Does memory reactivation during sleep support generalization at the cost of memory specifics?

Sleep is important for memory, but does it favor consolidation of specific details or extraction of generalized information? Both may occur together when memories are reactivated during sleep, or a loss of certain memory details may facilitate generalization. To examine these issues, we tested memory in participants who viewed landscape paintings by six artists. Paintings were cropped to show only a section of the scene. During a learning phase, each painting section was presented with the artist's name and with a nonverbal sound that had been uniquely associated with that artist. In a test of memory for specifics, participants were shown arrays of six painting sections, all by the same artist. Participants attempted to select the one that was seen in the learning phase. Generalization was tested by asking participants to view new paintings and, for each one, decide which of the six artists created it. After this testing, participants had a 90-minute sleep opportunity with polysomnographic monitoring. When slow-wave sleep was detected, three of the sound cues associated with the artists were repeatedly presented without waking the participants. After sleep, participants were again tested for memory specifics and generalization. Memory reactivation during sleep due to the sound cues led to a relative decline in accuracy on the specifics test, which could indicate the transition to a loss of detail that facilitates generalization, particularly details such as the borders. Generalization performance showed very little change after sleep and was unaffected by the sound cues. Although results tentatively implicate sleep in memory transformation, further research is needed to examine memory change across longer time periods.

An assessment of rapamycin for weakening binge-eating memories via reconsolidation: a pre-registered, double-blind randomised placebo-controlled experimental study.

BACKGROUND: Maladaptive learning linking environmental food cues to high-palatability food reward plays a central role in overconsumption in obesity and binge eating disorders. The process of memory reconsolidation offers a mechanism to weaken such learning, potentially ameliorating over-eating behaviour. Here we investigated whether putatively interfering with synaptic plasticity using the mammalian target of rapamycin (mTOR) inhibitor, rapamycin, could weaken retrieved chocolate reward memories through blockade of reconsolidation. METHODS: Seventy five healthy volunteers with a tendency to binge eat chocolate were randomised to retrieve chocolate reward memory under 10 mg rapamycin (RET + RAP, active condition), or placebo (RET + PBO), or they received 10 mg rapamycin without subsequent retrieval (NO RET + RAP). Indices of chocolate reward memory strength were assessed one week pre and post manipulation and at one month follow-up. RESULTS: Contrary to hypotheses, the RET + RAP group did not show any greater reduction than control groups on indices of motivational salience of chocolate cues, motivation to consume chocolate or liking of chocolate. Mild evidence of improvement in the RET + RAP group was found, but this was limited to reduced chocolate binge episodes and improved healthy food choices. CONCLUSIONS: We did not find convincing evidence of comprehensive naturalistic chocolate reward memory reconsolidation blockade by rapamycin. The effects on chocolate bingeing and food choices may warrant further investigation. These limited positive findings may be attributable to insufficient interference with mTOR signalling with 10 mg rapamycin, or failure to destabilise chocolate memories during retrieval.

Forward to the past: Revisiting the role of immediate recognition in the assessment of episodic memory.

Introduction: During the clinical assessment of episodic memory, encoding ability is typically inferred from immediate recall performance. This dependency on effortful retrieval may not be optimal for estimating encoding, particularly in the presence of executive dysfunction. We examined whether a test of immediate recognition memory could meaningfully supplement recall in estimating encoding and provide unique information about memory retention.Method: Fifty older adult outpatients were administered a neuropsychological test battery including original and revised versions of the Hopkins Verbal Learning Test; the former (HVLT) assesses recognition memory immediately after learning trials, while the latter (HVLT-R) assesses only delayed recognition. Hierarchical regressions evaluated the incremental value of immediate recognition in predicting both delayed verbal and visual recognition. ANCOVA was performed on subgroups defined by the number of impaired performances on executive functioning tests (EF-intact, EF-1, EF-2) to examine the influence of executive impairment on measures of immediate recall and recognition. Recall- and recognition-based estimates of verbal memory retention were also compared across groups to determine whether they yield distinct patterns of memory consolidation.Results: Immediate verbal recognition accounted for significant variance in both delayed verbal and visual recognition beyond immediate recall, age, and education. Although subgroups were demographically similar, EF-1 and EF-2 performed significantly worse than EF-intact across verbal and visual memory recall. Contrastingly, there were no group differences in immediate recognition. Subgroups attained similar scores on a conventional, recall-based memory retention measure, but EF-2 showed relatively greater forgetting on a recognition-based retention measure.Conclusions: Immediate verbal recognition is an independent determinant of delayed memory performance but is not captured in current test paradigms. Study results provide proof-of-concept that recognition testing at learning can provide a more comprehensive index of encoding ability than recall alone, may facilitate disentangling memory functions from executive deficits, and could have important downstream implications for estimating memory consolidation.

