Charles C. Finley, PhD, is a biomedical engineer and neurobiologist, who investigates the design and application of cochlear implant systems. His work includes clinically-based issues such as speech processor design and fitting, as well as in situ device evaluation. He also pursues basic research in understanding the anatomical and physiological basis for variable speech reception outcomes across patients.
This latter area of work involves the integration of high-resolution CT imaging, measurement of intracochlear evoked potentials and computer modeling to make predictions about the neural responsiveness and neural survival patterns in various regions of an individual patient’s implanted cochlea. This multidisciplinary work is being pursued in patients with the Clarion and Nucleus implant systems in collaboration with investigators at Washington University in St. Louis. In this study patients are being assessed pre- and post-operatively using high-resolution CT techniques to determine cochlear anatomy and electrode placement. Peripheral intracochlear physiological responses are also being measured to characterize the status of the cochlea. As part of this project, techniques are also being developed to derive an anatomically-based, finite-element, cochlear model for each individual patient using the CT anatomical information. This computational model will interface with a neural response model and will be used to help interpret intracochlear evoked response data to provide insight into neural survival patterns. Finley’s work in this area was recently recognized by the UNC-CH/NCSU/Duke Renaissance Computing Institute (RENCI) with the competitive award of a RENCI Faculty Fellowship for the academic year 2007-2008. During the year Finley worked with four colleagues at RENCI to implement and expand his model system which includes a full head, a detailed temporal bone and a high-resolution cochlea with implanted electrode array. The model system is implemented on various high performance computer clusters at RENCI. This latter study is motivated by the CT observations to date which show that surgical variation in electrode placement across patients regarding depth of insertion and scalar positioning each significantly influence speech reception performance. This observation was reported by Finley and colleagues in Otology and Neurotology in 2008 and has resulted in new emphasis by surgeons and manufacturers to improve electrode insertion techniques. Indicative of the broad interest by the implant community in this work, Finley and colleagues’ paper was recently designated as best all-round article in cochlear implants in 2008 by the Hearing Journal. Finley was also recently honored by the British Cochlear Implant Group as the keynote speaker at it’s annual conference at Cambridge University in June, 2009 and awarded lifetime membership in the organization.
Development of generic methods of monitoring and evaluating the functional performance of implanted cochlear implant systems in patients continues in Dr. Finley’s lab. In recent years this work spawned a series of basic science studies investigating the patterns of electrical artifact potentials appearing on the scalp of cochlear implant patients. Careful measurement, analysis and modeling of these electrical potential patterns has provided new insights into the pathways along which stimulation current flows during normal operation of cochlear implant systems. Of particular significance is the observation that the current flow pathways for apical and basal stimulation sites are significantly different contrary to conventional wisdom. This observation has served as a key piece of information to link disparate findings from CT imaging, intracochlear electrophysiological measures and psychophysical perceptions to hypothesize the existence of a stimulation mechanism that leads to ectopic stimulation of the auditory nerve in the internal meatus during intracochlear stimulation. This effect is thought to be a significant factor limiting the speech reception abilities of lower performing implant subjects. Several new stimulation strategies have been develop to alleviate this phenomenon and are presently being tested in patients.
Finley’s studies of electrical artifact patterns also have significant clinical utility in monitoring cochlear implant device function in situ. The FDA has recently approached Finley to apply his techniques in a multicenter, multidevice study of the impact of device failures on speech recognition outcomes in children. Finley is also applying similar techniques to study electrical stimulation mechanisms in blind patients implanted with a retinal prosthesis in collaboration with a device manufacturer. An additional area of activity for the next year will be a new NIH-funded project in collaboration with Dr. Fitzpatrick to explore basic science questions related to encoding of speech information using direct electrical stimulation applied to the inferior colliculus.