Retention Of Episodic Memories Research Articles

Dopamine D1 receptors activation rescues hippocampal synaptic plasticity and cognitive impairments in the MK-801 neonatal schizophrenia model

Schizophrenia is a disorder with a higher cognitive decline in early adulthood, causing impaired retention of episodic memories. However, the physiological and behavioral functions that underlie cognitive deficits with a potential mechanism to ameliorate and improve cognitive performance are unknown. In this study, we used the MK-801 neurodevelopmental schizophrenia-like model. Rats were divided into two groups: one received MK-801, and the other received saline for five consecutive days (7–11 postnatal days, PND). We evaluated synaptic plasticity late-LTP and spatial memory consolidation in early adolescence and young adulthood using extracellular field recordings in acute hippocampal slices and the Barnes maze task. Next, we examined D1 receptor (D1R) activation as a mechanism to ameliorate cognitive impairments. Our results suggest that MK-801 neonatal treatment induces impairment in late-LTP expression and deficits in spatial memory retrieval in early adolescence that is maintained until young adulthood. Furthermore, we found that activation of dopamine D1R ameliorates the impairments and promotes a robust expression of late-LTP and an improved performance in the Barnes maze task, suggesting a novel and potential therapeutic role in treating cognitive impairments in schizophrenia.

The effects of slow wave sleep characteristics on semantic, episodic, and procedural memory in people with epilepsy.

Slow wave sleep (SWS) is highly relevant for verbal and non-verbal/spatial memory in healthy individuals, but also in people with epilepsy. However, contradictory findings exist regarding the effect of seizures on overnight memory retention, particularly relating to procedural and non-verbal memory, and thorough examination of episodic memory retention with ecologically valid tests is missing. This research explores the interaction of SWS duration with epilepsy-relevant factors, as well as the relation of spectral characteristics of SWS on overnight retention of procedural, verbal, and episodic memory. In an epilepsy monitoring unit, epilepsy patients (N = 40) underwent learning, immediate and 12h delayed testing of memory retention for a fingertapping task (procedural memory), a word-pair task (verbal memory), and an innovative virtual reality task (episodic memory). We used multiple linear regression to examine the impact of SWS duration, spectral characteristics of SWS, seizure occurrence, medication, depression, seizure type, gender, and epilepsy duration on overnight memory retention. Results indicated that none of the candidate variables significantly predicted overnight changes for procedural memory performance. For verbal memory, the occurrence of tonic-clonic seizures negatively impacted memory retention and higher psychoactive medication load showed a tendency for lower verbal memory retention. Episodic memory was significantly impacted by epilepsy duration, displaying a potential nonlinear impact with a longer duration than 10years negatively affecting memory performance. Higher drug load of anti-seizure medication was by tendency related to better overnight retention of episodic memory. Contrary to expectations longer SWS duration showed a trend towards decreased episodic memory performance. Analyses on associations between memory types and EEG band power during SWS revealed lower alpha-band power in the frontal right region as significant predictor for better episodic memory retention. In conclusion, this research reveals that memory modalities are not equally affected by important epilepsy factors such as duration of epilepsy and medication, as well as SWS spectral characteristics.

Cognitive, behavioral and psychiatric symptoms in patients with spinal cord injury: a scoping review.

Spinal Cord Injury (SCI) is a condition where the spinal cord is damaged and experiences partial or complete loss of motor and/or sensory function, which is typically less than normal. After SCI, patients may exhibit more severe psychiatric symptoms and experience cognitive impairments, including reduced speed and attention processing capacity, as well as difficulties with executive function and episodic memory retention. Among the behavioral and psychiatric symptoms, depression, anxiety, substance use disorder, and posttraumatic stress disorder are the most common. This review aims to investigate the cognitive, behavioral, or psychiatric symptoms of the patient with SCI and their influence on the rehabilitation process. Studies were identified from an online search of PubMed, Web of Science, Cochrane Library, and Embase databases. Studies published between 2013-2023 were selected. This review has been registered on OSF (n) 3KB2U. We have found that patients with SCI are at high risk of cognitive impairment and experience a wide range of difficulties, including tasks based on processing speed and executive function. This clinical population may experience adjustment disorders with depression and anxiety, as well as other psychiatric symptoms such as fatigue, stress, and suicidal ideation. This review has demonstrated that SCI patients may experience psychiatric symptoms and cognitive impairments that affect their functioning. At the same time, these patients may be more prone to various adjustment and mood disorders. Moreover, these two aspects may interact with each other, causing a range of symptoms, increasing the risk of hospitalization, and delaying the rehabilitation process.

