Shock, immobilization, and exposure to predator-related stimuli have all been used to study fear conditioning in rodents, but they have never been used in conjunction in a single study. Experiment 1 compared the effec...Shock, immobilization, and exposure to predator-related stimuli have all been used to study fear conditioning in rodents, but they have never been used in conjunction in a single study. Experiment 1 compared the effects of these three reinforcers, alone and in various combinations, on the expression of long-term conditioned fear memory and extinction in adult male rats. Whereas foot shock conditioning, alone, was rapidly extinguished;the combination of immobilization and cat exposure, or all 3 stimuli together, produced a significant increase in the magnitude of fear conditioning and greater resistance to extinction, which persisted for at least 5 weeks post-training (p < 0.05). Experiment 2 assessed the role of the hippocampus in predator-based context and cued fear conditioning. Pharmacological suppression of hippocampal activity during fear conditioning produced a selective impairment of contextual, but not cued, fear memory. Experiment 3 investigated the effects of sleep deprivation prior to fear conditioning on the expression of fear memory. This experiment demonstrated that pre-training sleep deprivation blocked the expression of contextual (hippocampal-dependent), but not cued (hippocampal-independent), fear memory. Overall, this series of experiments has extended the use of predator exposure in conjunction with conventional reinforcers, such as foot shock and immobilization, to advance our understanding of the neurobiology of traumatic memory.展开更多
Most studies of predator-induced plasticity have focused on documenting how prey species re- spond to predators by modifying phenotypic traits and how traits correlate with fitness. We have previously shown that Pleur...Most studies of predator-induced plasticity have focused on documenting how prey species re- spond to predators by modifying phenotypic traits and how traits correlate with fitness. We have previously shown that Pleurodema thaul tadpoles exposed to the dragonfly Rhionaeschna varie- gata responded strongly by showing morphological changes, less activity, and better survival than non-exposed tadpoles. Here, we tested whether there is a functional link between morphological plasticity and increased survival in the presence of predators. Tadpoles that experienced predation risk were smaller, less developed, and much less active than tadpoles without this experience. Burst speed did not correlate significantly with morphological changes and predator-induced deeper tails did not act as a lure to divert predator strikes away from the head. Although we have previously found that tadpoles with predator-induced morphology survive better under a direct predator threat, our results on the functional link between morphology and fitness are not conclu- sive. Our results suggest that in P. thaultadpoles （1） burst speed is not important to evade preda- tors, （2） those exposed to predators reduce their activity, and （3） morphological changes do not divert predator attacks away from areas that compromise tadpole survivalEE. Our results show that morphological changes in P. thaul tadpoles do not explain burst speed or lure attraction, al- though there was a clear reduction of activity, which itself reduces predation. We propose that changes in tadpole activity could be further analyzed from another perspective, with morphological change as an indirect product of behavior mediated by physiological mechanisms.展开更多
文摘Shock, immobilization, and exposure to predator-related stimuli have all been used to study fear conditioning in rodents, but they have never been used in conjunction in a single study. Experiment 1 compared the effects of these three reinforcers, alone and in various combinations, on the expression of long-term conditioned fear memory and extinction in adult male rats. Whereas foot shock conditioning, alone, was rapidly extinguished;the combination of immobilization and cat exposure, or all 3 stimuli together, produced a significant increase in the magnitude of fear conditioning and greater resistance to extinction, which persisted for at least 5 weeks post-training (p < 0.05). Experiment 2 assessed the role of the hippocampus in predator-based context and cued fear conditioning. Pharmacological suppression of hippocampal activity during fear conditioning produced a selective impairment of contextual, but not cued, fear memory. Experiment 3 investigated the effects of sleep deprivation prior to fear conditioning on the expression of fear memory. This experiment demonstrated that pre-training sleep deprivation blocked the expression of contextual (hippocampal-dependent), but not cued (hippocampal-independent), fear memory. Overall, this series of experiments has extended the use of predator exposure in conjunction with conventional reinforcers, such as foot shock and immobilization, to advance our understanding of the neurobiology of traumatic memory.
文摘Most studies of predator-induced plasticity have focused on documenting how prey species re- spond to predators by modifying phenotypic traits and how traits correlate with fitness. We have previously shown that Pleurodema thaul tadpoles exposed to the dragonfly Rhionaeschna varie- gata responded strongly by showing morphological changes, less activity, and better survival than non-exposed tadpoles. Here, we tested whether there is a functional link between morphological plasticity and increased survival in the presence of predators. Tadpoles that experienced predation risk were smaller, less developed, and much less active than tadpoles without this experience. Burst speed did not correlate significantly with morphological changes and predator-induced deeper tails did not act as a lure to divert predator strikes away from the head. Although we have previously found that tadpoles with predator-induced morphology survive better under a direct predator threat, our results on the functional link between morphology and fitness are not conclu- sive. Our results suggest that in P. thaultadpoles （1） burst speed is not important to evade preda- tors, （2） those exposed to predators reduce their activity, and （3） morphological changes do not divert predator attacks away from areas that compromise tadpole survivalEE. Our results show that morphological changes in P. thaul tadpoles do not explain burst speed or lure attraction, al- though there was a clear reduction of activity, which itself reduces predation. We propose that changes in tadpole activity could be further analyzed from another perspective, with morphological change as an indirect product of behavior mediated by physiological mechanisms.
