Cochlear implants (CIs) are a device used to treat sensorineural hearing loss. The CI works by bypassing the hair cells of the cochlea and directly stimulating the auditory nerve. Most CI users tend to have excellent speech recognition in quiet and can even talk on the telephone. However, CI users tend to struggle with understanding speech in more difficult listening environments, such as in noisy restaurants. ❧ It is thought that CI users’ difficulty with speech perception in noise is due to channel interactions between stimulating electrodes – due to broad current spread, adjacent electrodes may stimulate overlapping populations of neurons; those electrodes therefore do not convey independent channels of information. Therefore, reducing current spread from a stimulating electrode may narrow the population of activated neurons, and consequently, reduce channel interactions and increase the number of independent channels of information transmitted by the CI. That is, reducing current spread could improve CI users’ speech perception ability in noise. ❧ The primary goal of this dissertation was to investigate current focusing as a method of reducing channel interactions in CIs. Current focusing was studied in both psychophysical and speech perception experiments. The results show that current focusing can reduce spread of excitation in the cochlea, improve signal discrimination, and improve speech perception in noise.
The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given.