Clinical and preclinical studies that have examined the neurobiology of persistent fear memory in posttraumatic stress disorder (PTSD) have focused on the medial prefrontal cortex, hippocampus, and amygdala. Sensory systems, the periaqueductal gray (PAG), and midline thalamic nuclei have been implicated in fear and extinction memory, but whether…

Evaluative conditioning (EC) is a change in liking of neutral conditioned stimuli (CS) following pairings with positive or negative stimuli (unconditioned stimulus, US). A dissociation has been reported between US expectancy and CS evaluation in extinction learning: When CSs are presented alone subsequent to CS-US pairings, participants cease to…

Stimuli encoded shortly before an aversive event are typically well remembered. Traditionally, this emotional memory enhancement has been attributed to beneficial effects of physiological arousal on memory formation. Here, we proposed an additional mechanism and tested whether memory formation is driven by the unpredictable nature of aversive…

The neuronal systems that promote protective defensive behaviours have been studied extensively using Pavlovian conditioning. In this paradigm, an initially neutral-conditioned stimulus is paired with an aversive unconditioned stimulus leading the subjects to display behavioural signs of fear. Decades of research into the neural bases of this…

Studies on the behavioral mechanisms underlying contextual fear conditioning (CFC) have demonstrated the importance of preshock context exposure in the formation of aversive context memories. However, there has been comparatively little investigation of the effects of context exposure immediately after the shock. Some models predict that…

The relative contributions of plasticity in the amygdala vs. its afferent pathways to conditioned fear remain controversial. Some believe that thalamic and cortical neurons transmitting information about the conditioned stimulus (CS) to the lateral amygdala (LA) serve a relay function. Others maintain that thalamic and/or cortical plasticity is…

According to the retrieved context theory of episodic memory, the cue for recall of an item is a weighted sum of recently activated cognitive states, including previously recalled and studied items as well as their associations. We show that this theory predicts there should be compound cuing in free recall. Specifically, the temporal contiguity…

Pairs of rats foraged in trials either together or separately in an open field apparatus for pellets hidden in discreet locations in a 5 x 5 matrix. Trial duration was either 1 or 4 min. The tendency to choose locations that had earlier been visited by another rat was examined by comparing the choices made in the presence and absence of the other…

We examined the roles of the amygdala and hippocampus in the formation of emotionally relevant memories using an ethological model of conditioned fear termed conditioned defeat (CD). Temporary inactivation of the ventral, but not dorsal hippocampus (VH, DH, respectively) using muscimol disrupted the acquisition of CD, whereas pretraining VH…

It is well known that emotions participate in the regulation of social behaviors and that the emotion displayed by a conspecific influences the behavior of other animals. In its simplest form, empathy can be characterized as the capacity to be affected by and/or share the emotional state of another. However, to date, relatively little is known…

Research has shown that animals and humans habituate on a variety of behavioral and physiological responses to repeated presentations of food cues, and habituation is related to amount of food consumed and cessation of eating. The purpose of this article is to provide an overview of experimental paradigms used to study habituation, integrate a…

Studies on human and animals shed light on the unique hippocampus contributions to relational memory. However, the particular role of each hippocampal subregion in memory processing is still not clear. Hippocampal computational models and theories have emphasized a unique function in memory for each hippocampal subregion, with the CA3 area acting…

Long-term memory formation is regulated by many distinct molecular mechanisms that control gene expression. An emerging model for effecting a stable, coordinated pattern of gene transcription involves epigenetic tagging through modifications of histones or DNA. In this study, we investigated the regulation of histone phosphorylation in the…

Human conditioning research shows that learning is closely related to consciously available contingency knowledge, requires attentional resources, and is influenced by language. This research suggests a cognitive model in which extinction consists of changes in contingency beliefs in long-term memory. Laboratory and clinical evidence on extinction…