Browsing by Author "Lagos, R."
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Item Attending to the heart is associated with posterior alpha band increase and a reduction in sensitivity to concurrent visual stimuli.(2017) Villena-González, M.; Moënne-Loccoz, C.; Lagos, R.; Alliende, Luz M.; Billeke, Pablo; Aboitiz, Francisco; López, V.; Cosmelli, D.Attentional mechanisms have been studied mostly in specific sensory domains, such as auditory, visuospatial, or tactile modalities. In contrast, attention to internal interoceptive visceral targets has only recently begun to be studied, despite its potential importance in emotion, empathy, and self-awareness. Here, we studied the effects of shifting attention to the heart using a cue-target detection paradigm during continuous EEG recordings. Subjects were instructed to count either a series of visual stimuli (visual condition) or their own heartbeats (heart condition). Visual checkerboard stimuli were used as attentional probes throughout the task. Consistent with previous findings, attention modulated the amplitude of the heartbeat-evoked potentials. Directing attention to the heart significantly reduced the visual P1/N1 amplitude evoked by the attentional probe. ERPs locked to the attention-directing cue revealed a novel frontal positivity around 300 ms postcue. Finally, spectral power in the alpha band over parieto-occipital regions was higher while attending to the heart-when compared to the visual task-and correlated with subject's performance in the interoceptive task. These results are consistent with a shared, resource-based attentional mechanism whereby allocating attention to bodily signals can affect early responses to visual stimuli.Item Collapse risk assessment of a Chilean dual wall-frame reinforced concrete office building(2019) Araya-Letelier, G.; Parra, P.F.; Lopez-Garcia, D.; Garcia-Valdes, A.; Candia, Gabriel; Lagos, R.Several code-conforming reinforced concrete buildings were severely damaged during the 2010 moment magnitude (Mw) 8.8 Chile earthquake, raising concerns about their real collapse margin. Although critical updates were introduced into the Chilean design codes after 2010, guidelines for collapse risk assessment of Chilean buildings remain insufficient. This study evaluates the collapse potential of a typical dual system (shear walls and moment frames) office building in Santiago. Collapse fragility functions were obtained through incremental dynamic analyses using a state-of-the-art finite element model of the building. Site-specific seismic hazard curves were developed, which explicitly incorporated epistemic uncertainty, and combined with the collapse fragility functions to estimate the mean annual frequency of collapse (λc) values and probabilities of collapse in 50-years (Pc(50)). Computed values of λc and Pc(50) were on the order of 10−5–10−4, and 0.1–0.7%, respectively, consistent with similar studies developed for buildings in the US. The results also showed that the deaggregation of λc was controlled by small to medium earthquake intensities and that different models of the collapse fragility functions and hazard curves had a non-negligible effect on λc and Pc(50), and thus, propagation of uncertainty in risk assessment problems must be adequately taken into account.