Synaptic Basis for Differential Orientation Selectivity between Complex and Simple Cells in Mouse Visual Cortex.

Area of Science:

• Neuroscience
• Visual System
• Cellular Electrophysiology

Background:

• Neurons in the primary visual cortex (V1) are classified as simple or complex cells based on receptive field structure.
• While the basis of orientation selectivity (OS) in simple cells is understood, it remains unclear for complex cells.

Purpose of the Study:

• To investigate the synaptic mechanisms underlying orientation selectivity in complex cells of the mouse V1.
• To compare the OS of complex and simple cells and identify the factors contributing to any differences.

Main Methods:

• In vivo loose-patch and whole-cell recordings were used to measure neuronal responses.
• Voltage-clamp recordings analyzed excitatory and inhibitory synaptic inputs.
• Receptive field (RF) structures of inhibitory and excitatory inputs were examined.

Main Results:

• Complex cells exhibited significantly weaker OS than simple cells at both spiking and subthreshold levels.
• Excitatory inputs showed similar OS in both cell types, but inhibition was more narrowly tuned in complex cells and broadly tuned in simple cells.
• The spatial organization of inhibitory inputs, specifically RF elongation, correlated with inhibitory tuning and OS differences.

Conclusions:

• Differential tuning of cortical inhibition, relative to excitation, shapes the OS of complex and simple cells.
• The spatial arrangement of inhibitory synaptic inputs contributes to these observed differences in OS.
• Distinct OS properties of complex and simple cells may lead to functionally different signals for downstream targets.