The case for LACE : Listening and auditory communication enhancement training

Human beings adapt to sensory deprivation in at least two manners. One, they modify their behavior in a way they believe, sometimes incorrectly, to be beneficial. Two, they undergo a physiologic adaptation by means of neural plasticity. Such an adaptation is often observed in the reorganization of sensory maps following damage to peripheral receptors.1 Furthermore, patients presenting similar audiometric profiles frequently obtain very different benefits from amplification. Various factors may account for this. One factor relates to an individual’s assimilation of acoustic, linguistic, and environmental cues. To optimize this integration, a person must call upon many skills and processes, including cognition, auditory memory, auditory closure, auditory learning, metalinguistics, use of pragmatics, semantics, grammatical shape, localization, visual cues, repair tactics, and—since communication is transactional, not one-way— effective interactive communication strategies. While modern hearing aids can make the acoustic signal audible, they may fail to rectify impaired frequency and temporal resolution, improve the skills listed above, or correct misguided compensatory strategies. Limitations in any of these areas, accompanied by the reduced redundancy found in adverse acoustic conditions, require the listener to make decisions based on acoustic information that is fragmented compared with what a normalhearing person receives. Given this fragmented signal, the hearing-impaired person must use compensatory strategies and skills to interpret it. When a person loses a limb and is fitted with a prosthetic device, professionals and the patient recognize the importance of physical therapy to strengthen adjacent muscles (the physiologic adaptation) and instruction to optimize function (the behavioral modification). Therapy also is normally recommended for patients displaying central auditory processing disorders. Central auditory processing disorders and loss of a limb have something in common with peripheral hearing loss: the likelihood that the physiologic deficit will lead the person to adopt behavioral modifications. Yet, therapy for persons with hearing loss is rarely considered. It is possible that the mere introduction of amplification will not produce the desired adaptation of the auditory system and auditory skills unless it is accompanied by training. Recent discoveries in neuroscience suggest that training may enhance auditory skills and even bring about changes in the central auditory system.2-4 We have long known that amplification alone does not fully meet the needs of a large percentage of hearingimpaired patients. Hearing healthcare professionals recognize that additional therapy can enhance the benefits of hearing aids. However, time and cost considerations often preclude the use of such therapy. In this article, we will discuss the theoretical foundations of individual Listening and Auditory Communication Enhancement (LACE) training and report on efforts at the University of California, San Francisco (UCSF) to develop a cost-effective method of providing such training. Our efforts have been guided by two main assumptions. (1) People can use even a fragmented speech signal (which, despite advances in hearing aids, continues to be the reality) and, through homebased training, adopt behavioral strategies, possibly coupled with accelerated and facilitated acclimatization via cortical plasticity, to improve communication effectiveness. (2) Such training is best implemented by means of an individualized protocol established by thorough testing that defines the strengths and limitations of a given patient’s communicative profile.