Dopamine participates in encoding memories and could either encode rewarding/aversive value of unconditioned stimuli or act as a novelty signal triggering contextual learning. Here we show that intraperitoneal injection of the dopamine D1/5R antagonist SCH23390 impairs contextual fear conditioning and tone-shock association, while intrahippocampal…

Awake quiescence immediately after encoding is conducive to episodic memory consolidation. Retrieval can render episodic memories labile again, but reconsolidation can modify and restrengthen them. It remained unknown whether awake quiescence after retrieval supports episodic memory reconsolidation. We sought to examine this question via an…

During associative retrieval, the brain reinstates neural representations that were present during encoding. The human medial temporal lobe (MTL), with its subregions hippocampus (HC), perirhinal cortex (PRC), and parahippocampal cortex (PHC), plays a central role in neural reinstatement. Previous studies have given compelling evidence for…

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…

Recognition memory judgments can be influenced by a variety of signals including fluency. Here, we investigated whether the neural correlates of memory illusions (i.e., misattribution of fluency to prior study) can be modulated by fluency context. Using a masked priming/recognition memory paradigm, we found memory illusions for low confidence…

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…

Why we remember emotional events with an increased subjective sense of remembering (SSR) is unclear. SSR for neutral events is linked to memory for various kinds of details. Using the Remember/Know paradigm, participants provided written justifications of their Remember responses indicating what they specifically recollected about a negative or…

Older adults exhibit disproportionate impairments in memory for item-associations. These impairments may stem from an inability to self-initiate deep encoding strategies. The present study investigates this using the "treasure-hunt task"; a what-where-when style episodic memory test that requires individuals to "hide" items…

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…

Declarative memory performance is superior for items that were encoded in temporal proximity to reward delivery or expectancy. How reward-predicting contexts affect subsequent declarative memory formation in those contexts are, however, unknown. Using an ecological experimental setup in the form of a naturalistic driving simulator task, we…

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…

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…

Extinction training during reconsolidation has been shown to persistently diminish conditioned fear responses across species. We investigated in humans if older fear memories can benefit similarly. Using a Pavlovian fear conditioning paradigm we compared standard extinction and extinction after memory reactivation 1 d or 7 d following acquisition.…

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…