Influence of early experience of speech and language on their processing and neural representation: A study of hearing infants with deaf mothers

该项目旨在确定早期言语和语言经验对大脑中语言处理和表征的影响。我将研究使用手语作为主要语言的失聪母亲的听力婴儿(Hod婴儿)和听力母亲的听力婴儿(HoH婴儿)。尽管听力正常，但HOD婴儿在言语和语言方面的早期体验与HOH婴儿不同。首先，由于手语失聪的母亲比听力正常的母亲更不可能使用听觉语言，她们的婴儿可能会减少接触听觉口语的机会。其次，HOD婴儿的经历既包括视觉形式的语言，例如英国手语(BSL)，也包括听觉形式的语言，例如英语(由母亲以及听力亲属和听力社区的其他成员使用)。由于HOD婴儿接触两种语言，他们将被与接触两种语言的HOD个体进行比较。我假设，Hod婴儿的经历会影响他们对语言的神经表征，他们在口语和手语感知过程中的眼睛凝视模式，以及他们的视听语言整合。将招募三组听力婴儿：30名来自单语英语环境的婴儿，30名来自母亲经常使用两种口语的双语环境中的婴儿，30名母亲以BSL为主要语言的聋人母亲的婴儿。实验1-口语的神经表征：我将使用近红外光谱(NIRS)来研究口语感知过程中大脑的激活。在婴儿期，口语激活左侧颞半球的区域与成年时相似。有人假设，这种模式是在接受母亲口语输入的过程中在产前发展起来的。我将通过研究早期听觉口语经验减少的Hod婴儿来检验这一假设。听力句子将用英语和一种不熟悉的语言呈现。我预测，早期听觉口语体验的减少会导致颞叶语言激活的减少。实验2-手语的神经表征：当婴儿看到BSL句子和一种不熟悉的手语时，我将使用近红外光谱来研究大脑的激活。成人神经成像研究表明，手语和口语是在一个类似的大脑网络中处理的，但这个网络在婴儿期从未被研究过。我假设，与不熟悉的手势相比，Hod婴儿在BSL的颞叶皮质中表现出更多的大脑活动。在实验1中，我将比较BSL和熟悉口语的优先激活：实验3-手语和口语知觉：我将使用眼动跟踪来研究婴儿在观看以视听英语或BSL呈现的句子时的眼神注视。与口语不同，手语需要注意说话者的视觉注意力，成年的母语手语者在感知手语时专注于手语者的面部而不是他们的手。我假设，在手语和口语感知过程中，HOD婴儿会比HHH婴儿花更多的时间看说话者的脸。实验4-视听语音整合：我将使用眼球跟踪和已建立的视听语音感知范式来比较Hod和HoH婴儿如何使用发音的视觉线索来区分语音。两个月大的婴儿就能整合语言的视听方面。HOD成人在唇读方面的表现优于HH成人，这表明他们从发音的视觉线索中提取更多信息。我假设Hod婴儿将更多地依赖语音感知中发音的视觉线索。同时，这项研究的结果将阐明早期经验在塑造大脑发育和语言学习方面的作用。

This project aims to determine the impact of early speech and language experience on language processing and representation in the brain. I will study hearing infants of deaf mothers who use a sign language as their dominant language (HoD infants) in comparison to hearing infants of hearing mothers (HoH infants). Despite normal hearing, HoD infants have a different early experience of speech and language to that of HoH infants. First, since deaf signing mothers are less likely to use auditory speech than hearing mothers, their infants are likely to have reduced exposure to auditory spoken language. Second, the experience of HoD infants includes both a language in the visual modality, e.g. British Sign Language (BSL), and one in the auditory modality, e.g. English (used by the mother, as well as by hearing relatives and the rest of the hearing community). Since HoD infants are exposed to two languages, they will be compared to HoH individuals who are exposed to two spoken languages. I hypothesise that the experience of HoD infants will influence their neural representation of language, their patterns of eye gaze during spoken and signed language perception and their audio-visual speech integration. Three groups of hearing infants will be recruited: 30 infants from a monolingual English speaking environment, 30 infants from a bilingual environment in which two spoken languages are frequently used by the mother, 30 infants with a deaf mother for whom BSL is the dominant language. Experiment 1- Neural representation of spoken language: I will use near infrared spectroscopy (NIRS) to study brain activation during spoken language perception. In infancy, spoken language activates similar areas of the left temporal hemisphere as in adulthood. It has been hypothesised that this pattern develops prenatally while receiving the input of the mother's spoken language. I will test this hypothesis by studying HoD infants with reduced early experience of auditory spoken language. Auditory sentences will be presented in English and an unfamiliar language. I predict that reduced early experience of auditory spoken language leads to a reduction in language activation in the temporal lobe.Experiment 2- Neural representation of signed language: I will use NIRS to study brain activation while infants are presented with sentences in BSL and an unfamiliar signed language. Adult neuroimaging studies demonstrate that signed language is processed in a similar brain network as spoken language, but this network has never been studied in infancy. I hypothesise that HoD infants will show increased brain activity in the temporal cortex for BSL compared to unfamiliar gestures. I will compare any preferential activation for BSL with that for a familiar spoken language in Experiment 1.Experiment 3- Signed and spoken language perception: I will use eye tracking to study infants' eye gaze while watching sentences presented either in audio-visual English or BSL. Unlike spoken languages, signed languages require visual attention to the speaker, and adult native signers focus on the signer's face and not their hands while perceiving signed language. I hypothesise that HoD infants will spend more time than HoH infants looking at the speaker's face during signed and spoken language perception. Experiment 4- Audio-visual speech integration: I will use eye tracking and an established audio-visual speech perception paradigm to compare how HoD and HoH infants use visual cues of articulation to discriminate speech sounds. Infants as young as two months can integrate the audio-visual aspects of speech. HoD adults outperform HoH adults in lip-reading, suggesting that they extract more information from visual cues of articulation. I hypothesise that HoD infants will rely more on the visual cues of articulation in speech perception.Together, the results of this study will shed light on the role of early experience in shaping brain development and language learning.