Electrical Stimulation of the Midbrain for Hearing Restoration: Insight into the Functional Organization of the Human Central Auditory System

Electrical Stimulation of the Midbrain for Hearing Restoration: Insight into the Functional Organization of the Human Central Auditory System Lim Lenarz Joseph Battmer Samii Samii Patrick Lenarz

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Electrical Stimulation of the Midbrain for Hearing Restoration: Insight into the Functional Organization of the Human Central Auditory System 2007 Journal of Neuroscience 10.1523/jneurosci.3123-07.2007 Lim2007-electrical-stimulation-of-the-midbrain-for-h Lim2007-electrical-stimulation-of-the-midbrain-for-h.txt, the project's staged copy ce9a0a3ff89ff9c79741d1f67f475ea2a6d8d3ec not-redistributable neuroscience

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0 spans located by searching the stored text for the quote's exact words, allowing any whitespace between them whether a penetrating electrode array in the inferior colliculus can restore useful hearing, and what stimulating different midbrain regions reveals about how the human auditory system is organised Quotation withheld because this record is not cleared for redistribution. whether stimulating along the tonotopic gradient of the human central nucleus produces ordered pitch percepts, as it does along the cochlea Quotation withheld because this record is not cleared for redistribution. the implant is safe and gives loudness, temporal and directional percepts and speech benefit comparable with the brainstem implant, but the ordered pitch the whole rationale predicted did not appear Quotation withheld because this record is not cleared for redistribution. method Quotation withheld because this record is not cleared for redistribution. auditory midbrain implant for hearing restoration Quotation withheld because this record is not cleared for redistribution. system-or-tool-building system-or-tool-building Quotation withheld because this record is not cleared for redistribution. mechanisms Sustained stimulation rates and patterns overdrive adaptation-prone neurons in the dorsal IC, raising the current needed over time Quotation withheld because this record is not cleared for redistribution. mechanisms Neurons higher in the auditory pathway lose the ability to phase-lock, and that loss of temporal synchronization is traded for a spatial, spike-rate-based code of temporal features, which is why the midbrain follows lower rates than the fibre pathway below it Quotation withheld because this record is not cleared for redistribution. mechanisms Ipsilaterally and contralaterally driven brainstem projections stay segregated as they ascend into the IC, so which region the array sits in determines the perceived direction of the sound Quotation withheld because this record is not cleared for redistribution. mechanisms The ipsilaterally excited fibre population is dominated by low-frequency-tuned neurons, so stimulating it yields low-pitch percepts Quotation withheld because this record is not cleared for redistribution. mechanisms An array lying outside the IC acts as a surface electrode, so current must travel further to reach neurons and activation levels rise Quotation withheld because this record is not cleared for redistribution. the central nucleus is chosen because it receives almost all ascending brainstem pathways, so it should give access to a more complete set of inputs than the cochlea or cochlear nucleus Quotation withheld because this record is not cleared for redistribution. the limited performance of tumour patients with the brainstem implant is attributed to tumour damage in the cochlear nucleus, which is the argument for moving upstream Quotation withheld because this record is not cleared for redistribution. segregated monaural and binaural pathways ascending into the midbrain are proposed to explain why each patient perceived only one direction Quotation withheld because this record is not cleared for redistribution. ipsilaterally driven pathways carry mostly low frequencies, which is offered as the reason one patient heard only low pitches Quotation withheld because this record is not cleared for redistribution. temporal synchrony degrades at successive stages of the pathway, so a site below the colliculus should follow faster rates - which is what happened Quotation withheld because this record is not cleared for redistribution. long shallow loudness tails are read as a non-homogeneous mix of excitatory and inhibitory neurons along the isofrequency dimension Quotation withheld because this record is not cleared for redistribution. rising activation levels in one patient are hypothesised to be neurons in the dorsal region being overdriven by the stimulation pattern status: the paper's own words: is not clear Quotation withheld because this record is not cleared for redistribution. Pitch data exist for only one patient whose array lay along the intended tonotopic gradient, so no definitive claim about human midbrain tonotopy can be made what this limits: any tonotopy claim about the human midbrain: BECAUSE WE ONLY HAVE PITCH DATA FOR ONE PATIENT WHOSE ARRAY IS SUPPOSEDLY ALIGNED ALONG THE TONOTOPIC GRADIENT OF THE ICC, WE CANNOT MAKE ANY DEFINITIVE CLAIMS Quotation withheld because this record is not cleared for redistribution. The standard temporal-resolution