Evoked cortical activity and speech recognition as a function of the number of simulated cochlear implant channels.
OBJECTIVE
(1) To determine if consonant-vowel-consonant (CVC) syllables [Hillenbrand J, Getty L, Clark M, Wheeler K. Acoustic characteristics of American English vowels. J Acoust Soc Am 1995;97:3099-3111] could be used to evoke cortical far field response patterns in humans, (2) to characterize the effects of cochlear implant-simulated channel number on the perception and physiological detection of these same CVC stimuli, and (3) to define the relationship between perception and the morphology of the physiological responses evoked by these speech stimuli.


METHODS
Ten normal hearing monolingual English speaking adults were tested. Unprocessed CVC naturally spoken syllables, containing medial vowels, as well as processed versions (2, 4, 8, 12, and 16 spectral channels) were used for behavioral and physiological testing.


RESULTS
(1) CVC stimuli evoked a series of overlapping P1-N1-P2 cortical responses. (2) Amplitude of P1-N1-P2 responses increased as neural conduction time (latency) decreased with increases in the number of spectral channels. Perception of the CVC stimuli improved with increasing number of spectral channels. (3) Coinciding changes in P1-N1-P2 morphology did not significantly correlate with changes in perception.


CONCLUSIONS
P1-N1-P2 responses can be recorded using CVC syllables and there is an effect of channel number on the latency and amplitude of these responses, as well as on vowel identification. However, the physiological detection of the acoustic changes does not fully account for the perceptual performance of these same syllables.


CONCLUSIONS
These results provide evidence that it is possible to use vocoded CVC stimuli to learn more about the physiological detection of acoustic changes contained within speech syllables, as well as to explore brain-behavior relationships.
Friesen
L M
LM
Department of Speech and Hearing Sciences, University of Washington, Seattle, WA 98105, USA. lendra.friesen@sunnybrook.ca
Tremblay
K L
KL
Rohila
N
N
Wright
R A
RA
Shannon
R V
RV
Başkent
D
D
Rubinstein
J T
JT
D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D000704:Analysis of Variance; D001303:Auditory Cortex / Q000502:physiology*; D019929:Cochlear Implantation; D004569:Electroencephalography / Q000379:methods; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D011571:Psychoacoustics; D011930:Reaction Time / Q000502:physiology; D021641:Recognition, Psychology / Q000502:physiology*; D013057:Spectrum Analysis; D013061:Speech Acoustics; D013067:Speech Perception / Q000502:physiology*; D055815:Young Adult