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Nature Reviews. Neuroscience Aug 2023There has been considerable speculation regarding the function of the dentate gyrus (DG) - a subregion of the mammalian hippocampus - in learning and memory. In this... (Review)
Review
There has been considerable speculation regarding the function of the dentate gyrus (DG) - a subregion of the mammalian hippocampus - in learning and memory. In this Perspective article, we compare leading theories of DG function. We note that these theories all critically rely on the generation of distinct patterns of activity in the region to signal differences between experiences and to reduce interference between memories. However, these theories are divided by the roles they attribute to the DG during learning and recall and by the contributions they ascribe to specific inputs or cell types within the DG. These differences influence the information that the DG is thought to impart to downstream structures. We work towards a holistic view of the role of DG in learning and memory by first developing three critical questions to foster a dialogue between the leading theories. We then evaluate the extent to which previous studies address our questions, highlight remaining areas of conflict, and suggest future experiments to bridge these theories.
Topics: Animals; Humans; Dentate Gyrus; Hippocampus; Mental Recall; Learning; Mammals
PubMed: 37316588
DOI: 10.1038/s41583-023-00710-z -
Science (New York, N.Y.) Nov 2023The hippocampus is critical for recollecting and imagining experiences. This is believed to involve voluntarily drawing from hippocampal memory representations of...
The hippocampus is critical for recollecting and imagining experiences. This is believed to involve voluntarily drawing from hippocampal memory representations of people, events, and places, including maplike representations of familiar environments. However, whether representations in such "cognitive maps" can be volitionally accessed is unknown. We developed a brain-machine interface to test whether rats can do so by controlling their hippocampal activity in a flexible, goal-directed, and model-based manner. We found that rats can efficiently navigate or direct objects to arbitrary goal locations within a virtual reality arena solely by activating and sustaining appropriate hippocampal representations of remote places. This provides insight into the mechanisms underlying episodic memory recall, mental simulation and planning, and imagination and opens up possibilities for high-level neural prosthetics that use hippocampal representations.
Topics: Animals; Rats; Brain-Computer Interfaces; Hippocampus; Imagination; Memory, Episodic; Mental Recall; Volition; Spatial Navigation; Brain Mapping
PubMed: 37917713
DOI: 10.1126/science.adh5206 -
Science (New York, N.Y.) Oct 2023Episodic memory involves learning and recalling associations between items and their spatiotemporal context. Those memories can be further used to generate internal...
Episodic memory involves learning and recalling associations between items and their spatiotemporal context. Those memories can be further used to generate internal models of the world that enable predictions to be made. The mechanisms that support these associative and predictive aspects of memory are not yet understood. In this study, we used an optogenetic manipulation to perturb the sequential structure, but not global network dynamics, of place cells as rats traversed specific spatial trajectories. This perturbation abolished replay of those trajectories and the development of predictive representations, leading to impaired learning of new optimal trajectories during memory-guided navigation. However, place cell assembly reactivation and reward-context associative learning were unaffected. Our results show a mechanistic dissociation between two complementary hippocampal codes: an associative code (through coactivity) and a predictive code (through sequences).
Topics: Animals; Rats; Conditioning, Classical; Hippocampus; Memory, Episodic; Mental Recall; Optogenetics; Theta Rhythm; Male; Rats, Long-Evans; Association Learning
PubMed: 37856604
DOI: 10.1126/science.adi8237 -
The Journal of Neuroscience : the... Nov 2023The ability to store information about the past to dynamically predict and prepare for the future is among the most fundamental tasks the brain performs. To date, the...
The ability to store information about the past to dynamically predict and prepare for the future is among the most fundamental tasks the brain performs. To date, the problems of understanding how the brain stores and organizes information about the past (memory) and how the brain represents and processes temporal information for adaptive behavior have generally been studied as distinct cognitive functions. This Symposium explores the inherent link between memory and temporal cognition, as well as the potential shared neural mechanisms between them. We suggest that working memory and implicit timing are interconnected and may share overlapping neural mechanisms. Additionally, we explore how temporal structure is encoded in associative and episodic memory and, conversely, the influences of episodic memory on subsequent temporal anticipation and the perception of time. We suggest that neural sequences provide a general computational motif that contributes to timing and working memory, as well as the spatiotemporal coding and recall of episodes.
