Rodrigo; Aboitiz Domínguez, Francisco Javier
    Background: Humans and other animals change the way they perceive the world due to experience. This process has been labeled as perceptual learning, and implies that adult nervous systems can adaptively modify the way in which they process sensory stimulation. However, the mechanisms by which the brain modifies this capacity have not been sufficiently analyzed.", "Methodology/Principal Findings: We studied the neural mechanisms of human perceptual learning by combining electroencephalographic (EEG) recordings of brain activity and the assessment of psychophysical performance during training in a visual search task. All participants improved their perceptual performance as reflected by an increase in sensitivity (d') and a decrease in reaction time. The EEG signal was acquired throughout the entire experiment revealing amplitude increments, specific and unspecific to the trained stimulus, in event-related potential (ERP) components N2pc and P3 respectively. P3 unspecific modification can be related to context or task-based learning, while N2pc may be reflecting a more specific attentional-related boosting of target detection. Moreover, bell and U-shaped profiles of oscillatory brain activity in gamma (30-60 Hz) and alpha (8-14 Hz) frequency bands may suggest the existence of two phases for learning acquisition, which can be understood as distinctive optimization mechanisms in stimulus processing.", "Conclusions/Significance: We conclude that there are reorganizations in several neural processes that contribute differently to perceptual learning in a visual search task. We propose an integrative model of neural activity reorganization, whereby perceptual learning takes place as a two-stage phenomenon including perceptual, attentional and contextual processes.
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    Shifting visual attention away from fixation is specifically associated with alpha band activity over ipsilateral parietal regions
    (2010) Cosmelli Sánchez, Diego José; López Hernández, Vladimir; Lachaux, Jean Philippe; López Calderón, Javier Ignacio; Renault, Bernard; Martinerie, Jacques; Aboitiz Domínguez, Francisco Javier
    We studied brain activity during the displacement of attention in a modified visuo-spatial orienting paradigm. Using a behaviorally relevant no-shift condition as a control, we asked whether ipsi- or contralateral parietal alpha band activity is specifically related to covert shifts of attention. Cue-related event-related potentials revealed an attention directing anterior negativity (ADAN) contralateral to the shift of attention and P3 and contingent negative variation waveforms that were enhanced in both shift conditions as compared to the no-shift task. When attention was shifted away from fixation, alpha band activity over parietal regions ipsilateral to the attended hemifield was enhanced relative to the control condition, albeit with different dynamics in the upper and lower alpha subbands. Contralateral-to-attended parietal alpha band activity was indistinguishable from the no-shift task.