Relationships between speech understanding and

WEDNESDAY

AFTERNOON,

10 OCTOBER 1984

WISCONSIN

ROOM, 1:00 TO 3:20 P.M.

SessionV. PsychologicalAcousticsIV: CochlearImplants and Tactile Aids Gregory P. Widin, Chairman Biosciences Laboratory,Life Sciences $ector/3M, 270-45-113M Center,Saint Paul, Minnesota55144 Chairman's

Introduction--1:00

ContributedPapers

1:05

V1. Interactions in a multichannel cochlear prosthesis.M. W. White (Departmentof Otolaryngology,U.C.S.F., SanFrancisco,CA 94143)

Multichannelelectricalstimulationof the auditorynervecan generate complexinteractionsbetweenthe individualelectrodechannels.One type of interchannel

interaction

can occur when two or more channels are

stimulatedsimultaneously.This type of interactionis describedas an "electric field interaction" becauseit may be the result of electric field summation and cancellation within the cochlea. Loudness and threshold

measuresin humansubjects,implantedwith scalatympanielectrodearrays,are significantlyalteredby reversingthe stimuluspolarityof oneof two simultaneouslystimulatedchannels.The nearerthe two channels,the greaterthe change.In somesubjects,significantinteractionsoccureven for very widely spacedelectrodechannels.In other subjects,the interactionsoccuronly overa restrictedregion[M. W. White, J. Gardi, and M. Merzenich,Arch. Otolaryngol.(in press)].The differencesbetweenthe subjectsmayberelatedto the quantityanddistributionof survivingnerve. Preliminary data from four subjectssuggesta relationshipbetweenthe spatial"spread"of channelinteractionand other psychophysical measures.[Work supportedby NIH and Hearing Research,Inc.]

A batteryof testshasbeenusedwith the 20 postlingually deafened, patientswhohavereceiveda ViennaCochlearImplantin Viennaand havehadtheir implantfor at least3 months.The batteryincludedtests determining thetemporaldifference limenfora 250-1000-Hzanda 20004000-Hznoisesignal,gapdetection testsusingthesametwosignals anda periodic/aperiodic discrimination test.The speechtestswereopenset one-syllable-word understanding, opensetsentence understanding, a 16consonantidentification,and an eight-vowelidentification.The four

speech testswereperformed withoutlipreading. Foralltemporal processingabilitytests,limitscouldbefoundwhichseparated those75% of the patients whowereableto understand single-syllable wordsandsentences to a varyingdegreeandthosewhowerenot.Correlations between the speech tests,exceptthevoweltest,andthetestsfortemporal processing abilities could be found. These correlations demonstrate that cochlear

implantpatients wearingananalogbroadband single-channel soundprocessor haveto relyheavilyontheirabilityfortemporalprocessing. [Work supported bytheAustrianResearch Fund.]

1:50

1:20

V4. Preliminary speechcomprehensionresults with the single-channel cochlear implant. F. B. Simmons, L. J. Dent (Division of Otolaryngology,StanfordUniversitySchoolof Medicine,Stanford,CA

V2. A model of temporal processing in cochlear implants. Robert V. Shannon(ColemanLaboratories863 HSE, UCSF, SanFrancisco,CA

94305},R. L. White (Departmentof ElectricalEngineering,Stanford University, Stanford, CA 94305), and L. A. Roberts (Stanford ElectronicsLaboratories,StanfordUniversity,Stanford,CA 94305)

Somepsychophysicalmeasuresof temporal processingin cochlear implantpatientsaresimilarto normalsbut othersarenot [R. V. Shannon, Hear. Res.11, 157-189(1983)].Forwardmaskingin implantsappearsto havea slightlylongertime coursethan acousticforward masking.Gap detectionthresholdsand temporalintegrationin implantsappearto be shorter than the same measures with acoustic stimulation.

This does not

necessarilymean that the temporal mechanismis differentor more impairedin implant patientsthan in normals.The differences can be describedby a new model basedon an earlier model by Zwislocki [J. J. Zwislocki,J. Acoust. Soc.Am. 46, 431-441 (1969)].The differencesin temporal measurescould be due to the steeploudnessversusintensity functionobserved in implants.This function,followedby normaltemporal processing, would yield apparentchangesin temporalmeasuresthat are in line with the observedimplant results.Electricalstimuli could be preprocessed so that the resultanttemporalmeasureswould be normal. [Work supportedby NIH.]

Four scala tympani implant subjects,two with multiple-electrode prostheses and two with single-electrode implants,were testedwith a single-channel wearablesoundprocessorafter 0-8 months'use.A comparisonbetweenpre- and post-implantscoreson the Minimal Auditory Capabilities(MAC) Testshowedlittle difference,exceptthat all subjects improvedon the postoperative lipreadingtestwhenelectricalstimulation was added ("aided" condition}.Improvementwas noted in aided over unaidedperformanceon videotapedtests,includinga medialconsonant test, two-digit numeralstest, and an open set sentencetest. Subjects showeda two- to fourfoldincreasein speechtrackingratesin the aided over the unaided condition. These baseline observations indicate that sub-

jectsquicklybeginto experienceimprovementin face-to-facecommunicationskillsevenduringthe firstmonthsof usinga single-channel cochlear prosthesis. [Work supportedby NIH.]

2:05

1:35

V3. Relationships between speech understanding and temporal processing abilitiesin cochlearimplantpatients.IngeborgJ. HochmairDesoyer, Helmut K. Stiglbrunner, and Ernst-Ludwig Wallenberg (Department of Electrical Engineering, Technical University, Gusshausstr. 27, A-1040 Vienna,Austria}

S48

J. Acoust. Soc. Am. SuppL 1, Vol. 76, Fall 1984

VS. An analysisof consonant confusions by single-channel cochlear implant users. L. J. Dent (Divisionof Otolaryngology, Stanford University, School ofMedicine,Stanford, CA 94305),D.A. Huntington, E. D. Schubert(Hearingand SpeechSciences, StanfordUniversity, Schoolof Medicine,Stanford,CA 94305),F. B. Simmons(Divisionof Otolaryngology, Stanford University, School of Medicine, Stanford, CA 94305), andR. L. White(Department ofElectrical Engineering, Stanford University,Stanford,CA 04305) 108th Meeting: AcousticalSociety of America

S48

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