title: Binaural masking level difference in skilled reading children and children with dyslexia.
abstract: BACKGROUND
  Combining stimuli arriving at both ears makes it possible to locate sounds in the environment and to better detect signals or understand speech in noise when the sound sources are separated spatially. The sensitivity of the binaural system to interaural differences in time and amplitude can be investigated by means of the binaural masking level difference (BMLD). The age at which the BMLD reaches adult levels appears to depend partly upon masker bandwidth. Less is known about the effect of masker's level on the development of BMLD in children. In the present study we assessed the effect of masker level on the BMLD of 3rd and 5th grade skilled reading children. In view of possible binaural hearing effects in dyslexia, the BMLD of a group of 5th grade children with reading difficulties was measured.
  
  
  METHODS
  Detection thresholds of 500 Hz pure tone were measured at noise levels of 40 dBHL, 50 dBHL and 60 dBHL.
  
  
  RESULTS
  All subjects presented increased MLD values with the rise of noise intensity between 40 dBHL and 60 dBHL. Among the skilled readers the results showed that younger children had smaller BMLDs than older children at all masker levels. However, a significant group-by-intensity interaction indicated that although the reading disabled group had reduced BMLD values than older skilled readers at noise levels of 50 dBHL and 60 dBHL, no difference was found between their BMLD values and those of the young skilled readers at noise levels of 50 dBHL and 60 dBHL. Moreover, their BMLD values at noise level of 40 dBHL were higher than those of the 3rd grade typically reading students while no difference was found between them and 5th grade efficient readers.
  
  
  CONCLUSIONS
  These results support the existence of both quantitative and qualitative differences in binaural hearing of children with developmental dyslexia.
authors.affiliation: Department of Communication Sciences and Disorders, Ono Academic College, Kiryat Ono, Israel. hputter@ono.ac.il
authors.forename: Hanna
authors.initials: H
authors.lastname: Putter-Katz
authors.forename: Irit
authors.initials: I
authors.lastname: Feldman
authors.forename: Minka
authors.initials: M
authors.lastname: Hildesheimer
mesh_terms: D000161:Acoustic Stimulation; D001301:Audiometry, Pure-Tone; D001302:Audiometry, Speech; D001309:Auditory Threshold; D002648:Child; D002657:Child Development; D004410:Dyslexia / Q000523:psychology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007557:Israel; D008297:Male; D009622:Noise / Q000009:adverse effects*; D010470:Perceptual Masking; D011932:Reading; D021641:Recognition, Psychology; D017603:Signal Detection, Psychological; D013067:Speech Perception