measures could not be run because of software limits, so a substitute continuity-rate judgement was used instead what this limits: the temporal-resolution results: THE COMMON TESTS ... ARE AMPLITUDE MODULATION DETECTION AND GAP DETECTION, WE COULD NOT PERFORM THESE TESTS WITH OUR SOFTWARE Quotation withheld because this record is not cleared for redistribution. One of the three patients produced no usable pitch-ordering data at all what this limits: the pitch-ordering data: NO RELIABLE PITCH ORDERING RESULTS WERE OBTAINED FOR AMI-1 WHO HAD DIFFICULTIES PERFORMING THESE TESTS - one of three patients Quotation withheld because this record is not cleared for redistribution. pitch data exist for only one patient whose array is aligned along the intended gradient, so no definitive claim about human midbrain tonotopy is made duplicate of: limitations[0] · what this limits: the same scope as limitations[0] - one aligned array, no definitive tonotopy claim Quotation withheld because this record is not cleared for redistribution. the standard tests for temporal resolution could not be run because the software would not do them, so a different measure was substituted what this limits: the same scope as limitations[1], with the substitute: INSTEAD, WE STIMULATED A GIVEN SITE WITH CONtinuous trains Quotation withheld because this record is not cleared for redistribution. loudness balancing across the different sites and pulse rates was difficult because of limitations in the testing software, and performance on this test was argued to depend on whether the patient could clearly hear the sound rather than on slight variations in loudness what this limits: every across-site and across-rate comparison: LOUDNESS BALANCING WAS DIFFICULT TO PERFORM ACROSS THE DIFFERENT SITES AND PULSE RATES ATTRIBUTABLE TO LIMITATIONS IN OUR TESTING SOFTWARE Quotation withheld because this record is not cleared for redistribution. imaging after implantation was impossible because the array distorts the scan, so location comes from a fused reconstruction what this limits: every anatomical claim about electrode position: ACCURATE MRI IMAGES OF THE MIDBRAIN COULD NOT BE OBTAINED AFTER AMI IMPLANTATION BECAUSE OF THE DISTORTION CAUSED BY THE ELECTRODE ARRAY Quotation withheld because this record is not cleared for redistribution. all three patients had tinnitus throughout and were asked to ignore it while judging the stimulus what this limits: every percept the patients reported: ALL PATIENTS HAVE TINNITUS, WHICH WAS PRESENT BEFORE AND AFTER SURGERY, and AMI STIMULATION COULD ALTER THEIR TINNITUS Quotation withheld because this record is not cleared for redistribution. one patient's activation levels rose until they reached the compliance voltage of the stimulator and the device had to be switched off for 48 days what this limits: the stimulation levels reported for that patient: they rose until they reached THE COMPLIANCE VOLTAGE OF THE STIMULATOR and the device could no longer deliver more Quotation withheld because this record is not cleared for redistribution. the work was supported by the company that makes the device, and one author is employed there what this limits: the independence of the evaluation, not its methods: THIS WORK WAS SUPPORTED BY COCHLEAR LIMITED, the manufacturer of the device under test Quotation withheld because this record is not cleared for redistribution. the tonotopic laminar organisation of the central nucleus, imported as the design principle for a human electrode array Quotation withheld because this record is not cleared for redistribution. pulse rates and pulse widths fixed at the point where greater total charge stopped lowering thresholds and shorter pulse widths and slower pulse rates raised them Quotation withheld because this record is not cleared for redistribution. fixed and stained midbrain sections, used as the reference against which each patient's fused scan is read Quotation withheld because this record is not cleared for redistribution. the patient scales the perceived pitch of each stimulated site on an environmental scale, selecting the environmental sound that most resembles it Quotation withheld because this record is not cleared for redistribution. the CT scans taken AT LEAST SIX WEEKS after implantation rather than immediately eliminates: post-surgical distortion of the brain as the apparent electrode position - imaging a freshly operated brain measures the swelling as much as the anatomy · outcome (stated by the tagger, no quotation): held Quotation withheld because this record is not cleared for redistribution. lateral lemniscus lateral lemniscus Quotation withheld because this record is not cleared for redistribution. loudness loudness Quotation withheld because this record is not cleared for redistribution. current level current level Quotation withheld because this record is not cleared for redistribution. temporal resolution temporal resolution Quotation withheld because this record is not cleared for redistribution. THE PREDICTION THAT JUSTIFIED THE WHOLE TARGET FAILED, AND THE PAPER SAYS SO IN ONE LINE: ordered pitch along the tonotopic gradient was hypothesised from the animal work, and 'However, this has not yet been the case.' Quotation withheld because this record is not cleared for redistribution. and the failure is not noise - stimulation of all sites in all three patients