Higher intensity exercise after encoding is more conducive to episodic memory retention than lower intensity exercise: A field study in endurance runners.

An acute bout of exercise in the moments after learning benefits the retention of new memories. This finding can be explained, at least partly, through a consolidation account: exercise provides a physiological state that is conducive to the early stabilisation of labile new memories, which supports their retention and subsequent retrieval. The modification of consolidation through non-invasive exercise interventions offers great applied potential. However, it remains poorly understood whether effects of exercise translate from the laboratory to naturalistic settings and whether the intensity of exercise determines the effect in memory. To this end, adult endurance runners were recruited as participants and completed two study sessions spaced two weeks apart. In each session, participants were presented with a list of words and asked to recall them on three occasions: (i) immediately following their presentation, (ii) after a 30-minute retention interval, and (iii) after 24 hours. Crucially, the 30-minute retention interval comprised our experimental manipulation: higher intensity exercise (running) in the first session and lower intensity exercise (walking) in the second, both completed in a naturalistic setting around participants' existing physical activity training programmes. Exertion was recorded through heart rate and rate of perceived exertion data. Alertness, mood, and arousal ratings were also collected before and after the 30-minute retention interval. Immediate memory for the two wordlists was matched, but participants retained significantly more words after 30 minutes and 24 hours when encoding was followed by higher than lower intensity exercise. Exertion data revealed that participants experienced vigorous and light exercise in the higher and lower intensity conditions, respectively. Significant improvements in alertness, mood, and arousal were observed following both exercise conditions, but especially in the higher intensity condition. These outcomes reveal that experiencing higher intensity physical activity in the field is conducive to declarative memory retention, possibly because it encourages consolidation.

10 Semantic Memory as a Predictor of Future Memory Decline

Objective:To determine if the degree of split between phonemic verbal fluency and semantic verbal fluency at initial visit is predictive of decline in memory performance between initial evaluation and follow-up.Participants and Methods:Data from a retrospective multidisciplinary memory clinic database at Spectrum Health was utilized. We examined data from 90 participants who had both an initial and follow-up evaluation completed (initial age = 77.1±4.7 years, follow-up age = 78.4±4.7 years, education = 13.9±3.1 years, race = 91% White, 7% Black, & 2% Hispanic, sex = 61% female, time between evaluations = 15.2±9.9 months). Patients who returned for follow-up did not meet criteria for dementia at time one. Split between phonemic and semantic fluency, termed the semantic-phonological delta (SPD) was measured at the initial evaluation by subtracting the Controlled Oral Word Association Test (COWAT; FAS) T-score from the Animal Naming Test (ANT) T-score. Change in memory score was defined in two ways: 1) subtracting the follow-up evaluation Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) List Recognition Score (RBANS percentiles were converted to a scaled score) from the initial evaluation List Recognition Score (List Recognition Delta), and 2) computing the difference in the RBANS Delayed Memory Index Standard Score between the initial evaluation and the follow-up evaluation (RBANS Memory Delta).Results:Average semantic fluency T scores were (M = 40.3, SD = 12.3) and phonemic fluency T scores were (M = 42.7, SD = 10.3) at initial evaluation. Bivariate correlations were used to determine the relationship between the clinical variables. SPD was significantly correlated with List Recognition Delta, r(88) = .23, p = .026, with greater discrepancies in verbal fluency scores associated with higher level of decline in List Recognition at follow-up. By comparison, Semantic Fluency performance itself at initial evaluation was not significantly correlated with List Recognition Delta, r(88) = .17, p = .097. The correlation between SPD and the RBANS Memory Delta was also not significant, r(88) = .14, p = .166. At follow-up evaluation, 39% of the sample received a diagnosis of Alzheimer’s disease. Of those diagnosed with Alzheimer’s disease, 66% had a negative SPD split at time one, performing worse on semantic fluency compared to phonemic fluency.Conclusions:SPD is a better predictor of decline in RBANS List Recognition performance between evaluations than semantic fluency alone, with a larger negative SPD score (worse semantic fluency performance compared to phonemic fluency) at initial evaluation predicting decline in List Recognition performance at follow-up evaluation. SPD at initial evaluation was not significantly correlated with change in RBANS Delayed Memory Index score between evaluations. This may be because there are some patients who are similarly impaired in both semantic and phonemic verbal fluency at initial evaluation who later demonstrate progressive decline in memory retrieval due to hippocampal-sparing etiologies (e.g., vascular dementia). Overall, these findings are consistent with previous work suggesting that declines in the semantic memory system precede declines in episodic memory retention in conditions such as Alzheimer’s disease.

