Model-based predictions for dopamine.
Abstract Phasic dopamine responses are thought to encode a prediction-error signal consistent with model-free reinforcement learning theories. However, a number of recent findings highlight the influence of model-based computations on dopamine responses, and suggest that dopamine prediction errors reflect more dimensions of an expected outcome than scalar reward value. Here, we review a selection of these recent results and discuss the implications and complications of model-based predictions for computational theories of dopamine and learning. PMID: 29096115 [PubMed - as supplied by publisher] (Source: Curre...
Source: Current Opinion in Neurobiology - October 30, 2017 Category: Neurology Authors: Langdon AJ, Sharpe MJ, Schoenbaum G, Niv Y Tags: Curr Opin Neurobiol Source Type: research

Environment matters: microglia function and dysfunction in a changing world.
Abstract The immune system is our interface with the environment, and immune molecules such as cytokines and chemokines and the cells that produce them within the brain, notably microglia, are critical for normal brain development. This recognition has in recent years led to the working hypothesis that inflammatory events during pregnancy or the early postnatal period, for example, in response to infection, may disrupt the normal developmental trajectory of microglia and consequently their interactions with neurons, thereby contributing to the risk for neurological disorders. The current article outlines recent fi...
Source: Current Opinion in Neurobiology - October 30, 2017 Category: Neurology Authors: Hanamsagar R, Bilbo SD Tags: Curr Opin Neurobiol Source Type: research

Neuronal activity in the glioma microenvironment.
Abstract Gliomas are the most common primary brain tumor and high-grade gliomas the leading cause of brain tumor-related death in both children and adults. An appreciation for the crucial role of the nervous system in the tumor microenvironment is emerging for cancers in general, and the neural regulation of glioma progression has come into sharp focus. Here, we review what is known about the influence of active neurons on glioma pathobiology. PMID: 29096244 [PubMed - as supplied by publisher] (Source: Current Opinion in Neurobiology)
Source: Current Opinion in Neurobiology - October 30, 2017 Category: Neurology Authors: Johung T, Monje M Tags: Curr Opin Neurobiol Source Type: research

Glial contributions to neuronal health and disease: new insights from Drosophila.
Abstract Glial cells are essential for proper formation and maintenance of the nervous system. During development, glia keep neuronal cell numbers in check and ensure that mature neural circuits are appropriately sculpted by engulfing superfluous cells and projections. In the adult brain, glial cells offer metabolic sustenance and provide critical immune support in the face of acute and chronic challenges. Dysfunctional glial immune activity is believed to contribute to age-related cognitive decline, as well as neurodegenerative disease risk, but we still know surprisingly little about the specific molecular pathw...
Source: Current Opinion in Neurobiology - October 30, 2017 Category: Neurology Authors: Logan MA Tags: Curr Opin Neurobiol Source Type: research

Unwrapping the unappreciated: recent progress in Remak Schwann cell biology.
Abstract Schwann cells (SCs) are specialized glial cells that myelinate and protect axons in the peripheral nervous system (PNS). Although myelinating SCs are more commonly studied, the PNS also contains a variety of non-myelinating SCs, including but not limited to Remak SCs (RSCs), terminal SCs, enteric glia. Although the field currently lacks many robust tools for interrogating the functions of non-myelinating SCs, recent evidence suggests that, like their myelinating counterparts, non-myelinating SCs are critical for proper PNS function. In this review, we focus specifically on RSCs and highlight recent advanc...
Source: Current Opinion in Neurobiology - October 27, 2017 Category: Neurology Authors: Harty BL, Monk KR Tags: Curr Opin Neurobiol Source Type: research

A microglia-cytokine axis to modulate synaptic connectivity and function.
Abstract Microglia have recently been recognized as key regulators of synapse development, function, and plasticity. Critical to progressing the field is the identification of molecular underpinnings necessary for microglia to carry out these important functions within neural circuits. Here, we focus a review specifically on roles for microglial cytokine signaling within developing and mature neural circuits. We review exciting new studies demonstrating essential roles for microglial cytokine signaling in axon outgrowth, synaptogenesis and synapse maturation during development, as well as synaptic transmission and...
Source: Current Opinion in Neurobiology - October 27, 2017 Category: Neurology Authors: Werneburg S, Feinberg PA, Johnson KM, Schafer DP Tags: Curr Opin Neurobiol Source Type: research

