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Khajeh R, Fumarola F, Abbott LF. Sparse balance: Excitatory-inhibitory networks with small bias currents and broadly distributed synaptic weights. PLoS Comput Biol 2022; 18:e1008836. [PMID: 35139071 PMCID: PMC8827417 DOI: 10.1371/journal.pcbi.1008836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Accepted: 01/08/2022] [Indexed: 11/18/2022] Open
Abstract
Cortical circuits generate excitatory currents that must be cancelled by strong inhibition to assure stability. The resulting excitatory-inhibitory (E-I) balance can generate spontaneous irregular activity but, in standard balanced E-I models, this requires that an extremely strong feedforward bias current be included along with the recurrent excitation and inhibition. The absence of experimental evidence for such large bias currents inspired us to examine an alternative regime that exhibits asynchronous activity without requiring unrealistically large feedforward input. In these networks, irregular spontaneous activity is supported by a continually changing sparse set of neurons. To support this activity, synaptic strengths must be drawn from high-variance distributions. Unlike standard balanced networks, these sparse balance networks exhibit robust nonlinear responses to uniform inputs and non-Gaussian input statistics. Interestingly, the speed, not the size, of synaptic fluctuations dictates the degree of sparsity in the model. In addition to simulations, we provide a mean-field analysis to illustrate the properties of these networks. A class of models in computational neuroscience that have been successful at describing a variety of effects in the neocortex involve a tight balance between excitatory, inhibitory and unrealistically large external input, without which the model cannot produce robust patterns of activity. In this work, we explore what happens when these inputs are smaller in size, and we provide an alternative solution for recovering robust network activity. This solution relies on broadly distributed synaptic strengths and, interestingly, gives rise to sparse subsets of neurons firing at any given time. Unlike the conventional models, the networks exhibit nonlinear responses to uniform external input.
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Affiliation(s)
- Ramin Khajeh
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Department of Neuroscience, Columbia University, New York City, New York, United States of America
- * E-mail:
| | - Francesco Fumarola
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Department of Neuroscience, Columbia University, New York City, New York, United States of America
- Laboratory for Neural Computation and Adaptation, RIKEN Center for Brain Science, Saitama, Japan
| | - LF Abbott
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Department of Neuroscience, Columbia University, New York City, New York, United States of America
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Russo AA, Khajeh R, Bittner SR, Perkins SM, Cunningham JP, Abbott LF, Churchland MM. Neural Trajectories in the Supplementary Motor Area and Motor Cortex Exhibit Distinct Geometries, Compatible with Different Classes of Computation. Neuron 2020; 107:745-758.e6. [PMID: 32516573 DOI: 10.1016/j.neuron.2020.05.020] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 12/25/2019] [Accepted: 05/11/2020] [Indexed: 12/21/2022]
Abstract
The supplementary motor area (SMA) is believed to contribute to higher order aspects of motor control. We considered a key higher order role: tracking progress throughout an action. We propose that doing so requires population activity to display low "trajectory divergence": situations with different future motor outputs should be distinct, even when present motor output is identical. We examined neural activity in SMA and primary motor cortex (M1) as monkeys cycled various distances through a virtual environment. SMA exhibited multiple response features that were absent in M1. At the single-neuron level, these included ramping firing rates and cycle-specific responses. At the population level, they included a helical population-trajectory geometry with shifts in the occupied subspace as movement unfolded. These diverse features all served to reduce trajectory divergence, which was much lower in SMA versus M1. Analogous population-trajectory geometry, also with low divergence, naturally arose in networks trained to internally guide multi-cycle movement.
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Affiliation(s)
- Abigail A Russo
- Department of Neuroscience, Columbia University, New York, NY 10027, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
| | - Ramin Khajeh
- Department of Neuroscience, Columbia University, New York, NY 10027, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA; Center for Theoretical Neuroscience, Columbia University, New York, NY 10027, USA
| | - Sean R Bittner
- Department of Neuroscience, Columbia University, New York, NY 10027, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA; Center for Theoretical Neuroscience, Columbia University, New York, NY 10027, USA
| | - Sean M Perkins
- Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA; Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - John P Cunningham
- Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA; Grossman Center for the Statistics of Mind, Columbia University, New York, NY 10027, USA; Center for Theoretical Neuroscience, Columbia University, New York, NY 10027, USA; Department of Statistics, Columbia University, New York, NY 10027, USA
| | - L F Abbott
- Department of Neuroscience, Columbia University, New York, NY 10027, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA; Grossman Center for the Statistics of Mind, Columbia University, New York, NY 10027, USA; Center for Theoretical Neuroscience, Columbia University, New York, NY 10027, USA; Department of Physiology and Cellular Biophysics, Columbia University Medical Center, New York, NY 10032, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10027, USA
| | - Mark M Churchland
- Department of Neuroscience, Columbia University, New York, NY 10027, USA; Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA; Grossman Center for the Statistics of Mind, Columbia University, New York, NY 10027, USA; Kavli Institute for Brain Science, Columbia University, New York, NY 10027, USA.
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Cao P, Bai P, Omrani AA, Xiao Y, Meaker KL, Tsai HZ, Yan A, Jung HS, Khajeh R, Rodgers GF, Kim Y, Aikawa AS, Kolaczkowski MA, Liu Y, Zettl A, Xu K, Crommie MF, Xu T. Preventing Thin Film Dewetting via Graphene Capping. Adv Mater 2017; 29:1701536. [PMID: 28722188 DOI: 10.1002/adma.201701536] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Revised: 04/11/2017] [Indexed: 05/27/2023]
Abstract
A monolayer 2D capping layer with high Young's modulus is shown to be able to effectively suppress the dewetting of underlying thin films of small organic semiconductor molecule, polymer, and polycrystalline metal, respectively. To verify the universality of this capping layer approach, the dewetting experiments are performed for single-layer graphene transferred onto polystyrene (PS), semiconducting thienoazacoronene (EH-TAC), gold, and also MoS2 on PS. Thermodynamic modeling indicates that the exceptionally high Young's modulus and surface conformity of 2D capping layers such as graphene and MoS2 substantially suppress surface fluctuations and thus dewetting. As long as the uncovered area is smaller than the fluctuation wavelength of the thin film in a dewetting process via spinodal decomposition, the dewetting should be suppressed. The 2D monolayer-capping approach opens up exciting new possibilities to enhance the thermal stability and expands the processing parameters for thin film materials without significantly altering their physical properties.
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Affiliation(s)
- Peigen Cao
- Department of Physics, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Peter Bai
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Materials Science and Engineering, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Arash A Omrani
- Department of Physics, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Yihan Xiao
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Materials Science and Engineering, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Kacey L Meaker
- Department of Physics, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Hsin-Zon Tsai
- Department of Physics, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Aiming Yan
- Department of Physics, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Han Sae Jung
- Department of Physics, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Ramin Khajeh
- Department of Physics, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Griffin F Rodgers
- Department of Physics, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Youngkyou Kim
- Department of Physics, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Andrew S Aikawa
- Department of Physics, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Mattew A Kolaczkowski
- The Molecular Foundry, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA, 94720, USA
| | - Yi Liu
- The Molecular Foundry, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA, 94720, USA
| | - Alex Zettl
- Department of Physics, University of California Berkeley, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Kavli Energy NanoSciences Institute, University of California Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Ke Xu
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA
| | - Michael F Crommie
- Department of Physics, University of California Berkeley, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Kavli Energy NanoSciences Institute, University of California Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Ting Xu
- Department of Materials Science and Engineering, University of California Berkeley, Berkeley, CA, 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA
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