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Background and Aim: To date, the function of auditory efferent system remains unclear. There is evidence that medial olivocochlear bundle receives descending input from the cortex. In this study, the effect of auditory selective attention on stimulus-frequency otoacoustic emissions (SFOAE) was analyzed to investigate the modification of peripheral auditory system by auditory cortex activity in frequency specific mode.
Methods: Thirty-six normal hearing adult subjects with their age ranging from 18 to 30 years (mean age: 21.9 years) participated in this cross-sectional study. Contralateral suppression of stimulus-frequency otoacoustic emissions was recorded in the right ear at 2 KHz. In order to eliminate the auditory attention, subjects were instructed to read a text. Besides, in order to evaluate the effect of auditory attention on contralateral suppression, subjects were instructed to detect target tones in background noise at 1000, 2000, and 4000 KHz.
Results: A significant increase at contralateral suppression of stimulus-frequency otoacoustic emissions was observed in auditory selective attention conditions (p≤0.001). The largest magnitude of stimulus-frequency otoacoustic emissions suppression was seen at 2 KHz.
Conclusion: The results of this study indicated that the activities of medial olivocochlear bundle enhanced by contralateral auditory selective attention increase the magnitude of stimulus-frequency otoacoustic emissions suppression. In fact, these results provided evidence for influence of auditory cortex on the peripheral auditory system via corticofugal pathways in a frequency specific way.

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Background and Aim: Phenylketonuria (PKU) is an inherited metabolic disease. The aim of this study was investigation the intelligence and language function in children with PKU based on the age of treatment onset and quality of dietary control.

Methods: In this cross-sectional study, the language and intelligence of 31 children with PKU at the age of 4 to 6.5 years were investigated by test of language development-third edition ( TOLD-3) and Wechsler preschool and primary scale of intelligence (WIPPSI), respectively the data compared with of 42 normal children. Patients were classified into 2 groups with different level of dietary control as good and poor [serum phenylalanine (Phe) level less and more than 6 mg/dl, respectively].

Results: There were significantly differences (p=0.001) between children with PKU and controls in intelligence and language scores. Early treatment improved significantly the intelligence and language scores in comparison with late treatment (p=0.019). Comparing late treatment before and after the age of 1 year showed that late treatment until 1 years of age improved significantly (p=0.050) all of functions except performance intelligence quotient (IQ). In early treated PKU, good dietary control improved significantly (p=0.021) and also, verbal and total IQ in comparison with poor dietary control.

Conclusion: Although, the language development in children with PKU is affected by age of treatment onset, cognitive development features such as verbal and total IQ is affected not only by the time of treatment onset but also by the quality of dietary control.