PERCEPTION OF MUSIC BY PATIENTS WITH COCHLEAR IMPLANTS

PERCEPTION OF MUSIC BY PATIENTS WITH COCHLEAR IMPLANTS Jaan Ross (University of Tartu and Estonian Academy of Music and Theatre, Tallinn) Inna V. Koroleva (Institute of Otolaryngology, St. Petersburg) Elena A. Ogorodnikova (Pavlov Institute of Physiology, St. Petersburg)

Cochlear implantation (1) Cochlear implantation is one of the most perspective directions in the rehabilitation of patients with significant hearing losses Cochlear implant is a surgically implantable device that provides hearing sensation to individuals with severe-to-profound hearing loss who do not benefit from hearing aids People with hearing losses in such range have absent or malfunctioning sensory cells in the cochlea 2

Cochlear implantation (2) In a normal ear, sound energy is converted to mechanical energy by the middle ear, which is then converted to mechanical fluid motion in the cochlea. Within the cochlea, the sensory cells (the inner and outer hair cells) are sensitive transducers that convert that mechanical fluid motion into electrical impulses in the auditory nerve. 3

Cochlear implantation (3) Cochlear implants are designed to substitute for the function of the middle ear, cochlear mechanical motion, and sensory cells, transforming sound energy into electrical energy that will initiate impulses in the auditory nerve Implant systems consist of both internal and external components 4

Cochlear implantation (4) The external components (over or next to the ear) include (1) a microphone, which converts sound into an electrical signal, (2) a speech processor, which manipulates and converts the signal into a special code and (3) a transmitter, which sends the coded electrical signal to the internal components The systems are powered by batteries located in the speech processor The surgically implanted components include (A) a receiver, which decodes the signal from the speech processor, and (B) an electrode array, which stimulates the cochlea with electrical current 5

Rehabilitation (1) Rehabilitation is the very important post-surgical stage of cochlear implantation It is a complex and long process which essentially depends on individual characteristics of the patient (auditory experience, general abilities and the absence of mental defects) It is accepted to distinguish between the two groups of patients with cochlear implants : pre-lingual - the hearing loss occurred before the patient has learned to speak (in general, before the second year of life) and post-lingual - when the hearing loss occurred in the age of four years or later (after the patient has learned to speak) 6

Rehabilitation (2) The main task of rehabilitation : o for post-lingual patients - the regeneration of the ability to perceive and to understand spoken language (the forming of connections between the distorted auditory information and previous internal patterns of speech and other sounds) o for pre-lingual patients - the development of the foundations of auditory perception from the beginning (includes the basic elementary operations - detection and discrimination of sounds) and building up the whole system of spoken language o So for all listeners with cochlear implants – a primary rehabilitation problem is the creation or correction of «new» auditory patterns 7

Rehabilitation and music o o cochlear implants have been designed primarily to enhance speech perception many implant recipients anticipate enjoying music following the implantation in fact, up to 38 per cent of implant recipients report they do not enjoy listening to music with their device (Leal et al. , Acta Otolaryngology 123, 826 (2003)) up to 86 per cent of post-lingual recipients report lower scores of listening habits after implantation 8

Hypothesis o pitch has been reported to be recognized with more difficulty than rhythm or timbre by implant recipients (because frequency encoding is robust in an implant), therefore temporal aspects of music are expected to be perceived better than pitch 9

Method o o about 150 cochlear implant receivers in St. Petersburg area by 2005 (Combi 40 or Combi 40+ by MED-EL) they are interviewed in order to study their postsurgical adaptation to listening music interviews are conducted at the Institute of Otolaryngology in St. Petersburg as a part of general rehabilitation program selected interviews are videotaped 10

Interview o o o Did you listen to speech, music, or noise? If this was music, was it singing or playing an instrument? If this was singing, was there just one performer or many of them? Were the singers male or female? If this was playing an instrument, was there just one instrument or many? String, wind, or percussion? Was this music joyful or sad? Fast or slow? Pleasant or not? Simple or complicated? Did this music sound in high, medium or low register? 11

Choice of music for the interview Four excerpts from world music, with different sound characteristics: o Japanese bamboo flute shakuhachi: one voice, long notes, timing plays little role o Saami jojk (Mari Boine): female singing, one voice, heterogeneous rhythm o Lithuanian sutartine: polyphonic female singing (facilitates harmonic dissonances), repetitive rhythm o Tuvan overtone singing (xöömij): a low fundamental of special timbre, with higher overtones made audible one-by-one 12

Long-term spectra of (1) Japanese bamboo flute shakuhachi (top left), (2) Saami jojk (top right), (3) Lithuanian dissonant polyphony (bottom left), and (4) Tuvan overtone singing (bottom right) 13

Interview results for 10 CI-recipients (age 10 to 55 years, post-surgical experience from 2 weeks to 4 years) music singing female singing joyful fast pleasant low pitch medium pitch high pitch flute 10 2 1 0 0 8 2 3 2 jojk 10 10 7 0 0 8 3 1 0 sutartine 10 10 7 8 8 8 1 1 6 xöömij 7 6 2 1 0 0 8 4 1 14

Listening preference score for ten CIrecipients 15

List of instruments for the timbre recognition task (those in yellow recognized more easily) MUSICAL INSTRUMENT ESTIMATED FREQUENCY RANGE 1 violin 180 -8000 2 cello 70 -8000 3 double bass 40 -5000 4 harp 30 -15000 5 piano 22 -6000 6 flute 250 -9600 7 organ 22 -16000 8 trumpet 160 -8000 9 cymbals 500 -16000 10 triangle 1200 -16000 11 kettledrum 16 -350 12 big drum 16 -350 16

Recognition of musical timbres before and after a training session 17

Long-term improvement of timbre recognition by cochlear implant recipients (without special training) 18

Excerpts from an interview (1) o o o o a post-lingual patient has used the implant for a couple of weeks describes Tuvan overtone singing as sound of a Jewish harp describes shakuhachi sound as singing confuses Saami jojk with Lithuanian polyphony noticeable progress during the interview admits using extramusical features (sound volume) to solve the task 19

Excerpts from an interview (2) - a post-lingual patient - has used the implant for 4 years - recognizes Lithuanian polyphonic and Tuvan overtone singing - confuses a shakuhachi sound with Saami jojk - claims to prefer the jojk to other excerpts 20

General conclusion o Many post-lingual patients with cochlear implants are and pre-lingual patients become strongly motivated to attend music even when its perceived acoustical characteristics only remotely resemble the patterns they expect to hear. This may be explained by an ecologically important function music fulfills in people’s everyday life. 21

Thanks to o Elvira I. Stoljarova of the Pavlov Institute of Physiology, St. Petersburg, for video recording of the interviews 22