Auditory, Visual, and Auditory-Visual Speech Perception by Individuals with Cochlear Implants versus Individuals with Hearing Aids
Most, Tova, Rothem, Hilla, Luntz, Michal, American Annals of the Deaf
THE RESEARCHERS evaluated the contribution of cochlear implants (CIs) to speech perception by a sample of prelingually deaf individuals implanted after age 8 years. This group was compared with a group with profound hearing impairment (HA-P), and with a group with severe hearing impairment (HA-S), both of which used hearing aids. Words and sentences were presented to the auditory channel alone, the visual channel alone, and the combined auditory-visual channel. Some of the results indicated better performance of the CI group than the HA-P group, thus indicating the advantage of CIs over hearing aids for "late" implantees, especially under difficult listening conditions. In addition, all participants relied on visual information under difficult auditory conditions. These last outcomes suggest that intervention with CI users should include exposure to visual as well as auditory information and should emphasize auditory-visual integration.
Cochlear implantation is an accepted and recommended option for auditory rehabilitation of children with prelin- gual deafness. The results of many studies support the notion that better speech perception is achieved when children receive implants at younger ages (Waltzman & Cohen, 1998). In re- cent years, however, candidacy for im- plantation has broadened to include older children with prelingual deaf- ness (Do well et al., 2002; Osberger, Fisher, Zimerman-Phillips, Geiger, & Barker, 1998; Schramm, Fitzpatrick, & Seguin, 2002; Waltzman, Roland, & Co- hen, 2002). Osberger and colleagues, for example, reported that children with prelingual deafness who were im- planted after age 5 years performed better with their implants than they had with their hearing aids. Dolan-Ash, Hodges, Butts, and Balkany (2000) reported great variability in performance among children with prelingual deafness who were implanted even later, after age 8 years. Inasmuch as some of the participants received excellent perception scores, Dolan and colleagues recommended that criteria for implant candidacy be broadened to include older prelingual deaf children as well.
Research has shown that demographic and audiological variables such as age at implantation, auditory experience before and after implantation, and duration of implant use have an effect on the success of performance after implantation (Fryauf-Bertsch, Tyler, Kelsay, Ganz, & Woodworth, 1997; Geers et al., 2002; Kirk et al., 2002). For example, longer duration of deafness prior to implantation was linked with less successful performance (Schramm et al., 2002; Waltzman et al., 2002). The conventional demographic and audiological factors, however, are not sufficient to explain the variability of speech perception performance among individuals with cochlear implants (Pisoni, 2000). Pisoni suggested that cognitive factors might also be considered. Lachs, Pisoni, and Kirk (2001) found that the great variability in speech perception shown by individuals with cochlear implants may be related to cognitive and language processes that are involved in the acquisition and analysis of spoken language. One of these factors is the ability to use and integrate the auditory and visual information of the spoken language, which can be assessed through comparison of perception levels in each channel and in the combined audiovisual mode.
Audiovisual perception has been researched with hearing individuals (Grant & Seitz, 2000; Heifer, 1997), as well as individuals with hearing impairment (Grant, Walden, & Seitz, 1998). In general, audiovisual perception of speech has been reported to surpass perception through each of the sensory channels alone. This has been found to be especially true in the case of distorted auditory information such as occurs in hearing impairment or the presence of noise or reverberations or other poor acoustical conditions (Bernstein, Demorest, & Tucker, 2000; Massaro & Cohen, 1999). Also, the advantage of the audiovisual condition has manifested itself in situations in which the auditory signal is intact but more challenging, such as when one is listening to highlevel language or foreign language (Summerfield, 1987). …