Kaganovich Natalya, Schumaker Jennifer, Macias Danielle, Gustafson Dana
Department of Speech, Language, and Hearing Sciences, Purdue University, USA.
Department of Psychological Sciences, Purdue University, USA.
Dev Sci. 2015 Sep;18(5):751-70. doi: 10.1111/desc.12263. Epub 2014 Nov 29.
Previous studies indicate that at least some aspects of audiovisual speech perception are impaired in children with specific language impairment (SLI). However, whether audiovisual processing difficulties are also present in older children with a history of this disorder is unknown. By combining electrophysiological and behavioral measures, we examined perception of both audiovisually congruent and audiovisually incongruent speech in school-age children with a history of SLI (H-SLI), their typically developing (TD) peers, and adults. In the first experiment, all participants watched videos of a talker articulating syllables 'ba', 'da', and 'ga' under three conditions - audiovisual (AV), auditory only (A), and visual only (V). The amplitude of the N1 (but not of the P2) event-related component elicited in the AV condition was significantly reduced compared to the N1 amplitude measured from the sum of the A and V conditions in all groups of participants. Because N1 attenuation to AV speech is thought to index the degree to which facial movements predict the onset of the auditory signal, our findings suggest that this aspect of audiovisual speech perception is mature by mid-childhood and is normal in the H-SLI children. In the second experiment, participants watched videos of audivisually incongruent syllables created to elicit the so-called McGurk illusion (with an auditory 'pa' dubbed onto a visual articulation of 'ka', and the expectant perception being that of 'ta' if audiovisual integration took place). As a group, H-SLI children were significantly more likely than either TD children or adults to hear the McGurk syllable as 'pa' (in agreement with its auditory component) than as 'ka' (in agreement with its visual component), suggesting that susceptibility to the McGurk illusion is reduced in at least some children with a history of SLI. Taken together, the results of the two experiments argue against global audiovisual integration impairment in children with a history of SLI and suggest that, when present, audiovisual integration difficulties in this population likely stem from a later (non-sensory) stage of processing.
先前的研究表明，特定语言障碍（SLI）儿童的视听言语感知至少某些方面存在受损情况。然而，有这种障碍病史的大龄儿童是否也存在视听加工困难尚不清楚。通过结合电生理和行为测量方法，我们研究了有SLI病史（H-SLI）的学龄儿童、发育正常（TD）的同龄人以及成年人对视听一致和视听不一致言语的感知。在第一个实验中，所有参与者在三种条件下观看一个说话者发出音节“ba”“da”和“ga”的视频——视听（AV）、仅听觉（A）和仅视觉（V）。与从所有参与者组的A和V条件总和测量得到的N1振幅相比，在AV条件下诱发的N1（而非P2）事件相关成分的振幅显著降低。由于N1对AV言语的衰减被认为可指示面部运动预测听觉信号起始的程度，我们的研究结果表明，视听言语感知的这一方面在童年中期已成熟，且在H-SLI儿童中是正常的。在第二个实验中，参与者观看了为引发所谓的麦格克错觉而制作的视听不一致音节的视频（将听觉上的“pa”与视觉上的“ka”发音叠加，若发生视听整合，预期感知为“ta”）。总体而言，H-SLI儿童比TD儿童或成年人更有可能将麦格克音节听成“pa”（与听觉成分一致）而非“ka”（与视觉成分一致），这表明至少一些有SLI病史的儿童对麦格克错觉的易感性降低。综合来看，这两个实验的结果反对有SLI病史儿童存在整体视听整合障碍的观点，并表明，若存在这种情况，该人群中的视听整合困难可能源于后期（非感官）加工阶段。