Improvement of episodic memory retention by a memory reactivation intervention across the lifespan: from younger adults to amnesic patients

Spontaneous reactivation of recently acquired memories is a fundamental mechanism of memory stabilization. Re-exposure to specific learned cues during sleep or awake states, namely targeted memory reactivation, has been shown to improve memory retention at long delays. Manipulation of memory reactivation could have potential clinical value in populations with memory deficits or cognitive decline. However, no previous study investigated a target memory reactivation approach on those populations. Here we tested the hypothesis that a reactivation-based intervention would improve episodic memory performance in healthy adults and amnestic patients. On Day 1, young adults, old adults and amnestic Mild Cognitive Impairment patients (n = 150) learned face-name pairs and 24 h later either received a reactivation intervention or a reactivation control (Day 2). On Day 3, associative and item memory were assessed. A robust Bayesian Generalized Mixed Model was implemented to estimate intervention effects on groups. Groups that underwent the reactivation-based intervention showed improved associative memory retention. Notably, amnestic patients benefited more from the intervention as they also had better item memory retention than controls. These findings support memory reactivation as stabilization and strengthening mechanism irrespectively of age and cognitive status, and provides proof-of-concept evidence that reactivation-based interventions could be implemented in the treatment and rehabilitation of populations with memory deficits.

P051 SLEEP SPINDLES AND SWA DIFFERENTIALLY CORRELATE WITH OVERNIGHT EPISODIC AND VISUOSPATIAL MEMORY CONSOLIDATION IN OLDER ADULTS WITH AND WITHOUT MILD COGNITIVE IMPAIRMENT

Abstract Introduction Sleep microarchitecture disruption is a feature of ageing that is further altered in neurodegenerative disorders. Sleep-memory links in younger adults have been established, however mechanistic pathways of this uncoupling in ageing is poorly understood. Method Our sample consisted of n=46 mild cognitively impaired (MCI) older adults and n=32 cognitively-intact controls who underwent overnight polysomnography and episodic (Rey Auditory Verbal Learning test) and visuospatial (Rey-Osterrieth Complex Figure task) memory tasks that were administered before and after sleep. We examined group differences in overnight memory % retention and associations with NREM slow oscillations (SO, 0.25–1 Hz), delta power (0.5–4 Hz), N2 spindle events (occurrence [11–16 Hz] and slow [11–13 Hz] and fast [13–16 Hz] spindle density p/min) and REM theta power (4.5–8 Hz). Results Repeated measures ANCOVA, controlling for age, indicated greater memory scores in Controls compared to MCI on the episodic task, F=6.7 (p=.01), and no group differences in the visuospatial task (F=1.8, p=.17). In Controls, greater delta power was associated with increased episodic memory retention (r=.515, p=.006). In the MCI group, episodic memory was associated with fast spindle density (r=-.352, p=.04), and visuospatial memory was also associated with fast spindle density (r=-.385, p=.01) and spindle occurrence (r=-.479, p=.003). Conclusion Sleep spindles appear to be negatively associated with memory retention, specifically in MCI. However, given the heterogeneity of MCI, further analysis of its cognitive subtypes is warranted. Comprehensive cognitive and neural pathophysiology profiling are required to better delineate the function of spindles in ageing.

Impaired posterior cingulate cortex-parahippocampus connectivity is associated with episodic memory retrieval problems in amnestic mild cognitive impairment.

