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Rxivist combines preprints from bioRxiv with data from Twitter to help you find the papers being discussed in your field. Currently indexing 62,933 bioRxiv papers from 279,142 authors.

Most downloaded bioRxiv papers, since beginning of last month

in category neuroscience

10,846 results found. For more information, click each entry to expand.

1: An integrated brain-machine interface platform with thousands of channels
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Posted to bioRxiv 17 Jul 2019

An integrated brain-machine interface platform with thousands of channels
11,301 downloads neuroscience

Elon Musk, Neuralink

Brain-machine interfaces (BMIs) hold promise for the restoration of sensory and motor function and the treatment of neurological disorders, but clinical BMIs have not yet been widely adopted, in part because modest channel counts have limited their potential. In this white paper, we describe Neuralink’s first steps toward a scalable high-bandwidth BMI system. We have built arrays of small and flexible electrode “threads”, with as many as 3,072 electrodes per array distributed across 96 threads. We have also built a neurosurgical robot capable of inserting six threads (192 electrodes) per minute. Each thread can be individually inserted into the brain with micron precision for avoidance of surface vasculature and targeting specific brain regions. The electrode array is packaged into a small implantable device that contains custom chips for low-power on-board amplification and digitization: the package for 3,072 channels occupies less than (23 × 18.5 × 2) mm3. A single USB-C cable provides full-bandwidth data streaming from the device, recording from all channels simultaneously. This system has achieved a spiking yield of up to 70% in chronically implanted electrodes. Neuralink’s approach to BMI has unprecedented packaging density and scalability in a clinically relevant package.

2: Prefrontal cortex as a meta-reinforcement learning system
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Posted to bioRxiv 06 Apr 2018

Prefrontal cortex as a meta-reinforcement learning system
3,086 downloads neuroscience

Jane X Wang, Zeb Kurth-Nelson, Dharshan Kumaran, Dhruva Tirumala, Hubert Soyer, Joel Z Leibo, Demis Hassabis, Matthew Botvinick

Over the past twenty years, neuroscience research on reward-based learning has converged on a canonical model, under which the neurotransmitter dopamine 'stamps in' associations between situations, actions and rewards by modulating the strength of synaptic connections between neurons. However, a growing number of recent findings have placed this standard model under strain. In the present work, we draw on recent advances in artificial intelligence to introduce a new theory of reward-based learning. Here, the dopamine system trains another part of the brain, the prefrontal cortex, to operate as its own free-standing learning system. This new perspective accommodates the findings that motivated the standard model, but also deals gracefully with a wider range of observations, providing a fresh foundation for future research.

3: Molecular Atlas Of The Adult Mouse Brain
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Posted to bioRxiv 27 Sep 2019

Molecular Atlas Of The Adult Mouse Brain
1,978 downloads neuroscience

Cantin Ortiz, Jose Fernandez Navarro, Aleksandra Jurek, Antje Martin, Joakim Lundeberg, Konstantinos Meletis

Brain maps are essential for integrating information and interpreting the structure-function relationship of circuits and behavior. We aimed to generate a systematic classification of the adult mouse brain organization based on unbiased extraction of spatially-defining features. Applying whole-brain spatial transcriptomics, we captured the gene expression signatures to define the spatial organization of molecularly discrete subregions. We found that the molecular code contained sufficiently detailed information to directly deduce the complex spatial organization of the brain. This unsupervised molecular classification revealed new area- and layer-specific subregions, for example in isocortex and hippocampus, and a new division of striatum. The whole-brain molecular atlas further supports the identification of the spatial origin of single neurons using their gene expression profile, and forms the foundation to define a minimal gene set (a brain palette) that is sufficient to spatially annotate the adult brain. In summary, we have established a new molecular atlas to formally define the identity of brain regions, and a molecular code for mapping and targeting of discrete neuroanatomical domains.

