Acute Aromatase Inhibition Impairs Neural and Behavioral Auditory Scene Analysis in Zebra Finches

Area of Science:

• Neuroscience
• Animal Behavior
• Auditory Processing

Background:

• Auditory perception relies on auditory scene analysis (ASA) to extract relevant sounds from noise.
• Zebra finches (a model organism for vocal communication) possess neurons in the caudomedial nidopallium (NCM) that encode song within noisy environments.
• Neuroestrogen synthesis is rapidly induced by conspecific song, suggesting a role in auditory processing.

Purpose of the Study:

• To investigate the role of neuroestrogens in supporting neural and behavioral auditory scene analysis (ASA) in both male and female zebra finches.
• To determine if inhibiting estrogen synthesis affects neural encoding of song within complex auditory scenes.
• To assess the behavioral impact of disrupting neuroestrogen synthesis on song detection in noisy environments.

Main Methods:

• Fadrozole (FAD), an aromatase inhibitor, was administered orally and bilaterally into the NCM of adult male and female zebra finches.
• In vivo extracellular recordings were used to measure NCM neuronal responses to songs and auditory scenes.
• Operant conditioning was employed to train birds on a song detection task in the presence of background noise.

Main Results:

• Fadrozole (FAD) impaired neural encoding of songs by decreasing responsiveness and timing reliability in inhibitory neurons within the NCM.
• FAD significantly decreased neural encoding of songs within scenes for both excitatory and inhibitory neurons, with a more pronounced effect in females.
• Systemic FAD administration altered behavioral performance, increasing response bias and decreasing correct rejections in females, while NCM-specific FAD had no behavioral impact.

Conclusions:

• Neuroestrogens modulate neural processing critical for auditory scene analysis (ASA) in the zebra finch NCM, particularly affecting inhibitory neurons and female song processing.
• While neuronal ASA was impaired by FAD, behavioral performance was not consistently disrupted, indicating potential neural resilience or compensatory mechanisms.
• The behavioral effects of systemic FAD suggest that estrogen synthesis in brain regions beyond the auditory pathway also contributes to auditory scene analysis (ASA).