1. Field of the Invention
The present invention relates generally to auditory prostheses and, more particularly, to automated fitting of an auditory prosthesis to a recipient.
2. Related Art
Hearing loss, which may be due to many different causes, is generally of two types, conductive and sensorineural. In some cases, a person may have hearing loss of both types. Conductive hearing loss occurs when the normal mechanical pathways that provide sound to hair cells in the cochlea are impeded due to, for example, damage to the ossicles. Conductive hearing loss is often addressed with conventional hearing aids which amplify sound.
On the other hand, sensorineural hearing loss is due to the absence or destruction of the cochlear hair cells which transduce acoustic signals into nerve impulses. Those suffering from sensorineural hearing loss are thus unable to derive suitable benefit from conventional hearing aids. As a result, stimulating auditory prostheses have been developed to provide persons having sensorineural hearing loss with the ability to perceive sound. Such auditory prostheses include, for example, auditory brain stimulators and cochlear™ prostheses (commonly referred to as cochlear™ prosthetic devices, cochlear™ implants, cochlear™ devices, and the like; simply “cochlea implants” herein.)
Cochlear implants use direct electrical stimulation of auditory nerve cells to bypass absent or defective hair cells that normally transduce acoustic vibrations into neural activity. Such devices generally use an electrode array implanted into the scala tympani of the cochlea so that the electrodes may differentially activate auditory neurons that normally encode differential pitches of sound. Auditory brain stimulators are used to treat a smaller number of recipients with bilateral degeneration of the auditory nerve. For such recipients, the auditory brain stimulator provides stimulation of the cochlear nucleus in the brainstem.
Typically, following the surgical implantation of a cochlear implant, the recipient must have the implant fitted or customized to conform to the specific physiology of that recipient. This procedure is often referred to as “programming,” “mapping” or “fitting” (“fitting” herein). Fitting an auditory prosthesis involves measuring and controlling the amount of electrical current delivered by the cochlea implant to provide comfortable and usable stimulation to the recipient. To do so, the fitting process involves the collection and determination of recipient-specific parameters such as threshold levels (T-levels) and comfort levels (C-levels) for each stimulation channel. This collection of recipient-specific parameters for each of a plurality of stimulation channels is commonly referred to as a “program” or “map” (“MAP” herein). The implementation of the MAP ensures that the stimulation from the cochlear implant provides a recipient with comfortable and accurate auditory perception, enabling the recipient to receive maximum benefit from the device.
Essentially, an audiologist or clinician performs what is commonly referred to as psychophysics measurements by applying stimulation pulses for each channel and subjectively interpreting a behavioral indication from the implant recipient as to the threshold and comfort levels of the perceived sound. For implants with a large number of stimulation channels this process is quite time consuming for the audiologist and relies heavily on the recipient's subjective impression of the stimulation. Also, the psychophysics approach is further limited in the cases of children, infants and prelingually or congenitally deaf recipients who are unable to provide an accurate impression of the resultant hearing sensation. Hence the fitting of the implant may be sub-optimal and may directly hamper the speech and hearing development of younger recipients.