What is the ASSR test?
Mar 16, 2022
Source: Cainiu Health
Dr. Shi Jizhou
Introduction
ASSR stands for Auditory Steady-State Response testing. In this test, sound waves of different frequencies serve as carrier tones, which are amplitude-modulated at distinct modulation frequencies. The modulated sounds are presented simultaneously to both ears, leveraging their phase-locked response to the stimulus. These amplitude-modulated tones can concurrently activate corresponding regions of the basilar membrane in the cochlea, thereby eliciting ASSRs and enabling determination of hearing thresholds at the respective carrier frequencies.
The term “ASSR” (Auditory Steady-State Response) is also referred to as multi-frequency steady-state response, multi-frequency steady-state evoked potential, multi-frequency auditory steady-state response, and multi-frequency steady-state potential. These terms all describe the same method of eliciting ASSR. So, what exactly is the ASSR test? The following section provides a detailed explanation.
What is the ASSR test?
ASSR stands for Auditory Steady-State Response testing. In this test, acoustic tones of different frequencies serve as carriers, which are then amplitude-modulated at distinct modulation frequencies. These modulated tones are simultaneously presented to both ears. Due to their phase-locked relationship with the stimulus, multiple amplitude-modulated tones can concurrently activate corresponding regions along the basilar membrane of the cochlea, thereby eliciting ASSRs and enabling determination of hearing thresholds at these carrier frequencies.
The underlying principle of ASSR is based on its evoked mechanism: when repetitive stimuli are delivered at or above threshold intensity, hair cells within the frequency-specific region of the cochlear basilar membrane become activated. Neural impulses then travel along the auditory pathway toward the auditory cortex; importantly, the firing rate of these neural responses matches the modulation frequency of the stimulus.
As a result, electroencephalographic (EEG) activity exhibits a response synchronized with—or closely following—the modulation frequency. This synchronization or entrainment of EEG activity to the modulation frequency is termed “phase locking.”
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