Browsing by Author "Lopez, Vladimir"

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    Beta Oscillations Distinguish Between Two Forms of Mental Imagery While Gamma and Theta Activity Reflects Auditory Attention
    (2018) Villena González, Mario; Palacios García, Ismael José; Rodriguez, Eugenio; Lopez, Vladimir
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    ERPs and contextual semantic discrimination: Degrees of congruence in wakefulness and sleep
    (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2006) Ibanez, Agustin; Lopez, Vladimir; Cornejo, Carlos
    This study explores whether the brain can discriminate degrees of semantic congruency during wakefulness and sleep. Experiment 1 was conducted during wakefulness to test degrees of congruency by means of N400 amplitude. In Experiment 2, the same paradigm was applied to a different group of participants during natural night sleep. Stimuli were 108 sentences (definitions with two attributes) with four possible degrees of congruence as ending targets. In both studies, the amplitude of N400-like effect showed modulation according to the degree of congruency. The results indicate that the brain can accomplish sentential semantic discriminations not only in wakefulness but also in sleep. (c) 2006 Elsevier Inc. All rights reserved.
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    Gesture and metaphor comprehension: Electrophysiological evidence of cross-modal coordination by audiovisual stimulation
    (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2009) Cornejo, Carlos; Simonetti, Franco; Ibanez, Agustin; Aldunate, Nerea; Ceric, Francisco; Lopez, Vladimir; Nunez, Rafael E.
    In recent years, studies have suggested that gestures influence comprehension of linguistic expressions, for example, eliciting an N400 component in response to a speech/gesture mismatch. In this paper, we investigate the role of gestural information in the understanding of metaphors. Event related potentials (ERPs) were recorded while participants viewed video clips of an actor uttering metaphorical expressions and producing bodily gestures that were congruent or incongruent with the metaphorical meaning of such expressions. This modality of stimuli presentation allows a more ecological approach to meaning integration. When ERPs were calculated using gesture stroke as time-lock event, gesture incongruity with metaphorical expression modulated the amplitude of the N400 and of the late positive complex (LPC). This suggests that gestural and speech information are combined online to make sense of the interlocutor's linguistic production in an early stage of metaphor comprehension. Our data favor the idea that meaning construction is globally integrative and highly context-sensitive. (C) 2008 Elsevier Inc. All rights reserved.
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    Methodological considerations related to sleep paradigm using event related potentials
    (SOC BIOLGIA CHILE, 2008) Ibanez, Agustin M.; San Martin, Rene; Hurtado, Esteban; Lopez, Vladimir
    In the last few decades, several works on event related potentials (ERPs hereafter) during sleep have been reported. In Spite of numerous Studies, clear methodological rules for this kind Of Study are often missing, making it difficult to valorize the scope of these results. We propose here a description of methodological aspects to be considered when evaluating ERPs during sleep. The use of Rechtschaffen and Kales rules versus automatic methods is assessed, Plus the additional use of certain quantitative rneasures. Additionally, two topics are discussed which Must be controlled in ERPs sleep studies: the First Night Effect, and sleep disturbances. Better control of experimental paradigms is relevant for the growth of (lie neuroscience of sleep.
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    Voluntary modulations of attention in a semantic auditory-visual matching Task: an ERP study
    (SOC BIOLGIA CHILE, 2008) Ortega, Rodrigo; Lopez, Vladimir; Aboitiz, Francisco
    The present study explores the neural correlates of voluntary modulations of attention in an auditory-visual matching task. Visual stimuli (a female or a male face) were preceded in close temporal proximity by auditory stimuli consisting of the Spanish word for "man" and "woman" ("hombre" or "mujer"). In 80% of the trials the gender of the two stimuli coincided. Participants were asked to mentally count the specific instances in which a female face appeared after hearing the word "man" (10 % of the trials). Our results show attention-related amplitude modulation of the early visual ERP components NI and anterior P2, but also amplitude modulations of (i) the N270 potential usually associated with conflict detection, (ii) a P300 wave related to infrequency, and (iii) an N400 potential related to semantic incongruence. The elicitation of these latter components varied according to task manipulations, evidencing the role of voluntary allocation of attention in fine-tuning cognitive processing, which includes basic processes like detection of infrequency or semantic incongruity often considered to be volition-independent.