Spaced conditioned stimulus presentation facilitates the extinction of strong fear memory in mice.

Inducing fear memory extinction by re-presenting a conditioned stimulus (CS) is the foundation of exposure therapy for post-traumatic stress disorder (PTSD). Investigating differences in the ability of different CS presentation patterns to induce extinction learning is crucial for improving this type of therapy. Using a trace fear conditioning paradigm in mice, we demonstrate that spaced presentation of the CS facilitated the extinction of a strong fear memory to a greater extent than continuous CS presentation. These results lay the groundwork for developing more effective exposure therapy techniques for PTSD.

[Retrograde Stanford Type A Aortic Dissection of Marfan Syndrome Long After Thoracic Endovascular Aortic Repair:Report of a Case].

A 52-year-old woman with Marfan syndrome developed Stanford type B aortic dissection and was treated with thoracic endovascular aortic repair. However, 29 months later, she presented with retrograde Stanford type A aortic dissection. We successfully performed aortic arch replacement with the frozen elephant trunk technique and valve-sparing aortic root replacement. The advantages of the frozen elephant trunk technique are that the distal anastomosis can be created without stent-graft resection and the cardiac arrest time is shortened. Therefore, the frozen elephant trunk technique was considered valuable and safe in this potentially lethal situation.

Fully automatic REM sleep stage-specific intervention systems using single EEG in mice.

Sleep stage-specific intervention is widely used to elucidate the functions of sleep and their underlying mechanisms. For this intervention, it is imperative to accurately classify rapid-eye-movement (REM) sleep. However, the proof of fully automatic real-time REM sleep classification in vivo has not been obtained in mice. Here, we report the in vivo implementation of a system that classifies sleep stages in real-time from a single-channel electroencephalogram (EEG). It enabled REM sleep-specific intervention with 90 % sensitivity and 86 % precision without prior configuration to each mouse. We further derived systems capable of classification with higher frequency sampling and time resolution. This attach-and-go sleep staging system provides a fully automatic accurate and scalable tool for investigating the functions of sleep.

Open-Source Software for Real-time Calcium Imaging and Synchronized Neuron Firing Detection.

We developed Carignan, a real-time calcium imaging software that can automatically detect activity patterns of neurons. Carignan can activate an external device when synchronized neural activity is detected in calcium imaging obtained by a one-photon (1p) miniscope. Combined with optogenetics, our software enables closed-loop experiments for investigating functions of specific types of neurons in the brain. In addition to making existing pattern detection algorithms run in real-time seamlessly, we developed a new classification module that distinguishes neurons from false-positives using deep learning. We used a combination of convolutional and recurrent neural networks to incorporate both spatial and temporal features in activity patterns. Our method performed better than existing neuron detection methods for false-positive neuron detection in terms of the F1 score. Using Carignan, experimenters can activate or suppress a group of neurons when specific neural activity is observed. Because the system uses a 1p miniscope, it can be used on the brain of a freely-moving animal, making it applicable to a wide range of experimental paradigms.

Novel Galectin-3 Roles in Neurogenesis, Inflammation and Neurological Diseases.

Galectin-3 (Gal-3) is an evolutionarily conserved and multifunctional protein that drives inflammation in disease. Gal-3's role in the central nervous system has been less studied than in the immune system. However, recent studies show it exacerbates Alzheimer's disease and is upregulated in a large variety of brain injuries, while loss of Gal-3 function can diminish symptoms of neurodegenerative diseases such as Alzheimer's. Several novel molecular pathways for Gal-3 were recently uncovered. It is a natural ligand for TREM2 (triggering receptor expressed on myeloid cells), TLR4 (Toll-like receptor 4), and IR (insulin receptor). Gal-3 regulates a number of pathways including stimulation of bone morphogenetic protein (BMP) signaling and modulating Wnt signalling in a context-dependent manner. Gal-3 typically acts in pathology but is now known to affect subventricular zone (SVZ) neurogenesis and gliogenesis in the healthy brain. Despite its myriad interactors, Gal-3 has surprisingly specific and important functions in regulating SVZ neurogenesis in disease. Gal-1, a similar lectin often co-expressed with Gal-3, also has profound effects on brain pathology and adult neurogenesis. Remarkably, Gal-3's carbohydrate recognition domain bears structural similarity to the SARS-CoV-2 virus spike protein necessary for cell entry. Gal-3 can be targeted pharmacologically and is a valid target for several diseases involving brain inflammation. The wealth of molecular pathways now known further suggest its modulation could be therapeutically useful.

