Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-08-10
2001-06-19
Jastrzab, Jeffrey R. (Department: 3737)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06249704
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to cochlear implant systems, and more particularly to a type of stimulation applied to a patient through a cochlear implant that enhances the effectiveness of the cochlear implant.
The currently most widely used sound and speech processing strategies in cochlear implants are CIS and SPEAK. Both arc sequential pulsatile strategies, whereby each and every current pulse delivered to the auditory nerve represents a processed quantum of acoustic information that is derived from sound that has been recorded by the microphone of the cochlear implant system. Each stimulation pulse is modulated in amplitude and/or pulse width by the amount of energy and/or information that is recorded at the output of a corresponding filter and/or envelope extraction stage of the speech processor, frequently referred to as “channel”. In the CIS strategy, if the output of a processing channel is zero for a given time period, the corresponding stimulation pulse will be of such amplitude as to fall below the patient's audible threshold, i.e. the pulse does not cause an auditory perception; nonetheless, it is delivered with the purpose of carrying a parcel of acoustic information (which happens to be zero at some points in time) to the auditory system.
In recent years, the modeling of acoustic nerve properties, as well as current laboratory research, indicate that better speech understanding and sound clarity for cochlear implant users may possibly be achieved by applying pulses to the auditory system at very high rates. The rationale is that very high pulse rates elicit a desirable stochastic response pattern in the auditory neural system. The purpose for generating very high stimulation rates is thus independent of the delivery of acoustic information to the auditory neural system.
Very high sequential pulse rates result in increasingly narrower pulse widths. Such increasingly narrower pulse widths make it difficult for the patient to perceive changes in loudness. This is because loudness as perceived by the patient is largely a function of charge (i.e. the combination of pulse width and pulse amplitude). In order to accomplish sufficient loudness growth with very narrow pulses, the pulse amplitude has to increase in proportion to the decrease of pulse width. Disadvantageously, very high pulse rates and ensuing narrow pulse widths are not practical for information delivery to the auditory neural system of transcutaneous cochlear implant users because of loudness growth limitations that result from limited compliance voltage. (The compliance voltage is the maximum voltage available within the cochlear implant device from which stimulation pulses may be derived.) Thus, it is seen that improvements are needed in the way high sequential pulse rates are delivered to a patient in order for such stimulation to be effective, e.g., in order to allow the patient to be able to perceive loudness.
SUMMARY OF THE INVENTION
The present invention addresses the above and other needs by providing a family of speech processing strategies for cochlear implants that includes the application of non-auditory-informative stimuli as well as auditory-informative stimuli. The non-auditory-informative stimuli is applied to the auditory neural system for the purpose of influencing the properties and response characteristics of the auditory system so that when the auditory-informative stimuli is applied, such stimuli is more effective at evoking a desired auditory response, i.e., is more effective at allowing the patient to perceive sound. The information-carrying stimuli may be applied to the auditory neural system at the same time as the non-auditory-informative stimuli, or at time slots between application of the non-auditory-informative stimuli.
In accordance with one aspect of the invention, there is provided a cochlear stimulation implant device having an electrode array attached thereto. The electrode array is adapted for insertion into the cochlea, and includes a plurality of spaced-apart electrodes formed along its length for stimulating various regions of the cochlea. The implant device includes means for sensing and generating or means for receiving auditory-informative data signals from which auditory-informative stimuli are generated and applied to selected pairs of the electrodes. The implant device also includes means for generating and applying non-auditory-informative stimuli through the electrodes. Advantageously, the non-auditory-informative stimuli elicit stochastic response patterns, or otherwise precondition and/or prepare the auditory nerve, so that application of the auditory-informative stimuli is more effective.
In accordance with another aspect of the invention, the non-auditory-informative stimuli that are used to elicit stochastic response patterns, and thereby precondition and/or prepare the auditory nerve to be more receptive to the auditory-informative stimuli, comprise low level stimuli, i.e., stimuli having an amplitude or magnitude that is essentially in the vicinity of (that is, just below or just above) the auditory threshold. As such, the preconditioning stimuli function primarily to bias the neurons of the auditory nerve so that when the auditory-informative stimuli are received, such neurons are readily triggered by the auditory-informative stimuli.
It is thus a feature of the present invention to improve the effectiveness of a cochlear implant system through application of both non-auditory-informative stimuli and auditory-informative stimuli to the auditory nerve.
It is an object of the invention to provide a cochlear stimulation device that delivers at least two types of stimuli to electrodes adapted for insertion in the cochlea: auditory-informative stimuli, and non-auditory-informative stimuli, wherein the non-auditory-informative stimuli makes application of the auditory-informative stimuli more effective.
It is a further object of the invention to provide a method of stimulating the auditory nerve that includes application of both non-auditory-informative stimuli and auditory-informative stimuli, wherein the non-auditory-informative precondition the neurons of the auditory nerve so that they are more effectively triggered by the auditory-informative stimuli when such stimuli are presented to the auditory nerve.
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Harrison William Vanbrooks
Maltan Albert A.
Advanced Bionics Corporation
Gold Bryant R.
Jastrzab Jeffrey R.
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