Topics: Brain; Mental Recall; Cognition; Memory, Short-Term; Memory, Episodic
PubMed: 37940593
DOI: 10.1523/JNEUROSCI.1430-23.2023 -
ELife May 2024Our ability to recall details from a remembered image depends on a single mechanism that is engaged from the very moment the image disappears from view.
Our ability to recall details from a remembered image depends on a single mechanism that is engaged from the very moment the image disappears from view.
Topics: Humans; Mental Recall
PubMed: 38700912
DOI: 10.7554/eLife.98274 -
Psychological Review Nov 2023Affective experiences are commonly represented by either transient emotional reactions to discrete events or longer term, sustained mood states that are characterized by...
Affective experiences are commonly represented by either transient emotional reactions to discrete events or longer term, sustained mood states that are characterized by a more diffuse and global nature. While both have considerable influence in shaping memory, their interaction can produce mood-congruent memory (MCM), a psychological phenomenon where emotional memory is biased toward content affectively congruent with a past or current mood. The study of MCM has direct implications for understanding how memory biases form in daily life, as well as debilitating negative memory schemas that contribute to mood disorders such as depression. To elucidate the factors that influence the presence and strength of MCM, here we systematically review the literature for studies that assessed MCM by inducing mood in healthy participants. We observe that MCM is often reported as enhanced accuracy for previously encoded mood-congruent content or preferential recall for mood-congruent autobiographical events, but may also manifest as false memory for mood-congruent lures. We discuss the relevant conditions that shape these effects, as well as instances of mood-incongruent recall that facilitate mood repair. Further, we provide guiding methodological and theoretical considerations, emphasizing the limited neuroimaging research in this area and the need for a renewed focus on memory consolidation. Accordingly, we propose a theoretical framework for studying the neural basis of MCM based on the neurobiological underpinnings of mood and emotion. In doing so, we review evidence for associative network models of spreading activation, while also considering alternative models informed by the cognitive neuroscience literature of emotional memory bias. (PsycInfo Database Record (c) 2024 APA, all rights reserved).
Topics: Humans; Affect; Emotions; Mental Recall; Memory; Cognition
PubMed: 36201828
DOI: 10.1037/rev0000394 -
Brain Research Bulletin Aug 2023Sharp wave ripples (SWRs) are high-frequency synchronization events generated by hippocampal neuronal circuits during various forms of learning and reactivated during... (Review)
Review
Sharp wave ripples (SWRs) are high-frequency synchronization events generated by hippocampal neuronal circuits during various forms of learning and reactivated during memory consolidation and recall. There is mounting evidence that SWRs are essential for storing spatial and social memories in rodents and short-term episodic memories in humans. Sharp wave ripples originate mainly from the hippocampal CA3 and subiculum, and can be transmitted to modulate neuronal activity in cortical and subcortical regions for long-term memory consolidation and behavioral guidance. Different hippocampal subregions have distinct functions in learning and memory. For instance, the dorsal CA1 is critical for spatial navigation, episodic memory, and learning, while the ventral CA1 and dorsal CA2 may work cooperatively to store and consolidate social memories. Here, we summarize recent studies demonstrating that SWRs are essential for the consolidation of spatial, episodic, and social memories in various hippocampal-cortical pathways, and review evidence that SWR dysregulation contributes to cognitive impairments in neurodegenerative and neurodevelopmental diseases.
Topics: Humans; Hippocampus; Neurons; Memory Consolidation; Mental Recall; Memory, Short-Term
PubMed: 37353037
DOI: 10.1016/j.brainresbull.2023.110695 -
Nature Communications Nov 2023Inaccessibility of stored memory in ensemble cells through the forgetting process causes animals to be unable to respond to natural recalling cues. While accumulating...