Caregiver burden and quality of life 2 years after attendance at a memory clinic.

OBJECTIVES: We aimed to describe (1) the burden and health-related quality of life (HRQL) of informal caregivers of new patients attending a memory assessment service (MAS), (2) changes in these outcomes over 2 years, and (3) satisfaction with services. METHODS: Informal caregivers of patients attending one of 73 MASs throughout England completed questionnaires at the patient's first appointment, and 6 and 12 months later. Participants from 30 of these MASs were also followed up at 24 months. Questionnaires covered caregivers' sociodemographic characteristics, Zarit Burden Interview, EQ-5D-3L, and satisfaction with services. We used multivariable linear regression to assess relationships between burden, HRQL, and caregiver and patient characteristics. RESULTS: Of 1020 caregivers at baseline, 569 were followed up at 6 months, 452 at 12 months, and 187 at 24 months. There was a small increase in caregiver burden over 2 years (effect size 0.30 SD). These changes were not associated with most caregiver or patient characteristics, except socio-economic deprivation, which was associated with larger increases in burden at 2 years. Caregivers' HRQL was weakly associated with burden and showed a small reduction over time (0.2 SD). Most caregivers were satisfied with services, but caregivers who were not satisfied with the services they received reported greater increases in burden. CONCLUSIONS: Increases in caregiver burden and reductions in HRQL appear to be small over the first 2 years after attending a MAS. However, the longer term impact on caregivers and those they care for needs investigating, as do strategies to reduce their burden.

Toward a complete taxonomy of resting state networks across wakefulness and sleep: an assessment of spatially distinct resting state networks using independent component analysis.

Resting state network (RSN) functional connectivity (FC) has been investigated under a wealth of different healthy and compromised conditions. Such investigations are often dependent on the defined spatial boundaries and nodes of so-called canonical RSNs, themselves the product of extensive deliberations over distinctions between functional magnetic resonance imaging (fMRI) noise and neural signal, specifically in the context of the healthy waking state. However, a similar unbiased cataloging of noise and networks remains to be done in other states, particularly sleep, a healthy alternate mode of the brain that supports distinct operations from wakefulness, such as dreaming and memory consolidation. The purpose of this study was to explicitly test the hypothesis that there are RSNs unique to sleep. Simultaneous electroencephalography (EEG) and fMRI was used to record brain activity of non-sleep-deprived participants. Independent component analysis was performed on both rapid eye movement (REM; N = 7) and non-REM sleep stage fMRI data (non-REM2; N = 28, non-REM3; N = 11), with the resulting components spatially correlated with the canonical RSNs, for the purpose of identifying spatially distinct RSNs. Surprisingly, all low-correlation components were positively identified as noise, and all high-correlation components comprised the canonical set of RSNs typically observed in wake, indicating that sleep is supported by much the same RSN architecture as wakefulness, despite the unique operations performed during sleep. This further indicates that the implicit assumptions of prior studies, i.e. that the canonical RSNs apply to sleep FC analysis, are valid and have not overlooked sleep-specific RSNs.

Extension to one week of verbal memory consolidation assessment.

