The Cortical Automatic Threshold Estimation in Adults

This article brings together the work we have been doing at the National Acoustic Laboratories (NAL) to make cortical threshold testing easy, fast, and accurate. Our aim is to improve techniques for estimating hearing thresholds on people who, for whatever reason, are unable to give reliable behavioural responses to indicate that they have heard a sound. The particular techniques described have general applicability to cortical testing, and have been evaluated within a practical package that will become part of the HEARLab family of test modules. Cortical testing nicely complements auditory brainstem testing both because it is best carried out while the patient is awake rather than asleep, and it measures more of the auditory system compared with brainstem testing. Our eventual goal is to have a test that can be used for babies with auditory neuropathy spectrum disorder - in whom cortical thresholds can often be measured even though auditory brainstem responses are absent. We have not achieved that goal yet, but as the article shows, we developed a test that automatically produces reliable threshold estimates in older children and adults. The technique is highly automated - in principle, only one button press, and no human decision making or intervention, is needed to obtain an audiogram in both ears. Our philosophy is that if a computer is better able than humans to examine the consistency of the cortical responses to, say, 50 repeated stimulus presentations, and is able do this simultaneously for eight different stimuli, then it should be left to perform tests uninterrupted by humans! Clinicians should continue doing what they do best: deal with truly complex issues. These include understanding client beliefs and behaviors, and developing inferences from the results of diverse auditory tests.