Page 58 - Spring 2019
P. 58

The Flernarkahle Cochlear Irnplant
distance combine to produce broad spreads of the excitation and said, "Hot damn, I want to take this one home with me!”
fields from each electrode along the length of the cochlea All three major manufacturers of C15 (which had more than
(length constant of about 10 mm or greater compared with 99% of the market share) implemented CIS in new versions of
the ~35-mm length of the human cochlea). Also, the fields their products in record times for medical devices after the re-
from each electrode overlap strongly with the fields from sults from the first set of subjects were published (Wilson et al.,
other electrodes. The aspect of processing is to present the 1991), and CIS became available for widespread clinical use
pulses across channels and their associated electrodes in a within just a few years thereafter. Thus, the subjects got their
sequence rather than simultaneously. The nonsirnultaneous wish and the Cl users who followed them benefitted as well.
or “interleaved” stimulation eliminates direct summation of _
electric fields from the different electrodes that otherwise Many other shmegles were developed hfier CIS’ but most
id Shir 1 dc fade the “Ce “mi inde endence of the were based on it (Fayad et al., 2008; Zeng and Canlon, 2015;
W0“ P Y S P P P . . . .
channels and electrodes. CIS gets its name from the continu- hehg’“2017)' CIS is Shh “hid ‘°d“_" and remains as the huh-
ous (and fixed rate) sampling of the mapped envelope signals mph ghld hahdhrd hghhh which hewer  Potehhhhy
by interleaved Pulses across the Channels‘ beneficial strategies are compared. Much more information
about CIS and the strategies that followed it is presented in
The overall approach is to utilize the perceptual space fully recent reviews (Wilson and Dorman, 2008, 2012; Zeng et al.,
and to present the information in ways that will preserve the 2008). Additionally, most of the prior strategies are described
independence of the channels and minimize perceptual dis- in Tyler et al. (1989) and Wilson (2004, 2015).
tortions as much as possible. Of course, in retrospect, this
approach also allowed the brain to work its magic. Once we parfonnanca af unilateral
designers “got out of the way” in presenting a relatively clear auchlaai. Implanta
and “nfeneied Sigiiai iaiiiei ‘iiaii doing "‘Y‘iiii"S more '3’ The performance for speech reception in otherwise quiet
more complicated, the brain could take over and do the rest. coriditioris is seen in Figure 3, which shows results from
Some of the first results from comparisons of CIS with the best ‘W0 iaige 5‘“die5 C°i"d“C‘9d "‘PPi’°xiim“eiY i5 Yea“ "‘P“i"- in
strategy iri clinical use at the time are Presented iri Figure 2_ Figure 3, the blue circles and lines show the results from a
Results from four tests are shown and range in difficulty from 5‘“dY C°i"d“C‘ed i’Y i'ieii'i"5 e‘ 31- (1997) in the mid'19905 and
easy to extremely diflicult for speech Presented in otherwise the green circles and lines show the results from tests with
quiet conditions. Each subject had had at least one year ofdai- patients who were implanted from 2011 to mid-2014 (data
ly experience with their cliriicel device arid Processing strategic courtesy of Rene Gifford at the Vanderbilt University Medi-
the luereidw Cl and the “compressed erielog" (CA) strategic re_ cal Center [VUMC]). For both studies, the subjects were
spectively, but no more than several hours of experience with P°5‘iii"g““iiY (“her ‘he aeqiii-5i‘i°i" °fi“iig““‘S9 ii‘ Ciiiidii°°d
Cls before the tests_ (The CA strategy Presented compressed with normal or nearly normal hearing) deafened adults, and
analog signals simultaneously to each of four ihtrecochleer the tests included recognition of sentences and monosyllabic
electrodes erid is described further in wilsorh 2015) -l-he words. The words were comparable in difficulty between the
green hues in Figure 2 show the results for at first set of suh_ studies, but the low-context Arizona Biomedical (AzBio)
iects selected for high Peiformehce with the CA strategy (date sentences used in the VUMC study were more diflicult than
from Wilson et al., 1991), which was fully representative of the ‘he iiigh'C°ii‘e"‘ H°Chi'i"“h"SCh“i‘Z'M°5e1’ (HSM) 5eh‘e1'|Ce5
best performances that had been obtained with Cls as of the “Ed ii‘ ‘he Helms e‘ 31- (1997) 5‘“dY- Me“‘5“i’e5 were imide 3‘
time oftestihg -l-he lilue hues in Figure 2 show the results for the indicated times after the initial fitting of the device, and
a second set of subjects who were selected for their more typi- ‘he means and 5‘“hd“i’d error of ‘he meal“ (SEMS) Of ‘he
cal levels of performance (data from Wilson et al., 1992). The 550795 are 5h°Wh ii‘ Fi§‘“’° 3- Dem-is aimii‘ ‘he 5“i’jeC‘5 "id
scores for all tests and subjects demonstrated an immediate ‘e5‘5 are Pi’e5ei"‘ed in Wilson e‘ 31- (2015)-
ahd highly _hghihCh-it hhpmvemeht whh CIS Compared whh The results demonstrate (1) high levels of speech reception
the hhemhhve hrhegy‘ for high-context sentences; (2) lower levels for low-context
Not surprisingly, the subjects were thrilled along with us by sentences; (3) improvements in the scores for all tests with
this outcome. One of the subjects said, for example, “Now increasing time out to 3-12 months depending on the test;
you’ve got it!” and another slapped the table in front of him (4) a complete overlapping of scores at every common test
as 1 AI:uuII:l:I Tbday 1 Spring 2019

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