Episodic memory retention and retrieval decline are the most common impairments observed in amnestic mild cognitive impairment (aMCI) patients who progress to Alzheimer's disease (AD). Clinical electroencephalography research shows that patients with dementia due to AD exhibit a slowing of neural electrical activity in the parietal cortex. Memory research has further suggested that successful memory performance is associated with changes in a posterior cingulate-parahippocampal cortical network together with increased θ-γ oscillatory coupling, where θ oscillations act as carrier waves for γ oscillations, which contain the actual information. However, the neurophysiological link between the memory research and clinical studies investigating aMCI and AD is lacking. In this study, we look at brain activity in aMCI and how it relates to memory performance. We demonstrate decreased γ power in the posterior cingulate cortex and the left and right parahippocampus in aMCI patients in comparison to control participants. This goes together with reduced θ coherence between the posterior cingulate cortex and parahippocampus associated with altered memory performance aMCI patients in comparison to control participants. In addition, comparing patients with aMCI to control participants reveals an effect for θ-γ coupling for the posterior cingulate cortex, and the left and right parahippocampus. Taken together, our results show that parahippocampus and posterior cingulate cortex interact via θ-γ coupling, which is associated with memory recollection and is altered in aMCI patients, offering a potential candidate mechanism for memory decline in aMCI.

Bi-Temporal Anodal Transcranial Direct Current Stimulation during Slow-Wave Sleep Boosts Slow-Wave Density but Not Memory Consolidation

Slow-wave sleep (SWS) has been shown to promote long-term consolidation of episodic memories in hippocampo–neocortical networks. Previous research has aimed to modulate cortical sleep slow-waves and spindles to facilitate episodic memory consolidation. Here, we instead aimed to modulate hippocampal activity during slow-wave sleep using transcranial direct current stimulation in 18 healthy humans. A pair-associate episodic memory task was used to evaluate sleep-dependent memory consolidation with face–occupation stimuli. Pre- and post-nap retrieval was assessed as a measure of memory performance. Anodal stimulation with 2 mA was applied bilaterally over the lateral temporal cortex, motivated by its particularly extensive connections to the hippocampus. The participants slept in a magnetic resonance (MR)-simulator during the recordings to test the feasibility for a future MR-study. We used a sham-controlled, double-blind, counterbalanced randomized, within-subject crossover design. We show that stimulation vs. sham significantly increased slow-wave density and the temporal coupling of fast spindles and slow-waves. While retention of episodic memories across sleep was not affected across the entire sample of participants, it was impaired in participants with below-average pre-sleep memory performance. Hence, bi-temporal anodal direct current stimulation applied during sleep enhanced sleep parameters that are typically involved in memory consolidation, but it failed to improve memory consolidation and even tended to impair consolidation in poor learners. These findings suggest that artificially enhancing memory-related sleep parameters to improve memory consolidation can actually backfire in those participants who are in most need of memory improvement.

EmoTan: enhanced flashcards for second language vocabulary learning with emotional binaural narration

We report on the design and evaluation of a flashcard application, enhanced with emotional binaural narration to support second language (L2) vocabulary learning. Typically, the voice narration used in English vocabulary learning is recorded by native speakers with a standard accent to ensure accurate pronunciation and clarity. However, a clear but monotonous narration may not always aid learners in retaining new vocabulary items in their semantic memory. As such, enhancing textual flashcards with emotional narration in the learner’s native language can foster the retention of new L2 words in episodic rather than semantic memory as greater emotive expression reinforces episodic memory retention. We evaluated the effects of binaural emotive narration with traditional textual flashcards on L2 word retention (immediate and delayed) in laboratory experiments with native Japanese-speaking English learners. Our results suggest that the learners were able to retain approximately 60% more L2 words long-term with the proposed approach compared to traditional flashcards.

Episodic memory improvements due to noninvasive stimulation targeting the cortical-hippocampal network: A replication and extension experiment.