On place and time: microglia in embryonic and perinatal brain development.
Abstract Microglia, the brain-resident macrophages, play key roles in regulating synapse density and homeostasis in the postnatal and adult brain. However, microglia enter the brain during embryogenesis and recent studies have revealed additional early functions of these immune cells in prenatal and perinatal cerebral development. Such findings are of importance since prenatal inflammation and microglia dysfunction have been associated with several neurodevelopmental disorders. This review provides a selective overview of the early roles of microglia, their link with a specific spatiotemporal distribution and how ...
Source: Current Opinion in Neurobiology - October 25, 2017 Category: Neurology Authors: Thion MS, Garel S Tags: Curr Opin Neurobiol Source Type: research

Diversity of oligodendrocytes and their progenitors.
Abstract The established function of oligodendrocytes and their progenitors is to drive the cellular events of myelination, a highly diversified process necessary to match the needs of various neuronal subtypes and networks. The morphological and molecular heterogeneity of oligodendrocytes and their progenitors point to functions beyond establishing saltatory nerve conduction. Here, we review the diversity in the oligodendroglial lineage as well as the classical and new functions identified for oligodendrocytes and their progenitors. Because oligodendroglia remain highly responsive to environmental changes, they l...
Source: Current Opinion in Neurobiology - October 24, 2017 Category: Neurology Authors: Dimou L, Simons M Tags: Curr Opin Neurobiol Source Type: research

Microglia: origins, homeostasis, and roles in myelin repair.
Abstract Microglia are the resident macrophages of the central nervous system (CNS), implicated in developmental processes, homeostasis, and responses to injury. Derived from the yolk sac during development, microglia self-renew, self-regulate their numbers during homeostatic conditions, and show a robust proliferative capacity even in adulthood. Together with monocyte-derived macrophages (MDM), microglia coordinate the regeneration of CNS myelin around axons, termed remyelination. Gene expression analyses and experimental modelling have identified pro-remyelination roles for microglia/MDM in clearance of myelin d...
Source: Current Opinion in Neurobiology - October 23, 2017 Category: Neurology Authors: Lloyd AF, Davies CL, Miron VE Tags: Curr Opin Neurobiol Source Type: research

Oligodendroglia-lineage cells in brain plasticity, homeostasis and psychiatric disorders.
Abstract Adult oligodendrocyte progenitor cells are uniformly distributed in both gray and white matter, displaying robust proliferative and migratory potential during health and disease. Recently, developments in new experimental approaches have brought about several novel insights about NG2-glia and myelinating oligodendrocytes, indicating a diverse toolkit of functions in experience-dependent myelination and homeostasis in the adult CNS. In this review, we summarize some of the topical studies that highlight newly emerging findings implicating oligodendroglia-lineage cells in brain plasticity, homeostasis and p...
Source: Current Opinion in Neurobiology - October 23, 2017 Category: Neurology Authors: Birey F, Kokkosis AG, Aguirre A Tags: Curr Opin Neurobiol Source Type: research

Myelin dynamics: protecting and shaping neuronal functions.
Abstract Myelinating glial cells are well-known to insulate axons and to speed up action potential propagation. Through adjustments in the axonal coverage with myelin, myelin sheath thickness and possibly nodal/internode length oligodendrocytes are involved in fine-tuning the brain's computational power throughout life. Be it motor skill learning or social behaviors in higher vertebrates, proper myelination is critical in shaping brain functions. Neurons rely on their myelinating partners not only for setting conduction speed, but also for regulating the ionic environment and fueling their energy demands with meta...
Source: Current Opinion in Neurobiology - October 21, 2017 Category: Neurology Authors: Saab AS, Nave KA Tags: Curr Opin Neurobiol Source Type: research

Control of brain energy supply by astrocytes.
Abstract Astrocytes form an anatomical bridge between the vasculature and neuronal synapses. Recent work suggests that they play a key role in regulating brain energy supply by increasing blood flow to regions where neurons are active, and setting the baseline level of blood flow. Controversy persists over whether lactate derived from astrocyte glycolysis is used to power oxidative phosphorylation in neurons, but astrocytes sustain neuronal ATP production by recycling neurotransmitter glutamate that would otherwise need to be resynthesised from glucose, and by providing a short-term energy store in the form of gly...
Source: Current Opinion in Neurobiology - October 17, 2017 Category: Neurology Authors: Nortley R, Attwell D Tags: Curr Opin Neurobiol Source Type: research

Myelin plasticity and behaviour-connecting the dots.
Abstract Myelin sheaths in the vertebrate nervous system enable faster impulse propagation, while myelinating glia provide vital support to axons. Once considered a static insulator, converging evidence now suggests that myelin in the central nervous system can be dynamically regulated by neuronal activity and continues to participate in nervous system plasticity beyond development. While the link between experience and myelination gains increased recognition, it is still unclear what role such adaptive myelination plays in facilitating and shaping behaviour. Additionally, fundamental mechanisms and principles und...
Source: Current Opinion in Neurobiology - October 17, 2017 Category: Neurology Authors: Kaller MS, Lazari A, Blanco-Duque C, Sampaio-Baptista C, Johansen-Berg H Tags: Curr Opin Neurobiol Source Type: research

