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Reichl L, Heide D, Löwel S, Crowley JC, Kaschube M, Wolf F. Coordinated optimization of visual cortical maps (I) symmetry-based analysis. PLoS Comput Biol 2012; 8:e1002466. [PMID: 23144599 PMCID: PMC3493482 DOI: 10.1371/journal.pcbi.1002466] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Accepted: 02/24/2012] [Indexed: 11/18/2022] Open
Abstract
In the primary visual cortex of primates and carnivores, functional architecture can be characterized by maps of various stimulus features such as orientation preference (OP), ocular dominance (OD), and spatial frequency. It is a long-standing question in theoretical neuroscience whether the observed maps should be interpreted as optima of a specific energy functional that summarizes the design principles of cortical functional architecture. A rigorous evaluation of this optimization hypothesis is particularly demanded by recent evidence that the functional architecture of orientation columns precisely follows species invariant quantitative laws. Because it would be desirable to infer the form of such an optimization principle from the biological data, the optimization approach to explain cortical functional architecture raises the following questions: i) What are the genuine ground states of candidate energy functionals and how can they be calculated with precision and rigor? ii) How do differences in candidate optimization principles impact on the predicted map structure and conversely what can be learned about a hypothetical underlying optimization principle from observations on map structure? iii) Is there a way to analyze the coordinated organization of cortical maps predicted by optimization principles in general? To answer these questions we developed a general dynamical systems approach to the combined optimization of visual cortical maps of OP and another scalar feature such as OD or spatial frequency preference. From basic symmetry assumptions we obtain a comprehensive phenomenological classification of possible inter-map coupling energies and examine representative examples. We show that each individual coupling energy leads to a different class of OP solutions with different correlations among the maps such that inferences about the optimization principle from map layout appear viable. We systematically assess whether quantitative laws resembling experimental observations can result from the coordinated optimization of orientation columns with other feature maps.
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Affiliation(s)
- Lars Reichl
- Max-Planck-Institute for Dynamics and Self-Organization, Göttingen, Germany
- Bernstein Center for Computational Neuroscience, Göttingen, Germany
- Bernstein Focus Neurotechnology, Göttingen, Germany
- Faculty of Physics, Georg-August University, Göttingen, Germany
- * E-mail: (LR); (FW)
| | - Dominik Heide
- Max-Planck-Institute for Dynamics and Self-Organization, Göttingen, Germany
- Frankfurt Institute of Advanced Studies, Frankfurt, Germany
| | - Siegrid Löwel
- Bernstein Focus Neurotechnology, Göttingen, Germany
- School of Biology, Georg-August University, Göttingen, Germany
| | - Justin C. Crowley
- Carnegie Mellon University, Department of Biological Sciences, Pittsburgh, Pennsylvania, United States of America
| | - Matthias Kaschube
- Frankfurt Institute of Advanced Studies, Frankfurt, Germany
- Physics Department and Lewis-Sigler Institute, Princeton University, Princeton, New Jersey, United States of America
| | - Fred Wolf
- Max-Planck-Institute for Dynamics and Self-Organization, Göttingen, Germany
- Bernstein Center for Computational Neuroscience, Göttingen, Germany
- Bernstein Focus Neurotechnology, Göttingen, Germany
- Faculty of Physics, Georg-August University, Göttingen, Germany
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California, United States of America
- * E-mail: (LR); (FW)
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Podgorski K, Dunfield D, Haas K. Functional clustering drives encoding improvement in a developing brain network during awake visual learning. PLoS Biol 2012; 10:e1001236. [PMID: 22253571 PMCID: PMC3254648 DOI: 10.1371/journal.pbio.1001236] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Accepted: 11/21/2011] [Indexed: 11/18/2022] Open
Abstract
Sensory experience drives dramatic structural and functional plasticity in developing neurons. However, for single-neuron plasticity to optimally improve whole-network encoding of sensory information, changes must be coordinated between neurons to ensure a full range of stimuli is efficiently represented. Using two-photon calcium imaging to monitor evoked activity in over 100 neurons simultaneously, we investigate network-level changes in the developing Xenopus laevis tectum during visual training with motion stimuli. Training causes stimulus-specific changes in neuronal responses and interactions, resulting in improved population encoding. This plasticity is spatially structured, increasing tuning curve similarity and interactions among nearby neurons, and decreasing interactions among distant neurons. Training does not improve encoding by single clusters of similarly responding neurons, but improves encoding across clusters, indicating coordinated plasticity across the network. NMDA receptor blockade prevents coordinated plasticity, reduces clustering, and abolishes whole-network encoding improvement. We conclude that NMDA receptors support experience-dependent network self-organization, allowing efficient population coding of a diverse range of stimuli.
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Affiliation(s)
- Kaspar Podgorski
- Department of Cellular and Physiological Sciences and the Brain Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
| | - Derek Dunfield
- Center for Neuroeconomics, Sloan School of Management, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Kurt Haas
- Department of Cellular and Physiological Sciences and the Brain Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
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Abstract
In mammalian visual cortex, neurons are organized according to their functional properties into multiple maps such as retinotopic, ocular dominance, orientation preference, direction of motion, and others. What determines the organization of cortical maps? We argue that cortical maps reflect neuronal connectivity in intracortical circuits. Because connecting distant neurons requires costly wiring (i.e., axons and dendrites), there is an evolutionary pressure to place connected neurons as close to each other as possible. Then, cortical maps may be viewed as solutions that minimize wiring cost for given intracortical connectivity. These solutions can help us in inferring intracortical connectivity and, ultimately, in understanding the function of the visual system.
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