IntroductionThe distributed cortical network of the human hippocampus is important for episodic memory. In a previous experiment, noninvasive stimulation of the hippocampal‐cortical network applied for five consecutive days improved paired‐associate learning measured after the stimulation regimen via cued recall (Wang et al., Science, 2014, 345, 1054). This finding has not yet been directly replicated. Furthermore, evidence for long‐lasting effects of stimulation on paired‐associate learning was obtained by analyzing relatively small subsamples (Wang & Voss, Hippocampus, 2015, 25, 877) and requires further evaluation.MethodsSixteen healthy young adults participated in this replication study using the same experimental design as the original study. Participants received 1 week of active stimulation and 1 week of sham stimulation, with memory assessments occurring at the beginning (pre) and end (post) of each week. Assessments included the paired‐associate task used in the original study, as well as a long‐term episodic memory retention task in order to test the hypothesis that increased paired‐associate learning could come at the cost of accelerated long‐term forgetting. Change in memory scores was evaluated within (pre vs. post) and across (active vs. sham) weeks.ResultsSimilar to Wang et al., paired‐associate learning was significantly improved after 1 week of active stimulation but not after 1 week of sham stimulation. We found no evidence that stimulation increased long‐term forgetting for either week.ConclusionThese findings confirm the beneficial effects of stimulation on episodic memory that were reported previously and indicate that stimulation‐related gains in new learning ability do not come at the price of accelerated long‐term forgetting.

Relationship of Sensory Modality to Retention of Episodic Memory

This study investigated the difference between episodic memory for verbal information presented in an oral format versus equivalent material presented in a written format. The study utilized the Logical Memory subtest of the Wechsler Memory Scales-Fourth Edition and the recently validated Morris Revision-IV Paragraphs. In a sample of 97 normal participants, auditory and visual memory performances were found to be significantly correlated (r = .651, p < .001). Post-hoc analysis revealed a slight though not clinically significant preference for retention in the visual modality. The results demonstrate a high-degree correlation for retention of episodic memory for these two sensory modalities in normal participants.

Sleep benefits in parallel implicit and explicit measures of episodic memory

Research in rats using preferences during exploration as a measure of memory has indicated that sleep is important for the consolidation of episodic-like memory, i.e., memory for an event bound into specific spatio-temporal context. How these findings relate to human episodic memory is unclear. We used spontaneous preferences during visual exploration and verbal recall as, respectively, implicit and explicit measures of memory, to study effects of sleep on episodic memory consolidation in humans. During encoding before 10-h retention intervals that covered nighttime sleep or daytime wakefulness, two groups of young adults were presented with two episodes that were 1-h apart. Each episode entailed a spatial configuration of four different faces in a 3 × 3 grid of locations. After the retention interval, implicit spatio-temporal recall performance was assessed by eye-tracking visual exploration of another configuration of four faces of which two were from the first and second episode, respectively; of the two faces one was presented at the same location as during encoding and the other at another location. Afterward explicit verbal recall was assessed. Measures of implicit and explicit episodic memory retention were positively correlated (r = 0.57, P < 0.01), and were both better after nighttime sleep than daytime wakefulness (P < 0.05). In the sleep group, implicit episodic memory recall was associated with increased fast spindles during nonrapid eye movement (NonREM) sleep (r = 0.62, P < 0.05). Together with concordant observations in rats our results indicate that consolidation of genuinely episodic memory benefits from sleep.

Prefrontal atrophy, disrupted NREM slow waves and impaired hippocampal-dependent memory in aging

Aging has independently been associated with regional brain atrophy, reduced non-rapid eye movement (NREM) slow-wave activity (SWA), and impaired long-term retention of episodic memories. However, that the interaction of these factors represents a neuropatholgical pathway associated with cognitive decline in later life remains unknown. Here, we show that age-related medial prefrontal cortex (mPFC) grey-matter atrophy is associated with reduced NREM SWA activity in older adults, the extent to which statistically mediates the impairment of overnight sleep-dependent memory retention. Moreover, this memory impairment was further associated with persistent hippocampal activation and reduced task-related hippocampal-prefrontal cortex connectivity, potentially representing impoverished hippocampal-neocortical memory transformation. Together, these data support a model in which age-related mPFC atrophy diminishes SWA, the functional consequence of which is impaired long-term memory. Such findings suggest that sleep disruption in the elderly, mediated by structural brain changes, represent a novel contributing factor to age-related cognitive decline in later life.

To have and to hold: Episodic memory in 3‐ and 4‐year‐old children

Episodic memory endows us with the ability to reflect on our past and plan for our future. Most theorists argue that episodic memory emerges during the preschool period and that its emergence might herald the end of childhood amnesia. Here, we show that both 3- and 4-year-old children form episodic memories, but that 3-year-old children fail to retain those memories following a delay (Experiments 1 and 2). In contrast, 4-year-old children retained episodic memories over delays of 24 hr (Experiment 1) and 1 week (Experiment 3). This marked change in the retention of episodic memories between 3 and 4 years of age suggests that it is our ability to retain, rather than to form, an episodic memory that limits our ability to recall episodes from early childhood.

