Auditory Change Complex Responses to Spectrotemporally Modulated Stimuli

Area of Science:

• Auditory Neuroscience
• Electrophysiology
• Hearing Science

Background:

• The Audible Contrast Threshold (ACT) test is a non-language-dependent hearing assessment tool.
• Current ACT requires active participation, posing challenges for infants and individuals with developmental differences.
• An electrophysiological version (E-ACT) is needed to overcome participation limitations.

Purpose of the Study:

• To design and specify an electrophysiological ACT (E-ACT) using auditory change complex (ACC) responses.
• To investigate optimal stimulus carriers, hemispheric differences, and ACC change direction for E-ACT design.
• To compare strategies for defining individual E-ACT thresholds.

Main Methods:

• Two experiments with 65 adult participants with normal hearing thresholds were conducted.
• Stimuli included spectrotemporally modulated targets alternating with unmodulated references.
• Electroencephalogram (EEG) data were analyzed using the Fmpi detector to assess ACC responses.

Main Results:

• Tonal-carrier stimuli yielded significantly more detected ACC responses than noise-carrier stimuli.
• Higher ACC detection rates were observed from the right mastoid compared to the left; averaging both mastoids yielded the highest rate.
• The reference-to-target ('On') change direction showed a higher detection rate than target-to-reference ('Off').

Conclusions:

• The E-ACT should utilize tonal-carrier stimuli for optimal performance.
• Individual E-ACT thresholds should be determined using the average of left and right hemispheric ACC responses.
• Using the individually strongest direction of auditory change during initial recording is recommended for threshold definition.