Effects of age on auditory and cognitive processing: implications for hearing aid fitting and audiologic rehabilitation

Abstract

Recent advances in research and clinical practice concerning aging and auditory communication have been driven by questions about age-related differences in peripheral hearing, central auditory processing, and cognitive processing. A "site-of-lesion'' view based on anatomic levels inspired research to test competing hypotheses about the contributions of changes at these three levels of the nervous system. A "processing'' view based on psychologic functions inspired research to test alternative hypotheses about how lower-level sensory processes and higher-level cognitive processes interact. In the present paper, we suggest that these two views can begin to be unified following the example set by the cognitive neuroscience of aging. The early pioneers of audiology anticipated such a unified view, but today, advances in science and technology make it both possible and necessary. Specifically, we argue that a synthesis of new knowledge concerning the functional neuroscience of auditory cognition is necessary to inform the design and fitting of digital signal processing in "intelligent'' hearing devices, as well as to inform best practices for resituating hearing aid fitting in a broader context of audiologic rehabilitation. Long-standing approaches to rehabilitative audiology should be revitalized to emphasize the important role that training and therapy play in promoting compensatory brain reorganization as older adults acclimatize to new technologies. The purpose of the present paper is to provide an integrated framework for understanding how auditory and cognitive processing interact when older adults listen, comprehend, and communicate in realistic situations, to review relevant models and findings, and to suggest how new knowledge about age-related changes in audition and cognition may influence future developments in hearing aid fitting and audiologic rehabilitation.

Figure 1.

From Davis (1964) as printed in Davis and Silverman (1970, p. 76). Diagram of the physical, anatomical, physiological, and psychological aspects of speech communication, from talker (left) to listener (right). The simplified anatomical diagram shows the ear, the eighth nerve, the major auditory tracts and nuclei of the medulla, the inferior colliculus of the midbrain, the medial geniculate body in the thalamus, and the primary auditory projection area in the superior convolution of the temporal lobe of the cortex. The centrally located reticular formation is also indicated. The cerebral hemispheres and the thalamus are cut in frontal section, the medulla and midbrain in cross section. Note the crossing of many but not all of the auditory pathways to the opposite side of the medulla and brain stem, and input to the reticular formation. Many other connections, for example, to the cerebellum, and the efferent pathways, are omitted. The physiological processes that correspond very roughly to the successive anatomical levels appear in the central column. The psychological processes (at the top) are not assigned to any particular level, but in general they require the participation of the cerebral cortex. (Modified from H. Davis in International Audiology, 3: 209–215 [1964].)

Figure 2.

The average annual number of publications in each of four 4-year periods. Squares represent articles on hearing and cognition. Circles represent the subset of the articles on hearing and cognition that were about aging. Triangles represent the subset of the articles on hearing and cognition and aging that were about hearing aids. Search terms for hearing included: hearing, auditory, auditive, and audition. Search terms for cognition included cognitive, cognition, memory, attention, inhibition, speed of processing, and top-down). Electronic bibliographic searches based on title, abstract and keywords were conducted for five journals: (1) Ear and Hearing, the (2) International Journal of Audiology (IJA) (searches for years before 2002 were conducted on the three journals that were amalgamated into IJA in 2002, namely Audiology, the British Journal of Audiology, and Scandinavian Audiology), (3) the Journal of the Acoustical Society of America; (4) the Journal of the American Academy of Audiology (note, inaugural issue printed 1990); and (5) the Journal of Speech, Language, and Hearing Research (searches prior to 1997 were conducted on the Journal of Speech and Hearing Research).