4: The Tolman-Eichenbaum Machine: Unifying space and relational memory through generalisation in the hippocampal formation
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Posted to bioRxiv 16 Sep 2019

The Tolman-Eichenbaum Machine: Unifying space and relational memory through generalisation in the hippocampal formation
1,668 downloads neuroscience

James C.R. Whittington, Timothy H. Muller, Shirley Mark, Guifen Chen, Caswell Barry, Neil Burgess, Timothy E.J. Behrens

The hippocampal-entorhinal system is important for spatial and relational memory tasks. We formally link these domains; provide a mechanistic understanding of the hippocampal role in generalisation; and offer unifying principles underlying many entorhinal and hippocampal cell-types. We propose medial entorhinal cells form a basis describing structural knowledge, and hippocampal cells link this basis with sensory representations. Adopting these principles, we introduce the Tolman-Eichenbaum machine (TEM). After learning, TEM entorhinal cells include grid, band, border and object-vector cells. Hippocampal cells include place and landmark cells, remapping between environments. Crucially, TEM also predicts empirically recorded representations in complex non-spatial tasks. TEM predicts hippocampal remapping is not random as previously believed. Rather structural knowledge is preserved across environments. We confirm this in simultaneously recorded place and grid cells. One Sentence Summary Simple principles of representation and generalisation unify spatial and non-spatial accounts of hippocampus and explain many cell representations.

5: Deep image reconstruction from human brain activity
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Posted to bioRxiv 28 Dec 2017

Deep image reconstruction from human brain activity
1,290 downloads neuroscience

Guohua Shen, Tomoyasu Horikawa, Kei Majima, Yukiyasu Kamitani

Machine learning-based analysis of human functional magnetic resonance imaging (fMRI) patterns has enabled the visualization of perceptual content. However, it has been limited to the reconstruction with low-level image bases or to the matching to exemplars. Recent work showed that visual cortical activity can be decoded (translated) into hierarchical features of a deep neural network (DNN) for the same input image, providing a way to make use of the information from hierarchical visual features. Here, we present a novel image reconstruction method, in which the pixel values of an image are optimized to make its DNN features similar to those decoded from human brain activity at multiple layers. We found that the generated images resembled the stimulus images (both natural images and artificial shapes) and the subjective visual content during imagery. While our model was solely trained with natural images, our method successfully generalized the reconstruction to artificial shapes, indicating that our model indeed reconstructs or generates images from brain activity, not simply matches to exemplars. A natural image prior introduced by another deep neural network effectively rendered semantically meaningful details to reconstructions by constraining reconstructed images to be similar to natural images. Furthermore, human judgment of reconstructions suggests the effectiveness of combining multiple DNN layers to enhance visual quality of generated images. The results suggest that hierarchical visual information in the brain can be effectively combined to reconstruct perceptual and subjective images.

6: Dendritic calcium signals in rhesus macaque motor cortex drive an optical brain-computer interface
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Posted to bioRxiv 24 Sep 2019

Dendritic calcium signals in rhesus macaque motor cortex drive an optical brain-computer interface
1,067 downloads neuroscience

Eric M. Trautmann, Daniel J. O’Shea, Xulu Sun, James H Marshel, Ailey Crow, Brian Hsueh, Sam Vesuna, Lucas Cofer, Gergő Bohner, Will Allen, Isaac Kauvar, Sean Quirin, Matthew MacDougall, Yuzhi Chen, Matthew P. Whitmire, Charu Ramakrishnan, Maneesh Sahani, Eyal Seidemann, Stephen I Ryu, Karl Deisseroth, Krishna V Shenoy

Calcium imaging has rapidly developed into a powerful tool for recording from large populations of neurons in vivo . Imaging in rhesus macaque motor cortex can enable the discovery of new principles of motor cortical function and can inform the design of next generation brain-computer interfaces (BCIs). Surface two-photon (2P) imaging, however, cannot presently access somatic calcium signals of neurons from all layers of macaque motor cortex due to photon scattering. Here, we demonstrate an implant and imaging system capable of chronic, motion-stabilized two-photon (2P) imaging of calcium signals from in macaques engaged in a motor task. By imaging apical dendrites, some of which originated from deep layer 5 neurons, as as well as superficial cell bodies, we achieved optical access to large populations of deep and superficial cortical neurons across dorsal premotor (PMd) and gyral primary motor (M1) cortices. Dendritic signals from individual neurons displayed tuning for different directions of arm movement, which was stable across many weeks. Combining several technical advances, we developed an optical BCI (oBCI) driven by these dendritic signals and successfully decoded movement direction online. By fusing 2P functional imaging with CLARITY volumetric imaging, we verify that an imaged dendrite, which contributed to oBCI decoding, originated from a putative Betz cell in motor cortical layer 5. This approach establishes new opportunities for studying motor control and designing BCIs.

