Functional brain stem circuits for control of nose motion.

Area of Science:

• Neuroscience
• Motor Control
• Sensory Processing

Background:

• Rodents exhibit side-to-side nose movements for active exploration and odor localization.
• The deflector nasi muscles drive this specific motor action.
• Understanding the premotor control of this behavior is essential for deciphering orofacial motor control.

Purpose of the Study:

• To investigate the premotor neural circuits controlling rodent nose deflection.
• To identify specific brain regions involved in the sensory-driven control of nose movements.

Main Methods:

• Transsynaptic viral tracing (rabies virus) to map inputs to the deflector nasi.
• Optogenetic activation of identified neuronal populations.
• Selective ablation of neurons in candidate premotor areas.

Main Results:

• Extensive premotor labeling found in reticular formations, trigeminal nuclei, and midbrain structures.
• Two key areas identified: nose retrofacial area and nose intermediate reticular region (IRt).
• Optogenetic stimulation of both areas induced nose deflection; ablation of the nose retrofacial area impaired odor-guided nose movement.

Conclusions:

• The nose retrofacial area acts as a critical conduit for sensory-driven orofacial motor actions, specifically odor-guided nose movements.
• The nose IRt and connections to the preBötzinger complex suggest roles in rhythmic components of nose motion.
• This study reveals novel premotor pathways essential for directed exploratory behaviors in rodents.