Long-term imaging reveals dynamic changes in the neuronal composition of the glomerular layer

Area of Science:

• Neuroscience
• Cell Biology
• Mammalian Olfactory System Dynamics

Background:

• The mammalian olfactory bulb (OB) features a complex interneuron network.
• Adult neurogenesis contributes to the continuous turnover of these interneurons.
• Detailed dynamics of specific neuronal subpopulations during adult neurogenesis are largely unknown.

Purpose of the Study:

• To investigate the long-term dynamics and turnover of dopaminergic (DA) neurons within the adult mouse OB.
• To quantify the addition and loss rates of DA neurons over an extended period.
• To understand how adult neurogenesis shapes specific neuronal populations in the OB.

Main Methods:

• Developed a novel chronic cranial window preparation for long-term in vivo time-lapse imaging in the mouse OB.
• Monitored the turnover of dopaminergic (DA) neurons for up to 9 months.
• Quantified cell addition and loss in the glomerular layer over time.

Main Results:

• Observed significant addition and loss of DA neurons in the OB glomerular layer over 9 months.
• Both cell addition and loss rates increased progressively during the observation period.
• Found consistently higher numbers of new DA cells compared to lost DA cells, indicating a net increase.
• Documented a net addition of approximately 13% in the DA neuron population over 9 months of adult life.

Conclusions:

• The composition of the bulbar interneuron network dynamically changes throughout adulthood.
• Adult neurogenesis actively contributes to the net expansion of specific neuronal populations like DA neurons.
• The findings challenge the notion of simple replenishment, highlighting active remodeling of the olfactory bulb circuitry.