Can Deaf Individuals Perceive Music With Implants?

25 Oct

How do deaf individuals with cochlear implants perceive music?  Cochlear implants convert acoustic sound into electrical signals that can be transmitted to and processed by the brain.  These devices allow deaf individuals to perceive speech but because the implants only pick up a limited spectral resolution, it is often difficult for these individuals to hear speech in noisy environments.  The processing algorithms have been shown to be ineffective in processing music material: previous research demonstrated these individuals are unable to recognize pitch patterns and familiar music from solely pitch cues.  However, these participants were able to recognize familiar pop songs from recordings or full instrumentals, remained intact.

Takayuki Nakata, Sandra E. Trehub, Chisato Mitani, and Yukihiko Kanda investigated  how effectively deaf children with cochlear implants could sing familiar songs with relation to relative pitch and temporal perception.

The 18 participants ranged from ages five to ten.  12 were congenitally deaf children that had been using cochlear implants for at least 10 months, while the remaining 6 were hearing children.  The researchers asked each participant to sing a familiar song as best as they could.  The subjects were tested independently in a quiet room, and recorded for further analysis.   Since the choice of song was selected by the  participants, a wide range of performances resulted during the study.  The researchers  decided to only analyze the songs they were most familiar with and used computer software to investigate the pitch relationships and singing tempo of the performances.  It was found that many of the participants were unable to articulate correct lyrics and thus language semantics were ignored.

The results showed that the deaf individuals with cochlear implants performed better on temporal replication than pitch replication. Interestedly, both the deaf and hearing children produced a less accurate singing tempo than older children or adults.  However this variation was absent between the deaf and hearing participants (could this provide basis for a critical period for rhythmic perception?).

The deaf individual’s range of sung pitch was less dynamic than the range of the hearing children (showing about a third less of a spread).  The researchers noted this should not be attributed to the production of speech, as the deaf participants were able to reach a wide range of pitch in casual conversation.  Furthermore, the deaf participants were unable to determine whether a pitch sequence rose or descended, which as the researchers speculate, might be the cause of their poor pitch productions.  Previous research has shown that deaf individuals are able to detect pitch changes, but in the context of this study might be unable to perceive the direction of the pitch change.   And finally, the researchers note that the deaf children performed analogous to those who are musically disabled yet have functional auditory systems (both groups demonstrate poor pitch processing, but maintain their temporal abilities), a discovery that is a sure fire-starter for future research.

Nakata, T., Trehub, S.E., Mitani, C., & Kanda, Yukihiko. (2006). Pitch and timing in the songs of deaf children with cochlear implants. Music Perception, 24(2), 147-154.

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