Conveying low frequency information through analog electrical stimulation in cochlear implants

Speech intelligibility in noisy environments and music perception are very limited using cochlear implants (CIs). One possible reason that explains these limitations is the poor pitch perception obtained through electrical stimulation. Research in the field of combined electric and acoustic hearing (EAS) has shown that low frequency information even below 300 Hz perceived through the residual acoustic hearing can improve speech perception in adverse listening situations. This paper investigates whether cochlear CI users can also make use of very low frequencies through electrical stimulation alone. A new strategy called extended low frequency HiRes (ELFHiRes) has been implemented in a research environment provided by Advanced Bionics. The new strategy uses analog stimulation to transmit the low frequencies. In a pilot study it was found that the pitch perceived as well as its quality were similar using both pulsatile and anlog stimulation. First tests in speech perception do not show any advantage for the ELFHiRes strategy, however there is potential for future developments to improve speech intelligibility by better transmission of low frequencies through a CI.