FUNCTIONAL ORGANIZATION OF THE VENTRAL STREAM IN NORMALLY DEVELOPING CHILDREN AN

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。本研究考察了在成人中发现的腹侧流区域，包括颞叶后皮层和枕叶腹外侧皮层的视觉对象类别依赖活动是否存在于发育过程中，以及该组织是否因发育障碍而中断。研究的疾病是威廉姆斯综合征（WS），一种罕见的遗传缺陷，以不均匀的认知特征为特征。尽管WS患者在视觉空间任务（如砌块构建）上存在严重障碍，但他们的面部识别能力完好无损。这种视觉能力的模式导致了一种建议，即WS的遗传缺陷不会改变腹侧流中物体识别的视觉表征，但会对由背侧流提供的视觉空间表征造成广泛的损害。这些研究的目的是通过详细检查WS的腹侧流功能来评估这一说法。我们将比较青少年和年轻WS患者与正常发育人群的fMRI激活模式。将使用两个正常发育的对照组，儿童在实足年龄上大致匹配（CA匹配：14-18岁），儿童在心理年龄上匹配（MA匹配：6-9岁）。目前，关于腹侧流发育的证据很少，因此我们将首先研究儿童是否表现出与先前在成人中发现的相似的腹侧流组织，然后研究WS患者是否与CA或MA匹配。这一证据将解决一个正在进行的争论，即具有严重后果的基因缺陷是否会导致新的策略和发育中的神经重组（Karmiloff-Smith, 1998）。为了验证这一点，我们提出了两个功能性MRI实验。其中一项任务将使用被动观看人脸、房屋、猫和鞋子来测试腹侧流功能。第二个任务将使用相同对象的工作记忆范式。通过使用多种物体类型作为刺激，我们可以研究WS中发现的保留的人脸识别能力是否表明一个功能完整的腹侧流，在Fusiform face area （FFA）中保留了一小部分功能，还是一个替代系统。被动观看提供了低任务要求的任务，从而最大限度地减少了与任务难度相关的混淆。建立良好的记忆范式也有明显的好处；除了产生强大的腹侧流活动外，它还使我们能够检查前额叶激活并评估激活与工作记忆任务表现之间的关系。在行为研究中，患有WS的人对某些物体类别表现出记忆障碍，这种缺陷可能反映了前额叶区域的异常激活。这些影像学研究，加上我们实验室所做的广泛的行为研究，将为WS患者和正常发育儿童的腹侧流和前额皮质所提供的视觉功能提供关键的详细信息。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The present studies examine whether the visual object category-dependent activity found maong adults in ventral stream areas, including posterior temporal and ventrolateral occipital cortices, exists during development and whether this organization is disrupted by a developmental disorder. The disorder examined is Williams Syndrome (WS), a rare genetic deficit characterized by an uneven cognitive profile. People with WS have intact face recognition capacities in spite of severe impairments on visual spatial tasks such as block construction. This pattern of visual abilities has led to the proposal that the genetic defect in WS does not alter the visual representations underlying object recognition in the ventral stream but does cause extensive damage to the visual spatial representations subserved by the dorsal stream. The purpose of these studies is to evaluate this claim by examining in detail ventral stream function in WS. We will compare the pattern of fMRI activation in adolescents and young adults with WS to normally developing populations. Two normally developing control groups will be used, children matched approximately on chronological age (CA matches: ages 14-18) and children matched in mental age (MA matches: ages 6-9). Currently, little evidence exists on the development of the ventral stream, so we will first examine whether children display similar ventral stream organization to that found previously in adults, and then whether people with WS resemble either CA or MA matches. This evidence will address an ongoing debate on whether genetic deficits with severe consequences lead to novel strategies and neural reorganization over development (Karmiloff-Smith, 1998). To examine this, two functional MRI experiments are proposed. One task will use passive viewing of human faces, houses, cats, and shoes to test ventral stream function. The second task will use a working memory paradigm with the same objects. By utilizing a variety of object kinds as stimuli, we can investigate whether the spared face recognition abilities found in WS indicate a fully functioning ventral stream, a small area of preserved function I the Fusiform Face Area (FFA), or an alternative system. Passive viewing provides a task with low task demands, thus minimizing confounds related to task difficulty. The well established memory paradigm also has distinct benefits; in addition to producing robust ventral stream activity, it enables us to examine prefrontal activation and assess the relationship between activation and performance on the working memory task. In behavioral studies, people with WS display memory impairments with some object categories, a deficit that may reflect abnormal activation in prefrontal areas. These imaging studies, together with the extensive behavioral studies done in our laboratory, will provide crucial, detailed information on the visual functions subserved by the ventral stream and prefrontal cortex in people with WS and normally developing children.