Endo-lysosomal dysfunction: a converging mechanism in neurodegenerative diseases.
Abstract Endo-lysosomal pathways are essential in maintaining protein homeostasis in the cell. Numerous genes in the endo-lysosomal pathways have been found to associate with neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and frontotemporal dementia (FTD). Mutations of these genes lead to dysfunction in multiple steps of the endo-lysosomal network: autophagy, endocytic trafficking and lysosomal degradation, resulting in accumulation of pathogenic proteins. Although the exact pathogenic mechanism varies for different disease-associated genes, dysfunction of the endo-lysoso...
Source: Current Opinion in Neurobiology - October 10, 2017 Category: Neurology Authors: Wang C, Telpoukhovskaia MA, Bahr BA, Chen X, Gan L Tags: Curr Opin Neurobiol Source Type: research

Brain energetics during the sleep-wake cycle.
Abstract Brain activity during wakefulness is associated with high metabolic rates that are believed to support information processing and memory encoding. In spite of loss of consciousness, sleep still carries a substantial energy cost. Experimental evidence supports a cerebral metabolic shift taking place during sleep that suppresses aerobic glycolysis, a hallmark of environment-oriented waking behavior and synaptic plasticity. Recent studies reveal that glial astrocytes respond to the reduction of wake-promoting neuromodulators by regulating volume, composition and glymphatic drainage of interstitial fluid. The...
Source: Current Opinion in Neurobiology - October 9, 2017 Category: Neurology Authors: DiNuzzo M, Nedergaard M Tags: Curr Opin Neurobiol Source Type: research

Premonitory urges and tics in Tourette syndrome: computational mechanisms and neural correlates.
inha AC, Maia TV Abstract Tourette syndrome is characterized by open motor behaviors - tics - but another crucial aspect of the disorder is the presence of premonitory urges: uncomfortable sensations that typically precede tics and are temporarily alleviated by tics. We review the evidence implicating the somatosensory cortices and the insula in premonitory urges and the motor cortico-basal ganglia-thalamo-cortical loop in tics. We consider how these regions interact during tic execution, suggesting that the insula plays an important role as a nexus linking the sensory and emotional character of premonitory urges ...
Source: Current Opinion in Neurobiology - October 6, 2017 Category: Neurology Authors: Conceição VA, Dias Â, Farinha AC, Maia TV Tags: Curr Opin Neurobiol Source Type: research

Coordinated morphogenesis of neurons and glia.
Abstract Glia adopt remarkable shapes that are tightly coordinated with the morphologies of their neuronal partners. To achieve these precise shapes, glia and neurons exhibit coordinated morphological changes on the time scale of minutes and on size scales ranging from nanometers to hundreds of microns. Here, we review recent studies that reveal the highly dynamic, localized morphological changes of mammalian neuron-glia contacts. We then explore the power of Drosophila and C. elegans models to study coordinated changes at defined neuron-glia contacts, highlighting the use of innovative genetic and imaging tools t...
Source: Current Opinion in Neurobiology - October 5, 2017 Category: Neurology Authors: Lamkin ER, Heiman MG Tags: Curr Opin Neurobiol Source Type: research

How linear response shaped models of neural circuits and the quest for alternatives.
Abstract In the past decades, many mathematical approaches to solve complex nonlinear systems in physics have been successfully applied to neuroscience. One of these tools is the concept of linear response functions. However, phenomena observed in the brain emerge from fundamentally nonlinear interactions and feedback loops rather than from a composition of linear filters. Here, we review the successes achieved by applying the linear response formalism to topics, such as rhythm generation and synchrony and by incorporating it into models that combine linear and nonlinear transformations. We also discuss the challe...
Source: Current Opinion in Neurobiology - October 3, 2017 Category: Neurology Authors: Herfurth T, Tchumatchenko T Tags: Curr Opin Neurobiol Source Type: research