7: How neurons move during action potentials
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Posted to bioRxiv 11 Sep 2019

How neurons move during action potentials
996 downloads neuroscience

Tong Ling, Kevin C. Boyle, Valentina Zuckerman, Thomas Flores, Charu Ramakrishnan, Karl Deisseroth, Daniel Palanker

Neurons undergo nanometer-scale deformations during action potentials, and the underlying mechanism has been actively debated for decades. Previous observations were limited to a single spot or the cell boundary, while movement across the entire neuron during the action potential remained unclear. We report full-field imaging of cellular deformations accompanying the action potential in mammalian neuron somas (-1.8nm~1.3nm) and neurites (-0.7nm~0.9nm), using fast quantitative phase imaging with a temporal resolution of 0.1ms and an optical pathlength sensitivity of <4pm per pixel. Spike-triggered average, synchronized to electrical recording, demonstrates that the time course of the optical phase changes matches the dynamics of the electrical signal, with the optical signal revealing the intracellular potential rather than its time derivative detected via extracellular electrodes. Using 3D cellular morphology extracted via confocal microscopy, we demonstrate that the voltage-dependent changes in the membrane tension induced by ionic repulsion can explain the magnitude, time course and spatial features of the phase imaging. Our full-field observations of the spike-induced deformations in mammalian neurons opens the door to non-invasive label-free imaging of neural signaling.

8: Cell type-specific enhancer-promoter connectivity maps in the human brain and disease risk association
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Posted to bioRxiv 22 Sep 2019

Cell type-specific enhancer-promoter connectivity maps in the human brain and disease risk association
985 downloads neuroscience

Alexi Nott, Inge R Holtman, Nicole G Coufal, Johannes C.M. Schlachetzki, Miao Yu, Rong Hu, Claudia Z Han, Monique Pena, Jiayang Xiao, Yin Wu, Zahara Keuelen, Martina P. Pasillas, Carolyn O'Connor, Simon T. Schafer, Zeyang Shen, Robert A Rissman, James B. Brewer, David Gosselin, David D. Gonda, Michael L. Levy, Michael G. Rosenfeld, Graham P McVicker, Fred H. Gage, Bing Ren, Christopher K Glass

Unique cell type-specific patterns of activated enhancers can be leveraged to interpret non-coding genetic variation associated with complex traits and diseases such as neurological and psychiatric disorders. Here, we have defined active promoters and enhancers for major cell types of the human brain. Whereas psychiatric disorders were primarily associated with regulatory regions in neurons, idiopathic Alzheimer's disease (AD) variants were largely confined to microglia enhancers. Interactome maps connecting GWAS variants in cell type-specific enhancers to gene promoters revealed an extended microglia gene network in AD. Deletion of a microglia-specific enhancer harboring AD-risk variants ablated BIN1 expression in microglia but not in neurons or astrocytes. These findings revise and expand the genes likely to be influenced by non-coding variants in AD and suggest the probable brain cell types in which they function.

9: Distinguishing between parallel and serial processing in visual attention from neurobiological data
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Posted to bioRxiv 02 Aug 2018

Distinguishing between parallel and serial processing in visual attention from neurobiological data
955 downloads neuroscience

Kang Li, Mikiko Kadohisa, Makoto Kusunoki, John Duncan, Claus Bundesen, Susanne Ditlevsen

