Integration of optogenetics with complementary methodologies in systems neuroscience

Instant noninvasive near-infrared deep brain stimulation using optoelectronic nanoparticles without genetic modification

Noninvasive transcranial neuromodulation of deep brain regions is a longstanding goal in neuroscience. While optogenetics enables remote neural control, it is constrained by shallow tissue penetration of visible light and delayed onset due to required opsin expression. Here, we introduce a neuromodulation technique using hybrid upconversion and photovoltaic (HUP) nanoparticles, which eliminates the need for genetic modification and affords near-infrared (NIR) activation of neurons in wild-type mice. This method converts deeply penetrating NIR light into localized electrical stimuli, enabling immediate and precise modulation in deep brain. In vitro patch-clamp experiments confirm neuronal activation upon HUP application. In vivo, we achieve remote NIR neuromodulation in the medial septum and ventral tegmental area 7 days postinjection, effectively modulating neuronal activity, suppressing seizures, and triggering dopamine release. This minimally invasive approach offers a versatile tool kit for investigating neural processes in mammals, with potential applications across diverse brain regions through customizable nanoparticle engineering.

Alleviating head-mounted weight burden for neural imaging in freely-behaving rodents

The recently developed miniaturized head-mounted two-photon (2P) imaging devices have served as a valuable tool for neuroscientists, enabling real-time functional neural imaging in freely-behaving animals. Although the current 2P fiberscopes and miniscopes are lightweight, the weight of any potential additional accessories inevitably imposes a burden on the animal. Here, we present a buoyancy levitation method to alleviate head-mounted weight burden on mice. By utilizing the buoyance of a helium-filled balloon to counteract the additional weight of up to 7 g, mice' motion behavior remains largely unaffected by the added load. Neuroimage analysis provides new insights into the effects of weight burden on neural activities. This easy-to-implement method offers a platform for studying neural network function in animals, effectively freeing them from the burden of head-mounted weight.

Noninvasive Optogenetics Realized by iPSC-Derived Tentacled Carrier in Alzheimer's Disease Treatment

Neural-activated optogenetics technique contributing to the "restart" of degenerative neurons offers hope for the treatment of several neurodegenerative diseases. However, the limitations of persistent invasiveness and inadequate repair of the pathological environment strongly hinder its further application. Here, a concept of differentiating stem cells is proposed to produce functional materials to enhance the therapeutic applicability of optogenetics. Induced pluripotent stem cells (iPSCs) are differentiated to generate the "tentacled" stem cells TenSCs. Their "tentacled" vesicles TenSCev, upon inheriting the biological functions of the parent cell, will possess both neural targeting capacity and pathological environment repair ability. Hence, TenSCev are utilized as functional carrier to deliver optogenetics elements for completely non-traumatic and controllable neuron activation, while also facilitating the comprehensive restoration of the pathological environment, thus effectively halted disease progression and significantly improved cognitive function in Alzheimer's disease or aged mice. Further, the concept of generating specialized biomaterials from differentiated stem cells as functional carriers holds the potential to broaden the applicability of various neuroregulatory techniques in the treatment of neurological disorders.

Multimodal Correspondence between Optogenetic fMRI, Electrophysiology, and Anatomical Maps of the Secondary Somatosensory Cortex in Nonhuman Primates

Optogenetic neuromodulation combined with functional MRI (opto-fMRI) enables noninvasive monitoring of brain-wide activity and probes causal connections. In this study, we focused on the secondary somatosensory (S2) cortex, a hub for integrating tactile and nociceptive information. By selectively stimulating excitatory neurons in the S2 cortex of monkeys using optogenetics, we observed widespread opto-fMRI activity in regions beyond the somatosensory system, as well as a strong spatial correspondence between opto-fMRI activity map and anatomical connections of the S2 cortex. Locally, optogenetically evoked fMRI BOLD signals from putative excitatory neurons exhibited standard hemodynamic response function. At low laser power, graded opto-fMRI signal changes are closely correlated with increases in local field potential (LFP) signals, but not with spiking activity. This indicates that LFP changes in excitatory neurons more accurately reflect the opto-fMRI signals than spikes. In summary, our optogenetic fMRI and anatomical findings provide causal functional and anatomical evidence supporting the role of the S2 cortex as a critical hub connecting sensory regions to higher-order cortical and subcortical regions involved in cognition and emotion. The electrophysiological basis of the opto-fMRI signals uncovered in this study offers novel insights into interpreting opto-fMRI results. Nonhuman primates are an invaluable intermediate model for translating optogenetic preclinical findings to humans.

Projection-specific and reversible functional blockage in the association cortex of macaque monkeys

The functional manipulation techniques based on optogenetics have been widely and effectively utilized in the rodent brain. However, the applications of these techniques to the macaque cerebral cortex, particularly those to the prefrontal cortex, have been limited due to the extensive size and complex functional organization of each prefrontal area. In this study, we developed projection-specific and reversible functional blockade methods applicable to areas of the macaque prefrontal cortex, based on chemogenetic techniques. In chemogenetics, once a pair of viral vectors has been injected into the regions of projection source and target, the projection-specific functional blockage can be initiated through the oral, intravenous, or intramuscular administration of an appropriate pharmaceutical agent. Two methods were developed using two different effector proteins, an inhibitory DREADD, hM4Di, and tetanus toxin, given the substantial discrepancy in the on-off time course of functional blockade between the two. The Cre-DIO system was combined with hM4Di, and the Tet-On system with tetanus toxin. The effectiveness of these methods was evaluated by developing an electrophysiological assay using photic stimulation and field potential recordings.

Longitudinal calcium imaging of BNST neurons in mice during optogenetic manipulation of paraventricular thalamus axon terminals

Here, we present a protocol to study neural circuits between the paraventricular thalamus (PVA) and the bed nucleus of the stria terminalis (BNST) in mice by combining calcium imaging with optogenetic stimulation of axon terminals. We describe steps for delivering GCaMP6f and ChrimsonR viruses and implanting the gradient-index (GRIN) lens for use with an Inscopix microscope. We then detail procedures for single-neuron tracking over an extended period through longitudinal recording and data smoothing and processing to enhance analysis.

A chemogenetic technology using insect Ionotropic Receptors to stimulate target cell populations in the mammalian brain

Chemogenetics uses artificially-engineered proteins to modify the activity of cells, notably neurons, in response to small molecules. Although a common set of chemogenetic tools are the G protein-coupled receptor-based DREADDs, there has been great hope for ligand-gated, ion channel-type chemogenetic tools that directly impact neuronal excitability. We have devised such a technology by exploiting insect Ionotropic Receptors (IRs), a highly divergent subfamily of ionotropic glutamate receptors that evolved to detect diverse environmental chemicals. Here, we review a series of studies developing and applying this "IR-mediated neuronal activation" (IRNA) technology with the Drosophila melanogaster IR84a/IR8a complex, which detects phenyl-containing ligands. We also discuss how variants of IRNA could be produced by modifying the composition of the IR complex, using natural or engineered subunits, which would enable artificial activation of different cell populations in the brain in response to distinct chemicals.

