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Updated: May 23, 2026
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Targeted Labeling of Neurons in a Specific Functional Micro-domain of the Neocortex by Combining Intrinsic Signal and Two-photon Imaging
Published on: December 12, 2012
The mechanism of orientation selectivity in primary visual cortex without a functional map
David Hansel1, Carl van Vreeswijk
1Institute of Neuroscience and Cognition, University Paris Descartes, Paris, France. david.hansel@parisdescartes.fr
Summary
Random connectivity in the visual cortex (V1) can generate orientation selectivity in neurons. This occurs when excitation and inhibition are balanced, allowing weak orientation tuning to emerge in neuronal responses.
Area of Science:
- Neuroscience
- Computational Neuroscience
- Systems Neuroscience
Background:
- Neurons in the primary visual cortex (V1) exhibit orientation selectivity, a fundamental property for visual processing.
- This selectivity exists even in species like mice and rats, where V1 lacks a clear orientation map, suggesting alternative mechanisms.
- The role of specific connectivity patterns versus random connectivity in generating this selectivity remains unclear.
Purpose of the Study:
- To investigate the mechanism of orientation selectivity in V1 neurons with a salt-and-pepper organization.
- To determine if feature-similarity-dependent connectivity is necessary or if random connectivity is sufficient.
- To model the emergence of orientation selectivity in a network with random connectivity.
Main Methods:
- A network model of layer 2/3 neurons in the primary visual cortex was developed.
- The model incorporated random recurrent connectivity and feedforward input from layer 4 neurons with random preferred orientations.
- Simulations analyzed neuronal responses to drifting gratings under balanced excitation/inhibition conditions.
Main Results:
- Despite weak orientation selectivity in total feedforward and recurrent inputs, strong selectivity emerged in neuronal spike responses.
- Balanced excitation/inhibition allowed untuned excitatory and inhibitory components to cancel, amplifying weak tuning.
- The nonlinear voltage-firing rate transfer function correlated preferred orientations of F0 and F1 components in spike responses.
Conclusions:
- Random recurrent connectivity is sufficient for generating orientation selectivity in V1 neurons, even without an orientation map.
- The balanced excitation/inhibition regime is crucial for amplifying weak orientation signals into strong neuronal selectivity.
- Network dynamics and neuronal nonlinearities play a key role in shaping orientation selectivity in the visual cortex.
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