Auditory Brainstem Response
The ActiveTwo system is able to measure a very large number of channels with the normal EEG bandwidth, for example 256 channels@2kHz samplerate. At the same time, the ActiveTwo can also be used for experiments requiring a lesser amount of channels at a much higher samplerate. The System is easily switched between these options with the speedmode switch on the front panel of the AD-box. The digital anti-aliasing filters and ActiView acquisition software automatically adjust to the selected samplerate. This option of adjusting the samplerate makes the system very versatile. Below is an example of the ActiveTwo used in an application with only a few channels on 16 kHz.
 
 

This picture shows the result of on-line averaging (8192 sweeps), x-axis is in milliseconds, y-axis is in uV, left ear (blue) has masking noise, right ear (red) has clicks at 19 Hz. Nearly identical curves were measured with the same subject connected to a dedicated (clinical) ABR machine.

1 Ultraflat electrode was placed behind each ear and 1 Ultraflat electrode was placed on the forehead for the reference.

     
 

This picture shows the neural pathway for ABR response purposed by Hall, J. W., III. (1992). Handbook of auditory evoked responses. Boston: Allyn & Bacon. Hood, L. J., (1998) Clinical applications of the auditory brainstem response, San Diego, CA: Singular Publishing Group.

More information about the principles of ABR measurements can be obtained from this document