The dorsal (DH) and ventral (VH) subregions of the hippocampus are involved in contextual fear conditioning. However, it is still unknown whether these two brain areas also play a role in defensive behavior induced by electrical stimulation of the dorsal periaqueductal gray (dPAG). In the present study, rats were implanted with electrodes into the dPAG to determine freezing and escape response ...

After acquisition, memories associated with contextual fear conditioning pass through a labile phase, in which they are vulnerable to hippocampal lesions, to a more stable state, via consolidation, in which they engage extrahippocampal structures and are resistant to such disruption. The process is accompanied by changes in the form of the memory from being context-specific to context-general. ...

Pre-exposure to the context facilitates the small amount of contextual fear conditioning that is normally produced by immediate shock. This context pre-exposure facilitation effect provides a convenient way to study the rat's learning about context. We recently reported that anterograde damage to dorsal hippocampus prevents this facilitation. The present experiments strengthen this conclusion b...

Recent research suggests that in addition to its prominent role in appetitive learning, the nucleus accumbens (NAC) may also be involved in fear conditioning. In the present study, we investigated whether temporary inactivation of the NAC, by injection of tetrodotoxin (TTX), affects acquisition and expression of conditioned fear, as measured by fear-potentiated startle (FPS). TTX injection into...

We examined the effects of acute injections of competitive N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonovaleric acid (APV) into the dorsal hippocampus on contextual fear conditioning and classical eyeblink conditioning in C57BL/6 mice. When injected 10 to 40 min before training, APV severely impaired contextual fear conditioning. Thus, APV injection under these conditions ...

Numerous studies show that sleep deprivation (SD) impacts negatively on cognitive processes, including learning and memory. Memory formation encompasses distinct phases of which acquisition, consolidation and retrieval are better known. Previous studies with pre-training SD induced by the platform method have shown impairment in fear conditioning tasks. Nonetheless, pre-training manipulations d...

Anxiety disorders, such as post-traumatic stress, are more prevalent in women and are characterized by impaired inhibition of learned fear and medial prefrontal cortex (mPFC) dysfunction. Here we examined sex differences in fear extinction and mPFC activity in rats. Females showed more learned fear expression during extinction and its recall, but not fear conditioning. They also showed more spo...

................................................................................................ 2 Introduction............................................................................................4 Classical Conditioning........................................................................ 4 Fear Conditioning.................................................................................