Threshold Estimation (CERA)
The reason the cortical response earns a place in the clinic: it estimates hearing thresholds objectively, in an awake adult, frequency by frequency — and it does so even when a patient cannot or will not give reliable voluntary responses.
The principle
Cortical electric response audiometry (CERA) rests on a simple relationship known since the 1960s: as stimulus level falls, the cortical response shrinks and lengthens in latency, until at some level no repeatable response can be distinguished from the background noise [2]. The lowest level that still yields a clear, repeatable response estimates the threshold for that stimulus.
Run frequency by frequency with tone bursts, this builds an objective audiogram. In cooperative adults the cortical thresholds typically sit within about 5–10 dB of the behavioural thresholds — close enough to be clinically useful, with a small, predictable correction [6].
Why the cortical response, and not the ABR?
For threshold estimation in adults the late response has real advantages. It uses frequency-specific tonal stimuli without the rate and timing compromises of the brainstem response; it reflects processing all the way to the cortex; and it is the most direct objective analogue of the behavioural audiogram [5]. The auditory steady-state response (ASSR) is an alternative frequency-specific objective method — and it works in sleep — so the two are often considered together depending on the patient[7].
The trade-off is state: CERA needs an awake, cooperative patient, so it is most at home in older children and adults rather than in sleeping infants, where ABR and ASSR lead.
Non-organic hearing loss and medicolegal testing
The most established clinical niche is the objective confirmation of threshold when the behavioural audiogram is in doubt — suspected non-organic (functional) hearing loss, or compensation and medicolegal claims. Because the obligatory response cannot be voluntarily suppressed and gives frequency-specific thresholds in an awake adult, CERA is the reference method here[5]. A cortical threshold markedly better than the claimed behavioural threshold objectively exposes the exaggeration.
Aided cortical assessment
Delivered in the free field to speech tokens, the cortical response can confirm that amplified sound is audible at the cortex. With the patient wearing their hearing aid, a present response to /m/, /g/ and /t/ shows that the low-, mid- and high-frequency regions of speech are getting through[13]. This is especially valuable in infants, who cannot report what they hear: an objective check that a fitting is actually delivering audible speech [12].