Listening with age: disentangling peripheral and cortical processing in the aging auditory system.

In daily life most speech communication information has to be captured in non-optimal acoustical environments and in the presence of interfering sound sources. In the auditory system, the complex speech signal needs to be analyzed acoustically and neurally, separated from the noise, and mapped to phonemes and words. This processing is found to be significantly affected by age. The elderly have more difficulties to follow the rapid temporal patterns of speech, to understand speech in the presence of a competing talker or noise, and to use the inter-aural cues of signals for understanding speech in spatially separated noise. Many of these observations are related to changes with age in the status of the peripheral auditory sensory system (the inner ear) and/or in the abilities of more central neural processes. Several of these issues have been studied before using behavioral measures (audiogram, speech understanding tests). However, while these functional measures yield importa nt information, they are indirect measures of auditory processing. The objective of the proposed research is to disentangle effects of age-related peripheral hearing deficits and central processing changes. We will focus on measures of the aging auditory system that relate to the observed difficulties: neural temporal processing, binaural processing, auditory stream segregation and cortical activity for speech-like stimuli. These will be investigated across age using a combination of objective neurophysiological and behavioral performance measures. These measures allow us to quantify auditory sensitivities from the peripheral (brainstem) to the central level (cortex). Both objective and behavioral data will be obtained from different adult normal hearing and hearing impaired age-cohorts, taking into account age-matching where appropriate. The aim of this research proposal is to investigate the neural correlates of age-related hearing loss and the co-morbidity between peripheral hearing loss and deficits in central auditory processing in orde r to be able to optimize communication. Understanding these neural correlates will lead to improved strategies to enhance central auditory plasticity in seniors (through training programs) and will support the development and application of better auditory prostheses (digital hearing aids and cochlear implants). The neural processing will be studied electro-physiologically by means of scalp recorded auditory potentials in the electroencephalogram (EEG), in response to different signals with speech-like modulations. The novel application of auditory steady state responses will allow zooming into precise oscillation and modulation frequencies of the brain, at different levels of the auditory pathway from brainstem to the auditory cortex, and locked to the modulations in the speech(-like) signal. Signal-to-noise ratio, source localization and coherence measures will be used. The experimental platforms for the different psychophysical and electrophysiological measurements are operational at the Dept. of Neurosciences, ExpORL.

Keywords:Behavioral, Electrophysiological, Cognitive, Brain, aAditory, Aging

Disciplines:Otorhinolaryngology, Speech, language and hearing sciences