Optogenetic stimulation of cell bodies versus axonal terminals generate comparable activity and functional connectivity patterns in the brain

Optogenetic techniques are often employed to dissect neural pathways with presumed specificity for targeted projections. In this study, we used optogenetic fMRI to investigate the effective landscape of stimulating the cell bodies versus one of its projection terminals. Specifically, we selected a long-range unidirectional projection from the ventral subiculum (vSUB) to the nucleus accumbens shell (NAcSh) and placed two stimulating fibers-one at the vSUB cell bodies and the other at the vSUB terminals in the NAcSh. Contrary to the conventional view that terminal stimulation confines activity to the feedforward stimulated pathway, our findings reveal that terminal stimulation induces brain activity and connectivity patterns remarkably similar to those of vSUB cell body stimulation. This observation suggests that the specificity of optogenetic terminal stimulation may induce antidromic activation, leading to broader network involvement than previously acknowledged.

A Rapid Cortical Learning Process Supporting Students' Knowledge Construction During Real Classroom Teaching

Classroom teaching is essential for cognitive development and cultural evolution, yet its neurocognitive mechanisms remain unclear. Here, this is explored in a university graduate course by combining wearable functional near-infrared spectroscopy (fNIRS) and machine learning models. The results show that blended teaching involving both students' recalling and teachers' lecturing leads to better learning outcomes than lecturing alone. Moreover, during the same lecturing phase, blended teaching induces knowledge construction in the middle frontal cortex (MFC), while lecturing alone induces knowledge representation in the right temporoparietal junction (TPJ), with the former significantly correlating with the final learning outcomes. Additionally, the MFC's construction begins during earlier recalling but is significantly facilitated by later lecturing. Finally, when teacher's TPJ activity precedes that of students' MFC, significant teacher-student neural synchronization is observed during lecturing of blended teaching and is correlated with learning outcomes. These findings suggest that, in the real classroom teaching, the MFC serves as a hub of a rapid cortical learning process, supporting knowledge construction through a projection from the teacher's TPJ.

Optogenetic therapy for retinal degenerative diseases: A review

Optogenetics, a cutting-edge tool in novel gene manipulation and drug discovery, holds significant therapeutic potential for a variety of neurological disorders, including retinal diseases. Retinal diseases such as age-related macular degeneration (AMD) and retinitis pigmentosa (RP), significantly impair quality of life and cause severe visual impairment due to limited treatment options and a general lack of awareness. The increasing incidence of these degenerative conditions underscores the need for innovative solutions, such as optogenetics. Optogenetic therapy introduces genes coding for light-sensitive proteins, which are controlled by light signals to make neurons photosensitive. This precise targeting approach does not require specific gene intervention and can bypass dysfunctional photoreceptors, offering a treatment option for various degenerative and dystrophic eye diseases. Successful outcomes in patients with late-stage genetic retinal diseases and numerous clinical trials suggest that optogenetics could be an effective treatment for humans. This review provides an overview of the current landscape of optogenetic therapy, discusses its challenges, and summarizes the findings of ongoing clinical trials for neural and visual restoration.

Integrating multimodal data to understand cortical circuit architecture and function

In recent years there has been a tremendous growth in new technologies that allow large-scale investigation of different characteristics of the nervous system at an unprecedented level of detail. There is a growing trend to use combinations of these new techniques to determine direct links between different modalities. In this Perspective, we focus on the mouse visual cortex, as this is one of the model systems in which much progress has been made in the integration of multimodal data to advance understanding. We review several approaches that allow integration of data regarding various properties of cortical cell types, connectivity at the level of brain areas, cell types and individual cells, and functional neural activity in vivo. The increasingly crucial contributions of computation and theory in analyzing and systematically modeling data are also highlighted. Together with open sharing of data, tools and models, integrative approaches are essential tools in modern neuroscience for improving our understanding of the brain architecture, mechanisms and function.

TRACKING THE TOPOLOGY OF NEURAL MANIFOLDS ACROSS POPULATIONS

Neural manifolds summarize the intrinsic structure of the information encoded by a population of neurons. Advances in experimental techniques have made simultaneous recordings from multiple brain regions increasingly commonplace, raising the possibility of studying how these manifolds relate across populations. However, when the manifolds are nonlinear and possibly code for multiple unknown variables, it is challenging to extract robust and falsifiable information about their relationships. We introduce a framework, called the method of analogous cycles, for matching topological features of neural manifolds using only observed dissimilarity matrices within and between neural populations. We demonstrate via analysis of simulations and in vivo experimental data that this method can be used to correctly identify multiple shared circular coordinate systems across both stimuli and inferred neural manifolds. Conversely, the method rejects matching features that are not intrinsic to one of the systems. Further, as this method is deterministic and does not rely on dimensionality reduction or optimization methods, it is amenable to direct mathematical investigation and interpretation in terms of the underlying neural activity. We thus propose the method of analogous cycles as a suitable foundation for a theory of cross-population analysis via neural manifolds.

Cutting-edge methodologies for tagging and tracing active neuronal coding in the brain

Decoding the neural substrates that underlie learning and behavior is a fundamental goal in neuroscience. Identifying "key players" at the molecular, cellular, and circuit levels has become possible with recent advancements in molecular technologies offering high spatiotemporal resolution. Immediate-early genes are effective markers of neural activity and plasticity, allowing for the identification of active cells involved in memory-based behavior. A calcium-dependent labeling system coupled with light or biochemical proximity labeling allows characterization of active cell ensembles and circuitry across broader brain regions within short time windows, particularly during transient behaviors. The integration of these systems expands the ability to address diverse research questions across behavioral paradigms. This review examines current molecular systems for activity-dependent labeling, highlighting their applications in identifying specific cell ensembles and circuits relevant to various scientific questions and further discuss their significance, along with future directions for the development of innovative methodologies.

