Prenatal and Early Postnatal Odorant Exposure Heightens Odor-Evoked Mitral Cell Responses in the Mouse Olfactory Bulb

Area of Science:

• Neuroscience
• Olfactory System Research
• Sensory Circuit Plasticity

Background:

• Early sensory experiences critically influence brain circuit development.
• In the mouse olfactory bulb (OB), prenatal and early postnatal odorant exposure via food pairings increases activated glomeruli volume and associated mitral and tufted cell (M/TC) numbers.
• Increased M/TCs per glomerulus may alter odor representation and lateral inhibition strength.

Purpose of the Study:

• To investigate the functional impact of long-term, early-life odorant exposure on mitral cell (MC) population activity.
• To determine how prenatal and early postnatal exposure to specific odorants affects odor-evoked MC responses in the OB.

Main Methods:

• Utilized viral GCaMP6s expression to monitor odor-evoked MC activity in mice.
• Implemented prenatal and early postnatal exposure to two distinct odorants: methyl salicylate (MS) and hexanal.
• Focused analysis on MC responses within the dorsal OB glomeruli activated by the tested odorants.

Main Results:

• Contrary to expectations that familiarity decreases response, early food-based odorant exposure significantly altered MC activity.
• Observed broad increases in the amplitude of excitatory MC responses across the dorsal OB.
• Documented an increased number and reliability of odor-evoked excitatory MC responses following early odorant exposure.

Conclusions:

• Early sensory exposure, specifically through food-odorant pairings, robustly enhances olfactory bulb MC responses.
• This paradigm leads to a significant potentiation of odor representation by increasing the overall excitatory output and reliability of MCs.
• Findings challenge previous notions of odor familiarity and highlight the profound impact of early experience on sensory processing plasticity.