الفهرس 
IntroductionOnly 14 pages are availabe for public view
Abstract
ortical auditory evoked potentials (CAEPs) are brain responses evoked by sound and are processed in or near the auditory cortex. To date, a number of CAEPs have been described in the literature. There has been considerable clinical and scientific interest in CAEPs to probe threshold and suprathreshold auditory processes because they are believed to reflect the neural detection and/or discrimination of sound underlying speech perception. These measures include obligatory evoked potentials such as P1, N1, and P2, and discriminative potentials such as mismatch negativity (MMN), P300 and acoustic change complex (ACC) which are all considered long latency auditory evoked potentials (LLAEP).
The Acoustic Change Complex (ACC) is a cortical auditory evoked potential (P1-N1-P2) elicited by a change within an ongoing sound stimulus. It may function as an electrophysiological measure of the neural processes that underlie detection of changes in an ongoing acoustic signal. Consequently, it has been suggested that the ACC response can serve as an index of auditory discrimination ability.
The present study was originally designed to standardize ACC evoked auditory cortical response in 41 normal hearing children aged from 2 to 10 years. Stimuli used in this study were specifically designed for auditory evoked potential (AEP) equipment that are capable of uploading short duration stimuli thus can be used in a regular AEP lab. ACC was elicited by three groups of stimuli 1. Gap-in-tones that represent temporal change (6, 10, 30 and 50 msec. gap introduced to 1000 Hz tone separately) 2. Frequency pairs that represent frequency change (2%, 4%, 10% and 25% change from base frequency 1000 Hz) 3. Vowel pairs that represent spectral change (/i-u/, /u-i/, /i-a/. /a-i/, /u-a/, /a-u/). The primary aim of the study was to reach the best stimuli that can elicit ACC and provide an objective tool for assessment of cortical auditory discrimination in normal hearing children.
Recording ACC response was analyzed regarding the following parameters using all the developed stimuli (percent detectability, morphology, latency and amplitude).
Results of the present study were demonstrated in five sections:
First, Description of onset response using no-change (1000 Hz, /a/, /i/ and /u/ stimuli) and change stimuli (mentioned above) and comparison was held between them to show how deviant was the onset response when elicited by change and no-change stimuli. Second, Description of ACC response. Third, Comparison between Onset Response and ACC Response parameters. Fourth, Effect of magnitude of stimulus change on ACC Response parameters. Fifth, Effect of subject’s age and gender on ACC response parameters