Learning & Memory

Sleep supports memory consolidation, and slow-wave sleep (SWS) in particular is assumed to benefit the consolidation of verbal learning material. Re-exposure to previously learned words during SWS with a technique known as targeted memory reactivation (TMR) consistently benefits memory. However, TMR has also been successfully applied during sleep stage N2, though a direct comparison between words selectively reactivated during SWS versus N2 is still missing. Here, we directly compared the effects of N2 TMR and SWS TMR on memory performance in a vocabulary learning task in a within-subject design...

Transitive inference is a measure of relational learning that has been shown to improve across sleep. Here, we examine this phenomenon further by studying the impact of encoding strength and joint rank. In experiment 1, participants learned adjacent premise pairs and were then tested on inferential problems derived from those pairs. In line with prior work, we found improved transitive inference performance after retention across a night of sleep compared with wake alone. Experiment 2 extended these findings using a within-subject design and found superior transitive inference performance on a hierarchy, consolidated across 27 h including sleep compared with just 3 h of wake...

Sleep benefits memory consolidation. However, factors present at initial encoding may moderate this effect. Here, we examined the role that encoding strategy plays in subsequent memory consolidation during sleep. Eighty-nine participants encoded pairs of words using two different strategies. Each participant encoded half of the word pairs using an integrative visualization technique, where the two items were imagined in an integrated scene. The other half were encoded nonintegratively, with each word pair item visualized separately...

Performing a motor response to a sensory stimulus creates a memory trace whose behavioral correlates are classically investigated in terms of repetition priming effects. Such stimulus-response learning entails two types of associations that are partly independent: (1) an association between the stimulus and the motor response and (2) an association between the stimulus and the classification task in which it is encountered. Here, we tested whether sleep supports long-lasting stimulus-response learning on a task requiring participants (1) for establishing stimulus-classification associations to classify presented objects along two different dimensions ("size" and "mechanical") and (2) as motor response (action) to respond with either the left or right index finger...

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Reward improves memory through both encoding and consolidation processes. In this preregistered study, we tested whether reward effects on memory generalize from high-rewarded items to low-rewarded but episodically related items. Fifty-nine human volunteers incidentally encoded associations between unique objects and repeated scenes. Some scenes typically yielded high reward, whereas others typically yielded low reward. Memory was tested immediately after encoding ( n = 29) or the next day ( n = 30). Overall, reward had only a limited influence on memory...

An inability to reduce fear in nonthreatening environments characterizes many anxiety disorders. The pathway from the ventral subiculum (vSUB) to the bed nucleus of the stria terminalis (BNST) is more active in safe contexts than in aversive ones, as indexed by FOS expression. Here, we used chemogenetic techniques to specifically activate the vSUB-BNST pathway during both context and cued fear expression by expressing a Cre-dependent hM3D(Gq) receptor in BNST-projecting vSUB neurons. Activation of the vSUB-BNST pathway reduced context but not cued fear expression...

Retrieving existing memories before new learning can lead to retroactive facilitation. Three experiments examined whether interpolated retrieval is associated with retroactive facilitation and memory interdependence that reflects integrative encoding. Participants studied two lists of cue-response word pairs that repeated across lists (A-B, A-B), appeared in list 1 (A-B, -), or included the same cues with changed responses in each list (A-B, A-C). For A-B, A-C pairs, the tasks interpolated between lists required recall of list 1 (B) responses (with or without feedback) or restudy of complete list 1 (A-B) pairs...

Fear conditioning is a laboratory paradigm commonly used to investigate aversive learning and memory. In context fear conditioning, a configuration of elemental cues (conditioned stimulus [CTX]) predicts an aversive event (unconditioned stimulus [US]). To quantify context fear acquisition in humans, previous work has used startle eyeblink responses (SEBRs), skin conductance responses (SCRs), and verbal reports, but different quantification methods have rarely been compared. Moreover, preclinical intervention studies mandate recall tests several days after acquisition, and it is unclear how to induce and measure context fear memory retention over such a time interval...

Prefrontal cortical and striatal areas have been identified by inactivation or lesion studies to be required for behavioral flexibility, including selecting and processing of different types of information. In order to identify these networks activated selectively during the acquisition of new reward contingency rules, rats were trained to discriminate orientations of bars presented in pseudorandom sequence on two video monitors positioned behind the goal sites on a T-maze with return arms. A second group already trained in the visual discrimination task learned to alternate left and right goal arm visits in the same maze while ignoring the visual cues still being presented...

