Brain-Wide Maps of Synaptic Input to Cortical Interneurons

Area of Science:

• Neuroscience
• Cell Biology

Background:

• Cortical inhibition relies on diverse interneuron types with distinct roles.
• Local input specificity is known, but distant input patterns remain unclear.

Purpose of the Study:

• To map brain-wide inputs to three major cortical interneuron classes: parvalbumin-positive, somatostatin-positive (SST+), and vasoactive intestinal peptide-positive (VIP+).
• To investigate differences in distant input sources and patterns among these interneuron types in the mouse somatosensory cortex.

Main Methods:

• Utilized a monosynaptic rabies virus system.
• Employed mice expressing Cre recombinase in specific interneuron populations (parvalbumin, SST, VIP).
• Mapped brain-wide inputs to targeted interneuron classes.

Main Results:

• All three interneuron classes receive input from cortical, thalamic, and basal forebrain cholinergic sources.
• VIP+ and SST+ neurons exhibit differential laminar origins of long-distance cortical inputs (deep vs. superficial).
• VIP+ interneurons receive the greatest cortical and thalamic input, while SST+ interneurons receive the least.

Conclusions:

• Cortical interneurons integrate feedforward and feedback information to modulate local circuits.
• Distinct input patterns suggest differential roles for cortical areas in modulating interneuron activity.
• Increased input to VIP+ neurons may facilitate cortical disinhibition via VIP+ inhibition of SST+ cells.