gave low pitches, and rates up to 2400 pulses per second produced no obvious rise over 250 Quotation withheld because this record is not cleared for redistribution. the paper then lists four rival explanations as open questions - the stimulus form, plastic loss of high frequency representation after six years of deafness, position along the isofrequency dimension or passing fibres, and species differences - and chooses none Quotation withheld because this record is not cleared for redistribution. AND REFUSES TO GENERALISE FROM ITS ONE INFORMATIVE PATIENT: with pitch data from a single correctly aligned array, no definitive claim about human midbrain tonotopy is made at all Quotation withheld because this record is not cleared for redistribution. THE ACCIDENT IS THE INDEPENDENT VARIABLE: the three arrays landed in three different places, and that unintended variation is what turns a safety trial into a map of the human auditory midbrain Quotation withheld because this record is not cleared for redistribution. the intended placement is stated separately from what happened, so the record contains both the plan and the deviation Quotation withheld because this record is not cleared for redistribution. THE ADVERSE EVENTS ARE MEASUREMENTS: dizziness and chest sensations, paresthesia in the face and upper body, paresthesia in the thigh and leg - each one locates the deep sites in a different non-auditory structure Quotation withheld because this record is not cleared for redistribution. and every percept here is a patient's spoken report, obtained while they were asked to ignore a tinnitus that all three had before and after surgery Quotation withheld because this record is not cleared for redistribution. THE SAME RESULT SUPPORTS TWO INCOMPATIBLE READINGS AND BOTH ARE KEPT: faster rate following in the patient implanted below the colliculus fits the degradation-along-the-pathway account, or the other two sites simply sit in regions of poor temporal resolution Quotation withheld because this record is not cleared for redistribution. THE COMPARISON GROUP IS MATCHED ON THE RATER, NOT JUST THE PROTOCOL: eleven brainstem implant patients tested in the same clinic under the same protocols, by the same speech therapist who tested these three Quotation withheld because this record is not cleared for redistribution. claim_type: method a second reading reaching the same value. Recorded: method — note: a second reading reaching the same value from a different sentence. Not applied - a person decides. Quotation withheld because this record is not cleared for redistribution. method: three patients implanted during tumour removal, array location reconstructed from fused imaging against fixed anatomical sections, then psychophysics per site - threshold, comfortable level, loudness growth, pitch ranking and scaling, rate discrimination, perceived direction - plus speech tests at six months a second reading DIFFERING from the recorded value. Recorded: system-or-tool-building — note: a second reading, verbatim-verified, disagreeing with the value on the record. Not applied - a person decides. Quotation withheld because this record is not cleared for redistribution. phenomenon: electrically evoked hearing: percepts of loudness, pitch, rate and direction produced by stimulating single sites in the human midbrain a second reading DIFFERING from the recorded value. Recorded: auditory midbrain implant for hearing restoration — note: a second reading, verbatim-verified, disagreeing with the value on the record. Not applied - a person decides. Quotation withheld because this record is not cleared for redistribution. builds-on → Lim and Anderson (2003, 2006); Lenarz et al. (2006a) animal studies of inferior colliculus stimulation Quotation withheld because this record is not cleared for redistribution. builds-on → the authors' own guinea pig work showing lower thresholds and more frequency-specific cortical activation from central nucleus stimulation than from the cochlea Quotation withheld because this record is not cleared for redistribution. contradicts → the animal-derived prediction that stimulating along the tonotopic gradient would produce ordered pitch percepts Quotation withheld because this record is not cleared for redistribution. qualifies → its own animal-derived expectation of lower thresholds, since the measured thresholds and dynamic ranges match the cochlear implant rather than beating it differs in: THE AXIS IS THE COMPARISON THE PREDICTION IS MEASURED AGAINST. 'AMI sites are in direct contact with surrounding neurons, UNLIKE CI SITES; thus, thresholds should be lower as shown in animal studies. However, AMI thresholds ... are 6-12 nC ..., and dynamic ranges are 7-9 dB, which are similar to those of the CI.' The animal-derived expectation is not refuted in animals; it fails to transfer to the human implant. Quotation withheld because this record is not cleared for redistribution. supports → the animal-derived account of segregated monaural and binaural pathways in the central auditory system Quotation withheld because this record is not cleared for redistribution. supports → the hypothesis that temporal synchronisation degrades at successive stations and is traded for a spatial rate code Quotation withheld because this record is not cleared for redistribution. extends → the observation that non-tumour brainstem implant patients do far better, which located the problem in tumour damage rather than in the site differs in: THE AXIS IS WHETHER THE PATIENT HAD A TUMOUR. 