The nature of parietal involvement in visual short-term memory

描述（由申请人提供）：本修订提案的目的是进一步详细说明后顶叶皮层（PPC）在视觉短期记忆（VSTM）中的作用。许多功能性磁共振成像（fMRI）研究观察到，在不同的VSTM任务中，双侧PPC激活。相比之下，PPC损伤与VSTM表现的普遍缺陷无关。已知右PPC损伤损害空间注意，而左PPC损伤损害数值量级的加工。功能磁共振成像和患者数据之间的冲突暗示了几种可能性：PPC患者的VSTM缺陷尚未得到仔细评估，或者神经成像激活是VSTM任务表现的副现象。在初步研究中，我发现单侧右侧PPC患者在物体、空间和物体-空间VSTM上对颜色、新形状和工具刺激类别表现出普遍的损害。左侧PPC患者没有表现出普遍的VSTM缺陷，在VSTM任务中表现正常。双侧PPC患者同时失认症（不能同时看到1个以上的东西）也会出现全局受损。双侧PPC也表现出对实验范式的敏感性，并且在新旧VSTM识别中的表现比在可比回忆任务中的表现更差。本研究的目的是探讨PPC参与VSTM的参数。解决了未解决的问题：VSTM损伤的机制（编码、维持、容量、检索），识别范式（旧/新识别与2种备选强迫选择）是否影响双侧PPC识别性能，以及左PPC激活是否由于参与加工量级。为了实现这一目标，我建议使用互补的方法来研究VSTM：单侧和双侧顶叶患者的神经心理学研究，以及正常受试者的功能磁共振成像（fMRI）。公共卫生相关性：这组研究与顶叶中风患者的康复特别相关。在美国，中风每年影响大约70万人，是第三大死亡原因，也是导致严重、长期残疾的主要原因。顶叶中风是相对常见的，对视力和行动的行为后果是毁灭性的。在拟议的研究中，对顶叶患者的VSTM损伤进行了评估。VSTM的缺陷与认知功能有直接的现实意义。这些数据可以提供负担得起的评估措施，并有助于指导康复策略。

DESCRIPTION (provided by applicant): The aim of this revised proposal is to further detail the role of the posterior parietal cortex (PPC) in visual short-term memory (VSTM). A number of functional magnetic resonance imaging (fMRI) studies observe bilateral PPC activations during varied VSTM tasks. In contrast, PPC damage is not associated with generalized deficits in VSTM performance. Right PPC damage is known to impair spatial attention while left PPC damage is known to impair processing of numerical magnitude. The conflict between fMRI and patient data suggests several possibilities: VSTM deficits in PPC patients have not been carefully evaluated, or neuroimaging activations are epiphenomenal to VSTM task performance. In preliminary studies, I show that unilateral right PPC patients exhibit general impairment at VSTM for object, spatial and object-spatial VSTM for colors, novel shapes and tools stimulus categories. Left PPC patients do not exhibit general VSTM deficits, performing normally in the VSTM tasks. Bilateral PPC patients with simultanagnosia (the inability to see more than 1 thing at a time) are also globally impaired. Bilateral PPC also demonstrate sensitivity to experimental paradigm and performed worse in old/new VSTM recognition than in comparable recall tasks. The goal of the proposed studies is to investigate the parameters of PPC involvement in VSTM. Unresolved issues are addressed: the mechanism of VSTM impairment (encoding, maintenance, capacity, retrieval), whether recognition paradigms (old/new recognition versus 2 alternative forced-choice) affect bilateral PPC recognition performance, and whether left PPC activitations are due to involvement in processing magnitude. To accomplish this goal, I propose studies examining VSTM using complimentary approaches: neuropsychological studies of unilateral and bilateral parietal patients, as well as functional magnetic resonance imaging (fMRI) with normal subjects. PUBLIC HEALTH RELEVANCE: This set of studies is particularly relevant to the rehabilitation of parietal stroke patients. In the United States, stroke affects approximately 700,000 people annually, is the third leading cause of death, and is the leading cause of serious, long-term disability. Parietal lobe strokes are relatively common and the behavioral consequences on vision and action are devastating. In the proposed studies, VSTM impairments in parietal patients are evaluated. Deficits in VSTM have direct real-world implications relating to cognitive function. These data may provide affordable assessment measures and help guide rehabilitation strategies.