In two instrumental conditioning experiments with rats, we examined the impacts of acquisition and extinction cues on ABC renewal of instrumental behavior. Animals were reinforced with food for lever pressing in one context, followed by extinction of the response in a second one. Presentations of a brief tone accompanied extinction in Experiment 1…

We investigated whether cycloheximide (CHX) would induce amnesia for the stress-induced impairment of extinction retrieval. First, a single restraint stress session was demonstrated to impair extinction retrieval, but not fear conditioning. A second experiment showed that when CHX was administered immediately after restraint, rats exhibited…

Signaled active avoidance (SAA) behavior requires the suppression of defensive reactions, such as freezing, that conflict with the avoidance response. The neural mechanisms of this inhibitory process are not well understood. Here, we demonstrate that ventromedial prefrontal cortex projections to the nucleus reuniens of the thalamus are recruited…

The present study evaluates the updating of long-term memory for duration. After learning a temporal discrimination associating one lever with a standard duration (4 sec) and another lever with both a shorter (1-sec) and a longer (16-sec) duration, rats underwent a single session for learning a new standard duration. The temporal generalization…

Females are at higher risk for certain opioid addictive behaviors, but the influence of ovarian hormones is unknown. In our rat model of heroin self-administration, females exhibited higher relapse rates that correlated with rates of heroin seeking on the first extinction session. We administered estradiol alone, or in combination with…

Trait anxiety is considered to be a risk factor for anxiety disorders. The aim of the present study was to investigate how trait anxiety affects associative learning during and after an aversive event in laboratory rats. For this, rats were first submitted to a light-dark box test, followed by relief, safety, and fear learning. Our data…

Temporal order memory was analyzed using a spontaneous object recognition (SOR) paradigm in rats. In SOR, animals were allowed to explore freely two or five different objects sequentially in the sample phase, and then, two different objects shown in the sample phase were simultaneously presented, and exploration time of object shown earlier…

Conditioned fear memories that are context-specific shortly after conditioning generalize over time. We exposed rats to a context reminder 30 d after conditioning, which served to reinstate context-specificity, and investigated how this reminder alters retrieval-induced activity in the hippocampus and anterior cingulate cortex (aCC) relative to a…

Signaled active avoidance (SigAA) is the key experimental procedure for studying the acquisition of instrumental responses toward conditioned threat cues. Traditional analytic approaches (e.g., general linear model) often obfuscate important individual differences, although individual differences in learned responses characterize both animal and…

Cognitive flexibility refers to various processes which enable behaviors to be modified on the basis of a change in the contingencies between stimuli or responses and their associated outcomes. Reversal learning is a form of cognitive flexibility which measures the ability to adjust responding based on a switch in the stimulus--outcome…

Recognition memory deficits, even after short delays, are sometimes observed following hippocampal damage. One hypothesis links the hippocampus with processes in updating contextual memory representation. Here, we used fornix transection, which partially disconnects the hippocampal system, and compares the performance of fornix-transected monkeys…

The severe amblyopia induced by chronic monocular deprivation is highly resistant to reversal in adulthood. Here we use a rodent model to show that recovery from deprivation amblyopia can be achieved in adults by a two-step sequence, involving enhancement of synaptic plasticity in the visual cortex by dark exposure followed immediately by visual…

Emerging research has demonstrated that the sex hormone estradiol regulates fear extinction in female rodents and women. Estradiol may also regulate fear extinction in males, given its role in synaptic plasticity in both sexes. Here we report that inhibition of estradiol synthesis during extinction training, via the aromatase inhibitor fadrozole,…

Lasting memories are likely to result from a lasting change in neurotransmission. In the nematode "Caenorhabditis elegans," spaced training with a tap stimulus induces habituation to the tap that lasts for greater than 24 h and is dependent on glutamate transmission, postsynaptic AMPA receptors, and CREB. Here we describe a distinct, presynaptic…

In "Aplysia," repeated trials of aversive stimuli produce long-term sensitization (LTS) of defensive reflexes and suppression of feeding. Whereas the cellular underpinnings of LTS have been characterized, the mechanisms of feeding suppression remained unknown. Here, we report that LTS training induced a long-term decrease in the excitability of…