'Recently, the ABI has been implanted in nontumor patients who would not benefit from CIs. Surprisingly, some of these patients achieve performance levels comparable with CI patients, suggesting that the limited per[formance] [in tumour patients has another cause].' The poor outcomes of the original population are reattributed to the tumour rather than to the implant site - so a device evaluated only in tumour patients was being judged on a confound. Quotation withheld because this record is not cleared for redistribution. pulse rate —distinct-from→ pitch pulse rate pitch strength of the relation: 1 · note: and the obvious escape route is closed in a parenthesis - rates to 2400 per second gave no obvious rise in pitch over 250 Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span asks what stimuli elicit higher pitch than pulse rate alone; distinct-from is loose. Quotation withheld because this record is not cleared for redistribution. deaf —causes→ plastic deaf plastic strength of the relation: 0.6 — the record marks this weak · note: one of four rival explanations offered as open questions and none of them chosen Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span is a question about plastic reorganization after deafness. Quotation withheld because this record is not cleared for redistribution. contralateral —distinct-from→ ipsilateral contralateral ipsilateral strength of the relation: 1 · note: and the percept does not vary across the 1.7 to 1.9 mm the active sites span, which is the argument for segregated ascending pathways Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span reports one directional percept per patient; distinct-from is loose. Quotation withheld because this record is not cleared for redistribution. monaural —distinct-from→ binaural monaural binaural strength of the relation: 1 Quotation withheld because this record is not cleared for redistribution. ipsilateral —causes→ pitch ipsilateral pitch strength of the relation: 0.7 · note: and the same anatomy is then used to explain that patient's low pitches, so one placement accounts for two separate anomalies Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span explains low pitches by ipsilateral low-frequency pathways; causes 'pitch' is terse. Quotation withheld because this record is not cleared for redistribution. temporal resolution —operationalised-as→ pulse rate temporal resolution pulse rate strength of the relation: 1 · note: THE MEASURE IS A SUBSTITUTE: modulation and gap detection could not be run because the software would not do them, so the rate at which pulses fuse into a continuous sound is used instead Quotation withheld because this record is not cleared for redistribution. threshold —operationalised-as→ current level threshold current level strength of the relation: 1 · note: found by raising the current until a sound is heard and lowering it until it is not, repeated until the patient is consistent Audit 2026-09-28: DOUBTFUL - read against its span and kept, but thresholds were measured in current level; operationalised-as is loose. Quotation withheld because this record is not cleared for redistribution. inferior colliculus —contrasted-with→ cochlear nucleus inferior colliculus cochlear nucleus strength of the relation: 1 · note: the target is chosen because nearly all ascending pathways converge there, so it should give access to a more complete set of inputs Quotation withheld because this record is not cleared for redistribution. midbrain —contrasted-with→ cochlear nucleus midbrain cochlear nucleus strength of the relation: 1 · note: the new target against the existing one - the whole clinical claim is a comparison with the alternative these patients would otherwise receive Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span contrasts the midbrain implant with the brainstem implant only by implication. Quotation withheld because this record is not cleared for redistribution. mean mean Quotation withheld because this record is not cleared for redistribution. standard deviation standard deviation Quotation withheld because this record is not cleared for redistribution. averaging of repeated measurements averaging of repeated measurements Quotation withheld because this record is not cleared for redistribution. mean ± SD mean ± SD Quotation withheld because this record is not cleared for redistribution. chance level chance level Quotation withheld because this record is not cleared for redistribution. Three NF2 patients were implanted with a penetrating auditory midbrain implant and the device proved safe, with the array showing minimal movement over time. Quotation withheld because this record is not cleared for redistribution. Midbrain stimulation delivered usable loudness, pitch, temporal and directional percepts. Quotation withheld because this record is not cleared for redistribution. All three patients gained lip-reading enhancement and environmental sound awareness, with speech perception on a par with NF2 auditory brainstem implant patients. Quotation withheld because this record is not cleared for redistribution. Contrary to the animal-derived prediction, stimulating successive depths along the ICC tonotopic gradient did not produce an ordered pitch