Individual Differences in the Frequency-Following Response: Relation to Pitch Perception.

Area of Science:

• Auditory Neuroscience
• Psychoacoustics
• Neurophysiology

Background:

• The scalp-recorded frequency-following response (FFR) measures auditory system's neural tracking of periodic sounds.
• Significant variability in FFRs among healthy individuals remains unexplained.
• FFR may indicate training, deficits, or clinical conditions.

Purpose of the Study:

• To investigate the relationship between FFR representation of complex tone frequency content and fundamental frequency pitch perception.
• To explore how the presence or absence of fundamental frequency energy in a stimulus affects FFR.
• To examine the neural mechanisms underlying voluntary shifts in pitch perception.

Main Methods:

• Assessed FFR fundamental frequency strength in 39 normal-hearing subjects listening to complex tones with and without fundamental frequency energy.
• Utilized a within-subjects paradigm to study reversible selection between fundamental and spectral pitch perception.
• Measured concurrent changes in FFR and cortical gamma activity during perceptual shifts.

Main Results:

• FFR fundamental representation strength correlated significantly with individual pitch perception tendencies for missing fundamental tones.
• While group-level FFR was not affected by stimulus fundamental frequency presence, individual differences were observed.
• Subjects could learn to reversibly switch between fundamental and spectral perception, accompanied by FFR and gamma activity changes.

Conclusions:

• Both fundamental and spectral neural representations coexist and are accessible for auditory processing.
• The relative strength of these representations can be modulated by processing demands, influencing FFR variability.
• Voluntary mode perception offers a novel paradigm for studying top-down and bottom-up auditory processing mechanisms.