Monosynaptic inputs to ErbB4-expressing inhibitory neurons in mouse primary somatosensory cortex

Area of Science:

• Neuroscience
• Cell Biology

Background:

• Previous studies mapped somatosensory cortex (S1) inputs but didn't identify specific recipient cell types.
• Identifying monosynaptic inputs to defined neuronal populations is crucial for understanding cortical circuits.

Purpose of the Study:

• To delineate the direct monosynaptic inputs to a subpopulation of inhibitory neurons in mouse S1 that express ErbB4.
• To characterize the sources and distribution of inputs targeting these specific interneurons.

Main Methods:

• Utilized a novel "bridge protein" system (TVB-NRG1) to selectively target ErbB4-expressing neurons.
• Employed EnvB pseudotyped lentivirus (LV) for rabies glycoprotein (RG) expression and a replication-incompetent rabies virus (RV) for transsynaptic tracing.
• RG provision by LV enabled RV spread only to directly connected monosynaptic inputs, preventing further transsynaptic transmission.

Main Results:

• Revealed long-range monosynaptic inputs from the thalamus, nucleus basalis, raphe nuclei, and distant cortical areas (motor, S2, retrosplenial, perirhinal cortex, contralateral S1).
• Identified local connections from ipsilateral S1 pyramidal neurons.
• The labeled input sources encompassed all previously described inputs to S1 using conventional tracers.

Conclusions:

• ErbB4-positive inhibitory neurons in mouse S1 receive direct inputs from a wide array of brain regions.
• These interneurons appear to integrate information broadly across S1 input pathways.
• The findings suggest a key role for ErbB4-positive interneurons in processing diverse sensory and cognitive information within S1.