Evidence suggests that extinction is new learning. Memory acquisition involves both short-term memory (STM) and long-term memory (LTM) components; however, few studies have examined early phases of extinction retention. Retention of auditory fear extinction was examined at various time points. Shortly (1-4 h) after extinction acquisition spontaneous recovery was high compared to that after long...

In humans, activation of the ventral striatum, a region associated with reward processing, is associated with the extinction of fear, a goal in the treatment of fear-related disorders. This evidence suggests that extinction of aversive memories engages reward-related circuits, but a causal relationship between activity in a reward circuit and fear extinction has not been demonstrated. Here, we ...

Extinction learning underlies the treatment for a variety of anxiety disorders. Most of what is known about the neurobiology of extinction is based on standard "delay" fear conditioning, in which awareness is not required for learning. Little is known about how complex, explicit associations extinguish, however. "Trace" conditioning is considered to be a rodent model of explicit fear because it...

introduction: activation of n-methyl-d-aspartate (nmda) glutamate receptors in the nucleus accumbens is a component of drug-induced reward mechanism. in addition, nmda receptors play a major role in brain reward system and activation of these receptors can change firing pattern of dopamine neurons. blockade of glutamatergic neurotransmission reduces the expression of conditioned place preferenc...

A series of experiments used rats to study the effect of a systemic or intra-amygdala infusion of the benzodiazepine, midazolam, on learning and re-learning to inhibit context conditioned fear (freezing) responses. Rats were subjected to two context-conditioning episodes followed by extinction under drug or vehicle, or to two cycles of context conditioning and extinction with the second extinct...

Previous research indicates that extinction of rodent maze behavior may occur without explicit performance of the previously acquired response. In latent extinction, confining an animal to a previously rewarded goal location without reinforcement is typically sufficient to produce extinction of maze learning. However, previous studies have not determined whether latent extinction may be success...

porcine necrotic ear syndrome (pnes) in pigs has been reported as an increasing health problem in many countries with intensive pig farming. the etiology of this disease is complex and the presumed triggering factors can be divided into infectious and non-infectious agents. the present report describes a case of porcine circovirus type 2 (pcv2), infection associated with lesions of pnes at the ...

the objective of the current study was to determine the anatomical features of the auditory ossicles inhamster. twenty temporal bones from 10 adult hamsters, weighing 275-300 g were used. after dissectingthem, the features of the ossicles were assessed with an ocular micrometer and photographed by astereomicroscope. finally, all data were evaluated and analysed using the sigma statt software. t...