Development of Cerebral Specializations

描述（由申请人提供）：本文提出的研究旨在确定哪些神经系统和相关功能在人类发育过程中最依赖于经验（即来自环境的输入）并受到经验的修改。我们将描述特定感知和语言系统显示经验依赖性变化的时间段（敏感期），并将这些系统与那些保留终身变化能力的系统进行对比。在这些研究中，我们将获得大脑的事件相关脑电位（ERP）以及结构和功能磁共振图像（MRI），以精确表征神经激活的时间和位置，因为这些受试者组执行旨在激活感官，注意力和语言功能的特定方面的任务。在一系列关于视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）相聋被试比正常被试对有注意和无注意的视觉刺激更敏感，并且表现出更广泛的神经激活，特别是在视野的远边缘（>20 <$s）;（2）聋者较健听者在低、高级视区、多模态区和初级、次级听皮层的神经激活增加;（3）同性聋个体的白色物质束的某些改变可归因于听觉剥夺，而另一些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言语分割的指标，以验证注意的一般领域方面是本族语者和晚期英语学习者言语感知技能的核心这一假设;（2）确定身份和时间-不同语言水平的听力正常的单语成年人句法和语义加工中重要的神经子系统的运作过程;（3）通过研究学习第二语言较晚且达到不同熟练程度的双语者，评估和比较第二语言（L2）习得延迟和语言熟练程度对这些相同子系统的影响;以及（4）评估以下假设：当本族语者在ASL中处理语音信息时，激活的神经系统与当本族语者处理英语语音时激活的系统广泛重叠，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，注意力和语言的方面，最改变的环境输入和时间段时，他们是最可修改的，这些研究可以贡献的信息，具有实际意义的发展，完善和评估的教育计划，听力和聋人和第二语言的后期学习者。

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.