Serial and parallel processing in visual search have been long debated in psychology but the processing mechanism remains an open issue. Serial processing allows only one object at a time to be processed, whereas parallel processing assumes that various objects are processed simultaneously. Here we present novel neural models for the two types of processing mechanisms based on analysis of simultaneously recorded spike trains using electrophysiological data from prefrontal cortex of rhesus monkeys while processing task-relevant visual displays. We combine mathematical models describing neuronal attention and point process models for spike trains. The same model can explain both serial and parallel processing by adopting different parameter regimes. We present statistical methods to distinguish between serial and parallel processing based on both maximum likelihood estimates and decoding analysis of the attention when two stimuli are presented simultaneously. Results show that both processing mechanisms are in play for the simultaneously recorded neurons, but neurons tend to follow parallel processing in the beginning after the onset of the stimulus pair, whereas they tend to serial processing later on. This could be explained by parallel processing being related to sensory bottom-up signals or feedforward processing, which typically occur in the beginning after stimulus onset, whereas top-down signals related to cognitive modulatory influences guiding attentional effects in recurrent feedback connections occur after a small delay, and is related to serial processing, where all processing capacities are being directed towards the attended object.

10: Precision calcium imaging of dense neural populations via a cell body-targeted calcium indicator
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Posted to bioRxiv 17 Sep 2019

Precision calcium imaging of dense neural populations via a cell body-targeted calcium indicator
928 downloads neuroscience

Or A. Shemesh, Changyang Linghu, Kiryl D. Piatkevich, Daniel Goodwin, Howard Gritton, Michael F. Romano, Cody A Siciliano, Ruixuan Gao, Chi-Chieh (Jay) Yu, Hua-an Tseng, Seth Bensussen, Sujatha Narayan, Chao-Tsung Yang, Limor Freifeld, Ishan Gupta, Habiba Noamany, Nikita Pak, Young-Gyu Yoon, Jeremy F.P. Ullmann, Burcu Guner-Ataman, Zoe R. Sheinkopf, Won Min Park, Shoh Asano, Amy Keating, James Trimmer, Jacob Reimer, Andreas Tolias, Kay M Tye, Xue Han, Misha B Ahrens, Edward S Boyden

Methods for one-photon fluorescent imaging of calcium dynamics in vivo are popular due to their ability to simultaneously capture the dynamics of hundreds of neurons across large fields of view, at a low equipment complexity and cost. In contrast to two-photon methods, however, one-photon methods suffer from higher levels of crosstalk between cell bodies and the surrounding neuropil, resulting in decreased signal-to-noise and artifactual correlations of neural activity. Here, we address this problem by engineering cell body-targeted variants of the fluorescent calcium indicator GCaMP6f. We screened fusions of GCaMP6f to both natural as well as engineered peptides, and identified fusions that localized GCaMP6f to within approximately 50 microns of the cell body of neurons in live mice and larval zebrafish. One-photon imaging of soma-targeted GCaMP6f in dense neural circuits reported fewer artifactual spikes from neuropil, increased signal-to-noise ratio, and decreased artifactual correlation across neurons. Thus, soma-targeting of fluorescent calcium indicators increases neuronal signal fidelity and may facilitate even greater usage of simple, powerful, one-photon methods of population imaging of neural calcium dynamics.

11: Using DeepLabCut for 3D markerless pose estimation across species and behaviors
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Posted to bioRxiv 24 Nov 2018

Using DeepLabCut for 3D markerless pose estimation across species and behaviors
918 downloads neuroscience

Tanmay Nath, Mackenzie W. Mathis, An Chi Chen, Amir Patel, Matthias Bethge

Noninvasive behavioral tracking of animals during experiments is crucial to many scientific pursuits. Extracting the poses of animals without using markers is often essential for measuring behavioral effects in biomechanics, genetics, ethology & neuroscience. Yet, extracting detailed poses without markers in dynamically changing backgrounds has been challenging. We recently introduced an open source toolbox called DeepLabCut that builds on a state-of-the-art human pose estimation algorithm to allow a user to train a deep neural network using limited training data to precisely track user-defined features that matches human labeling accuracy. Here, with this paper we provide an updated toolbox that is self contained within a Python package that includes new features such as graphical user interfaces and active-learning based network refinement. Lastly, we provide a step-by-step guide for using DeepLabCut.

