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Graph showing a typical Auditory Brainstem Response. The auditory brainstem response (ABR), also called brainstem evoked response audiometry (BERA) or brainstem auditory evoked potentials (BAEPs) or brainstem auditory evoked responses (BAERs) [1] [2] is an auditory evoked potential extracted from ongoing electrical activity in the brain and recorded via electrodes placed on the scalp.
Bone-conduction auditory brainstem response (BCABR) are similar to air conduction auditory brainstem responses, with the main difference being that the signal is transmitted via bone-conduction instead of air. The goal of bone ABR is to estimate cochlear function and to help identify the type of hearing loss present. [2]
The recording procedures for the scalp-recorded FFR are essentially the same as the ABR. A montage of three electrodes is typically utilized: An active electrode, located either at the top of the head or top of the forehead, a reference electrode, located on an earlobe, mastoid, or high vertebra, and a ground electrode, located either on the other earlobe or in the middle of the forehead.
Due to their small amplitude, 500 or more repetitions of the auditory stimulus are required in order to average out the random background electrical activity. Although it is possible to obtain a BAEP to a pure tone stimulus in the hearing range, a more effective auditory stimulus contains a range of frequencies in the form of a short sharp click.
Evoked potential audiometry N1-P2 cortical audio evoked potential (CAEP) audiometry; ABR is a neurologic tests of auditory brainstem function in response to auditory (click) stimuli. Electrocochleography a variant of ABR, tests the impulse transmission function of the cochlea in response to auditory (click) stimuli. It is most often used to ...
Bone conduction thresholds can differentiate sensorineural hearing loss from conductive hearing loss. Other tests, such as oto-acoustic emissions, acoustic stapedial reflexes, speech audiometry and evoked response audiometry are needed to distinguish sensory, neural and auditory processing hearing impairments.
The main source of the auditory evoked field is the auditory cortex and the association cortices. The earliest cortical components of AEF is equivalent to the middle latency response (MLR) of the EEG evoked potential, called the middle latency auditory evoked field (MLAEF), which occurs at 30 to 50 ms after the stimulus onset. [2]
An event-related potential (ERP) is the measured brain response that is the direct result of a specific sensory, cognitive, or motor event. [1] More formally, it is any stereotyped electrophysiological response to a stimulus. The study of the brain in this way provides a noninvasive means of evaluating brain functioning.