Memory consolidation

Much is known about the neural representations of current environmental location and direction within the hippocampal formation, but use of such a “cognitive map” requires the online representation of desired locations and how to get there, and the neural basis for this function has been more elusive. I will discuss how “theta sweeps” of place and grid cell firing encode the current location (at early phases of each theta cycle) while, at later phases, sampling around the forward direction during exploration and indicating the direction to desired locations during goal-directed navigation. I w

…during non-REM sleep, and is tied to memory consolidation and brain waste clearance. Prior work sought to localize the oscillatory generators of specific rhythms, but it is not clear what b

…stimuli or spontaneously during memory replay, a process essential for memory consolidation. Memory storage has traditionally been attributed to excitatory synaptic plasticity and the effect of inhibitory plasticity on memory capacity and recall remains underexplored. To elucidate how inhibitory plasticity affects memory capacity and recall, we compare two inhibitory plasticity rules in spiking autoassociative networks: a homeostatic plasticity rule and a rule that maintains firing rate heterogeneity. Our results

Accumulating evidence from electrocorticogram (ECoG) recordings and imaging challenge traditional views of brain oscillations as spatially stationary periodic sources. Understanding the spatio-temporal dynamics of cortical activity requires novel measurement and analysis methodologies. We recorded broadband local field potential (LFP) across the whole neocortex in freely behaving rats using high-density flexible surface arrays using active transistors. 3D tracking and spatio-spectral analysis of recordings over long sessions enabled automatic and accurate brain and behavioral states segmentati

Sharp-wave ripples (SWRs) are thought to play a crucial role in memory consolidation, learning, and the formation of long-term memories by facilitating the transfer of information from the hippocampus to neocortical networks. To understand the mechanisms governing SWRs, we have developed a closed-loop stimulation framework tailored for the real-time detection and suppression of SWRs, leveraging the ONIX electrophysiology acquisition system and BONSAI-RX acquisition software. As part of our Bonsai package, we developed a convolutional neural network (CNN) for detection of SWRs recorded with lam

…is thought to play a crucial role in memory consolidation and planning [1]. It is commonly modeled as a chain of activity, where links are formed based on temporal associations in the stimulus. Existing work [2,3] focuses on simple patterns, yet we know that the brain is capable of learning complex spatiotemporal dynamics. Specifically chaotic dynamics are even challenging for conventional deep learning algorithms due to exploding gradients. We demonstrate that by introducin

…various cognitive functions, including memory consolidation and both offline and online planning. These events have signatures across nearly all scales, from microscopic coordination at the level of individual spiking activity and synaptic dynamics [2] to macroscopic regulation in the thalamocortical system [3]. Despite the growing recogniti

Sleep deprivation is thought to affect 30% of the population worldwide. Yet our understanding of how sleep disorders develop, how to treat them, and how to prevent cognitive impairment associated with lack of sleep remains limited. Previous studies from our lab have suggested that orexinergic inputs to the hippocampus are more active when mice are sleep deprived, but whether this plays a role in the mechanism for disruption of hippocampal memories during sleep deprivation is unknown. We have used excitatory and inhibitory chemogenetic manipulations to bidirectionally modulate orexin neurons' a

…kingdom, and it is important for memory consolidation. Coordinated neuronal activity occurs during sleep, characterized by distinct events across different sleep states. Non-rapid eye movement (NREM) sleep features slow oscillations, delta waves, thalamocortical spindles and hippocampal sharp waves-ripples, while REM sleep is dominated by hippocampal theta oscillations and ponto-geniculo-occipital (PGO) waves, or pontine waves (“P-waves”) in rodents. Even though their origin from mesopontine cholinergic and glutamatergic nuclei is kn

Sharp wave ripples are brief, highly synchronous bursts of activity in the local field potential and population activity of the hippocampus. They occur predominantly during periods of inactivity and are crucial for the transfer of short-term memories in the hippocampus to long-term memories in the cortex. How this process exactly takes place at the neuronal level, however, is still largely unknown. To answer this question, we leveraged a large publicly available dataset of simultaneous Neuropixels recordings across the brain from the International Brain Laboratory collaboration. We analyzed 74

…activity may play a critical role in memory formation. However, the specific neural mechanisms that a

Memory consolidation involves the spontaneous activity of multiple brain areas potentially supporting the reprocessing of novel and more remote memories. Traditionally, study of these phenomena has focused on a handful of brain areas, such as hippocampus and the prefrontal cortex. Here, we are currently investigating how wider cortical networks support memory reprocessing. We are doing so by combining optical (wide-field) voltage imaging with laminarly-resolved hippocampal electrophysiology in mice, to get a large-scale view of the brain activity. Animals perform two virtual reality memory tas

With their Janus-faced property of being at once dynamic and stable, epigenetic mechanisms have for long been proposed to act as potential molecular mnemonics, but a cell type-specific, locus-restricted and temporally controllable interrogation thereof has thus far been lacking. Over the past years, accumulating evidence has shown that memories are likely encoded in sparse populations of brain cells, so-called engrams, which have, with a few exceptions, received little molecular attention. Here, we combine c-Fos driven engram tagging technologies with CRISPR-based epigenetic editing in vivo to