Beyond Mechanism-Extending Our Concepts of Causation in Neuroscience

In neuroscience, the search for the causes of behaviour is often just taken to be the search for neural mechanisms. This view typically involves three forms of causal reduction: first, from the ontological level of cognitive processes to that of neural mechanisms; second, from the activity of the whole brain to that of isolated parts; and third, from a consideration of temporally extended, historical processes to a focus on synchronic states. While modern neuroscience has made impressive progress in identifying synchronic neural mechanisms, providing unprecedented real-time control of behaviour, we contend that this does not amount to a full causal explanation. In particular, there is an attendant danger of eliminating the cognitive from our explanatory framework, and even eliminating the organism itself. To fully understand the causes of behaviour, we need to understand not just what happens when different neurons are activated, but why those things happen. In this paper, we introduce a range of well-developed, non-reductive, and temporally extended notions of causality from philosophy, which neuroscientists may be able to draw on in order to build more complete causal explanations of behaviour. These include concepts of criterial causation, triggering versus structuring causes, constraints, macroscopic causation, historicity, and semantic causation-all of which, we argue, can be used to undergird a naturalistic understanding of mental causation and agent causation. These concepts can, collectively, help bring cognition and the organism itself back into the picture, as a causal agent unto itself, while still grounding causation in respectable scientific terms.

Optogenetics and Its Application in Nervous System Diseases

Optogenetics is an emerging technology that uses the light-responsive effects of photosensitive proteins to regulate the function of specific cells. This technique combines genetics with optics, allowing for the precise inhibition or activation of cell functions through the introduction of photosensitive proteins into target cells and subsequent light stimulation to activate these proteins. In recent years, numerous basic and clinical studies have demonstrated the unique advantages of this approach in the research and treatment of neurological disorders. This review aims to introduce the fundamental principles and techniques of optogenetics, as well as its applications in the research and treatment of neurological diseases.

Testing the role of spontaneous activity in visuospatial perception with patterned optogenetics

A major debate in the field of consciousness pertains to whether neuronal activity or rather the causal structure of neural circuits underlie the generation of conscious experience. The former position is held by theoretical accounts of consciousness based on the predictive processing framework (such as neurorepresentationalism and active inference), while the latter is posited by the integrated information theory. This protocol describes an experiment, part of a larger adversarial collaboration, that was designed to address this question through a combination of behavioral tests in mice, functional imaging, patterned optogenetics and electrophysiology. The experiment will directly test if optogenetic inactivation of a portion of the visual cortex not responding to behaviorally relevant stimuli will affect the perception of the spatial distribution of these stimuli, even when the neurons being inactivated display no or very low spiking activity, so low that it does not induce a significant effect on other cortical areas. The results of the experiment will be compared against theoretical predictions, and will provide a major contribution towards understanding what the neuronal substrate of consciousness is.

Neuropixels Opto: Combining high-resolution electrophysiology and optogenetics

High-resolution extracellular electrophysiology is the gold standard for recording spikes from distributed neural populations, and is especially powerful when combined with optogenetics for manipulation of specific cell types with high temporal resolution. We integrated these approaches into prototype Neuropixels Opto probes, which combine electronic and photonic circuits. These devices pack 960 electrical recording sites and two sets of 14 light emitters onto a 1 cm shank, allowing spatially addressable optogenetic stimulation with blue and red light. In mouse cortex, Neuropixels Opto probes delivered high-quality recordings together with spatially addressable optogenetics, differentially activating or silencing neurons at distinct cortical depths. In mouse striatum and other deep structures, Neuropixels Opto probes delivered efficient optotagging, facilitating the identification of two cell types in parallel. Neuropixels Opto probes represent an unprecedented tool for recording, identifying, and manipulating neuronal populations.

Protein design accelerates the development and application of optogenetic tools

Optogenetics has substantially enhanced our understanding of biological processes by enabling high-precision tracking and manipulation of individual cells. It relies on photosensitive proteins to monitor and control cellular activities, thereby paving the way for significant advancements in complex system research. Photosensitive proteins play a vital role in the development of optogenetics, facilitating the establishment of cutting-edge methods. Recent breakthroughs in protein design have opened up opportunities to develop protein-based tools that can precisely manipulate and monitor cellular activities. These advancements will significantly accelerate the development and application of optogenetic tools. This article emphasizes the pivotal role of protein design in the development of optogenetic tools, offering insights into potential future directions. We begin by providing an introduction to the historical development and fundamental principles of optogenetics, followed by an exploration of the operational mechanisms of key photosensitive domains, which includes clarifying the conformational changes they undergo in response to light, such as allosteric modulation and dimerization processes. Building on this foundation, we reveal the development of protein design tools that will enable the creation of even more sophisticated optogenetic techniques.

Neural regulation of the thymus: past, current, and future perspectives

The thymus is a primary lymphoid organ critical for the development of mature T cells from hematopoietic progenitors. A highly structured organ, the thymus contains distinct regions, precise cytoarchitecture, and molecular signals tightly regulating thymopoiesis. Although the above are well-understood, the structural and functional implications of thymic innervation are largely neglected. In general, neural regulation has become increasingly identified as a critical component of immune cell development and function. The central nervous system (CNS) in the brain coordinates these immunological responses both by direct innervation through peripheral nerves and by neuroendocrine signaling. Yet how these signals, particularly direct neural innervation, may regulate the thymus biology is unclear and understudied. In this review, we highlight historical and current data demonstrating direct neural input to the thymus and assess current evidence of the neural regulation of thymopoiesis. We further discuss the current knowledge gaps and summarize recent advances in techniques that could be used to study how nerves regulate the thymic microenvironment.

A Massively Parallel CRISPR-Based Screening Platform for Modifiers of Neuronal Activity

Understanding the complex interplay between gene expression and neuronal activity is crucial for unraveling the molecular mechanisms underlying cognitive function and neurological disorders. Here, we developed pooled screens for neuronal activity, using CRISPR interference (CRISPRi) and the fluorescent calcium integrator CaMPARI2. Using this screening method, we evaluated 1343 genes for their effect on excitability in human iPSC-derived neurons, revealing potential links to neurodegenerative and neurodevelopmental disorders. These genes include known regulators of neuronal excitability, such as TARPs and ion channels, as well as genes associated with autism spectrum disorder and Alzheimer's disease not previously described to affect neuronal excitability. This CRISPRi-based screening platform offers a versatile tool to uncover molecular mechanisms controlling neuronal activity in health and disease.

The neuroimmune connectome in health and disease

The nervous and immune systems have complementary roles in the adaptation of organisms to environmental changes. However, the mechanisms that mediate cross-talk between the nervous and immune systems, called neuroimmune interactions, are poorly understood. In this Review, we summarize advances in the understanding of neuroimmune communication, with a principal focus on the central nervous system (CNS): its response to immune signals and the immunological consequences of CNS activity. We highlight these themes primarily as they relate to neurological diseases, the control of immunity, and the regulation of complex behaviours. We also consider the importance and challenges linked to the study of the neuroimmune connectome, which is defined as the totality of neuroimmune interactions in the body, because this provides a conceptual framework to identify mechanisms of disease pathogenesis and therapeutic approaches. Finally, we discuss how the latest techniques can advance our understanding of the neuroimmune connectome, and highlight the outstanding questions in the field.