The many worlds hypothesis of dopamine prediction error: implications of a parallel circuit architecture in the basal ganglia.
Abstract Computational models of reinforcement learning (RL) strive to produce behavior that maximises reward, and thus allow software or robots to behave adaptively [1]. At the core of RL models is a learned mapping between 'states'-situations or contexts that an agent might encounter in the world-and actions. A wealth of physiological and anatomical data suggests that the basal ganglia (BG) is important for learning these mappings [2,3]. However, the computations performed by specific circuits are unclear. In this brief review, we highlight recent work concerning the anatomy and physiology of BG circuits that su...
Source: Current Opinion in Neurobiology - October 3, 2017 Category: Neurology Authors: Lau B, Monteiro T, Paton JJ Tags: Curr Opin Neurobiol Source Type: research

Dysregulation of aversive signaling pathways: a novel circuit endophenotype for pain and anxiety disorders.
Abstract Aversive experiences activate dedicated neural instructive pathways which trigger memory formation and change behavior. The strength of these aversive memories and the degree to which they alter behavior is proportional to the intensity of the aversive experience. Dysregulation of aversive learning circuits can lead to psychiatric pathology. Here we review recent findings elucidating aversive instructive signaling circuits for fear conditioning. We then examine how chronic pain as well as stress and anxiety disrupt these circuits and the implications this has for understanding and treating psychiatric dis...
Source: Current Opinion in Neurobiology - September 28, 2017 Category: Neurology Authors: Yeh LF, Watanabe M, Sulkes-Cuevas J, Johansen JP Tags: Curr Opin Neurobiol Source Type: research

Editorial overview: Computational neuroscience.
PMID: 28965665 [PubMed - as supplied by publisher] (Source: Current Opinion in Neurobiology)
Source: Current Opinion in Neurobiology - September 28, 2017 Category: Neurology Authors: Machens C, Fairhall A Tags: Curr Opin Neurobiol Source Type: research

Closing gaps in brain disease-from overlapping genetic architecture to common motifs of synapse dysfunction.
Abstract Recent progress in the synaptic pathophysiology of brain diseases is reviewed. To emphasize the emergence of common motifs in synapse dysfunctions across neurodevelopmental, psychiatric and neurological disorders, conventional clinical boundaries are disregarded and a decidedly trans-diagnostic, potentially unifying view of altered synapse function is promoted. Based on the overlapping genetic architecture of brain disorders, which often converges on genes related to synaptic functions, disease-related changes in basic pre-synaptic and post-synaptic communication, neuromodulation-gated changes in Hebbian ...
Source: Current Opinion in Neurobiology - September 28, 2017 Category: Neurology Authors: Roeper J Tags: Curr Opin Neurobiol Source Type: research

Schwann cells as drivers of tissue repair and regeneration.
Abstract Current evidence suggests that peripheral nerve-associated Schwann cells possess the capacity to promote the repair and regeneration of multiple tissue types, in addition to peripheral nervous system axons. These findings shed light on the nerve-dependent nature of regeneration that has been well documented in various organs. This review outlines recent advances in knowledge surrounding endogenous regenerative functions of Schwann cells across species and tissue types, with a specific focus on the role of Sox2(+) dedifferentiated Schwann cells in regulating the proliferation of surrounding tissue-resident...
Source: Current Opinion in Neurobiology - September 27, 2017 Category: Neurology Authors: Carr MJ, Johnston AP Tags: Curr Opin Neurobiol Source Type: research

On texture, form, and fixational eye movements.
Abstract Recent studies show that small movements of the eye that occur during fixation are controlled in the brain by similar neural mechanisms as large eye movements. Information theory has been successful in explaining many properties of large eye movements. Could it also help us understand the smaller eye movements that are much more difficult to study experimentally? Here I describe new predictions for how small amplitude fixational eye movements should be modulated by visual context in order to improve visual perception. In particular, the amplitude of fixational eye movements is predicted to differ when loc...
Source: Current Opinion in Neurobiology - September 26, 2017 Category: Neurology Authors: Sharpee TO Tags: Curr Opin Neurobiol Source Type: research

Deciphering MECP2-associated disorders: disrupted circuits and the hope for repair.
Abstract MECP2 is a critical gene for neural development, mutations or duplication of which led to severe neurodevelopmental disorders, such as Rett syndrome (RTT) and autism spectrum disorders (ASD). Extensive works during the past decade yield ample insights into the molecular and cellular functions of MeCP2 in neural development. Furthermore, genetic manipulations in Mecp2 mouse models strongly suggested that deficiency in synaptic plasticity and various behaviors of Mecp2 null or transgenic mice could be rescued in adulthood. Further studies elucidating neural circuits responsible for symptoms in MECP2-associa...
Source: Current Opinion in Neurobiology - September 26, 2017 Category: Neurology Authors: Qiu Z Tags: Curr Opin Neurobiol Source Type: research

