Development of Cerebral Specializations

描述(申请人提供)：这里提出的研究旨在确定在人类发育过程中，哪些神经系统和相关功能最依赖于经验(即来自环境的输入)并被修改。我们将描述特定知觉和语言系统表现出依赖经验的变化的时间段(敏感期)，并将这些系统与那些在一生中保持变化能力的系统进行对比。在这些研究中，我们将获取大脑的事件相关脑电位(ERPs)以及结构和功能磁共振图像(MRI)，以准确地表征神经激活的时间和位置，因为这些受试者执行的任务旨在激活感觉、注意力和语言功能的特定方面。在一系列研究视觉知觉和注意的神经可塑性的研究中，我们将评估以下假设：(1)先天性耳聋受试者(SS)比听障受试者(SS)对有人和无人注意的视觉刺激都更敏感，并表现出更广泛的神经激活，特别是在视野的远外围(20)；(2)聋人比听力受试者更多的神经激活发生在较低水平和较高水平的视区、多峰区域以及初级和次级听觉皮质；(3)先天耳聋患者脑白质束的某些改变可归因于听觉剥夺，而其他改变则是阅读经验减少的结果。在语言子系统的神经可塑性研究中，我们将(1)评估和比较基于时间的注意和语音分割的指数，以检验英语母语学习者和英语学习后期学习者注意的领域一般方面是言语感知技能的核心这一假设；(2)表征听力正常的单语成人在句法和语义加工中重要的神经系统的特性和时程；(3)通过研究习得第二语言较晚且语言水平不同的双语者，评估和比较第二语言习得延迟和语言熟练水平对这些相同子系统的影响；以及(4)评估假设，即当本族语者处理ASL中的语音信息时，激活的神经系统与当本族语者处理英语音素时激活的神经系统广泛重叠，并且这些系统依赖于早期接触ASL。由于拟议的研究将确定感知、注意力和语言的哪些方面最容易受到环境输入的改变，以及它们最易改变的时间段，这些研究可以为听力和聋人以及第二语言后期学习者教育计划的制定、完善和评估提供具有实际意义的信息。

DESCRIPTION (provided by applicant): The research proposed here is directed toward determining which neural systems and related functions are most dependent on and modified by experience (i.e. input from the environment) during human development. We will characterize the time periods (sensitive periods) when particular perceptual and language systems display experience-dependent changes and contrast these systems with those that retain the ability to change throughout life. In these studies we will acquire event-related brain potentials (ERPs) and structural and functional magnetic resonance images (MRI) of the brain to precisely characterize both the timing and the location of neural activations as these groups of subjects perform tasks designed to activate specific aspects of sensory, attentional and language functions. In a series of studies investigating neuroplasticity of visual perception and attention, we will assess the hypotheses that: (1) congenially deaf subjects (Ss) are more sensitive to and display more extensive neural activations than hearing Ss to both attended and unattended visual stimuli, especially in the far periphery (>20¿) of the visual fields; (2) the increased neural activations in deaf compared to hearing Ss occur in lower- level and higher-level visual areas, multimodal areas and primary and secondary auditory cortices; and (3) certain alterations in white matter tracts in congenially deaf individuals are attributable to auditory deprivation while others are a consequence of reduced experience in reading. In studies investigating neuroplasticity of subsystems of language we will (1) assess and compare indices of temporally-based attention and speech segmentation to test the hypothesis that domain-general aspects of attention are central to speech perception skills in native and late learners of English; (2) characterize the identity and time-course of operation of the neural subsystems important in syntactic and semantic processing in normal hearing monolingual adults who vary in language proficiency; (3) assess and compare the effects of delays in second language (L2) acquisition and level of language proficiency on these same subsystems by studying bilinguals who acquired L2 late and who attained different proficiency levels; and (4) assess the hypotheses that the neural systems active when native signers process phonological information in ASL overlap extensively with systems active when native speakers process English phonology and that these systems are dependent on early exposure to ASL. Since the proposed research will determine aspects of perception, attention and language that are most altered by environmental input and the time periods when they are most modifiable, these studies can contribute information of practical significance for the development, refinement and evaluation of educational programs for hearing and deaf individuals and late learners of a second language.