shift, and every site in every patient sounded predominantly low-pitched. Quotation withheld because this record is not cleared for redistribution. With IC stimulation, patients perceived a continuous stimulus above 80 pps, mostly around 50 pps, a resolution of about 20 ms. Quotation withheld because this record is not cleared for redistribution. The patient implanted at the lateral lemniscus rather than in the IC still heard buzzing up to 220 pps, about three times the rate the IC-implanted patients could follow. Quotation withheld because this record is not cleared for redistribution. Perceived sound direction was fixed within each patient but differed by implant location: ipsilateral for the lateral-lemniscus placement and contralateral for the dorsomedial ICC placement. Quotation withheld because this record is not cleared for redistribution. Despite electrodes sitting directly among midbrain neurons, thresholds (6-12 nC) and dynamic ranges (7-9 dB) were no better than those of a cochlear implant. Quotation withheld because this record is not cleared for redistribution. Loudness grew monotonically with current level in all three patients, so level cues can be coded systematically from the midbrain. Quotation withheld because this record is not cleared for redistribution. In the patient implanted in the dorsal IC, threshold and comfortable levels drifted upward until they hit the stimulator's compliance voltage. Quotation withheld because this record is not cleared for redistribution. With the implant alone, two patients identified 23% and 40% of vowels against a 10% chance level. Quotation withheld because this record is not cleared for redistribution. Patients detected all instruments but could identify only the low-frequency ones. Quotation withheld because this record is not cleared for redistribution. THE FOUNDING PREDICTION FAILED: ordered pitch along the tonotopic gradient was hypothesised from animal work, and did not appear Quotation withheld because this record is not cleared for redistribution. stimulation of nearly all sites in all three patients gave low pitch percepts, below a man's voice Quotation withheld because this record is not cleared for redistribution. and pulse rates up to 2400 per second produced no obvious rise in pitch over 250 Quotation withheld because this record is not cleared for redistribution. pitch scores varied across days and even across different times on the same day, variability much greater than what is typically observed for CI patients Quotation withheld because this record is not cleared for redistribution. for the one correctly aligned array the deviation from the predicted order is left unexplained Quotation withheld because this record is not cleared for redistribution. FOUR RIVAL EXPLANATIONS ARE LISTED AS OPEN QUESTIONS and none is chosen: stimulus form, plastic loss of high frequency representation after six years of deafness, position along the isofrequency dimension or passing fibres, and species differences Quotation withheld because this record is not cleared for redistribution. AND NO DEFINITIVE CLAIM IS MADE about human midbrain tonotopy, because only one patient's array was aligned along the gradient Quotation withheld because this record is not cleared for redistribution. AMI thresholds and dynamic ranges are similar to those of the CI, though the sites are in direct contact with surrounding neurons and thresholds should be lower Quotation withheld because this record is not cleared for redistribution. and the animal explanation offered for that is questioned in the same paragraph Quotation withheld because this record is not cleared for redistribution. all patients gave monotonically increasing loudness with current, so level cues are transmissible Quotation withheld because this record is not cleared for redistribution. one patient showed long shallow loudness tails, read as a non-homogeneous mix of excitatory and inhibitory neurons along the lamina Quotation withheld because this record is not cleared for redistribution. ONE DIRECTION PER PATIENT: binaural throughout for the dorsal placement, ipsilateral throughout for the lemniscal one, contralateral throughout for the central nucleus one Quotation withheld because this record is not cleared for redistribution. and the direction did not change across the 1.7 to 1.9 mm the active sites span Quotation withheld because this record is not cleared for redistribution. which is taken as human support for segregated monaural and binaural pathways derived from animal work Quotation withheld because this record is not cleared for redistribution. the ipsilateral percepts are attributed to medial superior olive fibres, using the enlarged medial and reduced lateral olive of humans Quotation withheld because this record is not cleared for redistribution. and the same placement is used to explain that patient's low pitches, since ipsilaterally driven pathways carry mostly low frequencies Quotation withheld because this record is not cleared for redistribution. pulses fused into a continuous sound above 80 per second and usually near 50, a resolution of about 20 ms, against 250 to 300 for cochlear stimulation Quotation withheld because this record is not cleared for redistribution. the patient implanted below the colliculus followed about three times the rate of the other two Quotation withheld because this