OBJECTIVE: Although impairments of long-term recall affect everyday life, they may be missed by standard delayed recall tests, which typically assess the ability to retain new information within a few minutes, without encompassing the consolidation process. We adapted a verbal memory test to evaluate long-term memory consolidation in healthy volunteers. METHOD: A sample of 238 participants (M = 42.23 years old, SD = 16.45) was administered an adapted version of the French RL/RI-16 (Van der Linden & the members of GREMEM, 2004), the One-Week Free and Cued Selective Reminding Test-word version, in which special feature relies on a 30-min and a 1-week-delayed recall after encoding. We proposed normative data on 4 indicators, depending on participants' own performance during the test, to measure their encoding, storage and consolidation abilities, with a method using an ascendant step-by-step linear regression model and a percentile procedure. RESULTS: Results showed a better performance in women than in men for encoding and cueing scores (p < .01 and p < .05, respectively). We also highlighted an increase of the forgetting score according to the recall delay after encoding (30 min vs. 7 days; Z = 12.49, p < .001), the forgetting percentage 7 days after encoding being largely influenced by participants' age and gender (F[2, 236] = 248.1, p < .001; adjusted R2 = 67%). CONCLUSIONS: This study emphasized the role of demographic factors on long-term memory consolidation. The demographically adjusted normative data we provide for the One-Week Free and Cued Selective Reminding Test-word version make it a sensitive tool for long-term memory consolidation assessment in clinical and forensic practice. (PsycINFO Database Record

Major neurotransmitter systems in dorsal hippocampus and basolateral amygdala control social recognition memory.

Social recognition memory (SRM) is crucial for reproduction, forming social groups, and species survival. Despite its importance, SRM is still relatively little studied. Here we examine the participation of the CA1 region of the dorsal hippocampus (CA1) and the basolateral amygdala (BLA) and that of dopaminergic, noradrenergic, and histaminergic systems in both structures in the consolidation of SRM. Male Wistar rats received intra-CA1 or intra-BLA infusions of different drugs immediately after the sample phase of a social discrimination task and 24-h later were subjected to a 5-min retention test. Animals treated with the protein synthesis inhibitor, anisomycin, into either the CA1 or BLA were unable to recognize the previously exposed juvenile (familiar) during the retention test. When infused into the CA1, the ß-adrenoreceptor agonist, isoproterenol, the D1/D5 dopaminergic receptor antagonist, SCH23390, and the H2 histaminergic receptor antagonist, ranitidine, also hindered the recognition of the familiar juvenile 24-h later. The latter drug effects were more intense in the CA1 than in the BLA. When infused into the BLA, the ß-adrenoreceptor antagonist, timolol, the D1/D5 dopamine receptor agonist, SKF38393, and the H2 histaminergic receptor agonist, ranitidine, also hindered recognition of the familiar juvenile 24-h later. In all cases, the impairment to recognize the familiar juvenile was abolished by the coinfusion of agonist plus antagonist. Clearly, both the CA1 and BLA, probably in that order, play major roles in the consolidation of SRM, but these roles are different in each structure vis-à-vis the involvement of the ß-noradrenergic, D1/D5-dopaminergic, and H2-histaminergic receptors therein.

[Multiple sclerosis and verbal episodic memory: Critical review of cognitive processes and their assessment]. / Atteinte de la mémoire épisodique verbale dans la sclérose en plaques: revue critique des processus cognitifs concernés et de leur exploration.

Memory impairment, especially verbal episodic memory (VEM), represents a common ground for cognitive complaint in patients with multiple sclerosis (MS). Beyond the difficulty caused in daily life, these deficits may impact on occupational activities. Neuropsychological assessment of these patients has to include VEM tests, to describe the level of dysfunction of the different processes contributing to VEM and, if required, to guide adapted cognitive rehabilitation. The objective of the present paper is to propose a critique review of the literature on VEM abilities in MS. This review will present the conceptual references and the psychometric characteristics of the main VEM tests applied in MS (isolated tests or included within more general batteries developed specifically for MS). In a second phase, we propose an inventory of work on MS presented as a function of the cognitive processes involved. This approach provides an approach to the limitations of each conception and possible terminological ambiguities. Contributions to knowledge of MS memory impairments will be clarified, as well as the impact of the disease characteristics (MS forms, disease duration, EDSS).