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Recommended: Essays about cochlear implants

Auditory prostheses have been treating hearing loss for decades, with the cochlear implant (CI) being able to provide sufficient temporal and spectral cues required for speech understanding (Kral and O'Donoghue 2010; Shannon et al. 1995; Zeng 2004). For people without a functional auditory nerve or an implantable cochlea, central prostheses have been implanted in the brainstem since 1979. Unfortunately, the performance of the auditory brainstem implant (ABI) has generally been less successful than the CI, particularly for patients with neurofibromatosis type II (NF2), one of the key target populations for the implant (Colletti et al. 2009; Lim et al. 2009; Schwartz et al. 2008). While some ABI patients have shown performance levels approaching that of CI patients (Colletti et al. 2012; Sennaroglu et al. 2011), continued research into central auditory implants needs to be performed in order to improve hearing perception for the majority of patients who cannot benefit from a CI.
As an alternative approach to the ABI, particularly for the NF2 population, deaf patients have been implanted with a new auditory midbrain implant (AMI) consisting of a single-shank array (20 sites) designed for stimulation along the tonotopic gradient of the central nucleus of the inferior colliculus (ICC) (Lim et al. 2009; Lim et al. 2007). While AMI stimulation can activate frequency-specific neurons and transmit spectral cues to higher auditory centers, it appears to exhibit limited temporal coding abilities (Lenarz et al. 2006; Lim and Anderson 2006; Lim et al. 2013; Lim et al. 2008; McKay et al. 2013).
Calixto et al. (2012) investigated this limited performance of the AMI by stimulating the ICC of guinea pigs with the AMI array and recording the evok...

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...tory forebrain connections and circuits. In: The Auditory Cortex, edited by Winer JA, and Schreiner CE. New York: Springer Science+Business Media, Inc., 2010.
Winer JA. Structure of layer II in cat primary auditory cortex (AI). J Comp Neurol 238: 10-37, 1985.
Winer JA, Miller LM, Lee CC, and Schreiner CE. Auditory thalamocortical transformation: structure and function. Trends Neurosci 28: 255-263, 2005.
Winer JA, and Prieto JJ. Layer V in cat primary auditory cortex (AI): cellular architecture and identification of projection neurons. J Comp Neurol 434: 379-412, 2001.
Zeng FG. Trends in cochlear implants. Trends in amplification 8: 1-34, 2004.
Zurita P, Villa AE, de Ribaupierre Y, de Ribaupierre F, and Rouiller EM. Changes of single unit activity in the cat's auditory thalamus and cortex associated to different anesthetic conditions. Neurosci Res 19: 303-316, 1994.

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