record is not cleared for redistribution. TWO INCOMPATIBLE READINGS OF THAT ARE BOTH KEPT: synchrony degrading up the pathway, or the other two arrays simply sitting in regions of poor temporal resolution Quotation withheld because this record is not cleared for redistribution. THE ACCIDENT IS THE INDEPENDENT VARIABLE: three arrays landed in three different places, and that variation is what makes the trial a map of the auditory midbrain Quotation withheld because this record is not cleared for redistribution. the intention was to insert the array 45 degrees off the sagittal plane and into the ICC to position the sites within different anatomical layers, which supposedly correspond to different frequency laminas Quotation withheld because this record is not cleared for redistribution. deep sites in the first patient caused dizziness and chest and facial sensations and were switched off Quotation withheld because this record is not cleared for redistribution. the second array sat below the colliculus near the lateral lemniscus and every site mixed auditory with cold and paresthetic sensations Quotation withheld because this record is not cleared for redistribution. the third array reached the intended central nucleus, with deep sites producing paresthesia in the contralateral thigh, leg and foot Quotation withheld because this record is not cleared for redistribution. no pain or adverse functional effect resulted, and uncomfortable percepts were removed by switching sites off Quotation withheld because this record is not cleared for redistribution. the auditory sensations and side effects associated with each site have generally remained stable, indicating minimal movement of the implant over time Quotation withheld because this record is not cleared for redistribution. but the levels for AMI-1 continued to rise, reaching the compliance voltage of the stimulator, so the processor was turned off for 48 d, after which the activation levels decreased dramatically but not completely to the initial values Quotation withheld because this record is not cleared for redistribution. speech benefit at six months was comparable with eleven brainstem implant patients tested in the same clinic by the same speech therapist Quotation withheld because this record is not cleared for redistribution. and the brainstem group's own scores span a wide range, with six of eleven getting no consonant benefit at all Quotation withheld because this record is not cleared for redistribution. two patients scored above chance on vowels with the implant alone Quotation withheld because this record is not cleared for redistribution. both tested patients detected every instrument but could identify only the low frequency ones Quotation withheld because this record is not cleared for redistribution. and the reported gains are in everyday awareness - traffic, birds, doors, the telephone - and in one patient's control of her own voice Quotation withheld because this record is not cleared for redistribution. THE MEASURE IS A SUBSTITUTE: modulation and gap detection could not be run because the software would not do them Quotation withheld because this record is not cleared for redistribution. and loudness could not be balanced for that test either, which is argued not to matter for what it measures Quotation withheld because this record is not cleared for redistribution. before the pitch and direction tests every site was adjusted until the patient said they were equally loud Quotation withheld because this record is not cleared for redistribution. with no reference tone available, absolute pitch was scaled against familiar imagined environmental sounds Quotation withheld because this record is not cleared for redistribution. the stimulus parameters were chosen at the point where more charge stopped lowering thresholds and less charge raised them sharply Quotation withheld because this record is not cleared for redistribution. accurate MRI images of the midbrain could not be obtained after AMI implantation because of the distortion caused by the electrode array, so CT images were obtained at least 6 weeks after implantation Quotation withheld because this record is not cleared for redistribution. and those slices are read against fixed and stained human midbrain sections from an anatomical collection Quotation withheld because this record is not cleared for redistribution. all three patients had tinnitus before and after surgery and were instructed to ignore it during testing Quotation withheld because this record is not cleared for redistribution. the surgical method for placing the array was improved across these three patients Quotation withheld because this record is not cleared for redistribution. a three-dimensional array spanning the colliculus is proposed as the next design Quotation withheld because this record is not cleared for redistribution. the stated advantage over the brainstem implant is surgical - direct visual exposure, no tumour distortion, less risk to brainstem structures Quotation withheld because this record is not cleared for redistribution. the work was supported by the company that makes the device Quotation withheld because this record is not cleared for redistribution. lip-reading enhancement lip-reading enhancement Quotation withheld because this record is not cleared for redistribution. T level T level Quotation withheld