Our goal is to understand how the brain integrates sensory information and selects and executes appropriate actions. In particular, we aim to determine the organization and function of neural circuits underlying visually guided behaviors. We use the zebrafish as a model organism because it allows us to visualize and manipulate activity in neural circuits throughout a vertebrate brain. As early as one week post-fertilization, zebrafish display a rich repertoire of innate visual behaviors, following moving patterns, avoiding predators and tracking and capturing live prey. With no skull and transparent skin, the entire volume of the brain can be imaged non-invasively in one field of view, and many neurons are individually identifiable from fish to fish. Our approach has three main themes: 1) Quantitative analysis of behavior. 2) Whole brain imaging of neural activity dynamics in the behaving animal. 3) Perturbation of identified neurons to reveal their role in sensorimotor integration. In parallel, we are developing new genetic tools that allow more specific targeting and manipulation of identified cell types.
Vision to ActionOrger Lab firstname.lastname@example.org
Understanding the Neural Mechanisms that Control Swimming Speed in Zebrafish Larvae
Animals often use distinct gaits to move at different speeds, and this requires the engagement of distinct neural circuits. Zebrafish larvae use different motor patterns, and recruit different spinal interneurons, during slow and fast swimming. Currently, it is not known how the brain computes desired speed or relays this information to the spinal cord. We have developed a system to perform high-speed online analysis of tail kinematics in freely swimming fish, while presenting visual stimuli. We find that zebrafish will adjust their swim speed to track different moving patterns, and they do this by switching between two discrete motor patterns. We intend to discover the neural substrates responsible for this behaviour by imaging whole brain neural activity in restrained fish, during visually evoked swimming at different speeds in a closed-loop virtual reality environment. By thoroughly investigating the mechanisms of speed control in zebrafish larvae, from visual inputs to spinal circuits, we hope to uncover general principles of vertebrate locomotor control.
Neural circuits underlying the optokinetic response in larval zebrafish
How neural circuits integrate sensory information to produce appropriate actions is a fundamental question in neuroscience. We aim to address this question using optokinetic behavior, reflexive eye movements in response to whole field motion. Even these simple responses can involve coordinated activity in hundreds of neurons distributed in areas throughout the brain. We image the pattern of neural activity in the brains of transgenic fish, which express a genetically encoded calcium indicator in all of their neurons, while they track visual stimuli with their eyes. Since this behavior is very repeatable, we can systematically record responses from the whole brain with single cell resolution. Presentation of different stimuli, such as monocular, or binocularly conflicting gratings allows us to determine what sensory or motor signals are represented at each point. These experiments represent the first comprehensive analysis of the neural circuit underlying a sensorimotor behavior in a vertebrate brain.
Circuit mechanisms of visuospatial processing in the zebrafish brain
Complex visual behaviours, such as capturing moving prey or avoiding approaching predators, require animals to compute the location and salience of different objects moving in 3 dimensions. These computations depend on dynamic interactions between many interconnected visual areas in the brain. We use transgenic expression of optogenetic tools, and in vivo 2-photon functional imaging to reveal the cellular organization of these circuits and the dynamics of visual processing in response to complex stimuli. We aim to: (1) generate driver lines that target gene expression to specific cell types within the fish visual system, (2) characterize visual response properties and functional topography within these populations and (3) analyse the dynamics of population activity in the optic tectum and other visual areas, when the fish is presented with competing visual targets. Using optogenetics and laser ablations we will interfere with defined circuit components, to determine the link between circuit computations and behaviour.
From dusk till dawn – How zebrafish respond to changes in illumination
Larval zebrafish show several innate responses to spatial and temporal changes in illumination, from rapid orientation and taxis to sustained modulation of locomotor activity. However, little is known about the underlying neural circuits and how neuromodulators act on them to alter locomotor behavior. Using high-speed video tracking in a custom-built arena we quantitatively assess the fishes’ choice of swimming behavior in response to visual stimuli such as whole field luminance changes and local light and dark patches. We aim to determine the neural activity evoked by the same stimuli using in vivo calcium imaging of transgenic fish expressing genetically encoded calcium indicators. In parallel, we are building a library of short promoter sequences that target expression to distinct neuronal types, with the aim of developing a comprehensive set of transgenic driver lines. These can be combined with different reporter lines to optogenetically activate or silence these populations, and record activity in freely swimming fish using GFP-Aequorin.