[Adult-Born Neurons in the Dentate Gyrus Consolidate Memories during Sleep].

In the middle of the 20th century, adult neurogenesis and rapid eye movement sleep were discovered independently in mammals. The former prompted the idea to apply this rare cellular regenerative capacity in the adult central nervous system to restore damaged brain circuitry, and the latter led to the finding of dynamic brain state changes during sleep and their functional ramifications, including those for memory consolidation. Recently, calcium imaging analysis and optogenetic manipulation have enabled the examination of the activity of specific neuronal populations with precise timing. These technological advances, which allow for the investigation of adult-born neuron activity during sleep in mice, led us to discover its essential function for memory consolidation.

Real-time, automatic, open-source sleep stage classification system using single EEG for mice.

We developed a real-time sleep stage classification system with a convolutional neural network using only a one-channel electro-encephalogram source from mice and universally available features in any time-series data: raw signal, spectrum, and zeitgeber time. To accommodate historical information from each subject, we included a long short-term memory recurrent neural network in combination with the universal features. The resulting system (UTSN-L) achieved 90% overall accuracy and 81% multi-class Matthews Correlation Coefficient, with particularly high-quality judgements for rapid eye movement sleep (91% sensitivity and 98% specificity). This system can enable automatic real-time interventions during rapid eye movement sleep, which has been difficult due to its relatively low abundance and short duration. Further, it eliminates the need for ordinal pre-calibration, electromyogram recording, and manual classification and thus is scalable. The code is open-source with a graphical user interface and closed feedback loop capability, making it easily adaptable to a wide variety of end-user needs. By allowing large-scale, automatic, and real-time sleep stage-specific interventions, this system can aid further investigations of the functions of sleep and the development of new therapeutic strategies for sleep-related disorders.

Fear generalization immediately after contextual fear memory consolidation in mice.

Fear generalization is a symptom of anxiety-related disorders, including acute stress disorder and post-traumatic stress disorder. Using a contextual fear conditioning paradigm, we found that mice exposed to a similar neutral context but not a different neutral context soon after training showed fear generalization immediately after contextual fear memory consolidation (i.e., 6 h after training). This fear generalization was reflected by a change not only in the total amount but also the pattern of freezing between conditioned and generalized contexts. These results provide insight into the factors that influence fear generalization and can facilitate future studies investigating the underlying pathophysiological mechanisms of anxiety-related disorders.

Remapping of Adult-Born Neuron Activity during Fear Memory Consolidation in Mice.

The mammalian hippocampal dentate gyrus is a unique memory circuit in which a subset of neurons is continuously generated throughout the lifespan. Previous studies have shown that the dentate gyrus neuronal population can hold fear memory traces (i.e., engrams) and that adult-born neurons (ABNs) support this process. However, it is unclear whether ABNs themselves hold fear memory traces. Therefore, we analyzed ABN activity at a population level across a fear conditioning paradigm. We found that fear learning did not recruit a distinct ABN population. In sharp contrast, a completely different ABN population was recruited during fear memory retrieval. We further provide evidence that ABN population activity remaps over time during the consolidation period. These results suggest that ABNs support the establishment of a fear memory trace in a different manner to directly holding the memory. Moreover, this activity remapping process in ABNs may support the segregation of memories formed at different times. These results provide new insight into the role of adult neurogenesis in the mammalian memory system.

Metabolic fingerprints of fear memory consolidation during sleep.

