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Fearfulness Measures

DECREASING FEARFULNESS THROUGH PRENATAL AND POSTNATAL EXPOSURE TO FEAR-INDUCING AUDITORY STIMULI Michael Suarez & Robert Lickliter Florida International University Miami, FL. Introduction. Exploration Measures

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Fearfulness Measures

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  1. DECREASING FEARFULNESS THROUGH PRENATAL AND POSTNATAL EXPOSURE TO FEAR-INDUCING AUDITORY STIMULI Michael Suarez & Robert Lickliter Florida International University Miami, FL Introduction • Exploration Measures • Subjects exposed to the aversive tone for 24 hoursprenatally explored a significantly greater proportion of the maze in the presence of the tone than chicks receiving no prior exposure, (Z = -1.86, p ≤ .05; one-tailed). • Subjects exposed to the aversive tone for 24 hours eitherprenatally or postnally completed the maze in significantly less time than chicks receiving no prior exposure. Prenatal = (Z = -2..30, p ≤ .05; one-tailed) Postnatal = (Z = -2.24, p ≤ .05; one-tailed) • Subjects exposed to the aversive tone for 24 hours eitherprenatally or postnally traveled a significantly greater distance than those receiving no prior exposure. • Prenatal = (Z = -2.38, p ≤ .01; one-tailed) Postnatal = (Z = -2.90, p ≤ .005; one-tailed) • Measures of fearfulness included time spent immobile, mean velocity of movement, and latency to emerge from the first chamber of the maze. • Measures of exploration included percentage of the maze • explored, latency to maze completion, and total distance traveled. • The role of novelty and early life experience on the development of fearfulness is an area of research that has remained relatively unexplored. • Neophobia has been shown to develop early in life both in animals and humans, and may be a contributing factor to the extent to which stimuli initially develop fear-inducing properties that can be perpetuated throughout the life-cycle (Thorpe, 1963; Cavigelli & McClintock, 2003). • The goal of this study was to determine if fearfulness of a specific aversive auditory stimulus could be attenuated through either prenatal or postnatal exposure to that stimulus and to observe how this exposure can affect exploratory behavior when subsequently tested in the presence of the same aversive auditory stimulus. Results • Fearfulness Measures • Subjects exposed to the aversive tone for 24 hours eitherprenatally or postnally spent significantly less time • immobile than chicks receiving no prior exposure. • Prenatal = (Z = -1.99, p ≤ .05; one-tailed) Postnatal = (Z = -1.92, p ≤ .05; one-tailed) • Subjects exposed to the aversive tone for 24 hours eitherprenatally or postnally had a significantly higher mean velocity of movement than chicks receiving no prior exposure. Prenatal = (Z = -2.33, p ≤ .01; one-tailed) Postnatal = (Z = -2.83, p ≤ .005; one-tailed) • Latency to emerge from the starting chamber of the maze did not • differ significantly between subjects receiving prior exposure to the aversive tone and those receiving no prior exposure. Methods • Northern bobwhite quail (Colinus virginianus) chicks received either 24 hours of prenatal exposure, 24 hours of postnatal exposure, or no prior exposure to a novel aversive auditory stimulus. • Chicks were subsequently tested individually for 20 minutes within a novel maze in the presence of the aversive auditory stimulus at 24 hours of age. • A condition in which chicks were tested in the presence of a bobwhite maternal call served as a reference group for how chicks would behave when tested in the presence of a known attractive stimulus. * * * * * * * * * * Conclusions • The results of this study reveal that both prenatal and postnatal exposure to an aversive auditory stimulus can act to reduce fearfulness in quail chicks when they are subsequently tested in the presence of the same auditory stimulus. • These results also reveal that chicks exposed to an aversive auditory stimulus, either prenatally or postnatally, demonstrate increased willingness to explore a novel maze task when tested in the presence of the aversive stimulus. • These results suggest that it may be possible to attenuate fear of specific aversive stimuli by means of early life exposure, thereby potentially preventing those stimuli from attaining fear-inducing properties later in life. Acknowledgements This research was supported by NSF BCS1057898 RL) and by NIH/NIGMS R25 GM061347 (MS). Travel grant provided by NIH (NICHD) and the Sackler Institute (MS). References Cavigelli, S. A. & McClintock, M. K. (2003). Fear of novelty in infant rats predicts adult corticosterone dynamics and an early death. Proceedings of the National Academy of Sciences, 100, 16131-16136. Thorpe, W. H. (1963). Learning and Instinct in Animals, 2nd ed. (1st. ed., 1956), Methuen, London.

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