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The Subject

Planning or setting up your ABR experiment must begin with an understanding of the subject's normal hearing range and factors that might have an effect on its response or recording. ABRs have been measured for many species. In this guide, we'll focus on the three most common species used in ABR experiments and screening protocols: mice, rats, and guinea pigs.

Expected Hearing Range

ABR tests are typically focused on the range in which the species is commonly known to hear well.

Subject Standard Testing Range Typical Threshold Range
Mice 4 kHz to 32/48 kHz >25 - 30 dB at 16 kHz
Rats >4 kHz to 24/32 kHz >30 dB at 16 kHz
Guinea Pigs >1 kHz to 18 kHz >30 dB at 8 kHz


The hearing range of laboratory subjects may vary across different strains or colonies and can be affected by age, the environment, and anesthesia.

Many lab subjects experience hearing loss due to age. The rate of loss varies across species and strains. This effect has been observed as early as 12 weeks in mice.

Anesthesia Considerations

Two types of anesthesia protocols are typically used for ABR testing. Each has benefits and limitations. Check your IRB approved guidelines for dosages and protocol.

Xylazine(XYL) + Ketamine to start, Ketamine to Boost

This aesthetic protocol uses an injectable combination of muscle relaxer and sedative. Typically, the subject is unconscious in a few minutes, begins to wake ~45 minutes and is completely awake at ~90 minutes after initial sedation. If a subject wakes early or a test runs longer than ~45 minutes, a booster of ketamine can be used to keep the subject anesthetized. Be sure to follow your approved IRB protocol.

Isoflurane (ISO)

This aesthetic protocol uses a fast-acting inhalant with a short duration. The subject is typically fully sedated within 4-5 minutes and wakes very quickly when the gas is removed.