because this record is not cleared for redistribution. comfortable (C) level comfortable (C) level Quotation withheld because this record is not cleared for redistribution. auditory brainstem implant (ABI) auditory brainstem implant (ABI) Quotation withheld because this record is not cleared for redistribution. cochlear implant (CI) cochlear implant (CI) Quotation withheld because this record is not cleared for redistribution. auditory brainstem implant auditory brainstem implant Quotation withheld because this record is not cleared for redistribution. cochlear implant cochlear implant Quotation withheld because this record is not cleared for redistribution. temporal resolution temporal resolution Quotation withheld because this record is not cleared for redistribution. lip reading lip reading Quotation withheld because this record is not cleared for redistribution. electrode array electrode array Quotation withheld because this record is not cleared for redistribution. current level current level Quotation withheld because this record is not cleared for redistribution. pulse rate pulse rate Quotation withheld because this record is not cleared for redistribution. perceived pitch perceived pitch Quotation withheld because this record is not cleared for redistribution. azimuth azimuth Quotation withheld because this record is not cleared for redistribution. threshold threshold Quotation withheld because this record is not cleared for redistribution. pitch pitch Quotation withheld because this record is not cleared for redistribution. loudness loudness Quotation withheld because this record is not cleared for redistribution. temporal resolution temporal resolution Quotation withheld because this record is not cleared for redistribution. sound localization sound localization Quotation withheld because this record is not cleared for redistribution. Three — number of patients implanted with the auditory midbrain implant Quotation withheld because this record is not cleared for redistribution. 6.2 mm long with a diameter of 0.4 mm — dimensions of the penetrating AMI electrode array Quotation withheld because this record is not cleared for redistribution. 20 platinum ring electrodes linearly spaced at an interval of 200 μm — electrode count and spacing on the array Quotation withheld because this record is not cleared for redistribution. 6–12 nC ... 7–9 dB — AMI threshold charge and dynamic range in the patient implanted in the ICC Quotation withheld because this record is not cleared for redistribution. 42 ± 7 and 65 ± 8 pps — pulse rate at which buzzing fused into a continuous percept for the two IC-implanted patients Quotation withheld because this record is not cleared for redistribution. 220 pps (mean ± SD, 180 ± 17) — temporal fusion rate for the patient implanted at the lateral lemniscus Quotation withheld because this record is not cleared for redistribution. 23 and 40% correct (10% chance level) — vowel identification with AMI stimulation alone for AMI-2 and AMI-3 at 6 months Quotation withheld because this record is not cleared for redistribution. 12.5 and 10% — consonant and number test scores achieved above chance by AMI-3 with the implant alone Quotation withheld because this record is not cleared for redistribution. ∼2–11 words per minute — lip-reading enhancement in speech tracking obtained by adding the AMI to lip reading Quotation withheld because this record is not cleared for redistribution. ∼85–100 words per minute — speech tracking rate of normal-hearing subjects in the same clinic, as a reference Quotation withheld because this record is not cleared for redistribution. only four — number out of 11 ABI NF2 patients who beat AMI-3's 11 words-per-minute lip-reading enhancement Quotation withheld because this record is not cleared for redistribution. 2400 pps — pulse rates swept this high without any obvious increase in pitch over 250, which closes the most obvious escape from the failed prediction Quotation withheld because this record is not cleared for redistribution. 7–9 dB — dynamic range in the correctly placed patient, similar to the cochlear implant rather than better as animal work predicted Quotation withheld because this record is not cleared for redistribution. ∼20 ms — the temporal resolution implied by fusion near 50 pulses per second, against a few milliseconds for cochlear stimulation Quotation withheld because this record is not cleared for redistribution. 1.7–1.9 mm — the span of active sites across which the perceived direction never changed Quotation withheld because this record is not cleared for redistribution. 48 d — how long the device was switched off after one patient's levels reached the stimulator's compliance voltage Quotation withheld because this record is not cleared for redistribution. 6.2 mm — array length, carrying 20 sites at 200 micrometre spacing Quotation withheld because this record is not cleared for redistribution. 11 ABI NF2 patients — the comparison group, tested in the same clinic under the same protocols by the same speech therapist Quotation withheld because this record is not cleared for redistribution.

The full text of this article is not redistributable, so it is not included here. The evidence sentences are withheld with it; the tag layer and its grounding status remain. The article itself is at https://doi.org/10.1523/jneurosci.3123-07.2007.