Role of the ventral portion of intermediate arcopallium in stability of female Bengalese finch song preferences

The process of decision making is a complex procedure influenced by both external and internal conditions. Songbirds provide an excellent model to investigate the neural mechanisms of decision making, because females rely on acoustic signals called songs as important stimuli in directing their mate choice. Previous experiments by our group and others have implicated secondary auditory brain sites in female evaluation of song quality, including the caudal portions of the nidopallium (NC) and mesopallium (CM). Recent pathway tracing experiments reveal a convergence of those sites onto a third region, the ventral portion of the intermediate arcopallium (AIV), suggesting that AIV may also play an important role in song evaluation and mate choice. Here we combined behavioral testing with lesion inactivation to investigate the role of AIV in song preference of female Bengalese finches (Lonchura striata domestica). Inactivation of AIV was associated with destabilization of rank ordering of song preferences. These data suggest a model in which the convergence of auditory activity in AIV plays an important role in female perception of song quality and production of courtship behaviors. Together with previous results that also demonstrate a role for the auditory areas that converge onto AIV, these findings extend the experimental tractability of this emerging animal model of sensory perception and decision making.

Mystery of gamma wave stimulation in brain disorders

Neuronal oscillations refer to rhythmic and periodic fluctuations of electrical activity in the central nervous system that arise from the cellular properties of diverse neuronal populations and their interactions. Specifically, gamma oscillations play a crucial role in governing the connectivity between distinct brain regions, which are essential in perception, motor control, memory, and emotions. In this context, we recapitulate various current stimulation methods to induce gamma entrainment. These methods include sensory stimulation, optogenetic modulation, photobiomodulation, and transcranial electrical or magnetic stimulation. Simultaneously, we explore the association between abnormal gamma oscillations and central nervous system disorders such as Alzheimer's disease, Parkinson's disease, stroke, schizophrenia, and autism spectrum disorders. Evidence suggests that gamma entrainment-inducing stimulation methods offer notable neuroprotection, although somewhat controversial. This review comprehensively discusses the functional role of gamma oscillations in higher-order brain activities from both physiological and pathological perspectives, emphasizing gamma entrainment as a potential therapeutic approach for neuropsychiatric disorders. Additionally, we discuss future opportunities and challenges in implementing such strategies.

Neurobiology of Obsessive-Compulsive Disorder from Genes to Circuits: Insights from Animal Models

Obsessive-compulsive disorder (OCD) is a chronic, severe psychiatric disorder that has been ranked by the World Health Organization as one of the leading causes of illness-related disability, and first-line interventions are limited in efficacy and have side-effect issues. However, the exact pathophysiology underlying this complex, heterogeneous disorder remains unknown. This scenario is now rapidly changing due to the advancement of powerful technologies that can be used to verify the function of the specific gene and dissect the neural circuits underlying the neurobiology of OCD in rodents. Genetic and circuit-specific manipulation in rodents has provided important insights into the neurobiology of OCD by identifying the molecular, cellular, and circuit events that induce OCD-like behaviors. This review will highlight recent progress specifically toward classic genetic animal models and advanced neural circuit findings, which provide theoretical evidence for targeted intervention on specific molecular, cellular, and neural circuit events.

Nanomaterials for Flexible Neuromorphics

The quest to imbue machines with intelligence akin to that of humans, through the development of adaptable neuromorphic devices and the creation of artificial neural systems, has long stood as a pivotal goal in both scientific inquiry and industrial advancement. Recent advancements in flexible neuromorphic electronics primarily rely on nanomaterials and polymers owing to their inherent uniformity, superior mechanical and electrical capabilities, and versatile functionalities. However, this field is still in its nascent stage, necessitating continuous efforts in materials innovation and device/system design. Therefore, it is imperative to conduct an extensive and comprehensive analysis to summarize current progress. This review highlights the advancements and applications of flexible neuromorphics, involving inorganic nanomaterials (zero-/one-/two-dimensional, and heterostructure), carbon-based nanomaterials such as carbon nanotubes (CNTs) and graphene, and polymers. Additionally, a comprehensive comparison and summary of the structural compositions, design strategies, key performance, and significant applications of these devices are provided. Furthermore, the challenges and future directions pertaining to materials/devices/systems associated with flexible neuromorphics are also addressed. The aim of this review is to shed light on the rapidly growing field of flexible neuromorphics, attract experts from diverse disciplines (e.g., electronics, materials science, neurobiology), and foster further innovation for its accelerated development.

Alleviating Head-mounted Weight Burden for Neural Imaging in Freely-behaving Rodents Using a Helium-filled Balloon

The recently developed miniaturized head-mounted two-photon (2P) imaging devices have served as a valuable tool for neuroscientists, enabling real-time functional neural imaging in freely-behaving animals. Although the current 2P fiberscopes and miniscopes are lightweight, the weight of any potential additional accessories inevitably imposes a burden on the animal. Here, we present a buoyancy levitation method to alleviate head-mounted weight burden on mice. By utilizing the buoyance of a helium-filled balloon to counteract the additional weight of up to 7 g, both the motion behavior and neural activities remain unaffected by the added load. This easy-to-implement method provides a platform for studying neural network function in animals, effectively freeing them from the burden of head-mounted weight.

The therapeutic potential of low-intensity focused ultrasound for treating substance use disorder

Substance use disorder (SUD) is a persistent public health issue that necessitates the exploration of novel therapeutic interventions. Low-intensity focused ultrasound (LIFU) is a promising modality for precise and invasive modulation of brain activity, capable of redefining the landscape of SUD treatment. The review overviews effective LIFU neuromodulatory parameters and molecular mechanisms, focusing on the modulation of reward pathways in key brain regions in animal and human models. Integration of LIFU with established therapeutics holds promise for augmenting treatment outcomes in SUD. The current research examines LIFU's efficacy in reducing cravings and withdrawal symptoms. LIFU shows promise for reducing cravings, modulating reward circuitry, and addressing interoceptive dysregulation and emotional distress. Selecting optimal parameters, encompassing frequency, burst patterns, and intensity, is pivotal for balancing therapeutic efficacy and safety. However, inconsistencies in empirical findings warrant further research on optimal treatment parameters, physiological action mechanisms, and long-term effects. Collaborative interdisciplinary investigations are imperative to fully realize LIFU's potential in revolutionizing SUD treatment paradigms and enhancing patient outcomes.

