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Temporary Inactivation (temporary + inactivation)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Temporary inactivation of the perirhinal cortex by muscimol injections block acquisition and expression of fear-potentiated startle

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2004
Brigitte Schulz
Abstract The present study examined the role of the perirhinal cortex (PRh) in aversive information processing and emotional learning. Specifically, we studied the effects of temporary inactivation of the PRh on acquisition and expression of conditioned fear as measured by fear-potentiated startle in rats, as well as on shock sensitization of startle. Temporary inactivation of the PRh was induced by local injections of the GABAA agonist muscimol (0.0, 1.1, 2.2, 4.4 nmol/0.5 µL). Muscimol injections into the PRh blocked both the expression and acquisition of fear-potentiated startle, as well as shock sensitization of startle. Shock sensitivity was not affected by muscimol injections, indicating that the observed blockade of acquisition and shock sensitization was not caused by a disruption in the perception of shock. Taken together, the present data show that the PRh is critical for the processing of aversive information and is necessary for the expression of emotional learning. [source]

Cooperation and competition between the dorsal hippocampus and lateral amygdala in spatial discrimination learning

HIPPOCAMPUS, Issue 7 2006
Stephane Gaskin
Abstract The conditioned cue preference (CCP) was used to study how rats discriminate between adjacent arms on a radial maze. Chai and White (Behav Neurosci 2004, 118:770,784) showed that an intact dorsal hippocampus is required to learn this discrimination and that an amygdala-based conditioned approach response that produces an equal tendency to enter both arms is simultaneously acquired. In the present experiments, rats were preexposed to the maze with no food and trained by alternately confining them at the ends of two adjacent arms, one that contained food and one that did not. When given a choice between these arms with no food present, the rats spent more time on their food-paired arms, suggesting they had learned to discriminate their locations. Temporary inactivation of the dorsal hippocampus with muscimol during confinement on the food-paired arm had no effect on the discrimination, but inactivation while on the no-food arm impaired it. This pattern of effects was reversed in rats with amygdala lesions (inactivation on the food-paired arm impaired, but inactivation on the no-food arm had no effect on the discrimination), showing that hippocampus-based and amygdala-based learning interact to influence the behavior of normal rats in this situation. The dorsal hippocampus learns about locations that contain food and about locations that do not contain food. The amygdala-based tendency to enter the food-paired arm cooperates with hippocampus-based foraging for food on the food-paired, but the amygdala-based tendency to enter the no-food arm competes with hippocampus-based learning about the absence of food on that arm. © 2006 Wiley-Liss, Inc. [source]

Temporary inactivation of the perirhinal cortex by muscimol injections block acquisition and expression of fear-potentiated startle

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2004
Brigitte Schulz
Abstract The present study examined the role of the perirhinal cortex (PRh) in aversive information processing and emotional learning. Specifically, we studied the effects of temporary inactivation of the PRh on acquisition and expression of conditioned fear as measured by fear-potentiated startle in rats, as well as on shock sensitization of startle. Temporary inactivation of the PRh was induced by local injections of the GABAA agonist muscimol (0.0, 1.1, 2.2, 4.4 nmol/0.5 µL). Muscimol injections into the PRh blocked both the expression and acquisition of fear-potentiated startle, as well as shock sensitization of startle. Shock sensitivity was not affected by muscimol injections, indicating that the observed blockade of acquisition and shock sensitization was not caused by a disruption in the perception of shock. Taken together, the present data show that the PRh is critical for the processing of aversive information and is necessary for the expression of emotional learning. [source]

Disrupting basolateral amygdala function impairs unconditioned freezing and avoidance in rats

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2001
Almira Vazdarjanova
Abstract Lesions of the lateral/basolateral amygdala nuclei (BLC) disrupt freezing behaviour in response to explicit or contextual cues (conditioned stimuli , CS) paired previously with footshock (unconditioned stimulus). This deficit in expression of defensive behaviour in response to conditioned stimuli is often interpreted as inability of lesioned rats to learn CS,US associations. However, findings of several studies indicate that BLC-lesioned rats can rapidly learn CS,US associations. Such findings suggest that lesioned rats can learn CS,US associations but are impaired in the expression of freezing behaviour. In the present study we report that both temporary inactivation (lidocaine) and permanent excitotoxic (NMDA) lesions of the BLC impair the unconditioned freezing and avoidance behaviours of rats in response to a novel fear-eliciting stimulus, a ball of cat hair. These findings suggest that the BLC influences the expression of freezing and avoidance behaviours, and/or that it potentiates rats' experience of fear. Along with prior evidence of spared memory for aversive learning after BLC lesions, these findings suggest that disrupted freezing to conditioned cues in BLC-lesioned rats does not necessarily reflect inability to form CS,US associations. [source]