Measurement of the auditory brainstem response (ABR) to study auditory sensitivity in mice

The ABR is an electroencephalographic response measured with scalp electrodes. It provides a quick, easy, and reliable method for physiological assessment of auditory sensitivity in mice. A series of brief tone pips or clicks is presented to an anesthetized mouse at a high rate of speed; each click evokes waves of neural activity in the brainstem that are computer-averaged so they are differentiated from non-auditory background voltages. The intensity of the clicks is reduced in steps until an ABR can no longer be discerned, thereby defining the ABR threshold, which is closely related to the hearing threshold. Key procedural issues are: (1) accurate calibration of the acoustics (what sounds arrive at the mouse's ear), (2) anesthetization of the mouse, (3) setting up the recording electrodes, (4) the protocol for presenting acoustic stimuli and obtaining thresholds, and (5) interpretation of ABR data.