12: Automated Reconstruction of a Serial-Section EM Drosophila Brain with Flood-Filling Networks and Local Realignment
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Posted to bioRxiv 11 Apr 2019

Automated Reconstruction of a Serial-Section EM Drosophila Brain with Flood-Filling Networks and Local Realignment
855 downloads neuroscience

Peter H Li, Larry F. Lindsey, Michal Januszewski, Zhihao Zheng, Alexander Shakeel Bates, István Taisz, Mike Tyka, Matthew Nichols, Feng Li, Eric Perlman, Jeremy Maitin-Shepard, Tim Blakely, Laramie Leavitt, Gregory S.X.E. Jefferis, Davi Bock, Viren Jain

Reconstruction of neural circuitry at single-synapse resolution is an attractive target for improving understanding of the nervous system in health and disease. Serial section transmission electron microscopy (ssTEM) is among the most prolific imaging methods employed in pursuit of such reconstructions. We demonstrate how Flood-Filling Networks (FFNs) can be used to computationally segment a forty-teravoxel whole-brain Drosophila ssTEM volume. To compensate for data irregularities and imperfect global alignment, FFNs were combined with procedures that locally re-align serial sections and dynamically adjust image content. The proposed approach produced a largely merger-free segmentation of the entire ssTEM Drosophila brain, which we make freely available. As compared to manual tracing using an efficient skeletonization strategy, the segmentation enabled circuit reconstruction and analysis workflows that were an order of magnitude faster.

13: Direct-fit to nature: an evolutionary perspective on biological (and artificial) neural networks
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Posted to bioRxiv 10 Sep 2019

Direct-fit to nature: an evolutionary perspective on biological (and artificial) neural networks
845 downloads neuroscience

Uri Hasson, Samuel A. Nastase, Ariel Goldstein

Evolution is a blind fitting process by which organisms, over generations, adapt to the niches of an ever-changing environment. Does the mammalian brain use similar brute-force fitting processes to learn how to perceive and act upon the world? Recent advances in training deep neural networks has exposed the power of optimizing millions of synaptic weights to map millions of observations along ecologically relevant objective functions. This class of models has dramatically outstripped simpler, more intuitive models, operating robustly in real-life contexts spanning perception, language, and action coordination. These models do not learn an explicit, human-interpretable representation of the underlying structure of the data; rather, they use local computations to interpolate over task-relevant manifolds in a high-dimensional parameter space. Furthermore, counterintuitively, over-parameterized models, similarly to evolutionary processes, can be simple and parsimonious as they provide a versatile, robust solution for learning a diverse set of functions. In contrast to traditional scientific models, where the ultimate goal is interpretability, over-parameterized models eschew interpretability in favor of solving real-life problems or tasks. We contend that over-parameterized blind fitting presents a radical challenge to many of the underlying assumptions and practices in computational neuroscience and cognitive psychology. At the same time, this shift in perspective informs longstanding debates and establishes unexpected links with evolution, ecological psychology, and artificial life.

14: Beyond accuracy: Measures for assessing machine learning models, pitfalls and guidelines
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Posted to bioRxiv 22 Aug 2019

Beyond accuracy: Measures for assessing machine learning models, pitfalls and guidelines
791 downloads neuroscience

Richard Dinga, Brenda W.J.H. Penninx, Dick J. Veltman, Lianne Schmaal, Andre F. Marquand

Pattern recognition predictive models have become an important tool for analysis of neuroimaging data and answering important questions from clinical and cognitive neuroscience. Regardless of the application, the most commonly used method to quantify model performance is to calculate prediction accuracy, i.e. the proportion of correctly classified samples. While simple and intuitive, other performance measures are often more appropriate with respect to many common goals of neuroimaging pattern recognition studies. In this paper, we will review alternative performance measures and focus on their interpretation and practical aspects of model evaluation. Specifically, we will focus on 4 families of performance measures: 1) categorical performance measures such as accuracy, 2) rank based performance measures such as the area under the curve, 3) probabilistic performance measures based on quadratic error such as Brier score, and 4) probabilistic performance measures based on information criteria such as logarithmic score. We will examine their statistical properties in various settings using simulated data and real neuroimaging data derived from public datasets. Results showed that accuracy had the worst performance with respect to statistical power, detecting model improvement, selecting informative features and reliability of results. Therefore in most cases, it should not be used to make statistical inference about model performance. Accuracy should also be avoided for evaluating utility of clinical models, because it does not take into account clinically relevant information, such as relative cost of false-positive and false-negative misclassification or calibration of probabilistic predictions. We recommend alternative evaluation criteria with respect to the goals of a specific machine learning model.