Livin' On The Edge: glia shape nervous system transition zones.
Abstract The vertebrate nervous system is divided into two functional halves; the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which consists of nerves and ganglia. Incoming peripheral stimuli transmitted from the periphery to the CNS and subsequent motor responses created because of this information, require efficient communication between the two halves that make up this organ system. Neurons and glial cells of each half of the nervous system, which are the main actors in this communication, segregate across nervous system transition zones and n...
Source: Current Opinion in Neurobiology - September 25, 2017 Category: Neurology Authors: Fontenas L, Kucenas S Tags: Curr Opin Neurobiol Source Type: research

How thoughts arise from sights: inferotemporal and prefrontal contributions to vision.
Abstract We are rapidly approaching a comprehensive understanding of the neural mechanisms behind object recognition. How we use this knowledge of the visual world to plan and act is comparatively mysterious. To fill this gap, we must understand how visual representations are transformed within cognitive regions, and how these cognitive representations of visual information act back upon earlier sensory representations. Here, we summarize our current understanding of visual representation in inferotemporal cortex (IT) and prefrontal cortex (PFC), and the interactions between them. We emphasize the apparent consist...
Source: Current Opinion in Neurobiology - September 21, 2017 Category: Neurology Authors: Kornblith S, Tsao DY Tags: Curr Opin Neurobiol Source Type: research

With or without you: predictive coding and Bayesian inference in the brain.
Abstract Two theoretical ideas have emerged recently with the ambition to provide a unifying functional explanation of neural population coding and dynamics: predictive coding and Bayesian inference. Here, we describe the two theories and their combination into a single framework: Bayesian predictive coding. We clarify how the two theories can be distinguished, despite sharing core computational concepts and addressing an overlapping set of empirical phenomena. We argue that predictive coding is an algorithmic/representational motif that can serve several different computational goals of which Bayesian inference i...
Source: Current Opinion in Neurobiology - September 20, 2017 Category: Neurology Authors: Aitchison L, Lengyel M Tags: Curr Opin Neurobiol Source Type: research

The diverse actions of astrocytes during synaptic development.
Abstract In the developing brain, cortical circuits are established through a complex process of synaptogenesis, maturation, and synaptic pruning. Astrocytes carry out diverse functions during each of these stages to facilitate the formation of complex networks. Recent work has begun to demonstrate that these heterogeneous roles during excitatory synaptic development are determined by the astrocyte population, brain region, and neuron type. This review will focus on current findings which highlight cell type specific mechanisms of excitatory synaptogenesis, as well as multiple mechanisms engaged by astrocytes to f...
Source: Current Opinion in Neurobiology - September 19, 2017 Category: Neurology Authors: Bosworth AP, Allen NJ Tags: Curr Opin Neurobiol Source Type: research

Cortical inhibitory interneurons control sensory processing.
Abstract Inhibitory and excitatory neurons form intricate interconnected circuits in the mammalian sensory cortex. Whereas the function of excitatory neurons is largely to integrate and transmit information within and between brain areas, inhibitory neurons are thought to shape the way excitatory neurons integrate information, and they exhibit context-specific and behavior-specific responses. Over the last few years, work across sensory modalities has begun unraveling the function of distinct types of cortical inhibitory neurons in sensory processing, identifying their contribution to controlling stimulus selectiv...
Source: Current Opinion in Neurobiology - September 19, 2017 Category: Neurology Authors: Wood KC, Blackwell JM, Geffen MN Tags: Curr Opin Neurobiol Source Type: research

Texture and art with deep neural networks.
Abstract Although the study of biological vision and computer vision attempt to understand powerful visual information processing from different angles, they have a long history of informing each other. Recent advances in texture synthesis that were motivated by visual neuroscience have led to a substantial advance in image synthesis and manipulation in computer vision using convolutional neural networks (CNNs). Here, we review these recent advances and discuss how they can in turn inspire new research in visual perception and computational neuroscience. PMID: 28926765 [PubMed - as supplied by publisher] (Sou...
Source: Current Opinion in Neurobiology - September 16, 2017 Category: Neurology Authors: Gatys LA, Ecker AS, Bethge M Tags: Curr Opin Neurobiol Source Type: research

(Reinforcement?) Learning to forage optimally.
Abstract Foraging effectively is critical to the survival of all animals and this imperative is thought to have profoundly shaped brain evolution. Decisions made by foraging animals often approximate optimal strategies, but the learning and decision mechanisms generating these choices remain poorly understood. Recent work with laboratory foraging tasks in humans suggest their behaviour is poorly explained by model-free reinforcement learning, with simple heuristic strategies better describing behaviour in some tasks, and in others evidence of prospective prediction of the future state of the environment. We sugges...
Source: Current Opinion in Neurobiology - September 14, 2017 Category: Neurology Authors: Kolling N, Akam T Tags: Curr Opin Neurobiol Source Type: research