The Effect of the Optogenetic Stimulation of Astrocytes on Neural Network Activity in an In Vitro Model of Alzheimer's Disease

Optogenetics is a combination of optical and genetic technologies used to activate or, conversely, inhibit specific cells in living tissues. The possibilities of using optogenetics approaches for the treatment of epilepsy, Parkinson's and Alzheimer's disease (AD) are being actively researched. In recent years, it has become clear that one of the most important players in the development of AD is astrocytes. Astrocytes affect amyloid clearance, participate in the development of neuroinflammation, and regulate the functioning of neural networks. We used an adeno-associated virus carrying the glial fibrillary acidic protein (GFAP) promoter driving the optogenetic channelrhodopsin-2 (ChR2) gene to transduce astrocytes in primary mouse hippocampal cultures. We recorded the bioelectrical activity of neural networks from day 14 to day 21 of cultivation using multielectrode arrays. A single optogenetic stimulation of astrocytes at 14 day of cultivation (DIV14) did not cause significant changes in neural network bioelectrical activity. Chronic optogenetic stimulation from DIV14 to DIV21 exerts a stimulatory effect on the bioelectrical activity of primary hippocampal cultures (the proportion of spikes included in network bursts significantly increased since DIV19). Moreover, chronic optogenetic stimulation over seven days partially preserved the activity and functional architecture of neuronal network in amyloidosis modeling. These results suggest that the selective optogenetic activation of astrocytes may represent a promising novel therapeutic strategy for combating AD.

Tracking the topology of neural manifolds across populations

Neural manifolds summarize the intrinsic structure of the information encoded by a population of neurons. Advances in experimental techniques have made simultaneous recordings from multiple brain regions increasingly commonplace, raising the possibility of studying how these manifolds relate across populations. However, when the manifolds are nonlinear and possibly code for multiple unknown variables, it is challenging to extract robust and falsifiable information about their relationships. We introduce a framework, called the method of analogous cycles, for matching topological features of neural manifolds using only observed dissimilarity matrices within and between neural populations. We demonstrate via analysis of simulations and in vivo experimental data that this method can be used to correctly identify multiple shared circular coordinate systems across both stimuli and inferred neural manifolds. Conversely, the method rejects matching features that are not intrinsic to one of the systems. Further, as this method is deterministic and does not rely on dimensionality reduction or optimization methods, it is amenable to direct mathematical investigation and interpretation in terms of the underlying neural activity. We thus propose the method of analogous cycles as a suitable foundation for a theory of cross-population analysis via neural manifolds.

In Vivo Optogenetics Based on Heavy Metal-Free Photon Upconversion Nanoparticles

Photon upconversion (UC) from red or near-infrared (NIR) light to blue light is promising for in vivo optogenetics. However, the examples of in vivo optogenetics have been limited to lanthanide inorganic UC nanoparticles, and there have been no examples of optogenetics without using heavy metals. Here the first example of in vivo optogenetics using biocompatible heavy metal-free TTA-UC nanoemulsions is shown. A new organic TADF sensitizer, a boron difluoride curcuminoid derivative modified with a bromo group, can promote intersystem crossing to the excited triplet state, significantly improving TTA-UC efficiency. The TTA-UC nanoparticles formed from biocompatible surfactants and methyl oleate acquire water dispersibility and remarkable oxygen tolerance. By combining with genome engineering technology using the blue light-responding photoactivatable Cre-recombinase (PA-Cre), TTA-UC nanoparticles promote Cre-reporter EGFP expression in neurons in vitro and in vivo. The results open new opportunities toward deep-tissue control of neural activities based on heavy metal-free fully organic UC systems.

Comparative Validation of Scintillator Materials for X-Ray-Mediated Neuronal Control in the Deep Brain

When exposed to X-rays, scintillators emit visible luminescence. X-ray-mediated optogenetics employs scintillators for remotely activating light-sensitive proteins in biological tissue through X-ray irradiation. This approach offers advantages over traditional optogenetics, allowing for deeper tissue penetration and wireless control. Here, we assessed the short-term safety and efficacy of candidate scintillator materials for neuronal control. Our analyses revealed that lead-free halide scintillators, such as Cs3Cu2I5, exhibited significant cytotoxicity within 24 h and induced neuroinflammatory effects when injected into the mouse brain. In contrast, cerium-doped gadolinium aluminum gallium garnet (Ce:GAGG) nanoparticles showed no detectable cytotoxicity within the same period, and injection into the mouse brain did not lead to observable neuroinflammation over four weeks. Electrophysiological recordings in the cerebral cortex of awake mice showed that X-ray-induced radioluminescence from Ce:GAGG nanoparticles reliably activated 45% of the neuronal population surrounding the implanted particles, a significantly higher activation rate than europium-doped GAGG (Eu:GAGG) microparticles, which activated only 10% of neurons. Furthermore, we established the cell-type specificity of this technique by using Ce:GAGG nanoparticles to selectively stimulate midbrain dopamine neurons. This technique was applied to freely behaving mice, allowing for wireless modulation of place preference behavior mediated by midbrain dopamine neurons. These findings highlight the unique suitability of Ce:GAGG nanoparticles for X-ray-mediated optogenetics. The deep tissue penetration, short-term safety, wireless neuronal control, and cell-type specificity of this system offer exciting possibilities for diverse neuroscience applications and therapeutic interventions.

Treating Alzheimer's disease with brain stimulation: From preclinical models to non-invasive stimulation in humans

Alzheimer's disease (AD) is a severe and progressive neurodegenerative condition that exerts detrimental effects on brain function. As of now, there is no effective treatment for AD patients. This review explores two distinct avenues of research. The first revolves around the use of animal studies and preclinical models to gain insights into AD's underlying mechanisms and potential treatment strategies. Specifically, it delves into the effectiveness of interventions such as Optogenetics and Chemogenetics, shedding light on their implications for understanding pathophysiological mechanisms and potential therapeutic applications. The second avenue focuses on non-invasive brain stimulation (NiBS) techniques in the context of AD. Evidence suggests that NiBS can successfully modulate cognitive functions associated with various neurological and neuropsychiatric disorders, including AD, as demonstrated by promising findings. Here, we critically assessed recent findings in AD research belonging to these lines of research and discuss their potential impact on the clinical horizon of AD treatment. These multifaceted approaches offer hope for advancing our comprehension of AD pathology and developing novel therapeutic interventions.

