Noise-Induced Change of Cortical Temporal Processing in Cochlear Implant Users

Area of Science:

• Auditory Neuroscience
• Speech Perception
• Cochlear Implants

Background:

• Cochlear implant (CI) users often struggle with speech understanding in noisy environments due to impaired temporal processing.
• Voice onset time (VOT) is a critical acoustic cue for distinguishing speech sounds, particularly stop consonants, and its processing is sensitive to noise.
• Cortical auditory evoked potentials (CAEPs) offer a neural measure to investigate how noise affects speech sound processing.

Purpose of the Study:

• To examine the impact of noise on speech perception tests in CI users and normal-hearing (NH) individuals.
• To quantify neural processing changes using CAEPs (N1/P2, P3b) in response to noise.
• To investigate the relationship between neural measures (N1/P2 latency/amplitude) and behavioral speech perception performance in noise.

Main Methods:

• Ten adult CI users and 15 NH participants underwent speech perception tests and CAEP recordings.
• CAEPs were recorded under quiet and +5 dB SNR noise conditions, during passive and active listening tasks.
• Stimuli included synthesized consonant-vowels with 0 and 50 ms VOT; N1-P2 and P3b components were analyzed.

Main Results:

• CI users showed reduced performance on speech tests in noise.
• Noise prolonged N1 and P2 latencies in CAEPs for both groups.
• The change in P2 latency with VOT correlated with consonant perception accuracy in noise for CI users.

Conclusions:

• Noise masking significantly affects temporal processing in CI users, reflected in cortical responses.
• N1/P2 latencies are more sensitive indicators of noise effects than amplitude measures.
• P2 responses demonstrate a stronger correlation with speech perception abilities in CI users compared to N1.