**4.1 The auditory brainstem response (ABR)**

The auditory brainstem response (ABR), recorded from needle electrodes placed behind the ear and the vertex, reflects the synchronised neural activity to the onset of a stimulus. It is less invasive than single-fibre and CAP recordings for evaluating hearing status. Short tonepips elicit a typical ABR waveform in gerbils with peaks occurring at characteristic latencies. They have been termed i (1-2 ms), ii-iii (2-3.5 ms) and iv (4-5 ms) and can be homologised with the human ABR waves I (generated by the auditory nerve), III (generated by the cochlear nucleus or the MNTB) and V (generated by the lateral lemniscus and IC; Boettcher et al., 1993a).
