Multichannel, Temporally-Interlaced, Pulsatile Speech Processors

1986-1987

1. In 1986, RTI tested the same strategy 3 "max-rate" IP processor, but without the 'N-of-M' peak-picker add-on.  It was the CIS processor, except that its pulse-rate was far too low.  RTI called this processor the "maximum-rate IP processor."

2. In late 1987 RTI submitted a patent application that included the "max-rate IP" which is the CIS.  M White was listed as a co-inventor.

Descriptions and Quotes from the Literature:

• After UCSF's NIH grant was not renewed in 1985, M White accepted a tenure-track position at the Electrical and Computer Engineering Dept. of North Carolina State University in Raleigh.  In the summer of 1986, Mark White and his family moved to Raleigh, only about 15 miles from the Research Triangle Park area where the RTI group worked.  One of the reasons why M White moved to the Triangle was his desire to collaborate with the RTI group.

• At RTI in 1986: A "CIS processor" without the 'N-of-M' peak-picker was tested by RTI.  It was a CIS processor, except that its pulse-rate was again much too low.

• Just before the summer of 1987 RTI suggested that, since M White was conducting research on artificial neural networks, he might be able to help RTI by training a neural network to perform robust, accurate F0/voiced/unvoiced extraction.  M White suggested that RTI simply use higher-pulse-rates in the "max-rate IP" processor. He indicated that this might enable patients' to perform significantly better on F0/voiced/unvoiced tasks.   In addition, M White pointed out the significant additional advantages of communicating other, even finer-grain temporal information, such as F1 information.  However, RTI had concerns about higher pulse-rates:

  • RTI was concerned about inter-channel interactions that could occur during such high-rate non-simultaneous stimulation. In cochlear implant vernacular, this type of interaction is called a "temporal interaction."  M White indicated that (1) such interactions were far less substantial than those interactions caused by simultaneous stimuli and that (2) the "time-constant" and level of non-simultaneous interactions varied widely among patients -- with some patients having unmeasurable levels, even at short inter-pulse intervals and small physical separations between electrode-channels (for more information go to this "applied science" link).  Furthermore, (3) even if a patient exhibited interactions to non-simultaneous stimulation, it was unknown what the "relative trade-offs" were -- i.e., what the relative advantage of gaining finer-grain temporal information vs. the negative impact of channel interactions caused by non-simultaneous stimulation.  In M White's opinion, this "trade-off" could only be determined through patient testing.

  • RTI was also concerned that pulse-rates above 200-300 PPS were above the sustainable maximum discharge-rate of auditory nerve fibers.  RTI felt that it made no sense to drive the nerve at rates above their maximum discharge rate.  M White indicated that fibers may not be driven to such high discharge rates (i.e. many, or all, fibers might be driven stochastically -- i.e., at lower discharge probabilities).

• In late 1987 RTI submitted a patent application for a cochlear implant processing system. The inventors are listed in Form for Filing the Patent Application and the Formal Letter of Submission.  The diagram of the invention can be found in Figure 2 at the bottom of page 26.  A description of the general invention can be found on page 10, a description of the "max-rate" variation (renamed the CIS) of the invention can be found on page 11, along with a further description of the "max-rate" variation on the top of page 12.  The reason why it was considered inferior to other versions of the invention can be found on page 12 and page 13.   Follow this link to view the The complete Patent Application and related documentation.  So why did the "max-rate" version perform relatively poorly -- at least for some patients?  Sadly, as with their testing at UCSF, RTI had not used channel pulse rates significantly higher than 300 PPS.  See the publication in the journal Nature (excerpt from page xxx of ///TBD linked), also a 1990 Scientific American article, and (excerpt from page xxx of RTI publication ///TBD linked) for additional information.  Amazingly, M White had not even been aware that a patent application was "in the works" or had occurred until sometime shortly after the application had been filed.  He became aware of the application when he received a copy of the application with a copy of a letter (page 1 and page 2) sent to RTI's contract officer from the patent attorneys.  After receiving this material, M White told Charlie Finley that he thought the concepts contained in the application had been put in the public domain long before.  Click here for more information on the patent Application, invention disclosure, negotiations for a licensing agreement, and later assignment to the public domain.