What are the goals of cochlear implants?
- Detection of environmental speech
- Speech understanding (in quiet*; in noise?)
- Music?
- IMPROVED QOL**
What technological factors contribute to difficulties in music perception with a CI?
- Music is more complex in terms of spectral, temporal, and timbral aspects (as well as DR)
- Pitch is most severely degraded due to reliance on place (spectral) and temporal cues
- 22 physical elements need to compensate for functional loss of 3500 IHCs
- Incoming signal is BPF for speech signals (~250-8000 Hz)
- Spectral spread from electrical fields leads to further degradation
What surgical/anatomical factors contribute to difficulties in music perception with a CI?
- Further reduces spatial sensitivity
- Electrode proximity to nerve fibers
- Less-than-ideal electrode placement
- Cochlear abnormalities
How high is rate-pitch info in NH? CI?
- For NH, synchronized nerve firing produces rate-pitch info up to 5000 Hz, whereas CIs saturate at 300 Hz
- Increased rates needed to represent rate-pitch info above 300 Hz lead to channel interaction
- CI users also have trouble perceptually integrating rate cues with changes in signal envelope
What biological factors contribute to difficulties in music perception with a CI?
- Loss of peripheral nerve fibers/cell bodies = lead to the need for increased current levels, spread of excitation (loss of specificity)
- Loss of myelination = prolonged latencies, altered refractory periods, reduced temporal resolution, diminished neural efficacy (greater power consumption)
- Unclear how many remaining nerve fibers are needed for music appreciation
- Synaptic loss and increased response latencies in the CN and IC further decrease temporal resolution
What acoustical factors contribute to difficulties in music perception with a CI?
- Rhythm
- Tempo
- Melody
- Timbre
What is rhythm?
- Series of beats and rests that produce patterns over time
- Independent of tempo (speed) of music
- Temporal gaps and amp modulated pulse trains encode rhythmic patterns
- CI users do well with rhythm, regardless of type of music (similar to NH)
What is tempo?
- Speed or rate (beats per minute)
- Creates the effective mood of the piece
- Remains relatively intact for CI users
- Discrimination is ~4-6 bpm
What is melody?
- Sequential series of pitches that create the musical phase
- Accuracy for closed set discrimination ranges from 0 to 95% correct (for familiar melodies or real world songs)
- Generally much worse than NH controls
What is timbre?
- The feature that distinguishes 2 notes of the same pitch, loudness, and duration; “tone quality”
- Discriminating between 2 instruments
- Wide range of performance for CI users on identification task, but consistently
- Utilizes envelope and fine structure cues (NH uses both, but CI relies solely on envelope)
Is music presented as fundamental components or streams?
- Streams
- Auditory stream segregation allows us to process complex signals
- Perceptually similar sounds are grouped into a single stream
- Separate melody from background accompaniment
- CI listeners are largely effected by competing instruments for timbre and melody tasks
- Fusion vs. fission
What is fusion?
-Envelopes are similar so hear one continuous strand of music
What is fission?
-Envelopes are different enough to distinguish, can hear multiple streams of music
How do we improve music perception for CI users?
- Music rehab may improve melodic contour and timbre identification w/ subjective improvements in appraisal (degree of improvement related to amount of training)
- Music appraisal ratings and perception abilities do not generally improve with incidental exposure like speech perception does
- Melody training significantly improves abilities (similar in adults and peds)
- However, limited music rehab programs exist
What are the proposed theories of pitch perception?
- Temporal theory
- Tonotopic theory
- Combo
What is the temporal theory of pitch perception?
-Pitch is conveyed by the rte of the nerve fibers
What is the tonotopic theory of pitch perception?
-Pitch is conveyed by the place of stim in the cochlea
Describe pitch perception for CI users.
- Pitch conveys melody
- The listener needs to get an accurate perception of the pattern of the pitches, not just the isolated stimuli
- Due to poor LF info access, limited # of spectral channels, inappropriate encoding/smearing of TFS in the stim pattern
Describe timbre identification for CI users.
- Character of the sound quality
- NH identification mistakes are within the same instrument family
- CI errors are across families
What music is best for perception of rhythm/beat?
- Country or ballroom dance
- Rock or rap may be more easily deciphered
How do lyrics help with music perception?
- The speech component
- Familiarity of the song
- Reading along helps
- Lipreading
What music factors are the biggest downfall for CI users?
- Individual notes
- Melodies
- Current technology is not well suited for transmitting music pitch or detecting whether one note is higher or lower than another
What tips could improve music listening skills for someone with no experience with music?
- Experiment with accessories
- Use a hearing aid in opposite ear
- Make adjustments to processor settings
- Simple tunes w/ strong beat
- Children’s music
- Keep a journal
What tips could improve music listening skills for someone who wants to enjoy music again?
- Start with familiar music
- Experiment with different types of music
- Use 2 ears (bilateral or bimodal)
- Listening repetitively
- Make adjustments to processor
- Use lyrics to read along
- Ask partner to sing along
- Dance to music with partner
- Use processor accessories
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Basic Operation of Cochlear Implants, Brief Introduction, Histor24
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Cochlear Implant Candidacy24
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Cochlear Implant Programming74
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Cochlear Implant Processing Strategies11
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Troubleshooting14
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Challenging Listening Environments22
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Music Perception25
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Surgical Perspective14
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Pediatrics36
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Geriatrics11
