What Are Auditory Evoked Potentials?

Auditory evoked potentials (AEP): is the bioelectrical response of the central nervous system caused by the stimulation of the auditory nervous system.

Auditory evoked potential

1.Time lock and signal average superposition technology

According to AEP, it always appears within a fixed time (latency period) after stimulation, and its waveform and amplitude are basically the same. The spontaneous electrical activity such as EEG has no fixed relationship with the stimulus. When the results of multiple stimuli are added up, the AEP amplitude becomes very large, while other radio waves are positively and negatively offset. This is the superposition technique, which divides the superimposed amplitude by the The number of superimpositions to restore the AEP to its original appearance is the average technique.

2.Filtering

The waveform of the evoked potential recording includes many unwanted components, such as too high or too low frequency components and 50Hz interference components of public electricity. The concept of filtering is to filter out unwanted components through a filter. Filters can be divided into high-pass filters, low-pass filters, band-pass filters and notches according to their frequency. The high-pass filter only allows high-frequency signals above a certain frequency to pass through the filter without attenuation to filter out waveforms below the set-point frequency component. The low-pass filter only allows low-frequency signals below a certain frequency to pass through the filter without attenuation to filter out waveforms above the set point frequency component. Bandpass filters A combination of high-pass and low-pass filters forms a band-pass filter. The notch mainly aims to eliminate noise interference at a specific frequency point, such as 50Hz public electrical interference.

Auditory evoked potentials are composed of a series of peaks or waves, with different characteristics such as polarity, order, latency, amplitude, waveform, and distribution, and have a predetermined description method.

Classification by incubation period-refers to three groups according to the time after the response

Early latency or short latency response: 0-10ms, such as ECochG, ABR, etc.

Mid-latency response: 10-50ms, such as 40Hz event-related potential

Long latency response:> 50ms, such as P300

A test environment

The sound insulation room should be far away from electrical equipment. On the inner wall (six sides) of the sound insulation room, copper screen is installed for electrical shielding. The indoor power leads should be shielded, and the shield should be grounded.

Test equipment

Including earphones (plug-in headphones, speakers, bone conduction headphones, earmuffs), electrodes, bio-signal amplifier filters (differential preamp, main amplifier, bandpass filter), signal averaging device, computer and printer.

Three subjects status

1.Adult

Use the supine position and encourage them to close their eyes and try to fall asleep during the test.

2.Infants and young children

An appointment should be made to use sleep deprivation: explain to parents that they go to bed at night before the child's test, and get up early (try to sleep as little as possible) to facilitate falling asleep during the test. Sedative: 10% chloral hydrate.