15: Context-dependent decision making in a premotor circuit
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Posted to bioRxiv 03 Sep 2019

Context-dependent decision making in a premotor circuit
754 downloads neuroscience

Zheng Wu, Ashok Litwin-Kumar, Philip Shamash, Alexei Taylor, Richard Axel, Michael N. Shadlen

Cognitive capacities afford contingent associations between sensory information and behavioral responses. We studied this problem using an olfactory delayed match to sample task whereby a sample odor specifies the association between a subsequent test odor and rewarding action. Multi-neuron recordings revealed representations of the sample and test odors in olfactory sensory and association cortex, which were sufficient to identify the test odor as match/non-match. Yet, inactivation of a downstream premotor area (ALM), but not orbitofrontal cortex, confined to the epoch preceding the test odor, led to gross impairment. Olfactory decisions that were not context dependent were unimpaired. Therefore, ALM may not receive the outcome of a match/non-match decision from upstream areas but contextual information--the identity of the sample--to establish the mapping between test odor and action. A novel population of pyramidal neurons in ALM layer 2 may mediate this process.

16: Reconstruction of 1,000 projection neurons reveals new cell types and organization of long-range connectivity in the mouse brain
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Posted to bioRxiv 01 Feb 2019

Reconstruction of 1,000 projection neurons reveals new cell types and organization of long-range connectivity in the mouse brain
732 downloads neuroscience

Johan Winnubst, Erhan Bas, Tiago A. Ferreira, Zhuhao Wu, Michael N Economo, Patrick Edson, Ben J. Arthur, Christopher Bruns, Konrad Rokicki, David Schauder, Donald J. Olbris, Sean D. Murphy, David G. Ackerman, Cameron Arshadi, Perry Baldwin, Regina Blake, Ahmad Elsayed, Mashtura Hasan, Daniel Ramirez, Bruno Dos Santos, Monet Weldon, Amina Zafar, Joshua T. Dudmann, Charles R Gerfen, Adam W Hantman, Wyatt Korff, Scott M. Sternson, Nelson Spruston, Karel Svoboda, Jayaram Chandrashekar

Neuronal cell types are the nodes of neural circuits that determine the flow of information within the brain. Neuronal morphology, especially the shape of the axonal arbor, provides an essential descriptor of cell type and reveals how individual neurons route their output across the brain. Despite the importance of morphology, few projection neurons in the mouse brain have been reconstructed in their entirety. Here we present a robust and efficient platform for imaging and reconstructing complete neuronal morphologies, including axonal arbors that span substantial portions of the brain. We used this platform to reconstruct more than 1,000 projection neurons in the motor cortex, thalamus, subiculum, and hypothalamus. Together, the reconstructed neurons comprise more than 75 meters of axonal length and are available in a searchable online database. Axonal shapes revealed previously unknown subtypes of projection neurons and suggest organizational principles of long-range connectivity.

17: Learning Divisive Normalization in Primary Visual Cortex
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Posted to bioRxiv 12 Sep 2019

Learning Divisive Normalization in Primary Visual Cortex
729 downloads neuroscience

Max F. Günthner, Santiago A Cadena, George H Denfield, Edgar Y Walker, Andreas S. Tolias, Matthias Bethge, Alexander S Ecker

Deep convolutional neural networks have emerged as the state of the art for predicting single-unit responses in a number of visual areas. While such models outperform classical linear-nonlinear and wavelet-based feature representations, we currently do not know what additional nonlinear computations they approximate. Divisive normalization (DN) has been suggested as one such nonlinear, canonical cortical computation, which has been found to be crucial for explaining nonlinear responses to combinations of simple stimuli such as gratings. However, it has neither been tested rigorously for its ability to account for spiking responses to natural images nor do we know to what extent it can close the gap to high-performing black-box models. Here, we developed an end-to-end trainable model of DN that learns the pool of normalizing neurons and the magnitude of their contribution directly from the data. We used this model to investigate DN in monkey primary visual cortex (V1) under stimulation with natural images. We found that this model outperformed linear-nonlinear and wavelet-based feature representations and came close to the performance of deep neural networks. Surprisingly, within the classical receptive field, oriented features were normalized preferentially by features with similar orientation preference rather than non-specifically as assumed by current models of DN. Thus, our work provides a new, quantitative and interpretable predictive model of V1 applicable to arbitrary images and refines our view on the mechanisms of gain control within the classical receptive field.

