Complementary networks of cortical somatostatin interneurons enforce layer specific control

Area of Science:

• Neuroscience
• Cortical circuit mapping
• Cellular neuroscience

Background:

• The neocortex is organized into layers, with layer 4 receiving bottom-up sensory input and layers 2/3 and 5 receiving top-down predictive input.
• Cortical somatostatin (SST) neurons, specifically Martinotti cells, are known to regulate top-down input to layers 2/3 and 5, but their role in layer 4 is unclear.

Purpose of the Study:

• To investigate the role of somatostatin (SST) neurons in regulating cortical circuit activity, particularly in layer 4.
• To identify distinct SST neuron subtypes and their specific circuit connections within the mouse barrel cortex.

Main Methods:

• High-precision circuit mapping
• In vivo optogenetic perturbations
• Single-cell transcriptional profiling

Main Results:

• Identified genetically distinct SST neuron subtypes with complementary circuit functions.
• Martinotti cells connect with layers 2/3 and 5, while non-Martinotti cells connect with layer 4.
• Demonstrated layer-specific inhibition by these SST subnetworks, regulating bottom-up and top-down input balance.

Conclusions:

• Parallel SST subnetworks independently control the balance of bottom-up and top-down information flow in the neocortex.
• Distinct SST neuron subtypes play crucial, layer-specific roles in cortical information processing.