Learning with three factors: modulating Hebbian plasticity with errors.
Abstract Synaptic plasticity is a central theme in neuroscience. A framework of three-factor learning rules provides a powerful abstraction, helping to navigate through the abundance of models of synaptic plasticity. It is well-known that the dopamine modulation of learning is related to reward, but theoretical models predict other functional roles of the modulatory third factor; it may encode errors for supervised learning, summary statistics of the population activity for unsupervised learning or attentional feedback. Specialized structures may be needed in order to generate and propagate third factors in the ne...
Source: Current Opinion in Neurobiology - September 14, 2017 Category: Neurology Authors: Kuśmierz Ł, Isomura T, Toyoizumi T Tags: Curr Opin Neurobiol Source Type: research

Can circular inference relate the neuropathological and behavioral aspects of schizophrenia?
dri R Abstract Schizophrenia is a complex and heterogeneous mental disorder, and researchers have only recently begun to understand its neuropathology. However, since the time of Kraepelin and Bleuler, much information has been accumulated regarding the behavioral abnormalities usually encountered in patients suffering from schizophrenia. Despite recent progress, how the latter are caused by the former is still debated. Here, we argue that circular inference, a computational framework proposed as a potential explanation for various schizophrenia symptoms, could help end this debate. Based on Marr's three levels of...
Source: Current Opinion in Neurobiology - September 11, 2017 Category: Neurology Authors: Leptourgos P, Denève S, Jardri R Tags: Curr Opin Neurobiol Source Type: research

Misdeed of the need: towards computational accounts of transition to addiction.
Abstract Drug addiction is a complex behavioral and neurobiological disorder which, in an emergent brain-circuit view, reflects a loss of prefrontal top-down control over subcortical circuits governing drug-seeking and drug-taking. We first review previous computational accounts of addiction, focusing on cocaine addiction and on prevalent dopamine-based positive-reinforcement and negative-reinforcement computational models. Then, we discuss a recent computational proposal that the progression to addiction is unlikely to result from a complete withdrawal of the goal-oriented decision system in favor the habitual on...
Source: Current Opinion in Neurobiology - September 8, 2017 Category: Neurology Authors: Keramati M, Ahmed SH, Gutkin BS Tags: Curr Opin Neurobiol Source Type: research

Computational models of basal ganglia dysfunction: the dynamics is in the details.
Abstract The development, simulation, and analysis of mathematical models offer helpful tools for integrating experimental findings and exploring or suggesting possible explanatory mechanisms. As models relating to basal ganglia dysfunction have proliferated, however, there has not always been consistency among their findings. This work points out several ways in which biological details, relating to ionic currents and synaptic pathways, can influence the dynamics of models of the basal ganglia under parkinsonian conditions and hence may be important for inclusion in models. It also suggests some additional useful...
Source: Current Opinion in Neurobiology - September 7, 2017 Category: Neurology Authors: Rubin JE Tags: Curr Opin Neurobiol Source Type: research

Modelling plasticity in dendrites: from single cells to networks.
Abstract One of the key questions in neuroscience is how our brain self-organises to efficiently process information. To answer this question, we need to understand the underlying mechanisms of plasticity and their role in shaping synaptic connectivity. Theoretical neuroscience typically investigates plasticity on the level of neural networks. Neural network models often consist of point neurons, completely neglecting neuronal morphology for reasons of simplicity. However, during the past decades it became increasingly clear that inputs are locally processed in the dendrites before they reach the cell body. Dendri...
Source: Current Opinion in Neurobiology - September 7, 2017 Category: Neurology Authors: Bono J, Wilmes KA, Clopath C Tags: Curr Opin Neurobiol Source Type: research

Periodic population codes: From a single circular variable to higher dimensions, multiple nested scales, and conceptual spaces.
Abstract Across the nervous system, neurons often encode circular stimuli using tuning curves that are not sine or cosine functions, but that belong to the richer class of von Mises functions, which are periodic variants of Gaussians. For a population of neurons encoding a single circular variable with such canonical tuning curves, computing a simple population vector is the optimal read-out of the most likely stimulus. We argue that the advantages of population vector read-outs are so compelling that even the neural representation of the outside world's flat Euclidean geometry is curled up into a torus (a circle ...
Source: Current Opinion in Neurobiology - September 6, 2017 Category: Neurology Authors: Herz AV, Mathis A, Stemmler M Tags: Curr Opin Neurobiol Source Type: research