Toward a Theory of Aesthetic Learning Experiences

The purpose of this article is to reveal ways to provide the opportunity for students to have aesthetically engaged learning experiences. Using John Dewey’s ideas from Art as Experience as a framework, the author uses aesthetic theory to show how such ends can be reached. In addition, he suggests six themes that teachers can draw upon to help students attain engaged learning experiences. The themes, which are elaborated upon fully in this article, include connections, active engagement, sensory experience, perceptivity, risk taking, and imagination. In addition to providing engaged learning, the upshot of providing aesthetic learning experiences is likely to include student satisfaction, an increase in perceptual knowledge, episodic memory retention, meaning making, and creativity and innovation.

Development of extended memory

Memory development is described in terms of a bio-social–cultural theory of human cognition. The development from a private unshareable system of basic memory in infancy and very early childhood is framed within an experiential perspective wherein all memory is derived from experience. It is the nature of changing experience, the result of both biological and social–cultural conditions that eventuates in a changed memory system that enables long-term retention of episodic memories, thus establishing the autobiographical memory system. The sequence of developments that interact to bring this about, many dependent on the acquisition of language, are discussed.

SSR180711, a Novel Selective α7 Nicotinic Receptor Partial Agonist: (II) Efficacy in Experimental Models Predictive of Activity Against Cognitive Symptoms of Schizophrenia

SSR180711 (4-bromophenyl 1,4diazabicyclo(3.2.2) nonane-4-carboxylate, monohydrochloride) is a selective alpha7 nicotinic receptor (n-AChR) partial agonist. Based on the purported implication of this receptor in cognitive deficits associated with schizophrenia, the present study assessed efficacy of SSR180711 (i.p. and p.o.) in different types of learning and memory involved in this pathology. SSR180711 enhanced episodic memory in the object recognition task in rats and mice (MED: 0.3 mg/kg), an effect mediated by the alpha7 n-AChR, as it was no longer seen in mice lacking this receptor. Efficacy was retained after repeated treatment (eight administrations over 5 days, 1 mg/kg), indicating lack of tachyphylaxia. SSR180711 also reversed (MED: 0.3 mg/kg) MK-801-induced deficits in retention of episodic memory in rats (object recognition). The drug reversed (MED: 0.3 mg/kg) selective attention impaired by neonatal phencyclidine (PCP) treatment and restored MK-801- or PCP-induced memory deficits in the Morris or linear maze (MED: 1-3 mg/kg). In neurochemical and electrophysiological correlates of antipsychotic drug action, SSR180711 increased extracellular levels of dopamine in the prefrontal cortex (MED: 1 mg/kg) and enhanced (3 mg/kg) spontaneous firing of retrosplenial cortex neurons in rats. Selectivity of SSR180711 was confirmed as these effects were abolished by methyllycaconitine (3 mg/kg, i.p. and 1 mg/kg, i.v., respectively), a selective alpha7 n-AChR antagonist. Additional antidepressant-like properties of SSR180711 were demonstrated in the forced-swimming test in rats (MED: 1 mg/kg), the maternal separation-induced ultrasonic vocalization paradigm in rat pups (MED: 3 mg/kg) and the chronic mild stress procedure in mice (10 mg/kg o.d. for 3 weeks). Taken together, these findings characterize SSR180711 as a promising new agent for the treatment of cognitive symptoms of schizophrenia. The antidepressant-like properties of SSR180711 are of added interest, considering the high prevalence of depressive symptoms in schizophrenic patients.

Motoric encoding and retention of pictures in Alzheimer's disease.

20 patients with Alzheimer's disease were shown line drawings of common objects on two trials. During the second trial they were asked to pantomime an action for the object and then provided a standard motoric cue or were asked to name it and then provided a standard semantic cue. Semantic cueing served as a stimulus-processing control condition. Memory for pictures was assessed at a 48-hr. delay interval using a yes-no recognition-memory procedure. Discrimination of stimulus pictures from distractors at 48 hours was similar for the motoric and control (semantic) encoding condition. These findings suggest that motoric encoding does not enhance long-term retention of episodic memories for pictures in such patients.