Inaccessibility of stored memory in ensemble cells through the forgetting process causes animals to be unable to respond to natural recalling cues. While accumulating evidence has demonstrated that reactivating memory-stored cells can switch cells from an inaccessible state to an accessible form and lead to recall of previously learned information, the underlying cellular and molecular mechanisms remain elusive. The current study used Drosophila as a model to demonstrate that the memory of one-trial aversive olfactory conditioning, although inaccessible within a few hours after learning, is stored in KCαβ and retrievable after mild retraining. One-trial aversive conditioning triggers protein synthesis to form a long-lasting cellular memory trace, approximately 20 days, via creb in KCαβ, and a transient cellular memory trace, approximately one day, via orb in MBON-α3. PPL1-α3 negatively regulates forgotten one-trial conditioning memory retrieval. The current study demonstrated that KCαβ, PPL1-α3, and MBON-α3 collaboratively regulate the formation of forgotten one-cycle aversive conditioning memory formation and retrieval.
Topics: Animals; Drosophila; Memory; Learning; Conditioning, Psychological; Mental Recall
PubMed: 37935667
DOI: 10.1038/s41467-023-42753-x -
Nutrients Dec 2023A relationship between excessive sugar consumption and cognitive function has been described in animal models, but the specific effects of sugars in humans remains... (Meta-Analysis)
Meta-Analysis Review
A relationship between excessive sugar consumption and cognitive function has been described in animal models, but the specific effects of sugars in humans remains unclear. This systematic review and meta-analysis aimed to evaluate the current knowledge, research characteristics, and quality of evidence of studies investigating the impacts of free and added sugars on human cognition in healthy participants. The review identified 77 studies (65 experimental trials, = 3831; 9 cross-sectional studies, = 11,456; and 3 cohort studies, = 2059). All cohort studies and eight of the nine cross-sectional studies found significant positive correlations between added sugar consumption and risk of cognitive impairment. Four studies identified reduced risk of cognitive impairment associated with natural fructose-containing foods. The majority of randomised control trials assessed short-term glucose facilitation effects on cognitive outcomes. The results from these studies suggest the need for a tightly regulated blood glucose level, dependent on individualised physiological factors, for optimal cognitive function. A meta-analysis of a subset of studies that assessed the impact of glucose on recall found improvements in immediate free recall compared to controls ( = 0.002). The findings highlight the potentially detrimental effect of excessive, long-term, or prenatal added sugar consumption on cognitive function. Further research is needed to examine the specific effects of free and added sugars on cognitive function.
Topics: Animals; Female; Pregnancy; Humans; Sugars; Cross-Sectional Studies; Cognition; Glucose; Dietary Sugars
PubMed: 38201905
DOI: 10.3390/nu16010075 -
Frontiers in Psychology 2023The present study examined the relative effectiveness of two free-recall-based retrieval practice methods for text learning among students with ADHD.
INTRODUCTION
The present study examined the relative effectiveness of two free-recall-based retrieval practice methods for text learning among students with ADHD.
METHOD
Participants with and without ADHD read texts and practiced them by freely recalling the information either after reading each section or after reading the whole text. Two days later, participants completed a free-recall criterion test on the texts.
RESULTS
The results suggested that although more idea units were recalled during practice in the section recall condition than in the whole-text recall condition, the whole-text recall condition outperformed the section recall condition on the criterion test in terms of the proportion of idea units recalled, although neither retrieval practice conditions outperformed restudying. These findings were obtained for both groups. Exploratory analyses further demonstrated a benefit of the whole-text over section recall also in terms of the order in which idea unites were recalled and suggested that the recall of ADHD participants was less well ordered compared with participants without ADHD.
DISCUSSION
Based on these findings, when using retrieval practice, whole-text free-recall can be recommended for students with ADHD, along with implementing strategies to enhance the mental organization of the studied materials.
PubMed: 38090165
DOI: 10.3389/fpsyg.2023.1301726