Metabolites underlying brain function and pathology are not as well understood as genes. Here, we applied a novel metabolomics approach to further understand the mechanisms of memory processing in sleep. As hippocampal dentate gyrus neurons are known to consolidate contextual fear memory, we analyzed real-time changes in metabolites in the dentate gyrus in different sleep-wake states in mice. Throughout the study, we consistently detected more than > 200 metabolites. Metabolite profiles changed dramactically upon sleep-wake state transitions, leading to a clear separation of phenotypes between wakefulness and sleep. By contrast, contextual fear memory consolidation induced less obvious metabolite phenotypes. However, changes in purine metabolites were observed upon both sleep-wake state transitions and contextual fear memory consolidation. Dietary supplementation of certain purine metabolites impaired correlations between conditioned fear responses before and after memory consolidation. These results point toward the importance of purine metabolism in fear memory processing during sleep.

Calcium imaging of adult-born neurons in freely moving mice.

Adult-born neurons (ABNs) in the dentate gyrus bestow unique cellular plasticity to the mammalian brain. We recently found that the activity of ABNs during sleep is necessary for memory consolidation. Here, we describe our method for Ca2+ imaging of ABN activity using a miniaturized fluorescent microscope and sleep recordings. As preparatory surgery and post-recording data processing can be major obstacles, we provide detailed descriptions and problem-solving tips. For complete details on the use and execution of this protocol, please refer to Kumar et al. (2020).

Mechanisms Underlying Memory Consolidation by Adult-Born Neurons During Sleep.

The mammalian hippocampus generates new neurons that incorporate into existing neuronal networks throughout the lifespan, which bestows a unique form of cellular plasticity to the memory system. Recently, we found that hippocampal adult-born neurons (ABNs) that were active during learning reactivate during subsequent rapid eye movement (REM) sleep and provided causal evidence that ABN activity during REM sleep is necessary for memory consolidation. Here, we describe the potential underlying mechanisms by highlighting distinct characteristics of ABNs including decoupled firing from local oscillations and ability to undergo profound synaptic remodeling in response to experience. We further discuss whether ABNs constitute the conventional definition of engram cells by focusing on their active and passive roles in the memory system. This synthesis of evidence helps advance our thinking on the unique mechanisms by which ABNs contribute to memory consolidation.

Sparse Activity of Hippocampal Adult-Born Neurons during REM Sleep Is Necessary for Memory Consolidation.

The occurrence of dreaming during rapid eye movement (REM) sleep prompts interest in the role of REM sleep in hippocampal-dependent episodic memory. Within the mammalian hippocampus, the dentate gyrus (DG) has the unique characteristic of exhibiting neurogenesis persisting into adulthood. Despite their small numbers and sparse activity, adult-born neurons (ABNs) in the DG play critical roles in memory; however, their memory function during sleep is unknown. Here, we investigate whether young ABN activity contributes to memory consolidation during sleep using Ca2+ imaging in freely moving mice. We found that contextual fear learning recruits a population of young ABNs that are reactivated during subsequent REM sleep against a backdrop of overall reduced ABN activity. Optogenetic silencing of this sparse ABN activity during REM sleep alters the structural remodeling of spines on ABN dendrites and impairs memory consolidation. These findings provide a causal link between ABN activity during REM sleep and memory consolidation.

Progressive Changes in Sleep and Its Relations to Amyloid-ß Distribution and Learning in Single App Knock-In Mice.

Alzheimer's disease (AD) patients often suffer from sleep disturbances. Alterations in sleep, especially rapid eye movement sleep (REMS), can precede the onset of dementia. To accurately characterize the sleep impairments accompanying AD and their underlying mechanisms using animal models, it is crucial to use models in which brain areas are affected in a manner similar to that observed in the actual patients. Here, we focused on AppNL-G-F mice, in which expression levels and patterns of mutated amyloid precursor protein (APP) follow the endogenous patterns. We characterized the sleep architecture of male AppNL-G-F homozygous and heterozygous mice at two ages (six and 12 months). At six months, homozygous mice exhibited reduced REMS, which was further reduced at 12 months together with a slight reduction in non-REMS (NREMS). By contrast, heterozygous mice exhibited an overall normal sleep architecture. Homozygous mice also exhibited decreased electroencephalogram γ to δ power ratio during REMS from six months, resembling the electroencephalogram slowing phenomenon observed in preclinical or early stages of AD. In addition, homozygous mice showed learning and memory impairments in the trace fear conditioning (FC) at both ages, and task performance strongly correlated with REMS amount at 12 months. Finally, histologic analyses revealed that amyloid-ß accumulation in the pontine tegmental area and ventral medulla followed a course similar to that of the REMS reduction. These findings support the notion that changes in REMS are an early marker of AD and provide a starting point to address the mechanism of sleep deficits in AD and the effects on cognition.

