Habituation of the eyeblink response in humans with stimuli presented in a sequence of incremental intensity

In an experiment we examined whether the repeated presentation of tones of gradually increasing intensities produces greater decrement in the eyeblink reflex response in humans than the repetition of tones of constant intensities. Two groups of participants matched for their initial level of response were exposed to 110 tones of 100-ms duration. For the participants in the incremental group, the tones increased from 60- to 90- dB in 3-dB steps, whereas participants in the constant group received the tones at a fixed 90-dB intensity. The results indicated that the level of response in the last block of 10 trials, in which both groups received 90-dB tones, was significantly lower in the incremental group than in the constant group. These findings support the data presented by Davis and Wagner (7) with the acoustic response in rats, but differ from several reports with autonomic responses in humans, where the advantage of the incremental condition has not been observed unambiguously. The discussion analyzes theoretical approaches to this phenomenon and the possible involvement of separate neural circuits.

Factores ambientales y psicosociales vinculados a síntomas de ataque de pánico después del terremoto y tsunami del 27 de febrero de 2010 en la zona central de Chile / Environmental and psychosocial factors associated with panic attack symptoms after the February 27 2010 earthquake and tsunami in the Central Zone of Chile

La presente investigación proporciona una primera evaluación de síntomas de ataque de pánico y su relación con algunas variables asociadas con la magnitud del daño sufrido por las personas expuestas al terremoto del 27 de Febrero de 2010 en la zona central de Chile. Un total de 150 habitantes de diversas localidades fueron evaluados para determinar la presencia de síntomas de ataque de pánico dentro de las dos semanas posteriores a la catástrofe. Los resultados indican más síntomas de crisis de pánico en aquellas personas que sufrieron pérdidas de bienes y en aquellos que estuvieron expuestos al tsunami o riesgo de tsunami. Se discute la necesidad de evaluar otros trastornos (p.e., estrés post-traumático) y poblaciones (p.e., niños), así como también la importancia de crear indicadores cuantitativos del impacto de estas catástrofes, basados en la combinación de variables tales como la intensidad del sismo y la magnitud del daño personal.

The present research provides a first screening of the presence of panic attack symptoms and their relation to some variables associated with the magnitude of the damage suffered by individuals exposed to the earthquake occurred on February 27 2010 in the central zone of Chile. A total of 150 adults that lived in several cities and villages of the central zone of Chile were as-sessed to determine the presence of panic attack symptoms within the first two weeks after the catastrophe. The results indicate more physical and psychical panic attack symptoms on those individuals that lose some of their belongings and on those that were exposed to the tsunami or risk of tsunami. The discussion emphasizes the need for evaluating further disorders (e.g., post-traumatic stress) and to examine at-risk populations (e.g., children). It is suggested the importance of creating quantitative indexes based on variables such as extent of the loss, physical damage and quake intensity, to asses the individual impact of this sort of catastrophes.

Asociaciones excitatorias entre el contexto y la consecuencia en la reinstalación de respuestas extinguidas en el aprendizaje causal humano / Excitatory context-consequence associations in the reinstatement of extinguished responses in human causal learning

En dos experimentos, estudiantes universitarios aprendieron una relación predictiva entre un evento y una consecuencia, la que posteriormente fue extinguida presentando el evento sin la consecuencia. En el Experimento 1, se presentó la consecuencia por sí sola después de la extinción, ocasionando la reaparición de la relación predictiva aprendida originalmente, asemejándose al fenómeno del condicionamiento Pavloviano conocido como "reinstalación". Este experimento demostró además, que no es necesario apelar a asociaciones inhibitorias para explicar la reinstalación, sino que solamente a asociaciones excitatorias entre el contexto y la consecuencia. El Experimento 2 confirmó la generalidad de estos hallazgos utilizando otro procedimiento de aprendizaje causal. Se discuten estos hallazgos en términos de las diferencias entre el aprendizaje causal y el condicionamiento Pavloviano y de la posible existencia de dos mecanismos alternativos de extinción: desaprendizaje para extinguir asociaciones no consolidadas e inhibición para las consolidadas.

In two experiments, undergraduates learned a predictive relationship between an event and a consequence, which was subsequently extinguished by presenting the event without the consequence. In Experiment 1, participants were exposed to the consequence by itself after extinction, occasioning the reappearance of the originally learned predictive relationship, resembling a phenomenon known as Reinstatement in the field of Pavlovian conditioning. This experiment further demonstrated that reinstatement can be explained without appealing to inhibitory associations, but only by mean of excitatory associations between the context and the consequence. Experiment 2 confirmed the generality of these findings using a different procedure of causal learning. The findings are discussed in terms of differences between Pavlovian conditioning and causal learning and of the possible existence of two mechanisms of extinction: unlearning to extinguish non consolidated associations and inhibition for the consolidated associations.