A spatial-temporal map of glutamatergic neurogenesis in the murine embryonic cerebellar nuclei uncovers a high degree of cellular heterogeneity

The nuclei are the main output structures of the cerebellum. Each and every cerebellar cortical computation reaches several areas of the brain by means of cerebellar nuclei processing and integration. Nevertheless, our knowledge of these structures is still limited compared to the cerebellar cortex. Here, we present a mouse genetic inducible fate-mapping study characterizing rhombic lip-derived glutamatergic neurons of the nuclei, the most conspicuous family of long-range cerebellar efferent neurons. Glutamatergic neurons mainly occupy dorsal and lateral territories of the lateral and interposed nuclei, as well as the entire medial nucleus. In mice, they are born starting from about embryonic day 9.5, with a peak between 10.5 and 12.5, and invade the nuclei with a lateral-to-medial progression. While some markers label a heterogeneous population of neurons sharing a common location (BRN2), others appear to be lineage specific (TBR1, LMX1a, and MEIS2). A comparative analysis of TBR1 and LMX1a distributions reveals an incomplete overlap in their expression domains, in keeping with the existence of separate efferent subpopulations. Finally, some tagged glutamatergic progenitors are not labeled by any of the markers used in this study, disclosing further complexity. Taken together, our results obtained in late embryonic nuclei shed light on the heterogeneity of the excitatory neuron pool, underlying the diversity in connectivity and functions of this largely unexplored cerebellar territory. Our findings contribute to laying the groundwork for a comprehensive functional analysis of nuclear neuron subpopulations.

Central post-stroke pain: advances in clinical and preclinical research

Central poststroke pain (CPSP) is a medical complication that arises poststroke and significantly impacts the quality of life and social functioning of affected individuals. Despite ongoing research, the exact pathomechanisms of CPSP remain unclear, and practical treatments are still unavailable. Our review aims to systematically analyse current clinical and preclinical studies on CPSP, which is critical for identifying gaps in knowledge and guiding the development of effective therapies. The review will clarify the clinical characteristics, evaluation scales and contemporary therapeutic approaches for CPSP based on clinical investigations. It will particularly emphasise the CPSP model initiated by stroke, shedding light on its underlying mechanisms and evaluating treatments validated in preclinical studies. Furthermore, the review will not only highlight methodological limitations in animal trials but also offer specific recommendations to researchers to improve the quality of future investigations and guide the development of effective therapies. This review is expected to provide valuable insights into the current knowledge regarding CPSP and can serve as a guide for future research and clinical practice. The review will contribute to the scientific understanding of CPSP and help develop effective clinical interventions.

Local and long-range input balance: A framework for investigating frontal cognitive circuit maturation in health and disease

Frontal cortical circuits undergo prolonged maturation across childhood and adolescence; however, it remains unknown what specific changes are occurring at the circuit level to establish adult cognitive function. With the recent advent of circuit dissection techniques, it is now feasible to examine circuit-specific changes in connectivity, activity, and function in animal models. Here, we propose that the balance of local and long-range inputs onto frontal cognitive circuits is an understudied metric of circuit maturation. This review highlights research on a frontal-sensory attention circuit that undergoes refinement of local/long-range connectivity, regulated by circuit activity and neuromodulatory signaling, and evaluates how this process may occur generally in the frontal cortex to support adult cognitive behavior. Notably, this balance can be bidirectionally disrupted through various mechanisms relevant to psychiatric disorders. Pharmacological or environmental interventions to normalize or reset the local and long-range balance could hold great therapeutic promise to prevent or rescue cognitive deficits.

Neural stimulation and modulation with sub-cellular precision by optomechanical bio-dart

Neural stimulation and modulation at high spatial resolution are crucial for mediating neuronal signaling and plasticity, aiding in a better understanding of neuronal dysfunction and neurodegenerative diseases. However, developing a biocompatible and precisely controllable technique for accurate and effective stimulation and modulation of neurons at the subcellular level is highly challenging. Here, we report an optomechanical method for neural stimulation and modulation with subcellular precision using optically controlled bio-darts. The bio-dart is obtained from the tip of sunflower pollen grain and can generate transient pressure on the cell membrane with submicrometer spatial resolution when propelled by optical scattering force controlled with an optical fiber probe, which results in precision neural stimulation via precisely activation of membrane mechanosensitive ion channel. Importantly, controllable modulation of a single neuronal cell, even down to subcellular neuronal structures such as dendrites, axons, and soma, can be achieved. This bio-dart can also serve as a drug delivery tool for multifunctional neural stimulation and modulation. Remarkably, our optomechanical bio-darts can also be used for in vivo neural stimulation in larval zebrafish. This strategy provides a novel approach for neural stimulation and modulation with sub-cellular precision, paving the way for high-precision neuronal plasticity and neuromodulation.

Neuroelectrophysiology-compatible electrolytic lesioning

Lesion studies have historically been instrumental for establishing causal connections between brain and behavior. They stand to provide additional insight if integrated with multielectrode techniques common in systems neuroscience. Here, we present and test a platform for creating electrolytic lesions through chronically implanted, intracortical multielectrode probes without compromising the ability to acquire neuroelectrophysiology. A custom-built current source provides stable current and allows for controlled, repeatable lesions in awake-behaving animals. Performance of this novel lesioning technique was validated using histology from ex vivo and in vivo testing, current and voltage traces from the device, and measurements of spiking activity before and after lesioning. This electrolytic lesioning method avoids disruptive procedures, provides millimeter precision over the extent and submillimeter precision over the location of the injury, and permits electrophysiological recording of single-unit activity from the remaining neuronal population after lesioning. This technique can be used in many areas of cortex, in several species, and theoretically with any multielectrode probe. The low-cost, external lesioning device can also easily be adopted into an existing electrophysiology recording setup. This technique is expected to enable future causal investigations of the recorded neuronal population's role in neuronal circuit function, while simultaneously providing new insight into local reorganization after neuron loss.

ARViS: a bleed-free multi-site automated injection robot for accurate, fast, and dense delivery of virus to mouse and marmoset cerebral cortex

Genetically encoded fluorescent sensors continue to be developed and improved. If they could be expressed across multiple cortical areas in non-human primates, it would be possible to measure a variety of spatiotemporal dynamics of primate-specific cortical activity. Here, we develop an Automated Robotic Virus injection System (ARViS) for broad expression of a biosensor. ARViS consists of two technologies: image recognition of vasculature structures on the cortical surface to determine multiple injection sites without hitting them, and robotic control of micropipette insertion perpendicular to the cortical surface with 50 μm precision. In mouse cortex, ARViS sequentially injected virus solution into 100 sites over a duration of 100 min with a bleeding probability of only 0.1% per site. Furthermore, ARViS successfully achieved 266-site injections over the frontoparietal cortex of a female common marmoset. We demonstrate one-photon and two-photon calcium imaging in the marmoset frontoparietal cortex, illustrating the effective expression of biosensors delivered by ARViS.

