الفهرس 
CENTRAL/TEMPORAL AUDITORY PROCESSINGOnly 14 pages are availabe for public view
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Abstract
T
emporal processing refers to the processing of acoustic stimuli over time. Temporal processing is very important for us to be able to understand speech in quiet and in background noise. Temporal aspects of audition include temporal resolution, temporal masking, temporal integration and temporal ordering.
Auditory evoked potentials testing is one of the objective modes of assessment to check the integrity of the auditory function and neuroplasticity. These measures complement the information provided by behavioral measures.
The obligatory cortical evoked potential consists of three peaks that are recorded within a latency range extending from 50 to 200 ms., traditionally labeled individually as P1, N1, and P2. The P1-N1-P2 recorded from the auditory cortex following presentation of an acoustic stimulus is believed to reflect the neural encoding of a sound signal, but this provides no information regarding sound discrimination.
The neural processing underlying behavioral discrimination capacity can be measured by modifying the traditional methodology for recording the P1-N1-P2. These cortical potentials, when obtained in response to a 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 validate the clinical use of ACC as an objective tool in children who had been diagnosed as having Auditory Temporal Processing Disorders (ATPD) and explore how far the ACC evoked potential could be correlated to behavioral tests of temporal processing.
The study group comprised 30 children diagnosed as having ATPD with age ranging from 6 to 12 years and from whom reliable consistent behavioral thresholds could be obtained. A group of 39 age-matched normal hearing children served as the control group whose data were obtained from a previous research. For ACC testing, stimuli used were 500 msec. with spectral change (/i/ to /u/ and /u/ to /i/ vowels), temporal change (50 msec. to 150 msec. gap-in-1000 Hz tones) and frequency change (10%, 25%, 50% using 1000 Hz tone). ACC response parameters were studied and compared to AFT, PPD and PPS behavioral test results.
Results of the present study showed that ACC using short stimuli was successfully recorded in ATPD children, but at much higher magnitude of change compared to the control group. The highest percent identification was in temporal change, followed by frequency change, then spectral (vowel) change. When using gap change ACC, latency changes systematically with the magnitude of change, thus is considered superior to amplitude measures. ACC using short stimuli could not replace behavioral tests for temporal processing used in this study since there was no consistent significant correlation between both tests.
It is recommended to screen young or difficult-to-test children for ATPD by ACC using 30 msec. temporal change. If no response is obtained, ATPD is suspected, and the child should be assessed using a larger magnitude of change. Further research is needed to study the effect of remediation in ATPD children by comparing ACC response pre- and post-remediation. Also, more research is needed to study the complex relationship between electrophysiological and behavioral tests for ATP.