Maximum entropy models as a tool for building precise neural controls.
Abstract Neural responses are highly structured, with population activity restricted to a small subset of the astronomical range of possible activity patterns. Characterizing these statistical regularities is important for understanding circuit computation, but challenging in practice. Here we review recent approaches based on the maximum entropy principle used for quantifying collective behavior in neural activity. We highlight recent models that capture population-level statistics of neural data, yielding insights into the organization of the neural code and its biological substrate. Furthermore, the MaxEnt fram...
Source: Current Opinion in Neurobiology - September 1, 2017 Category: Neurology Authors: Savin C, Tkačik G Tags: Curr Opin Neurobiol Source Type: research

From the statistics of connectivity to the statistics of spike times in neuronal networks.
Abstract An essential step toward understanding neural circuits is linking their structure and their dynamics. In general, this relationship can be almost arbitrarily complex. Recent theoretical work has, however, begun to identify some broad principles underlying collective spiking activity in neural circuits. The first is that local features of network connectivity can be surprisingly effective in predicting global statistics of activity across a network. The second is that, for the important case of large networks with excitatory-inhibitory balance, correlated spiking persists or vanishes depending on the spati...
Source: Current Opinion in Neurobiology - August 29, 2017 Category: Neurology Authors: Ocker GK, Hu Y, Buice MA, Doiron B, Josić K, Rosenbaum R, Shea-Brown E Tags: Curr Opin Neurobiol Source Type: research

Dopaminergic dysfunction in neurodevelopmental disorders: recent advances and synergistic technologies to aid basic research.
Abstract Neurodevelopmental disorders (NDDs) represent a diverse group of syndromes characterized by abnormal development of the central nervous system and whose symptomatology includes cognitive, emotional, sensory, and motor impairments. The identification of causative genetic defects has allowed for creation of transgenic NDD mouse models that have revealed pathophysiological mechanisms of disease phenotypes in a neural circuit- and cell type-specific manner. Mouse models of several syndromes, including Rett syndrome, Fragile X syndrome, Angelman syndrome, Neurofibromatosis type 1, etc., exhibit abnormalities i...
Source: Current Opinion in Neurobiology - August 26, 2017 Category: Neurology Authors: Robinson JE, Gradinaru V Tags: Curr Opin Neurobiol Source Type: research

Chromatin-remodeling enzymes in control of Schwann cell development, maintenance and plasticity.
Abstract Gene regulation is essential for cellular differentiation and plasticity. Schwann cells (SCs), the myelinating glia of the peripheral nervous system (PNS), develop from neural crest cells to mature myelinating SCs and can at early developmental stage differentiate into various cell types. After a PNS lesion, SCs can also convert into repair cells that guide and stimulate axonal regrowth, and remyelinate regenerated axons. What controls their development and versatile nature? Several recent studies highlight the key roles of chromatin modifiers in these processes, allowing SCs to regulate their gene expres...
Source: Current Opinion in Neurobiology - August 26, 2017 Category: Neurology Authors: Jacob C Tags: Curr Opin Neurobiol Source Type: research

Mechanisms of M üller glial cell morphogenesis.
Mechanisms of Müller glial cell morphogenesis. Curr Opin Neurobiol. 2017 Aug 26;47:31-37 Authors: MacDonald RB, Charlton-Perkins M, Harris WA Abstract Müller Glia (MG), the radial glia cells of the retina, have spectacular morphologies subserving their enormous functional complexity. As early as 1892, the great neuroanatomist Santiago Ramon y Cajal studied the morphological development of MG, defining several steps in their morphogenesis [1,2]. However, the molecular cues controlling these developmental steps remain poorly understood. As MG have roles to play in every cellular and plexiform ...
Source: Current Opinion in Neurobiology - August 26, 2017 Category: Neurology Authors: MacDonald RB, Charlton-Perkins M, Harris WA Tags: Curr Opin Neurobiol Source Type: research

Quantifying behavior to solve sensorimotor transformations: advances from worms and flies.
Abstract The development of new computational tools has recently opened up the study of natural behaviors at a precision that was previously unachievable. These tools permit a highly quantitative analysis of behavioral dynamics at timescales that are well matched to the timescales of neural activity. Here we examine how combining these methods with established techniques for estimating an animal's sensory experience presents exciting new opportunities for dissecting the sensorimotor transformations performed by the nervous system. We focus this review primarily on examples from Caenorhabditis elegans and Drosophil...
Source: Current Opinion in Neurobiology - August 26, 2017 Category: Neurology Authors: Calhoun AJ, Murthy M Tags: Curr Opin Neurobiol Source Type: research