Concomitant operation for pulmonary artery aneurysm and pulmonary valve regurgitation.

A 48-year-old man with a pulmonary artery aneurysm was referred to our hospital. Enhanced computed tomography revealed an aneurysm extending from the main trunk to the bilateral pulmonary branch (maximum diameter 6.4 cm) of the artery. Echocardiography revealed moderate pulmonary valve (PV) regurgitation with right ventricle dilatation. Surgery was indicated because of the pulmonary aneurysm and dyspnea on exertion due to moderate PV regurgitation. Intra-operatively, two cusps were found to be normal in shape, whereas a third left-facing cusp was thick and resembled a small ridge. Therefore, we created one neo-cusp with autologous pericardium using a custom-made template and sutured it along a new, predetermined annulus. We then replaced the pulmonary aneurysm with a T-shaped artificial graft. Postoperative echocardiography showed satisfactory movement of the neo-cusp without pulmonary regurgitation and reduced right ventricular size.

Miniaturized microscope with flexible light source input for neuronal imaging and manipulation in freely behaving animals.

Simultaneous imaging and manipulation of a genetically defined neuronal population can provide a causal link between its activity and function. Here, we designed a miniaturized microscope (or 'miniscope') that allows fluorescence imaging and optogenetic manipulation at the cellular level in freely behaving animals. This miniscope has an integrated optical connector that accepts any combination of external light sources, allowing flexibility in the choice of sensors and manipulators. Moreover, due to its simple structure and use of open source software, the miniscope is easy to build and modify. Using this miniscope, we demonstrate the optogenetic silencing of hippocampal CA1 neurons using two laser light sources-one stimulating a calcium sensor (i.e., jGCaAMP7c) and the other serving as an optogenetic silencer (i.e., Jaws). This new miniscope can contribute to efforts to determine causal relationships between neuronal network dynamics and animal behavior.

Memory consolidation during sleep and adult hippocampal neurogenesis.

In anticipation of the massive burden of neurodegenerative disease within super-aged societies, great efforts have been made to utilize neural stem and progenitor cells for regenerative medicine. The capacity of intrinsic neural stem and progenitor cells to regenerate damaged brain tissue remains unclear, due in part to the lack of knowledge about how these newly born neurons integrate into functional circuitry. As sizable integration of adult-born neurons naturally occurs in the dentate gyrus region of the hippocampus, clarifying the mechanisms of this process could provide insights for applying neural stem and progenitor cells in clinical settings. There is convincing evidence of functional correlations between adult-born neurons and memory consolidation and sleep; therefore, we describe some new advances that were left untouched in our recent review.

[Congenital Unicuspid Aortic Valve Diagnosed by Intraoperative Findings].

A unicuspid aortic valve is an extremely rare congenital aortic valvular abnormality. We herein present 2 cases of unicuspid aortic valve diagnosed based on intraoperative findings. In case 1, a 75-year-old man was admitted to our hospital because of severe aortic regurgitation. We performed aortic valve replacement using a bioprosthetic valve, and a unicuspid aortic valve was definitively diagnosed according to the intraoperative findings. In case 2, a 54-year-old man developed dyspnea due to severe aortic stenosis. Aortic valve replacement using mechanical valve was performed, and we were able to diagnose unicuspid aortic valve intraoperatively. Achieving a preoperative definitive diagnosis of congenital unicuspid aortic valve by transthoracic echocardiography is reportedly difficult;however, transesophageal echocardiography may be effective for preoperative definitive diagnosis.