Clin Exp Otorhinolaryngol.  2012 Apr;5(Suppl 1):S6-S9.

Auditory Evoked Potentials under Active and Passive Hearing Conditions in Adult Cochlear Implant Users

• Obuchi C
• Harashima
• Shiroma M

Abstract

OBJECTIVES
Speech perception abilities, which vary widely among cochlear implant (CI) users, are considered to be associated with the integrity of the central auditory pathways from the auditory nerve to the cortex. Therefore, auditory evoked potentials (AEPs) are used to evaluate central auditory processing, which is thought to contribute to speech perception in CI subjects. In AEPs, the P300 component reflects the cognitive ability of subjects to detect and respond to stimuli and has most frequently been used and investigated in CI subjects. Other studies have used mismatched negativity (MMN) to examine central auditory processing. It is important to compare MMN and P300 and examine the auditory processing mechanisms involved in these components. Our study therefore aimed to investigate the relationship between P300 and MMN using both active and passive hearing paradigms in CI and normal hearing (NH) subjects.
METHODS
Our subjects consisted of 3 CI subjects and 3 NH subjects. An oddball paradigm was used to deliver the stimuli on both components. The frequent stimuli were 1,000-Hz tone bursts, whereas the rare stimuli were 1,500, 2,000, and 4,000-Hz.
RESULTS
As the frequency contrasts increased, the P3 latencies increased in the CI subjects. However, the latency in NH subjects did not change significantly across the frequency contrast conditions. MMNs were identified for both the CI and NH subjects; the latencies in the CI subjects were longer than those in the NH subjects. However, there were no differences in the latencies of either the CI or NH subjects in the 3 frequency contrast tasks.
CONCLUSION
Our results indicated that different auditory processing pathways are involved in the active and passive hearing conditions based on the P300 and MMN data and that a combination of both responses plays an important role in the comprehension of auditory processing mechanisms in CI subjects.

Keyword

Auditory evoked potential; Cochlear implant; P300; Mismatched negativity

MeSH Terms

Adult
Auditory Pathways
Cochlear Implants
Cochlear Nerve
Comprehension
Event-Related Potentials, P300
Evoked Potentials, Auditory
Hearing
Humans
Speech Perception

Figure

• 

  Fig. 1 Individual P3 latencies (ms) at the Cz electrode of cochlear implant (CI) subjects (CI1-CI3) and normal hearing (NH) subjects (NH1-NH3) in the 3 frequency contrast tasks. 1,000-1,500 Hz signal contrast (blue bars), 1,000-2,000 Hz signal contrast (yellow bars), and 1,000-4,000 Hz signal contrast (green bars) tasks.

• 

  Fig. 2 Individual P3 amplitudes (µV) at the Cz electrode of cochlear implant (CI) subjects (CI1-CI3) and normal hearing (NH) subjects (NH1-NH3) in the 3 frequency contrast tasks. 1,000-1,500 Hz signal contrast (blue bars), 1,000-2,000 Hz signal contrast (yellow bars), and 1,000-4,000 Hz signal contrast (green bars) tasks.

• 

  Fig. 3 Individual mismatched negativity (MMN) peak latencies (ms) at the Cz electrode of cochlear implant (CI) subjects (CI1-CI3) and normal hearing (NH) subjects (NH1-NH3) in the 3 frequency contrast tasks. 1,000-1,500 Hz signal contrast (blue bars), 1,000-2,000 Hz signal contrast (yellow bars), and 1,000-4,000 Hz signal contrast (green bars) tasks.

• 

  Fig. 4 Individual mismatched negativity (MMN) peak amplitudes (µV) at the Cz electrode of cochlear implant (CI) subjects (CI1-CI3) and normal hearing (NH) subjects (NH1-NH3) in the 3 frequency contrast tasks. 1,000-1,500 Hz signal contrast (blue bars), 1,000-2,000 Hz signal contrast (yellow bars), and 1,000-4,000 Hz signal contrast (green bars) tasks.

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