This proposal continues ongoing analysis of the mechanisms by which neural circuits in primary visual cortex represent stimulus features. Work from this lab has been exploring the contribution of feedforward projections from layer 4 and recurrent connections within layer 2/3 to the orientation selective responses of layer 2/3 neurons. The experiments proposed here will expand on this line of inquiry by investigating how other properties of the stimulus such as luminance and color, and how multiple stimulus orientations, are represented in the responses of orientation selective layer 2/3 neurons. As demonstrated by preliminary results, changes in background luminance exert a powerful suppressive influence over the response of orientation tuned layer 2/3 neurons, dramatically delaying the emergence of a tuned response and virtually eliminating an ongoing tuned response.
The first aim explores the feedforward and recurrent mechanisms that contribute to this effect.
The second aim probes whether the mechanism that is responsible for representing edge orientations at short wavelengths of light is distinct from that responsible for representing edge orientations at longer wavelengths. Specifically, experiments will test whether the short wavelength-sensitive cone system, which preliminary results show is capable of driving orientation selective responses in layer 2/3, does so independent of feedforward inputs from layer 4. Finally, the third aim examines how two edge orientations presented simultaneously are represented in the responses of layer 2/3 neurons. Preliminary results demonstrate that the addition of a second grating stimulus alters the response of layer 2/3 neurons in a highly predictable fashion; the mechanisms that underlie these effects will be explored. The proposed experiments employ intracellular, extracellular, and optical recording techniques to probe these issues at both the single cell and population level. Taken together they should provide new insights into the functional organization of local circuits in visual cortex, information that is crucial for understanding the neural basis of visual perception.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY006821-20
Application #
7201582
Study Section
Central Visual Processing Study Section (CVP)
Program Officer
Oberdorfer, Michael
Project Start
1987-09-01
Project End
2010-03-31
Budget Start
2007-04-01
Budget End
2008-03-31
Support Year
20
Fiscal Year
2007
Total Cost
$373,847
Indirect Cost
Name
Duke University
Department
Biology
Type
Schools of Medicine
DUNS #
044387793
City
Durham
State
NC
Country
United States
Zip Code
27705
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Meng, Yicong; Tanaka, Shigeru; Poon, Chi-Sang (2012) Comment on ""Universality in the evolution of orientation columns in the visual cortex"". Science 336:413; author reply 413
Johnson, Elizabeth N; Van Hooser, Stephen D; Fitzpatrick, David (2010) The representation of S-cone signals in primary visual cortex. J Neurosci 30:10337-50
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MacEvoy, Sean P; Tucker, Thomas R; Fitzpatrick, David (2009) A precise form of divisive suppression supports population coding in the primary visual cortex. Nat Neurosci 12:637-45
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