In human

neuroanatomy Neuroanatomy is the study of the structure and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry have segregated, defin ...

, brainstem auditory evoked potentials (BAEPs), also called brainstem auditory evoked responses (BAERs), are very small

auditory evoked potential An evoked potential or evoked response is an electrical potential in a specific pattern recorded from a specific part of the nervous system, especially the brain, of a human or other animals following presentation of a stimulus such as a light fla ...

s in response to an auditory stimulus, which are recorded by

electrodes An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...

placed on the scalp. They reflect neuronal activity in the

auditory nerve The cochlear nerve (also auditory nerve or acoustic nerve) is one of two parts of the vestibulocochlear nerve, a cranial nerve present in amniotes, the other part being the vestibular nerve. The cochlear nerve carries auditory sensory information ...

cochlear nucleus The cochlear nuclear (CN) complex comprises two cranial nerve nuclei in the human brainstem, the ventral cochlear nucleus (VCN) and the dorsal cochlear nucleus (DCN). The ventral cochlear nucleus is unlayered whereas the dorsal cochlear nucleus ...

, superior olive, and

inferior colliculus The inferior colliculus (IC) (Latin for ''lower hill'') is the principal midbrain nucleus of the auditory pathway and receives input from several peripheral brainstem nuclei in the auditory pathway, as well as inputs from the auditory cortex. The ...

of the

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is cont ...

. They typically have a response latency of no more than six milliseconds with an

amplitude The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of amplit ...

of approximately one microvolt. 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 Hearing range describes the range of frequencies that can be heard by humans or other animals, though it can also refer to the range of levels. The human range is commonly given as 20 to 20,000 Hz, although there is considerable variati ...

, a more effective auditory stimulus contains a range of frequencies in the form of a short sharp click. Long and Allen were the first to report the abnormal BAEPs in an alcoholic woman who recovered from

acquired central hypoventilation syndrome Central hypoventilation syndrome (CHS) is a sleep-related breathing disorder that causes ineffective breathing, apnea, or respiratory arrest during sleep (and during wakefulness in severe cases). CHS can either be congenital (CCHS) or acquired (A ...

. These investigators hypothesized that their patient's brainstem was poisoned, but not destroyed, by her chronic alcoholism. BAER testing is also recommended for dogs.

References

Electroencephalography Evoked potentials Hearing Audiology {{Neuroscience-stub