Porter Heather L, Grantham D Wesley, Ashmead Daniel H, Tharpe Anne Marie
1Department of Hearing and Speech Sciences, Vanderbilt University, Nashville, Tennessee, USA; and 2Department Of Otolaryngology-Head and Neck Surgery University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Ear Hear. 2014 Jul-Aug;35(4):e134-42. doi: 10.1097/AUD.0000000000000026.
Binaural hearing results in a number of listening advantages relative to monaural hearing, including enhanced hearing sensitivity and better speech understanding in adverse listening conditions. These advantages are facilitated in part by the ability to detect and use interaural cues within the central auditory system. Binaural hearing for children with Down syndrome could be impacted by multiple factors including, structural anomalies within the peripheral and central auditory system, alterations in synaptic communication, and chronic otitis media with effusion. However, binaural hearing capabilities have not been investigated in these children. This study tested the hypothesis that children with Down syndrome experience less binaural benefit than typically developing peers.
Participants included children with Down syndrome aged 6 to 16 years (n = 11), typically developing children aged 3 to 12 years (n = 46), adults with Down syndrome (n = 3), and adults with no known neurological delays (n = 6). Inclusionary criteria included normal to near-normal hearing sensitivity. Two tasks were used to assess binaural ability. Masking level difference (MLD) was calculated by comparing threshold for a 500-Hz pure-tone signal in 300-Hz wide Gaussian noise for N0S0 and N0Sπ signal configurations. Binaural intelligibility level difference was calculated using simulated free-field conditions. Speech recognition threshold was measured for closed-set spondees presented from 0-degree azimuth in speech-shaped noise presented from 0-, 45- and 90-degree azimuth, respectively. The developmental ability of children with Down syndrome was estimated and information regarding history of otitis media was obtained for all child participants via parent survey.
Individuals with Down syndrome had higher masked thresholds for pure-tone and speech stimuli than typically developing individuals. Children with Down syndrome had significantly smaller MLDs than typically developing children. Adults with Down syndrome and control adults had similar MLDs. Similarities in simulated spatial release from masking were observed for all groups for the experimental parameters used in this study. No association was observed for any measure of binaural ability and developmental age for children with Down syndrome. Similar group psychometric functions were observed for children with Down syndrome and typically developing children in most instances, suggesting that attentiveness and motivation contributed equally to performance for both groups on most tasks.
The binaural advantages afforded to typically developing children, such as enhanced hearing sensitivity in noise, were not as robust for children with Down syndrome in this study. Children with Down syndrome experienced less binaural benefit than typically developing peers for some stimuli, suggesting that they could require more favorable signal-to-noise ratios to achieve optimal performance in some adverse listening conditions. The reduced release from masking observed for children with Down syndrome could represent a delay in ability rather than a deficit that persists into adulthood. This could have implications for the planning of interventions for individuals with Down syndrome.
与单耳听力相比，双耳听力具有许多聆听优势，包括听力敏感度增强以及在不利聆听条件下能更好地理解言语。这些优势部分得益于中枢听觉系统检测和利用双耳线索的能力。唐氏综合征患儿的双耳听力可能受到多种因素影响，包括外周和中枢听觉系统的结构异常、突触通讯改变以及慢性渗出性中耳炎。然而，尚未对这些患儿的双耳听力能力进行研究。本研究检验了以下假设：唐氏综合征患儿获得的双耳益处比发育正常的同龄人少。
参与者包括6至16岁的唐氏综合征患儿（n = 11）、3至12岁的发育正常儿童（n = 46）、成年唐氏综合征患者（n = 3）以及无已知神经功能延迟的成年人（n = 6）。纳入标准包括听力敏感度正常至接近正常。使用两项任务评估双耳能力。通过比较在300赫兹宽高斯噪声中N0S0和N0Sπ信号配置下500赫兹纯音信号的阈值来计算掩蔽级差（MLD）。使用模拟自由场条件计算双耳清晰度级差。分别测量在0度、45度和90度方位呈现的言语噪声中，从0度方位呈现的闭集扬扬格词的言语识别阈值。通过家长调查问卷估计唐氏综合征患儿的发育能力，并获取所有儿童参与者的中耳炎病史信息。
唐氏综合征患者的纯音和言语刺激掩蔽阈值高于发育正常的个体。唐氏综合征患儿的MLD明显小于发育正常的儿童。成年唐氏综合征患者和对照成年人的MLD相似。对于本研究中使用的实验参数，所有组在模拟空间掩蔽释放方面观察到相似性。未观察到唐氏综合征患儿的任何双耳能力测量指标与发育年龄之间存在关联。在大多数情况下，唐氏综合征患儿和发育正常儿童观察到相似的群体心理测量函数，这表明注意力和动机对两组在大多数任务中的表现贡献相同。
在本研究中，发育正常儿童所具有的双耳优势，如在噪声中听力敏感度增强，对唐氏综合征患儿而言并不那么显著。对于某些刺激，唐氏综合征患儿获得的双耳益处比发育正常的同龄人少，这表明他们在某些不利聆听条件下可能需要更有利的信噪比才能达到最佳表现。唐氏综合征患儿观察到的掩蔽释放减少可能代表能力延迟而非持续到成年期的缺陷。这可能对唐氏综合征个体的干预计划有影响。