Glucocorticoids are potent memory modulators that can modify behavior in an adaptive or maladaptive manner. Elevated glucocorticoid levels after learning promote memory consolidation at recent time points, but their effects on remote time points are not well established. Here we set out to assess whether corticosterone (CORT) given after learning modifies remote fear memory. To that end, mice were exposed to a mild auditory fear conditioning paradigm followed by a single 2 mg/kg CORT injection, and after 28 d, auditory memory was assessed...

The hippocampus supports distinctive encoding, enabling discrimination of perceptions from similar memories. Here, an experimental and individual differences approach examined the role of encoding quality in the classification of similar lures. An object recognition task included thought probes during study and similar lures at test. On-task study reports were associated with lure discrimination in within-subject and between-subjects analyses. Within-subject on-task reports were also associated with false classifications of lures as studied objects...

Long-term memory (LTM) formation is dependent on neurochemical changes that guarantee that a recently formed memory (short-term memory [STM]) remains in the specific neural circuitry via the consolidation process. The persistence of recognition memory has been evidenced by using behavioral tagging in young adult rats, but it has not been effective on aging. Here, we investigated the effects of treatment with a standardized extract of Ginkgo biloba (EGb) associated with novelty on the consolidation of object location memory (OLM) and its persistence after weak training of spatial object preference in young adult and aged rats...

Auditory fear conditioning in rats is a widely used method to study learning, memory, and emotional responding. Despite procedural standardizations and optimizations, there is substantial interindividual variability in fear expression during test, notably in terms of fear expressed toward the testing context alone. To better understand which factors could explain this variation between subjects, we here explored whether behavior during training and expression of AMPA receptors (AMPARs) after long-term memory formation in the amygdala could predict freezing during test...

Strong evidence has implicated proteasome-mediated protein degradation in the memory consolidation process. However, due to the use of pharmacological approaches, the cell type specificity of this remains unknown. Here, we used neuron-specific and novel astrocyte-specific CRISPR-dCas9-KRAB-MECP2 plasmids to inhibit protein degradation in a cell type-specific manner in the amygdala of male rats. We found that while inhibition of neuronal, but not astrocytic, protein degradation impaired performance during the training session, both resulted in impaired contextual fear memory retention...

A widely accepted view in memory research is that recently stored information can be reactivated during sleep, leading to memory strengthening. Two recent studies have shown that this effect can be reversed in participants with highly disrupted sleep. To test whether weakening of reactivated memories can result directly from sleep disruption, in this experiment we varied the intensity of memory reactivation cues such that some produced sleep arousals. Prior to sleep, participants (local community members) learned the locations of 75 objects, each accompanied by a sound naturally associated with that object...

The hippocampal formation (HF) facilitates declarative memory, with subfields providing unique contributions to memory performance. Maturational differences across subfields facilitate a shift toward increased memory specificity, with peripuberty sitting at the inflection point. Peripuberty is also a sensitive period in the development of anxiety disorders. We believe HF development during puberty is critical to negative overgeneralization, a common feature of anxiety disorders. To investigate this claim, we examined the relationship between mnemonic generalization and a cross-sectional pubertal maturity index (PMI) derived from partial least squares correlation (PLSC) analyses of subfield volumes and structural connectivity from T1-weighted and diffusion-weighted scans, respectively...

Memory is well known to decline over the course of healthy aging. However, memory is not a monolith and draws from different kinds of representations. Historically, much of our understanding of age-related memory decline stems from recognition of isolated studied items. In contrast, real-life events are often remembered as narratives, and this kind of information is generally missed in typical recognition memory studies. Here, we designed a task to tax mnemonic discrimination of event details, directly contrasting perceptual and narrative memory...

How the dynamic evolution of forgetting changes for different material types is unexplored. By using a common experimental paradigm with stimuli of different types, we were able to directly cross-examine the emerging dynamics and found that even though the presentation sets differ minimally by design, the obtained curves appear to fall on a discrete spectrum. We also show that the resulting curves do not depend on physical time but rather on the number of items shown. All measured curves were compatible with our previously developed mathematical model, hinting to a potential common underlying mechanism of forgetting...

During sleep, recently acquired episodic memories (i.e., autobiographical memories for specific events) are strengthened and transformed, a process termed consolidation. These memories are contextual in nature, with details of specific features interwoven with more general properties such as the time and place of the event. In this study, we hypothesized that the context in which a memory is embedded would guide the process of consolidation during sleep. To test this idea, we used a spatial memory task and considered changes in memory over a 10-h period including either sleep or wake...