Distorted Coarse Axon Targeting and Reduced Dendrite Connectivity Underlie Dysosmia after Olfactory Axon Injury

Area of Science:

• Neuroscience
• Olfactory System Biology
• Sensory Neuroscience

Background:

• The glomerular map in the olfactory bulb (OB) is critical for odor recognition and is generally stable despite olfactory sensory neuron (OSN) turnover.
• Traumatic injury to adult OSN axons can cause dysosmia, altering olfaction, but the mechanisms behind OB map distortion remain unclear.

Purpose of the Study:

• To investigate how OSN axon injury disturbs the glomerular map and affects odor information processing in the OB.
• To elucidate the mechanisms underlying OB map distortion following adult OSN axon injury.

Main Methods:

• Utilized a mouse model of dysosmia to study OB map alterations after OSN axon injury.
• Examined OSN axon targeting and mitral/tufted cell dendritic connectivity post-injury.

Main Results:

• OSN axon injury disrupted anterior-posterior coarse targeting within the OB, while local sorting mechanisms remained intact.
• Mitral/tufted cell dendritic connectivity was reduced post-injury, leading to diminished odor responses.
• These findings indicate that existing OSN axons are essential for maintaining the adult olfactory circuit's integrity.

Conclusions:

• The integrity of the olfactory circuit, including both OSN axons and mitral/tufted cell dendrites, relies on existing OSN axons as a scaffold in the adult.
• OSN axon injury leads to significant disruptions in OB organization and function, contributing to olfactory deficits.