Multimodal Technologies for Closed-Loop Neural Modulation and Sensing

Existing methods for studying neural circuits and treating neurological disorders are typically based on physical and chemical cues to manipulate and record neural activities. These approaches often involve predefined, rigid, and unchangeable signal patterns, which cannot be adjusted in real time according to the patient's condition or neural activities. With the continuous development of neural interfaces, conducting in vivo research on adaptive and modifiable treatments for neurological diseases and neural circuits is now possible. In this review, current and potential integration of various modalities to achieve precise, closed-loop modulation, and sensing in neural systems are summarized. Advanced materials, devices, or systems that generate or detect electrical, magnetic, optical, acoustic, or chemical signals are highlighted and utilized to interact with neural cells, tissues, and networks for closed-loop interrogation. Further, the significance of developing closed-loop techniques for diagnostics and treatment of neurological disorders such as epilepsy, depression, rehabilitation of spinal cord injury patients, and exploration of brain neural circuit functionality is elaborated.

Neural circuit-selective, multiplexed pharmacological targeting of prefrontal cortex-projecting locus coeruleus neurons drives antinociception

Selective manipulation of neural circuits using optogenetics and chemogenetics holds great translational potential but requires genetic access to neurons. Here, we demonstrate a general framework for identifying genetic tool-independent, pharmacological strategies for neural circuit-selective modulation. We developed an economically accessible calcium imaging-based approach for large-scale pharmacological scans of endogenous receptor-mediated neural activity. As a testbed for this approach, we used the mouse locus coeruleus due to the combination of its widespread, modular efferent neural circuitry and its wide variety of endogenously expressed GPCRs. Using machine learning-based action potential deconvolution and retrograde tracing, we identified an agonist cocktail that selectively inhibits medial prefrontal cortex-projecting locus coeruleus neurons. In vivo, this cocktail produces synergistic antinociception, consistent with selective pharmacological blunting of this neural circuit. This framework has broad utility for selective targeting of other neural circuits under different physiological and pathological states, facilitating non-genetic translational applications arising from cell type-selective discoveries.

Advanced rehabilitation in ischaemic stroke research

At present, due to the rapid progress of treatment technology in the acute phase of ischaemic stroke, the mortality of patients has been greatly reduced but the number of disabled survivors is increasing, and most of them are elderly patients. Physicians and rehabilitation therapists pay attention to develop all kinds of therapist techniques including physical therapy techniques, robot-assisted technology and artificial intelligence technology, and study the molecular, cellular or synergistic mechanisms of rehabilitation therapies to promote the effect of rehabilitation therapy. Here, we discussed different animal and in vitro models of ischaemic stroke for rehabilitation studies; the compound concept and technology of neurological rehabilitation; all kinds of biological mechanisms of physical therapy; the significance, assessment and efficacy of neurological rehabilitation; the application of brain-computer interface, rehabilitation robotic and non-invasive brain stimulation technology in stroke rehabilitation.

Optogenetics in oral and craniofacial research

Optogenetics combines optics and genetic engineering to control specific gene expression and biological functions and has the advantages of precise spatiotemporal control, noninvasiveness, and high efficiency. Genetically modified photosensory sensors are engineered into proteins to modulate conformational changes with light stimulation. Therefore, optogenetic techniques can provide new insights into oral biological processes at different levels, ranging from the subcellular and cellular levels to neural circuits and behavioral models. Here, we introduce the origins of optogenetics and highlight the recent progress of optogenetic approaches in oral and craniofacial research, focusing on the ability to apply optogenetics to the study of basic scientific neural mechanisms and to establish different oral behavioral test models in vivo (orofacial movement, licking, eating, and drinking), such as channelrhodopsin (ChR), archaerhodopsin (Arch), and halorhodopsin from Natronomonas pharaonis (NpHR). We also review the synergic and antagonistic effects of optogenetics in preclinical studies of trigeminal neuralgia and maxillofacial cellulitis. In addition, optogenetic tools have been used to control the neurogenic differentiation of dental pulp stem cells in translational studies. Although the scope of optogenetic tools is increasing, there are limited large animal experiments and clinical studies in dental research. Potential future directions include exploring therapeutic strategies for addressing loss of taste in patients with coronavirus disease 2019 (COVID-19), studying oral bacterial biofilms, enhancing craniomaxillofacial and periodontal tissue regeneration, and elucidating the possible pathogenesis of dry sockets, xerostomia, and burning mouth syndrome.

In-silico predicted mouse melanopsins with blue spectral shifts deliver efficient subcellular signaling

Melanopsin is a photopigment belonging to the G Protein-Coupled Receptor (GPCR) family expressed in a subset of intrinsically photosensitive retinal ganglion cells (ipRGCs) and responsible for a variety of processes. The bistability and, thus, the possibility to function under low retinal availability would make melanopsin a powerful optogenetic tool. Here, we aim to utilize mouse melanopsin to trigger macrophage migration by its subcellular optical activation with localized blue light, while simultaneously imaging the migration with red light. To reduce melanopsin's red light sensitivity, we employ a combination of in silico structure prediction and automated quantum mechanics/molecular mechanics modeling to predict minimally invasive mutations to shift its absorption spectrum towards the shorter wavelength region of the visible spectrum without compromising the signaling efficiency. The results demonstrate that it is possible to achieve melanopsin mutants that resist red light-induced activation but are activated by blue light and display properties indicating preserved bistability. Using the A333T mutant, we show that the blue light-induced subcellular melanopsin activation triggers localized PIP3 generation and macrophage migration, which we imaged using red light, demonstrating the optogenetic utility of minimally engineered melanopsins.

Toward Optogenetic Hearing Restoration

The cochlear implant (CI) is considered the most successful neuroprosthesis as it enables speech comprehension in the majority of the million otherwise deaf patients. In hearing by electrical stimulation of the auditory nerve, the broad spread of current from each electrode acts as a bottleneck that limits the transfer of sound frequency information. Hence, there remains a major unmet medical need for improving the quality of hearing with CIs. Recently, optogenetic stimulation of the cochlea has been suggested as an alternative approach for hearing restoration. Cochlear optogenetics promises to transfer more sound frequency information, hence improving hearing, as light can conveniently be confined in space to activate the auditory nerve within smaller tonotopic ranges. In this review, we discuss the latest experimental and technological developments of optogenetic hearing restoration and outline remaining challenges en route to clinical translation.

Activation of Ventral Tegmental Area Dopaminergic Neurons Projecting to the Parabrachial Nucleus Promotes Emergence from Propofol Anesthesia in Male Rats

Since the clinical introduction of general anesthesia, its underlying mechanisms have not been fully elucidated. The ventral tegmental area (VTA) and parabrachial nucleus (PBN) play pivotal roles in the mechanisms underlying general anesthesia. However, whether dopaminergic (DA) projections from the VTA to the PBN play a role in mediating the effects of general anesthesia is unclear. We microinjected 6-hydroxydopamine into the PBN to damage tyrosine hydroxylase positive (TH+) neurons and found a prolonged recovery time from propofol anesthesia. We used calcium fiber photometry recording to explore the activity of TH + neurons in the PBN. Then, we used chemogenetic and optogenetic approaches either activate the VTADA-PBN pathway, shortening the propofol anesthesia emergence time, or inhibit this pathway, prolonging the emergence time. These data indicate the crucial involvement of TH + neurons in the PBN in regulating emergence from propofol anesthesia, while the activation of the VTADA-PBN pathway facilitates the emergence of propofol anesthesia.

