Human Auditory Detection and Discrimination Measured with the Pupil Dilation Response

Area of Science:

• Audiology
• Neuroscience
• Ophthalmology

Background:

• Standard Hughson-Westlake audiometry relies on voluntary patient responses, limiting its use in individuals unable to follow instructions, such as infants.
• The pupillary dilation response (PDR), an involuntary orienting response to novel stimuli, offers a potential alternative for objective auditory assessment.

Purpose of the Study:

• To investigate the efficacy of the pupillary dilation response (PDR) as an objective indicator of sound detection and auditory discrimination.
• To compare PDR-derived hearing thresholds with those obtained from standard audiometric tests.

Main Methods:

• Pupil size changes were monitored using infrared videography in 31 adult participants during a hearing test.
• Participants indicated sound detection via button press while narrowband noises at various frequencies (1-8 kHz) were presented.
• Pupil size was analyzed within the initial 1750 ms post-stimulus to capture the PDR, excluding cognitive effort-related dilations.

Main Results:

• PDR yielded hearing thresholds comparable to standard audiometry across all tested frequencies, indicating similar sensitivity.
• Habituation of the PDR was minimized at near-threshold stimulus levels.
• Stimulus discrimination was demonstrated as PDR habituation could be reversed by altering sound frequency or level.

Conclusions:

• The pupillary dilation response (PDR) is a sensitive and viable alternative to traditional audiometry for assessing hearing detection.
• PDR can be utilized for auditory discrimination testing, particularly in populations unable to provide reliable voluntary responses.
• This objective measure holds potential for expanding audiological assessment capabilities.