الفهرس 
SELECTIVE AUDITORY ATTENTIONOnly 14 pages are availabe for public view
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Abstract
SUMMARY
S
elective auditory attention (SAA) is defined as the ability to acknowledge some stimuli while ignoring other stimuli that occur at the same time. Difficulty in understanding speech in the presence of background noise is a commonly reported problem. This perceptual difficulty becomes increasingly severe as competing background noise levels increase (i.e., signal‐to‐noise ratio (SNR) decreases). As with speech recognition performance, neural responses as measured by evoked potentials are typically weakened when increasing levels of noise. It is not surprising then, that strong correlations exist between cortical auditory evoked potentials (CAEPs) and speech perception‐in‐noise measures
The cortical auditory evoked potentials (CAEPs) are brain responses evoked by sound and are processed in or near the auditory cortex. 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.
The neural processing underlying behavioral discrimination capacity can be measured by modifying the traditional methodology for recording the P1-N1-P2. When obtained in response to an acoustic change within a sound or in response to stimulus that contains multiple time-varying acoustic changes such as speech, the resulting waveform has been referred to as the acoustic change complex (ACC).
This study was designed to assess if that ACC provoked by specifically designed speech in noise stimuli can be used as an objective tool for assessment of cortical auditory discrimination in normal individuals and to apply the developed ACC protocol in children with SAA deficit.
The present study was consisted of two groups, control group (30 normal children their ages range from 5 to13 years) and study group (15 children with SAA deficit their ages range from 6 to 14 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 two types of stimuli: Stimulus with No-Change: vowel /o/ and its duration 500 msec. Stimuli with Change which is Speech stimulus (vowel /o/, its duration 300 mesc) in presence of noise (pink noise,its duration 500 msec) based on the recommendation presented at 80 dBnHL at different signal to noise ratio (+8, +4, 0, -4, -8), The vowel /o/ presented at 200 msec from the beginning of the stimulus then they merged together.
Results of the present study were demonstrated in three sections:
First, Electrophysiological tests which include: Onset Response in control and study groups, ACC Response in control group and ACC Response in study group. Second, Behavioral test which include: WIN results test in control and study groups. Third, Comparison between electrophysiological test and behavioral test results.
Results of the present study showed that ACC was recorded in all normal children and two children with SAA in +8 SNR only. In general latency increased and amplitude decreased as SNR decreased.
We concluded that CAEPs to short duration speech-in-noise stimuli was successfully recorded in all normal hearing children and children with SAA deficit, with significant shift in latency and decrease in amplitude. ACC was detected in the majority of normal hearing children, with a cutoff of normalcy of zero SNR. With few exceptions, children with SAA deficit failed to show ACC response using the present research’s protocol. ACC P1 latency and amplitude in normal hearing children is a better indicator of cortical discrimination compared to ACC N2 latency and amplitude as it is consistently affected by magnitude of change. When CAEP to speech-in-noise stimuli were compared to behavioral tests, few correlations were obtained at selected SNRs
It is recommended to measure ACC at 0 SNR in screening young children who are suspected to have SAA deficit, and cannot be assessed behaviorally due to age or language limitations and to study the complex relationship between electrophysiological and behavioral tests for SAA using different methodologies and paradigms
More research is needed use SNRs higher than +8 SNR that may elicit ACC with higher percent detectability in children with SAA deficit.