Auditory Midbrain Implant

Lenarz, Minoo; Lim, Hubert H.; Lenarz, Thomas; Reich, Uta; Marquardt, Nadine; Klingberg, Marc N.; Paasche, Gerrit; Reuter, G.; Stan, Alexandru C.

doi:10.1097/mao.0b013e318159e74f

Cited by 33 publications

(11 citation statements)

References 36 publications

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“…The development of the AMI was based upon hypotheses that poor outcomes with the auditory brainstem implant (ABI) were related to tumor or surgical damage to important cells in the cochlear nucleus (CN) (Colletti 2006), and the theoretical ability to access frequency layers in the IC. Early studies with the first recipients of the AMI device (Lenarz et al 2006a,b, 2007; Lim et al 2007, 2008a,b, 2009) showed that patients gained benefits for speech understanding, when combined with lip-reading, that were similar to those generally observed for patients using ABIs for stimulation of the CN (McCreery 2008; Schwartz et al 2008; Colletti et al 2009). Although these outcomes are poorer than expected for CI users, it is possible that performance could be improved with development of more appropriate electrode array designs and processing strategies that are optimized for stimulation of the IC.…”

Section: Introductionmentioning

confidence: 74%

Temporal Processing in the Auditory System

McKay

Lim

Lenarz

2012

JARO

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Central auditory processing in humans was investigated by comparing the perceptual effects of temporal parameters of electrical stimulation in auditory midbrain implant (AMI) and cochlear implant (CI) users. Four experiments were conducted to measure the following: effect of interpulse intervals on detection thresholds and loudness; temporal modulation transfer functions (TMTFs); effect of duration on detection thresholds; and forward masking decay. The CI data were consistent with a phenomenological model that based detection or loudness decisions on the output of a sliding temporal integration window, the input to which was the hypothetical auditory nerve response to each stimulus pulse. To predict the AMI data, the model required changes to both the neural response input (i.e., midbrain activity to AMI stimuli, compared to auditory nerve activity to CI stimuli) and the shape of the integration window. AMI data were consistent with a neural response that decreased more steeply compared to CI stimulation as the pulse rate increased or interpulse interval decreased. For one AMI subject, the data were consistent with a significant adaptation of the neural response for rates above 200 Hz. The AMI model required an integration window that was significantly wider (i.e., decreased temporal resolution) than that for CI data, the latter being well fit using the same integration window shape as derived from normal-hearing data. These models provide a useful way to conceptualize how stimulation of central auditory structures differs from stimulation of the auditory nerve and to better understand why AMI users have difficulty processing temporal cues important for speech understanding.

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Section: Introductionmentioning

confidence: 74%

Temporal Processing in the Auditory System

McKay

Lim

Lenarz

2012

JARO

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“…In humans, the inferior colliculus is surgically accessible (Kaku et al 1999;Simmons et al 1964). Similar to the ABI surgery in NF2 patients, AMI implantation can be performed after tumor removal with minimal added risk using a lateral supracerebellar infratentorial approach performed through a lateral suboccipital craniotomy (semisitting position) (Lenarz et al 2003(Lenarz et al , 2004. Using this approach, an AMI array can be inserted along the tonotopic gradient of the ICC.…”

Section: Introductionmentioning

confidence: 99%

Antidromic Activation Reveals Tonotopically Organized Projections From Primary Auditory Cortex to the Central Nucleus of the Inferior Colliculus in Guinea Pig

Lim¹,

Anderson²

2007

Journal of Neurophysiology

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. Auditory cortical responses to electrical stimulation of the inferior colliculus: implications for an auditory midbrain implant. J Neurophysiol 96: 975-988, 2006. First published May 24, 2006 doi:10.1152/jn.01112.2005. The success and limitations of cochlear implants (CIs) along with recent advances in deep brain stimulation and neural engineering have motivated the development of a central auditory prosthesis. In this study, we investigated the effects of electrical stimulation of the inferior colliculus central nucleus (ICC) on primary auditory cortex (A1) activity to determine the potential benefits of an auditory midbrain implant (AMI). We recorded multiunit activity in A1 of ketamine-anesthetized guinea pigs in response to single-pulse (200 s/phase) monopolar stimulation of the ICC using multisite silicon-substrate probes. We then compared measures of threshold, dynamic range, and tonotopic spread of activation for ICC stimulation with that of published data for CI stimulation. Our results showed that compared with cochlear stimulation, ICC stimulation achieved: 1) thresholds about 8 dB lower; 2) dynamic ranges Ն4 dB greater; and 3) more localized, frequency-specific activation, even though frequency specificity was partially lost at higher stimulus levels for low-frequency ICC regions. Our results also showed that stimulation of rostral ICC regions elicited lower thresholds but with greater activation spread along the tonotopic gradient of A1 than did stimulation of more caudal regions. These results suggest that an AMI may improve frequency and level coding with lower energy requirements compared with CIs. However, a trade-off between lower perceptual thresholds and better frequency discrimination may exist that depends on location of stimulation along the caudorostral dimension of the ICC. Overall, this study provides the foundation for future AMI research and development.

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“…Prior to the clinical trial, these researchers and clinicians had shown that ICC stimulation achieves low threshold and frequency-specific auditory activation in animals that was better or comparable to CI stimulation (Lenarz et al, 2006a; Lim et al, 2006). They also showed in a cat model that long-term implantation and stimulation of the AMI device was safe without any major side effects and induced minimal tissue damage that was comparable to other clinically approved brain implants (Lenarz et al, 2007). In terms of sound coding, multiple studies have shown that ICC neurons are capable of following the temporal modulations of acoustic stimuli up to or beyond 100 Hz and the ICC has a well-defined tonotopic organization (Geniec et al, 1971; Joris et al, 2004; Langner et al, 2002; Oliver, 2005; Rees et al, 2005; Schreiner et al, 1997).…”

Section: Findings From the First Clinical Trialmentioning

confidence: 79%

Auditory midbrain implant: Research and development towards a second clinical trial

Lim¹,

Lenarz

2015

Hearing Research

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The cochlear implant is considered one of the most successful neural prostheses to date, which was made possible by visionaries who continued to develop the cochlear implant through multiple technological and clinical challenges. However, patients without a functional auditory nerve or implantable cochlea cannot benefit from a cochlear implant. The focus of the paper is to review the development and translation of a new type of central auditory prosthesis for this group of patients, which is known as the auditory midbrain implant (AMI) and is designed for electrical stimulation within the inferior colliculus. The rationale and results for the first AMI clinical study using a multi-site single-shank array will be presented initially. Although the AMI has achieved encouraging results in terms of safety and improvements in lip-reading capabilities and environmental awareness, it has not yet provided sufficient speech perception. Animal and human data will then be presented to show that a two-shank AMI array can potentially improve hearing performance by targeting specific neurons of the inferior colliculus. Modifications to the AMI array design, stimulation strategy, and surgical approach have been made that are expected to improve hearing performance in the patients implanted with a two-shank array in an upcoming clinical trial funded by the National Institutes of Health. Positive outcomes from this clinical trial will motivate new efforts and developments toward improving central auditory prostheses for those who cannot sufficiently benefit from cochlear implants.

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Auditory Midbrain Implant

Cited by 33 publications

References 36 publications

Temporal Processing in the Auditory System

Temporal Processing in the Auditory System

Antidromic Activation Reveals Tonotopically Organized Projections From Primary Auditory Cortex to the Central Nucleus of the Inferior Colliculus in Guinea Pig

Auditory midbrain implant: Research and development towards a second clinical trial

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