Memory consolidation is promoted by sleep. However, there is also evidence for consolidation into long-term memory during wakefulness via processes that preferentially affect nonhippocampal representations. We compared, in rats, the effects of 2-h postencoding periods of sleep and wakefulness on the formation of long-term memory for objects and their associated environmental contexts. We employed a novel-object recognition (NOR) task, using object exploration and exploratory rearing as behavioral indicators of these memories. Remote recall testing (after 1 wk) confirmed significant long-term N

…how shifts in the composition of memory-encoding neuronal ensembles influence a memory properties’ evolution over time. Here we leveraged a developmental approach to target distinct subpopulations of principal neurons (“birthdated neurons”), and used calcium imaging, optogenetics, chemogenetics, in association with multiple hippocampus-dependent learning tasks to investigate their contribution to memory engrams over time

Memories are evolving constructs prone to modifications. Here, we explore the temporal rules that determine whether memories are associated, by cooperation, or selected and lost, by competition. To tackle this question, we have built a conceptual model of the rules underlying synaptic cooperation and competition between the cortical and thalamic afferents to projection neurons of the lateral amygdala (LA), a circuit necessary for the formation of fear-conditioning memories. We found that heterosynaptic cooperation and competition between thalamic and cortical inputs to the LA follow a strict t

…to identify early alterations in memory formation. Our findings indicate that Aβ1

The consolidation of long-term memory is thought to critically rely on sleep. However, first evidence from a study in drosophila suggests that hunger as another brain state can benefit memory consolidation as well. Here, we report two human (within-subjects crossover) experiments examining the effects of fasting (versus satiated conditions) during a 10-hour post-encoding consolidation period on later recall of declarative and procedural memories in healthy men. In Experiment 1, participants (n = 16), after an 18.5-hour fasting period, encoded 3 memory tasks (verbal word paired associates, a vi

Tone discrimination is a behavioral task to investigate learning and memory processes in rodents. Additional punishment (aP) can be applied to enhance discrimination abilities; however, some animals have difficulties learning the task with aP. To understand this effect, we conducted auditory fMRI in Mongolian gerbils throughout discrimination training with rising (GO) and falling (noGo) frequency-modulated (FM) tones in ten daily sessions (S), enforced through foot shocks for “Miss”; a second group additionally received aP for “False‑Alarm”. Gerbils of each training group were divided into “go

The interaction between sleep function and memory processing is widely observed in both animals and humans, especially in how sleep supports memory consolidation and forgetting. However, whether memory activity during sleep has any regulatory effect on sleep processes is poorly investigated. Here we find that sensory stimuli-triggered emotional memory reactivation significantly affects sleep strategies after learning, as negative memory promotes alertness in sleep while positive memory protects sleep from perturbation. By combining EEG/EMG recording and engram cell activity tracing, our data r

…(SPW-Rs) play a crucial role in memory consolidation. Hippocampal-dependent memories undergo replay during SPW-Rs, facilitating coordinated ensemble reactivation in the neocortex. This orchestrated mechanism is essential for transferring memory traces from the hippocampus to long-term storage in the neocortex. Following memory consolidation in the neocortex, it is hypothesized that downstream neuronal ensembles are stabilized in diverse cortical regions. The stability of neuronal ensembles across several months has not been

Physical exercise benefits the dorsal hippocampus (dHPC) and promotes learning and memory. We have focused on light exercise (LEX) and have revealed that this accessible form of exercise can effectively increase hippocampal activity and enhance memory performance. However, the circuit mechanism underlying this benefit remains largely undetermined. Our recent findings demonstrate that LEX can stimulate tyrosine hydroxylase-positive (TH+) neurons in the locus coeruleus (LC) and the ventral tegmental area (VTA), and increase noradrenaline (NA) and dopamine (DA) release in the dHPC. This raises th

The hippocampus plays an important role in memory formation. Hippocampal sharp wave ripples (SWRs) are critical for memory consolidation, during which a large number of hippocampal pyramidal neurons fire synchronously. Recent studies indicate that the participation of hippocampal pyramidal neurons in SWRs is variable. The variability may be explained by gene expression pattterns. However, there are no adequate methods to comprehensively analyze these molecular properties of a single neuron in the context of its electrophysiological spike patterns. Here, we developed an experimental technique t

The hippocampus is crucial for episodic memories and is characterized by unique sharp wave ripple complexes (SWRs). These hallmark oscillations, 150-250 Hz in the local field potential (LFP), are produced by fast signaling between synaptically coupled pyramidal neurons (PNs) and parvalbumin-positive basket cells (PV+BCs). Although much has been learned about the synaptic and microcircuit properties mediating ripple oscillations, whether and how myelination of the hippocampus contributes remains unresolved. Here, we performed LFP measurements in combination with paired recordings between PV+BCs