If Necessary, Can We Reduce the Amount of Information Communicated, and Reduce
Inter-Electrode-Channel Interactions, by Choosing a Subset of Channels to Stimulate
during each Time-Frame?
Quotes from the Literature:
The original concept of the peak-picker came from Peterson
E. and Cooper F.S., 1957, "Peak-picker: A Bandwidth Compression Device,"
JASA 29:777 (A). The second author should be of particular interest
to the cochlear implant community because Frank Cooper made contributions
to cochlear implant research, in addition to his well-known contributions
to speech science. He was a founder of Haskins Laboratory at Yale.
Our laboratory at UCSF had the benefit of Frank's advice an support
a number of times: My first experience with Frank was when he was the chair
of our first NIH site visit -- for the first NIH-funded research for
testing cochlear implants in humans. He was very knowledgeable, interested,
and kind. It was inspiring to realize that Frank ended-up helping
to develope major "regions" of speech science as a result of his
original (and continued) interest in developing a reading machine for the
blind! "An engineer turned scientist" for two wonderful
reasons: (1) to benefit his fellow man and (2) to try to understand a part
The peak-picker strategy is better viewed as a "processor-modification-strategy"
or a "processor-add-on-strategy" since it can be applied or "added-on"
to most multi-channel cochlear implant processing strategies.
Use of peak-picking (and a "soft-form" of peak-picking) to reduce
channel interactions in cochlear implants: excerpt
from page 501 of White,
Merzenich, and Gardi, 1984.
The previous excerpts presented two "uses" for peak-picking:
(1) Peak-picking to reduce the "information-load" on the CNS --
by only stimulating a subset of channels, presumably those channels that
convey the most information. For this rationale to of value, some
patients' CNS may receive speech better when only "attending to"
the most important information. This may also be viewed as a form
of feature detection/extraction, or "information-importance" detection/extraction.
In that sense, this "use-case" involves feature extraction.
-- ["use-case" is software-geek-lingo -- sorry but I like the
(2) Peak-picking to "directly" reduce inter-channel interactions
-- by reducing the number of driven electrode channels; or by reducing the
stimulus amplitude driving some channels. Because fewer electrodes
are receiving higher amplitude currents, the likelihood that the electric
fields will interact (at the nerve) is reduced. The number of channels that
"are picked-from" can be very high thereby allowing potentially
very high frequency resolution. -- however the number of channels, that
are driven heavily, is limited. So, the effective spatial resolution
of the system could be quite high -- depending on a number of factors!
Interestingly, the peak-picker strategy was first applied to an
Analog speech processor (see: excerpt
from page 11 of the 7th
QPR from RTI (1985)).
The first implementation of the CIS processor did not include the peak-picker
modification/add-on (see the implementation section for information about
the UCSF CIS processor).
A peak-picker strategy was applied to an IP speech processor, which was
implemented by RTI and tested at UCSF (see: excerpt
from page 13 of the 7th
QPR from RTI (1985).
RTI renamed the
peak-picker strategy "the n-of-m processor:" see excerpt
from page 3 of QPR 1 (1995).
Also, see QPR 2 (1995) and
QPR 3 (1996). RTI originally
called the "m of n" the "peak-picker." Why did
RTI change the name, particularly since the original name, "peak-picker,"
was historically accurate both in origins and concept. Furthermore, "peak-picker"
communicated the algorithm's operation better IMO.
1999 Letter to the Hochmairs by M White: Letter
with referenced excerpts, excerpt 1, excerpt 2, and excerpt 3 from White,
1978; and the excerpt from Bruce, et al, 1999.
In 2000, RTI describes the "n of m" processor in interesting
detail: see the excerpt
from page 37 and the excerpt
from page 38 of the 5th RTI QPR
(submitted to NIH in 2000). IMO, some of the material in these
excerpts appears to be some sort of circular rationale, and perhaps even
some slight concession, related to their renaming of the peak-picker algorithm.
One of the reasons that many investigators are unaware that RTI renamed
the peak-picker strategy is due to the availability of RTI's quarterly progress
reports: None of RTI's QPRs for Contract # N01-NS-9-2401, covering
the period 1988-1992, were available on NIH's web site -- until recently:
click-here to see a "snap-shot"
of the previous web site's contents. All other RTI QPRs were available
(QPRs before and after this 1988-1992 period) through
the web site. After I made a request, a new staff member at NIH made
all of RTI's QPRs available. However, recently, they were unexpectedly removed from the NIH website. Fortunately, in 2004 I had copied
the reports from the NIH web site and I have made the QPRs available at