Patent number 8600515 is assigned to
The following quote was obtained by the news editors from the background information supplied by the inventors: "Prior to the past several decades, scientists generally believed that it was impossible to restore hearing to the deaf. However, scientists have had increasing success in restoring normal hearing to the deaf through electrical stimulation of the auditory nerve. The initial attempts to restore hearing were not very successful, as patients were unable to understand speech. However, as scientists developed different techniques for delivering electrical stimuli to the auditory nerve, the auditory sensations elicited by electrical stimulation gradually came closer to sounding more like normal speech. The electrical stimulation is implemented through a prosthetic device, called cochlear implant, which is implanted in the inner ear to restore partial hearing to profoundly deaf people.
"Such cochlear implants generally employ an electrode array that is inserted in the cochlear duct, usually in the scala tympani. One or more electrodes of the array selectively stimulate different auditory nerves at different places in the cochlea based on the pitch of a received sound signal. Within the cochlea, there are two main cues that convey 'pitch' (frequency) information to the patient. There are (1) the place or location of stimulation along the length of a cochlear duct and (2) the temporal structure of the stimulating waveform. In the cochlea, sound frequencies are mapped to a 'place' in the cochlea, generally from low to high sound frequencies mapped from the apical to basilar direction. The electrode array is fitted to the patient to arrive at a mapping scheme such that electrodes near the base of the cochlea are stimulated with high frequency signals, while electrodes near the apex are stimulated with low frequency signals.
"The position of each electrode is not very precise. That is, there are only a limited number of electrodes, e.g., numbering about 16 to 24 electrodes, spread along the length of the electrode array, inserted into one of the spiraling ducts of the cochlea. Hence, accurately mapping to a 'place' within the cochlea can be difficult, as the mapping is limited by the resolution of the discretely placed electrodes.
"In a conventional cochlear implant, an envelope is extracted in each channel, and the remaining information, i.e., fine structure, is discarded. Given the number of channels in current processors, information in the fine structure can be very important for hearing certain sounds, particularly music. In previous disclosures, methods for encoding the fine time structure have been proposed. In these methods, stimulation is presented on one or more virtual or physical channels that has been optimally selected based on the estimate of the fine structure in each analysis band. However, these methods do not take into account the recent findings that non-simultaneous stimulation of nearby physical or virtual electrodes is perceived as a single pitch. For example, if in one band, the desired stimulation location is that corresponding to 1000 Hz, and in an adjacent band the desired location corresponds to 1300 Hz, then if both are present, the subject might perceive a pitch corresponding to 1150 Hz. This is known as decreased resolution, and it has a negative impact on the performance of current implants that seek to improve hearing by increasing the number of electrodes or using virtual electrodes to increase the number places to stimulate on a cochlea."
In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventor's summary information for this patent: "The present inventors recognized a need to improve the functionality of newer generation implants that utilize increased numbers of electrodes or virtual electrodes. Disclosed are methods and systems for reducing the effects of decreased resolution in a cochlear implant, for example, by encoding the fine time structure of sound signals in the presence of substantial interaction across an electrode array.
"In one aspect, a method of reducing the effects of decreased resolution in a cochlear implant includes analyzing an incoming sound within a plurality of frequency bands. One or more dominant components in each frequency band is estimated. The dominant components are analyzed to determine if any two or more are within a resolution region of one another. Of any two or more components that are within a resolution region of one another, the component with the lesser associated energy is removed, thereby producing a sound signal with a reduced pattern of components. The reduced pattern signal is transmitted to an array of electrodes associated with a cochlear implant.
"In another aspect, a cochlear stimulation system includes a plurality of analysis channels. Each channel has a filter associated with a frequency band. A processor is in communication with the plurality of analysis channels. The processor estimates the dominant components in each frequency band. The system also includes means for analyzing the dominant components and determining if any two or more are within a resolution region of one another. Additionally, the system includes means for removing the component that has lesser associated energy of two or more components that are within a resolution region of one another, thereby producing a sound signal with a reduced pattern of components.
"In another aspect, a method of reducing the effects of decreased resolution in a cochlear implant includes determining the value of an individual's resolution region. A plurality of dominant components within a sound signal are analyzed. A component that has lesser associated energy of two or more components that are within the resolution region of one another is removed, thereby producing a sound signal with a reduced pattern of components. The reduced pattern signal is transmitted to an array of electrodes associated with the cochlear implant.
"In another aspect, a method for estimating a resolution region associated with a cochlear implant used by an individual includes providing a first sound having a predetermined frequency. A second sound in close succession to the first sound is provided. The second sound has a predetermined frequency different from the first sound. It is determined if the individual hears two sounds. These steps are repeated until it is determined that the individual does not hear two separate sounds. The second sound has a frequency closer to the frequency of the first sound upon each consecutive repetition of the above steps.
"In another aspect, a stimulation strategy can be customized for a cochlear implant implanted in an individual by testing at least a pair of electrodes selected from an array of electrodes associated with the cochlear implant. Testing the at least a pair of electrodes includes applying a first stimulation to the at least a pair of electrodes using a first pair of pulse trains that are out of phase, and applying a second stimulation to the at least a pair of electrodes using a second pair of pulse trains that are out of phase. A determination is made on whether the at least a pair of electrodes stimulate the same neural population based on a sensitivity of the individual to detect a perceived difference between the two pairs of pulse trains. The one or more electrodes of the array of electrodes are selectively stimulated based on the determination.
"Implementations can optionally include one or more of the following features. The sensitivity of the individual can be determined using a psychophysical method. The at least a pair of electrodes can be selectively not stimulated when detected that the at least a pair of electrodes stimulate the same neural population.
"In another aspect, a stimulation strategy can be customized for a cochlear implant implanted in an individual by determining an excitation pattern for at least a first electrode and a second electrode selected from an array of electrodes associated with the cochlear implant. Determining the excitation pattern includes applying a masking stimulus and a probing stimulus separated by a time delay to each electrode, and determining an ability of the individual to distinguish the masking and probing stimuli. The excitation pattern for the first electrode can be compared against the excitation pattern for the second electrode. Based on the comparison, the one or more electrodes of the array of electrodes is selectively stimulating.
"Implementations can optionally include one or more of the following features. The ability of the individual to distinguish the masking and probing stimuli can be determined using a psychophysical method. Also, the excitation patterns for the first and second electrodes can be compared to determine whether the excitation pattern for the first electrode overlaps with the excitation pattern for the second electrode. When detected that the excitation pattern for the first electrode overlaps with the excitation pattern for the second electrode, the first and second electrodes can be selectively not stimulated. In some instances, the tests for independence of two or more electrodes can be encoded using an implantable device (e.g., implantable cochlear stimulator alone or together with a speech processor.)
"The subject matter described in this specification can be implemented as a method or as a system or using computer program products, tangibly embodied in information carriers, such as a CD-ROM, a DVD-ROM, a semiconductor memory, and a hard disk. Such computer program products may cause a data processing apparatus to conduct one or more operations described in this specification.
"In addition, the subject matter described in this specification can also be implemented as a system including a processor and a memory coupled to the processor. The memory may encode one or more programs that cause the processor to perform one or more of the method acts described in this specification. Further the subject matter described in this specification can be implemented using various data processing machines.
"The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims."
URL and more information on this patent, see: Litvak,
Keywords for this news article include: Biotechnology, Bioengineering, Machine Learning,
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