Authors: Lina Motlagh Zadeh1*; Meghan Grojean2; Nathan Clevenger1 ; David Moore1
1Cincinnati Children’s Hospital Medical Center
2University of Cincinnati
Background Each year, about 50000 children in the US are diagnosed with auditory processing disorder (APD) due to listening difficulty (LiD), but with normal audiometry. Recent work suggests that LiD/APD is primarily dependent on cognitive, including linguistic problems. However, there is also evidence that a deficit in spatial hearing and difficulty hearing speech-in-noise may indicate a disorder of the central auditory system. This study aimed to isolate cognitive from auditory contributions to spatial release from masking (SRM). We compared speech reception thresholds (SRTs) on two tasks: 1) Spatial Advantage measure of the Listening in Spatialized Noise – Sentences (LiSN-S). Distracting sentences were virtually co-located with, or ±90o from, target sentences at 0o; 2) Sound-field Digits-in-Noise (sfDiN).
Method Babble noises were co-located with, or ±90o from, target digits at 0o. sfDiN was overall a less demanding task in terms of memory and linguistic interference than LiSN-S. Participants were 8-17 years old. All children underwent audiometric and behavioral testing of related skills. Typically developing children (TD; n=18) and children with LiD (n=17) had lower (better) SRTs on both tasks when the noise was at ±90o.
Results Despite similar performance at 0o in sfDIN, LiD children had significantly (p = 0.008) higher (poorer) SRTs than TD children at 90o resulting in significantly (p = 0.03) poorer SRM. In contrast, SRM in the LiSN-S task was not significantly different between the two groups. However, sfDIN-SRM was significantly correlated with the LiSN-S-SRM. Overall, we found significantly poorer ability of LiD children to differentiate target from background noise when the task was less demanding; sfDIN was more sensitive to LiD than LiSN-S.
Conclusion A related difference in SRM between LiD and TD groups on both tasks provides long-sought evidence that brain mechanisms primarily serving bottom-up auditory perception may contribute to listening difficulties in children with APD.