Sheila Pratt, PhD
The field of audiology was an outgrowth of the military aural rehabilitation programs during World War II. The field of audiology expanded as instrumentation became more elaborate in the 1950s and research became more sophisicated in the 1960s. At that point the emphasis turned toward diagnosis, instrumentation, and research. There is a growing body of research documenting the benefits of providing aural/audiologic rehabilitation/habilitation to adults with hearing loss. According to Raymond Hull, aural/audiologic rehabilitation is "an attempt to reduce the barriers to communication that result from hearing impairment and facilitate adjustment to the possible psychosocial, educational, and occupational impact of that auditory deficit." Those services may include a program of auditory training as a means of improving the individual's auditory discrimination abilities.
The goal of auditory training is to develop the ability to recognize speech using the auditory signal and to interpret auditory experiences. The procedures and techniques used have evolved over time. While the value of using residual hearing has been realized for a long time, rapid advances in technology during the 20th and 21st centuries have increased the range of services necessary in order for individuals to maximize the use of amplification instrumentation available. In addition, computers and training packages have changed the complexion of auditory training.
With adults, the goals for auditory training usually depend on the needs of the patient, the treatment bias of the clinician, and far too often, whether services can be reimbursed by third-party payers. Auditory training typically is used to improve auditory function, auditory behaviors, and the manner in which a patient approaches auditory tasks. Historically it has been associated with the rehabilitation of patients with hearing loss, although there is increasing use of auditory training with other populations that may have underlying auditory processing problems. For example, auditory training has been used to improve auditory processing in children with dyslexia, autism, specific language impairment, and phonologic disorder, and is a substantive component of many of the commercially available training programs that target these populations (Bettison, 1996; Habib et al., 1999; Merzenich et al., 1996; Wharry, Kirkpatrick, & Stokes, 1987). The treatment of children diagnosed with central auditory processing disorders frequently includes auditory training (Musiek, 1999). It also is a common component of second language training programs for adults (Solma & Adepoju, 1995).
Research looking at plasticity of the auditory system relative to speech perception (particularly the mutability of speech-sound categories and the neural substrates of speech perception learning) has used auditory training experimentally as a means of altering audition (Bradlow, Pisoni, Akahane-Yamada, & Tohkura, 1997; Tremblay, Kraus, Carrell, & McGee, 1997; Tremblay, Kraus, & McGee, 1998; Wang, Spence, Jongman, & Sereno, 1999; Werker & Tees, 1984). However, many of the auditory plasticity studies have used short-term training procedures that were restricted to simple identification or cross-category discrimination tasks. Controlling sources of learning, as well as documenting and accounting for treatment effects has been limited. From this literature it also is difficult to separate shifts in auditory bias from actual perceptual learning. Moreover, little has been attempted to determine what features of the training paradigms are most effective at producing auditory change. As a result, the treatment approaches used in many of these studies are not readily applicable to clinical populations such as adults with hearing loss. However, if auditory training stimulates cortical and subcortical reorganization, as has been proposed by Kraus, Tremblay, and colleagues, then major influences on the auditory system, such as the fitting of hearing aids or cochlear implants, should result in substantive neural reorganization (Kraus, Carrell, King, Tremblay, & Nicol, 1995; Russo, Nicol, Zecker, Hayes, & Kraus, 2005; Tremblay & Kraus, 2002; Tremblay et al., 1997,1998). It also could be argued that the auditory system would be sensitive to auditory training during this reorganization period and that perceptual learning would be facilitated.
Most auditory training programs for persons with hearing loss are organized around three parameters: auditory processing approach, auditory skill, and stimulus difficulty level (Erber, 1982; Erber & Hirsh, 1978; Tye-Murray, 1998, 2004). Auditory training is not routinely used with all adults with hearing loss, but tends to be reserved for those individuals for whom there has been a recent change in auditory function or an increase in auditory demands. For example, recent cochlear implant recipients might benefit from intensive auditory training subsequent to the initial activation and mapping of their implants. Other potential candidates include adults with sudden deafness, people who have switched to dramatically different hearing aid signal processing schemes, and individuals who are beginning a new job or training program that is auditorally demanding. In addition, patients who have not made reasonable improvements in audition and speech production after the fitting of hearing aids or cochlear implants are reasonable candidates for auditory training. However, most adults receiving audiologic services are not aware of auditory training as a treatment option. Moreover, few adult patients are referred for auditory training by their audiologists or other hearing health care professionals. The lack of referrals for auditory training may be due to limited reimbursement for aural rehabilitation services, which may relate to the paucity of data documenting the effectiveness and efficacy of auditory training programs.
Few studies have been published that have examined auditory training outcomes with adults with hearing loss. Walden, Erdman, Montgomery, Schwartz, and Prosek (1981) found that adults newly fitted with hearing aids benefited from systematic consonant discrimination training. However, Kricos and Holmes (1996) found that older adults with previous hearing aid experience did not improve from vowel and consonant discrimination training, but they did benefit from active listening training. With a group of successful hearing aid wearers, Rubinstein and Boothroyd (1987) observed only modest benefit with sentence and syllable-level auditory training, but did observe maintenance of gains that were obtained. Auditory training usually focuses on speech and language stimuli, but music perceptual training programs have been developed for cochlear implant recipients and appear to be effective (Gfeller, Witt, Kim, Adamek, & Coffman, 1999). A pending advancement is an auditory training program developed by Sweetow and colleagues for adults who have hearing loss. The program currently is being beta-tested at a number of clinical sites across the country.
Although supporting literature is limited with respect to auditory training with the hearing-impaired populations (including children), perceptual training studies with normal hearing individuals suggest that the impact of auditory training on perception may be underestimated (Bradlow et al, 1997; Wang et al., 1999; Werker & Tees, 1984). This work has shown that not all speech contrasts can be learned equally well and that performance varies by age and linguistic environment, but that the effects of training are retained over months and show generalization within and across sound categories (Lively, Pisoni, Yamada, Tohkura, & Yamada, 1994; McClaskey, Pisoni, & Carrell, 1983; Tremblay et al., 1997). Auditory training with digitally altered speech signals do not always improve speech perception in expected ways, but shaping speech perception by systematically adjusting perceptually difficult acoustic properties is under investigation in various disordered populations (Bradlow et al., 1999; Habib et al., 1999; Merzinich et al., 1996; Thibodeau, Friel-Patti, & Britt, 2001). The results of these studies may provide useful training information that can be implemented in future studies with persons with hearing loss.
Sheila Pratt, PhD
Department of Communication Science and Disorders
University of Pittsburgh
Geriatric Research, Education and Clinical Center
Department of Audiology and Speech Pathology
VA Pittsburgh Healthcare System