Midbrain auditory sensitivity in the spring peeper (Pseudacris crucifer): correlations with behavioral studies

Area of Science:

• Bioacoustics
• Neuroethology
• Auditory Neuroscience

Background:

• The spring peeper (Pseudacris crucifer) is a common anuran species whose advertisement calls are crucial for mating.
• Understanding the auditory processing of these calls is vital for comprehending mate selection and acoustic communication in this species.

Purpose of the Study:

• To characterize the auditory sensitivity of spring peepers by deriving audiograms.
• To investigate potential sex-based differences in auditory tuning, particularly in relation to advertisement call frequencies.
• To explore the relationship between auditory tuning and behavioral selectivity in this species.

Main Methods:

• Recordings of multiunit activity in the torus semicircularis of male and female spring peepers.
• Free-field stimulation using tone bursts (500–6000 Hz) mimicking advertisement call properties.
• Derivation of audiograms to assess auditory sensitivity and tuning.

Main Results:

• Audiograms revealed two regions of maximal auditory sensitivity: low (500–700 Hz) and high (2000–4000 Hz).
• Males showed broader high-frequency tuning than females, relevant to advertisement call frequencies.
• Significant individual variation in absolute thresholds and tuning was observed, with no evidence of tonotopy.

Conclusions:

• Auditory tuning in spring peepers exhibits sex-specific differences, with males being more broadly tuned in the critical high-frequency range.
• Individual variability in auditory sensitivity suggests that 'average' audiograms may not fully predict behavioral selectivity.
• Behavioral studies should consider individual hearing differences and playback levels above threshold for accurate interpretation of selectivity.