Anatomy and function of an excitatory network in the visual cortex

Area of Science:

• Neuroscience
• Computational Neuroscience
• Systems Neuroscience

Background:

• Understanding the structure of local neural circuits in the cerebral cortex is crucial for relating circuit activity to network organization.
• In the superficial layers of the mouse visual cortex (V1), it is hypothesized that neurons with similar visual response properties excite one another, but the anatomical basis remains unclear.

Purpose of the Study:

• To investigate the anatomical basis of recurrent synaptic networks in the excitatory layer 2/3 network of the mouse visual cortex (V1).
• To determine if functionally similar neurons exhibit preferential anatomical connectivity.

Main Methods:

• Combined physiological imaging with large-scale electron microscopy to map synaptic connections in V1.
• Analyzed the relationship between neuronal response properties (orientation selectivity) and anatomical connectivity patterns.

Main Results:

• Layer 2/3 neurons in V1 form subnetworks based on anatomical connectivity, with higher connection probability within groups than between them.
• Pyramidal neurons with similar orientation selectivity preferentially form synapses with each other.
• Synapse size is larger between neurons with similar orientation tuning, suggesting enhanced synaptic specificity.

Conclusions:

• Functional specificity in cortical excitatory networks is established at the level of individual synapses, likely involving dendritic spines.
• Preferential synaptic connections between functionally similar neurons contribute to the organizational logic of cortical circuits.
• Functional connectomics provides a powerful approach to dissecting the structure-function relationships in neural networks.