The synaptic architecture of layer 5 thick tufted excitatory neurons in mouse visual cortex

Area of Science:

• Neuroscience
• Computational Neuroscience
• Cellular Neuroscience

Background:

• Understanding synaptic connectivity is crucial for deciphering neural circuit function.
• Characterizing individual excitatory neuron connections in the neocortex remains challenging.

Purpose of the Study:

• To investigate the synaptic connectivity of mouse visual cortex thick tufted layer 5 pyramidal cells (L5-ETns).
• To identify the specific inhibitory and excitatory partners of L5-ETns within the neocortex.

Main Methods:

• Utilized a 1 mm³ electron microscopy dataset of the mouse visual cortex.
• Employed automated approaches for synapse recognition and cell typing.
• Analyzed the local and long-range connectivity patterns of L5-ETns.

Main Results:

• L5-ETns primarily connect with specific inhibitory cell types in their vicinity, which reciprocate the connection.
• The most common excitatory targets of L5-ETns are layer 5 intertelencephalic neurons (L5-ITns) and layer 6 pyramidal cells.
• Long-range connections of L5-ETns show a higher preference for excitatory targets.

Conclusions:

• Identified a circuit motif involving L5-ETns forming a subcircuit with specific inhibitory interneurons.
• The findings provide insights into the specific roles of L5-ETns in cortical processing.
• The automated framework enables future exploration of other neuron type connectivities.