Co-coding of head and whisker movements by both VPM and POm thalamic neurons

Rodents continuously move their heads and whiskers in a coordinated manner while perceiving objects through whisker-touch. Studies in head-fixed rodents showed that the ventroposterior medial (VPM) and posterior medial (POm) thalamic nuclei code for whisker kinematics, with POm involvement reduced in awake animals. To examine VPM and POm involvement in coding head and whisker kinematics in awake, head-free conditions, we recorded thalamic neuronal activity and tracked head and whisker movements in male mice exploring an open arena. Using optogenetic tagging, we found that in freely moving mice, both nuclei equally coded whisker kinematics and robustly coded head kinematics. The fraction of neurons coding head kinematics increased after whisker trimming, ruling out whisker-mediated coding. Optogenetic activation of thalamic neurons evoked overt kinematic changes and increased the fraction of neurons leading changes in head kinematics. Our data suggest that VPM and POm integrate head and whisker information and can influence head kinematics during tactile perception.

In vivo photocontrol of orexin receptors with a nanomolar light-regulated analogue of orexin-B

Orexinergic neurons are critically involved in regulating arousal, wakefulness, and appetite. Their dysfunction has been associated with sleeping disorders, and non-peptide drugs are currently being developed to treat insomnia and narcolepsy. Yet, no light-regulated agents are available to reversibly control their activity. To meet this need, a photoswitchable peptide analogue of the endogenous neuroexcitatory peptide orexin-B was designed, synthesized, and tested in vitro and in vivo. This compound - photorexin - is the first photo-reversible ligand reported for orexin receptors. It allows dynamic control of activity in vitro (including almost the same efficacy as orexin-B, high nanomolar potency, and subtype selectivity to human OX2 receptors) and in vivo in zebrafish larvae by direct application in water. Photorexin induces dose- and light-dependent changes in locomotion and a reduction in the successive induction reflex that is associated with sleep behavior. Molecular dynamics calculations indicate that trans and cis photorexin adopt similar bent conformations and that the only discriminant between their structures and activities is the positioning of the N-terminus. This, in the case of the more active trans isomer, points towards the OX2 N-terminus and extra-cellular loop 2, a region of the receptor known to be involved in ligand binding and recognition consistent with a "message-address" system. Thus, our approach could be extended to several important families of endogenous peptides, such as endothelins, nociceptin, and dynorphins among others, that bind to their cognate receptors through a similar mechanism: a "message" domain involved in receptor activation and signal transduction, and an "address" sequence for receptor occupation and improved binding affinity.

Engineering magnetic nanosystem for TRPV1 and TRPV4 channel activation

Recently, physical tools for remotely stimulating mechanical force-sensitive and temperature-sensitive proteins to regulate intracellular pathways have opened up novel and exciting avenues for basic research and clinical applications. Among the numerous modes of physical stimulation, magnetic stimulation is significantly attractive for biological applications due to the advantages of depth penetration and spatial-temporally controlled transduction. Herein, the physicochemical parameters (e.g., shape, size, composition) that influence the magnetic properties of magnetic nanosystems as well as the characteristics of transient receptor potential vanilloid-1 (TRPV1) and transient receptor potential vanilloid-4 (TRPV4) channels are systematically summarized, which offer opportunities for magnetic manipulation of cell fate in a precise and effective manner. In addition, representative regulatory applications involving magnetic nanosystem-based TRPV1 and TRPV4 channel activation are highlighted, both at the cellular level and in animal models. Furthermore, perspectives on the further development of this magnetic stimulation mode are commented on, with emphasis on scientific limitations and possible directions for exploitation. This article is categorized under: Diagnostic Tools > Biosensing Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

The anterior chamber of the eye technology and its anatomical, optical, and immunological bases

The anterior chamber of the eye (ACE) is distinct in its anatomy, optics, and immunology. This guarantees that the eye perceives visual information in the context of physiology even when encountering adverse incidents like inflammation. In addition, this endows the ACE with the special nursery bed iris enriched in vasculatures and nerves. The ACE constitutes a confined space enclosing an oxygen/nutrient-rich, immune-privileged, and less stressful milieu as well as an optically transparent medium. Therefore, aside from visual perception, the ACE unexpectedly serves as an excellent transplantation site for different body parts and a unique platform for noninvasive, longitudinal, and intravital microimaging of different grafts. On the basis of these merits, the ACE technology has evolved from the prototypical through the conventional to the advanced version. Studies using this technology as a versatile biomedical research platform have led to a diverse range of basic knowledge and in-depth understanding of a variety of cells, tissues, and organs as well as artificial biomaterials, pharmaceuticals, and abiotic substances. Remarkably, the technology turns in vivo dynamic imaging of the morphological characteristics, organotypic features, developmental fates, and specific functions of intracameral grafts into reality under physiological and pathological conditions. Here we review the anatomical, optical, and immunological bases as well as technical details of the ACE technology. Moreover, we discuss major achievements obtained and potential prospective avenues for this technology.

Optogenetic fMRI reveals therapeutic circuits of subthalamic nucleus deep brain stimulation

While deep brain stimulation (DBS) is widely employed for managing motor symptoms in Parkinson's disease (PD), its exact circuit mechanisms remain controversial. To identify the neural targets affected by therapeutic DBS in PD, we analyzed DBS-evoked whole brain activity in female hemi-parkinsonian rats using functional magnetic resonance imaging (fMRI). We delivered subthalamic nucleus (STN) DBS at various stimulation pulse repetition rates using optogenetics, allowing unbiased examination of cell-type specific STN feedforward neural activity. Unilateral optogenetic STN DBS elicited pulse repetition rate-dependent alterations of blood-oxygenation-level-dependent (BOLD) signals in SNr (substantia nigra pars reticulata), GP (globus pallidus), and CPu (caudate putamen). Notably, this modulation effectively ameliorated pathological circling behavior in animals expressing the kinetically faster Chronos opsin, but not in animals expressing ChR2. Furthermore, mediation analysis revealed that the pulse repetition rate-dependent behavioral rescue was significantly mediated by optogenetic DBS induced activity changes in GP and CPu, but not in SNr. This suggests that the activation of GP and CPu are critically involved in the therapeutic mechanisms of STN DBS.