Striatal synapses, circuits, and Parkinson's disease.
Abstract The striatum is a hub in the basal ganglia circuitry controlling goal directed actions and habits. The loss of its dopaminergic (DAergic) innervation in Parkinson's disease (PD) disrupts the ability of the two principal striatal projection systems to respond appropriately to cortical and thalamic signals, resulting in the hypokinetic features of the disease. New tools to study brain circuitry have led to significant advances in our understanding of striatal circuits and how they adapt in PD models. This short review summarizes some of these recent studies and the gaps that remain to be filled. PMID: ...
Source: Current Opinion in Neurobiology - August 24, 2017 Category: Neurology Authors: Zhai S, Tanimura A, Graves SM, Shen W, Surmeier DJ Tags: Curr Opin Neurobiol Source Type: research

Parsing learning in networks using brain-machine interfaces.
Abstract Brain-machine interfaces (BMIs) define new ways to interact with our environment and hold great promise for clinical therapies. Motor BMIs, for instance, re-route neural activity to control movements of a new effector and could restore movement to people with paralysis. Increasing experience shows that interfacing with the brain inevitably changes the brain. BMIs engage and depend on a wide array of innate learning mechanisms to produce meaningful behavior. BMIs precisely define the information streams into and out of the brain, but engage wide-spread learning. We take a network perspective and review exi...
Source: Current Opinion in Neurobiology - August 24, 2017 Category: Neurology Authors: Orsborn AL, Pesaran B Tags: Curr Opin Neurobiol Source Type: research

Modeling the mammalian sleep cycle.
Abstract During sleep, the mammalian brain transitions through repeated cycles of non-rapid-eye-movement (NREM) and rapid-eye-movement (REM) sleep. The physiological implementation of this slow ultradian brain rhythm is largely unknown. Two differing dynamical mechanisms have been proposed to underlie the NREM-REM cycle. The first model type relies on reciprocal interactions between inhibitory and excitatory neural populations resulting in stable limit cycle oscillations. Recent experimental findings instead favor a model, in which mutually inhibitory interactions between REM sleep-promoting (REM-on) and REM sleep...
Source: Current Opinion in Neurobiology - August 22, 2017 Category: Neurology Authors: Weber F Tags: Curr Opin Neurobiol Source Type: research

Characterizing and interpreting the influence of internal variables on sensory activity.
Abstract The concept of a tuning curve has been central for our understanding of how the responses of cortical neurons depend on external stimuli. Here, we describe how the influence of unobserved internal variables on sensory responses, in particular correlated neural variability, can be understood in a similar framework. We suggest that this will lead to deeper insights into the relationship between stimulus, sensory responses, and behavior. We review related recent work and discuss its implication for distinguishing feedforward from feedback influences on sensory responses, and for the information contained in ...
Source: Current Opinion in Neurobiology - August 22, 2017 Category: Neurology Authors: Lange RD, Haefner RM Tags: Curr Opin Neurobiol Source Type: research

New insights into olivo-cerebellar circuits for learning from a small training sample.
Abstract Artificial intelligence such as deep neural networks exhibited remarkable performance in simulated video games and 'Go'. In contrast, most humanoid robots in the DARPA Robotics Challenge fell down to ground. The dramatic contrast in performance is mainly due to differences in the amount of training data, which is huge and small, respectively. Animals are not allowed with millions of the failed trials, which lead to injury and death. Humans fall only several thousand times before they balance and walk. We hypothesize that a unique closed-loop neural circuit formed by the Purkinje cells, the cerebellar deep...
Source: Current Opinion in Neurobiology - August 19, 2017 Category: Neurology Authors: Tokuda IT, Hoang H, Kawato M Tags: Curr Opin Neurobiol Source Type: research

Neurobiology of autoimmune encephalitis.
Abstract Autoimmune encephalitis presenting with amnesia, seizures, and psychosis is highly topical in basic and clinical neuroscience. Recent studies have identified numerous associated autoantibodies, targeting cell-surface synaptic proteins including neurotransmitter receptors (e.g. NMDA receptors (NMDARs)) and a secreted protein, LGI1. In vitro and in vivo analyses of the influence of the autoantibodies have begun to clarify their causal roles. Of particular interest is the generation of recombinant monoclonal antibodies from patients' B cells with anti-NMDAR encephalitis. Patient monoclonal antibodies could b...
Source: Current Opinion in Neurobiology - August 19, 2017 Category: Neurology Authors: Fukata M, Yokoi N, Fukata Y Tags: Curr Opin Neurobiol Source Type: research