Functional thalamocortical innervation of VIP- and SST-expressing GABAergic interneurons in mouse barrel cortex

Area of Science:

• Neuroscience
• Sensory processing
• Cortical circuits

Background:

• Conscious perception involves complex excitatory and inhibitory circuits in sensory cortices.
• The thalamus provides subcortical sensory input via the ventral posteromedial nucleus (VPM) and the medial part of the posterior nucleus (POm).
• The extent to which VPM and POm inputs drive feedforward inhibition in cortical layers by synapsing on GABAergic neurons is not fully understood.

Purpose of the Study:

• To investigate the projections from VPM and POm to specific interneuron populations in the barrel cortex.
• To determine how thalamic inputs influence feedforward inhibition mediated by interneurons.

Main Methods:

• Utilized optogenetics for targeted stimulation of VPM and POm projections.
• Employed sensitive stimulation and recording techniques in the barrel cortex.
• Examined projections to vasoactive intestinal polypeptide (VIP)- and somatostatin (SST)-expressing interneurons.

Main Results:

• VPM and POm extensively project to both VIP and SST interneurons in the barrel cortex.
• Thalamic input to these interneurons is largely independent of their laminar location or cellular properties.
• Demonstrated that thalamus-mediated feedforward inhibition is a common feature in VIP and SST interneuron circuits.

Conclusions:

• Thalamic inputs play a significant role in initiating feedforward inhibition via VIP and SST interneurons.
• These inhibitory circuits are likely utilized differentially based on specific whisker behaviors.
• Provides insight into the circuit mechanisms underlying sensory perception and information processing.