Main Menu (Mobile)- Block

Main Menu - Block

janelia7_blocks-janelia7_fake_breadcrumb | block
Freeman Lab / Publications
general_search_page-panel_pane_1 | views_panes

7 Publications

Showing 1-7 of 7 results
Your Criteria:
    Svoboda LabFreeman Lab
    12/23/15 | Neural coding in barrel cortex during whisker-guided locomotion.
    Sofroniew NJ, Vlasov YA, Andrew Hires S, Freeman J, Svoboda K
    eLife. 2015 Dec 23;4:. doi: 10.7554/eLife.12559

    Animals seek out relevant information by moving through a dynamic world, but sensory systems are usually studied under highly constrained and passive conditions that may not probe important dimensions of the neural code. Here, we explored neural coding in the barrel cortex of head-fixed mice that tracked walls with their whiskers in tactile virtual reality. Optogenetic manipulations revealed that barrel cortex plays a role in wall-tracking. Closed-loop optogenetic control of layer 4 neurons can substitute for whisker-object contact to guide behavior resembling wall tracking. We measured neural activity using two-photon calcium imaging and extracellular recordings. Neurons were tuned to the distance between the animal snout and the contralateral wall, with monotonic, unimodal, and multimodal tuning curves. This rich representation of object location in the barrel cortex could not be predicted based on simple stimulus-response relationships involving individual whiskers and likely emerges within cortical circuits.

    View Publication Page
    Freeman Lab
    10/30/15 | Mapping nonlinear receptive field structure in primate retina at single cone resolution.
    Freeman J, Field GD, Li PH, Greschner M, Gunning DE, Mathieson K, Sher A, Litke AM, Paninski L, Simoncelli EP, Chichilnisky EJ
    eLife. 2015 Oct 30;4:. doi: 10.7554/eLife.05241

    The function of a neural circuit is shaped by the computations performed by its interneurons, which in many cases are not easily accessible to experimental investigation. Here, we elucidate the transformation of visual signals flowing from the input to the output of the primate retina, using a combination of large-scale multi-electrode recordings from an identified ganglion cell type, visual stimulation targeted at individual cone photoreceptors, and a hierarchical computational model. The results reveal nonlinear subunits in the circuity of OFF midget ganglion cells, which subserve high-resolution vision. The model explains light responses to a variety of stimuli more accurately than a linear model, including stimuli targeted to cones within and across subunits. The recovered model components are consistent with known anatomical organization of midget bipolar interneurons. These results reveal the spatial structure of linear and nonlinear encoding, at the resolution of single cells and at the scale of complete circuits.

    View Publication Page
    Branson LabFreeman Lab
    10/22/15 | Imaging the neural basis of locomotion.
    Branson K, Freeman J
    Cell. 2015 Oct 22;163(3):541-2. doi: 10.1016/j.cell.2015.10.014

    To investigate the fundamental question of how nervous systems encode, organize, and sequence behaviors, Kato et al. imaged neural activity with cellular resolution across the brain of the worm Caenorhabditis elegans. Locomotion behavior seems to be continuously represented by cyclical patterns of distributed neural activity that are present even in immobilized animals.

    View Publication Page
    08/11/15 | Whole-central nervous system functional imaging in larval Drosophila.
    Lemon WC, Pulver SR, Höckendorf B, McDole K, Branson KM, Freeman J, Keller PJ
    Nature Communications. 2015 Aug 11;6:7924. doi: 10.1038/ncomms8924

    Understanding how the brain works in tight concert with the rest of the central nervous system (CNS) hinges upon knowledge of coordinated activity patterns across the whole CNS. We present a method for measuring activity in an entire, non-transparent CNS with high spatiotemporal resolution. We combine a light-sheet microscope capable of simultaneous multi-view imaging at volumetric speeds 25-fold faster than the state-of-the-art, a whole-CNS imaging assay for the isolated Drosophila larval CNS and a computational framework for analysing multi-view, whole-CNS calcium imaging data. We image both brain and ventral nerve cord, covering the entire CNS at 2 or 5 Hz with two- or one-photon excitation, respectively. By mapping network activity during fictive behaviours and quantitatively comparing high-resolution whole-CNS activity maps across individuals, we predict functional connections between CNS regions and reveal neurons in the brain that identify type and temporal state of motor programs executed in the ventral nerve cord.

    View Publication Page
    Freeman Lab
    06/01/15 | Open source tools for large-scale neuroscience.
    Freeman J
    Current Opinion in Neurobiology. 2015 Jun;32:156-63. doi: 10.1016/j.conb.2015.04.002

    New technologies for monitoring and manipulating the nervous system promise exciting biology but pose challenges for analysis and computation. Solutions can be found in the form of modern approaches to distributed computing, machine learning, and interactive visualization. But embracing these new technologies will require a cultural shift: away from independent efforts and proprietary methods and toward an open source and collaborative neuroscience.

    View Publication Page
    04/21/15 | A cellular resolution map of barrel cortex activity during tactile behavior.
    Peron SP, Freeman J, Iyer V, Guo C, Svoboda K
    Neuron. 2015 Apr 21;86(3):783-99. doi: 10.1016/j.neuron.2015.03.027

    Comprehensive measurement of neural activity remains challenging due to the large numbers of neurons in each brain area. We used volumetric two-photon imaging in mice expressing GCaMP6s and nuclear red fluorescent proteins to sample activity in 75% of superficial barrel cortex neurons across the relevant cortical columns, approximately 12,000 neurons per animal, during performance of a single whisker object localization task. Task-related activity peaked during object palpation. An encoding model related activity to behavioral variables. In the column corresponding to the spared whisker, 300 layer (L) 2/3 pyramidal neurons (17%) each encoded touch and whisker movements. Touch representation declined by half in surrounding columns; whisker movement representation was unchanged. Following the emergence of stereotyped task-related movement, sensory representations showed no measurable plasticity. Touch direction was topographically organized, with distinct organization for passive and active touch. Our work reveals sparse and spatially intermingled representations of multiple tactile features.

    View Publication Page
    Freeman Lab
    01/27/15 | Representing "stuff" in visual cortex.
    Ziemba CM, Freeman J
    Proceedings of the National Academy of Sciences of the United States of America. 2015 Jan 27;112(4):942-3. doi: 10.1073/pnas.1423496112