Orger MB, Portugues R. (2016) Correlating Whole Brain Neural Activity with Behavior in Head-Fixed Larval Zebrafish. Methods Mol Biol 1451 , 307-320 (doi:10.1007/978-1-4939-3771-4_21)
Orger MB. (2016) The Cellular Organization of Zebrafish Visuomotor Circuits Curr. Biol. 26 (9), R377-R385 (doi:10.1016/j.cub.2016.03.054)
Feierstein Claudia E, Portugues Ruben, Orger Michael B. (2015) Seeing the whole picture: A comprehensive imaging approach to functional mapping of circuits in behaving zebrafish Neuroscience 296 , 26-38
Severi KE, Portugues R, Marques JC, O'Malley DM, Orger MB, Engert F. (2014) Neural Control and Modulation of Swimming Speed in the Larval Zebrafish Neuron 83 (2), 00578-9 (doi:10.1016/j.neuron.2014.06.032)
Portugues R, Feierstein CE, Engert F, Orger MB (2014) Whole-Brain Activity Maps Reveal Stereotyped, Distributed Networks for Visuomotor Behavior Neuron 81 (6), 1328-1343 (doi:10.1016/j.neuron.2014.01.019)
Tsai-Wen Chen, Trevor J. Wardill, Yi Sun, Stefan R. Pulver, Sabine L. Renninger, Amy Baohan, Eric R. Schreiter, Rex A. Kerr, Michael B. Orger, Vivek Jayaraman, Loren L. Looger, Karel Svoboda & Douglas S. Kim (2013) Ultrasensitive fluorescent proteins for imaging neuronal activity Nature (499), 295–300 (doi:10.1038/nature12354)
Renninger SL, Orger MB. (2013) Two-photon imaging of neural population activity in zebrafish. Methods S1046-2023 (13), 00166-7 (doi:10.1016/j.ymeth.2013.05.016)
Misha B Ahrens, Michael B Orger, Drew N Robson, Jennifer M Li & Philipp J Keller (2013) Whole-brain functional imaging at cellular resolution using light-sheet microscopy Nat. Methods (doi:10.1038/nmeth.2434)
Jasper Akerboom, Nicole Carreras Calderón, Lin Tian, Sebastian Wabnig, Matthias Prigge, Johan Tolö, Andrew Gordus, Michael B. Orger, Kristen E. Severi, John J. Macklin, Ronak Patel, Stefan R. Pulver, Trevor J. Wardill, Elisabeth Fisch (2013) Genetically encoded calcium indicators for multi-color neural activity imaging and combination with optogenetics. Front. Mol. Neurosci. (doi:10.3389/fnmol.2013.00002)
Marvin JS, Borghuis BG, Tian L, Cichon J, Harnett MT, Akerboom J, Gordus A, Renninger SL, Chen TW, Bargmann CI, Orger MB, Schreiter ER, Demb JB, Gan WB, Hires SA, Looger LL. (2013) An optimized fluorescent probe for visualizing glutamate neurotransmission. Nat. Methods (doi:10.1038/nmeth.2333)
Akerboom J, Mutlu S, Orger MB et al Looger LL. (2012) Optimization of a GCaMP Calcium Indicator for Neural Activity Imaging. J. Neurosci. 32 (40), 13819-13840 (doi:10.1523/?JNEUROSCI.2601-12.2012 )
Bianco IH, Ma LH, Schoppik D, Robson DN, Orger MB, Beck JC, Li JM, Schier AF, Engert F, Baker R (2012) The Tangential Nucleus Controls a Gravito-inertial Vestibulo-ocular Reflex Curr. Biol. (doi:10.1016/j.cub.2012.05.026)
Ahrens MB, Li JM, Orger MB, Robson DN, Schier AF, Engert F, Portugues R. (2012) Brain-wide neuronal dynamics during motor adaptation in zebrafish. Nature 485 (7399), 471-7 (doi:10.1038/nature11057)
Orger MB, Kampff AR, Severi KE, Bollmann JH, Engert F (2008) Control of visual behavior by distinct populations of spinal projection neurons. Nat. Neurosci. 11 (3), 327-333 (doi:10.1038/nn2048)
Smear MC, Tao HW, Staub W, Orger MB, Gosse NJ, Liu Y, Takahashi K, Poo MM, Baier H (2007) Vesicular glutamate transport at a central synapse limits the acuity of visual perception in zebrafish. Neuron 53 (1), 65-77 (doi:10.1016/j.neuron.2006.12.013)
Muto A, Orger MB, Wehman A, Smear MC, Kay JN, Page-McCaw P, Gahtan E, Xiao T, Nevin LM, Gosse NJ, Staub W, Finger-Baier K, Baier H (2005) Forward genetic analysis of visual behaviors in zebrafish. PLoS Genet. 1 (5), e66 (doi:10.1371/journal.pgen.0010066)
Orger MB & Baier H (2005) Channeling of red and green cone inputs to the zebrafish optomotor response. Vis. Neurosci. 22 (3), 275-81 (doi:10.1017/S0952523805223039)
Orger MB, Gahtan E, Muto A, Page-McCaw P, Smear MC, Baier H (2004) Behavioral screening assays in zebrafish. Methods Cell Biol. 77 , 53-68
Orger MB, Smear MC, Anstis SM, Baier H (2000) Perception of Fourier and non-Fourier motion by larval zebrafish. Nat. Neurosci. 3 (11), 1128-1133 (doi:10.1038/80649)