Oregon Health & Science University Psychological and Physiological Acoustics The encoding and interpreting of sound energy by biological systems Frederick J. Gallun, PhD National Center for Rehabilitative Auditory Research Portland VA Medical Center and Oregon Health & Science University

Hearing Research is Multidisciplinary Physiology Psychology Acoustics Audiology Engineering Computer Science Statistics Animal Bioacoustics Speech Music

The investigation and the dissemination of information about psychological and physiological responses to sound in humans and other species Areas of interest include, but are not limited to: Perception and perceptual organization of simple and complex sounds, including speech Anatomy and function of the auditory pathways, including all physical and biological responses to auditory stimulation Hearing disorders, hearing loss, and auditory prostheses Vibrotactile and vestibular sensation, and the interaction of hearing with other sensory modalities Developmental, aging, learning and plasticity effects in auditory function Theories and models of auditory processes

Filtering a pure tone Amplitude Time Low Frequency High Frequency

Functions of the Central Auditory System Thalamus: Organization and updating of cortical-brainstem connections Inferior Colliculus: Coding of basic timing and frequency patterns Superior Olivary Complex: Spatial Processing Cochlear Nucleus: Timing and frequency extraction

Functions of the Central Auditory System Frederick Gallun, PhD Anna Diedesch, AuD 5/21/2010 Functions of the Central Auditory System Corpus Callosum: Transfer information between left and right hemispheres Frontal Cortex: Control of attention, task-dependent activity, and plasticity of the system over time. Parietal Cortex: Spatial information Auditory Cortex: Feature-specific processing of auditory information Frederick.Gallun@va.gov

The Hearing Aid Hearing aids amplify sounds in the frequency regions where sensitivity is impaired. Modern hearing aids are small and powerful – and expensive. While very effective at the job it does, the hearing aid is still only able to provide rehabilitation for peripheral dysfunction.

The Cochlear Implant Cochlear implants are the only devices currently in wide clinical use that replace sensory input with direct electrical stimulation. An electrode inserted into the cochlea uses electrical pulses to stimulate the auditory nerve, which then fires in temporal patterns matching the input sounds. With as few as four to eight independent channels of stimulation, many users can learn to understand speech well enough to speak on the telephone.

Challenges to Restoring Hearing via Cochlear Implants Recreating ‘normal’ temporal activity in the auditory nerve Providing good electrical separation between neighboring electrodes Courtesy of R. V. Shannon, House Ear Institute, Los Angeles, MA

Future Technology: The Brainstem Implant A large number of clinical trials have already been conducted that demonstrate the ability of cochlear nucleus implants to provide auditory input to patients with damage to the auditory nerve. Some patients with damage to the cochlear nucleus have even had implants inserted that stimulate the inferior colliculus.

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