18: A neural network model of flexible grasp movement generation
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Posted to bioRxiv 24 Aug 2019

A neural network model of flexible grasp movement generation
728 downloads neuroscience

Jonathan A. Michaels, Stefan Schaffelhofer, Andres Agudelo-Toro, Hansjörg Scherberger

One of the main ways we interact with the world is using our hands. In macaques, the circuit formed by the anterior intraparietal area, the hand area of the ventral premotor cortex, and the primary motor cortex is necessary for transforming visual information into grasping movements. We hypothesized that a recurrent neural network mimicking the multi-area structure of the anatomical circuit and trained to transform visual features into the muscle fiber velocity required to grasp objects would recapitulate neural data in the macaque grasping circuit. While a number of network architectures produced the required kinematics, modular networks with visual input and activity that was encouraged to be biologically realistic best matched neural data and the inter-area differences present in the biological circuit. Network dynamics could be explained by simple rules that also allowed the correct prediction of kinematics and neural responses to novel objects, providing a potential mechanism for flexibly generating grasping movements.

19: Relationship between spiking activity and simultaneously recorded fluorescence signals in transgenic mice expressing GCaMP6
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Posted to bioRxiv 01 Oct 2019

Relationship between spiking activity and simultaneously recorded fluorescence signals in transgenic mice expressing GCaMP6
688 downloads neuroscience

Lawrence Huang, Ulf Knoblich, Peter Ledochowitsch, Jerome Lecoq, R. Clay Reid, Saskia E. J. de Vries, Michael A. Buice, Gabe J Murphy, Jack Waters, Christof Koch, Hongkui Zeng, Lu Li

Two-photon calcium imaging is often used with genetically encoded calcium indicators (GECIs) to investigate neural dynamics, but the relationship between fluorescence and action potentials (spikes) remains unclear. Pioneering work linked electrophysiology and calcium imaging in vivo with viral GECI expression, albeit in a small number of cells. Here we characterized the spike-fluorescence transfer function in vivo of 91 layer 2/3 pyramidal neurons in primary visual cortex in four transgenic mouse lines expressing GCaMP6s or GCaMP6f. We found that GCaMP6s cells have spike-triggered fluorescence responses of larger amplitude, lower variability and greater single-spike detectability than GCaMP6f cells. Single spike detection rates differed substantially across neurons in each line. They declined from ~40-90% at 5% false positive rate under high-resolution imaging to ~10-15% when imaging hundreds of neurons across a larger field of view. Our dataset thus provides quantitative insights to support more refined inference of neuronal activity from calcium imaging data.

20: The structure of behavioral variation within a genotype
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Posted to bioRxiv 23 Sep 2019

The structure of behavioral variation within a genotype
664 downloads neuroscience

Zachary Werkhoven, Alyssa Bravin, Kyobi S Kakaria, Pablo Reimers, Luisa F Pallares, Julien Ayroles, Benjamin L de Bivort

Individual animals vary in their behaviors. This is true even when they share the same genotype and were reared in the same environment. Clusters of covarying behaviors constitute behavioral syndromes, and an individual's position along such axes of covariation is a representation of their personality. Despite these conceptual frameworks, the structure of behavioral covariation within a genotype is essentially uncharacterized and its mechanistic origins unknown. Passing hundreds of isogenic Drosophila individuals through an experimental pipeline that captured hundreds of behavioral measures, we found correlations only between sparse pairs of behaviors. Thus, the space of behavioral variation has many independent dimensions. Manipulating the physiology of the brain, and specific neural populations, altered specific correlations. We also observed that variation in gene expression can predict an individual's position on some behavior axes. This work represents the first steps in understanding the biological mechanisms determining the structure of behavioral variation within a genotype.

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