Functional organization of the human hippocampus: insights from high-resolution functional magnetic resonance imaging.

对于基础和临床神经科学来说，理解记忆是如何在人脑中维持和存储的仍然是一个关键挑战。海马体参与情景记忆已被广泛接受。海马体的损伤会导致广泛的记忆障碍，包括所有的形式，并跨越多个领域。在人类，海马体沿着前后轴被细分为子区域：海马头、海马体和海马尾。除大型解剖亚区外，海马体是一种异质结构，可进一步划分为几个组织学定义的亚区，包括腺角、齿状回和下丘。 有人认为，每个海马区和亚区可能与不同的记忆功能有关。然而，大多数结构和功能磁共振成像(MRI)研究都是将海马体作为单个结构或单个子区域内的海马子区进行研究。因此，有必要了解整个海马体的记忆是如何组织的，以便预测疾病过程或医疗干预将如何影响记忆的许多功能，并减少记忆丧失的风险。 虽然常规的fMRI采集序列没有足够的空间分辨率来识别单个海马亚区和亚区，但最近的人类高场fMRI研究提供了足够的空间分辨率(2 mm或更小)来更精确地定位海马的激活。我们的NSERC计划将通过应用一种新的高分辨率高场fMRI技术来扩展我们之前对海马体的研究，以确定人类海马体中记忆系统是如何组织和相互作用的。我们将测试海马体中的不同部分对正常记忆表现的贡献是否存在差异。 这些知识对于预测疾病进程或医疗干预将如何影响记忆功能，以及降低记忆丧失的风险都是必不可少的。在短期内，我们的目标是发现海马体内不同分区支持的特殊角色，以及它们与其他内侧颞叶结构的独特相互联系。从长远来看，更好地了解记忆在海马体中是如何组织的，对于改善各种疾病的记忆缺陷的预防和治疗至关重要。FMRI扫描将在彼得·S·艾伦MR研究中心的4.7特斯拉扫描仪上进行，该研究中心是生物医学工程部内的100%研究机构。 这项拟议的研究将对记忆和海马体的神经生物学研究产生重大影响，并将有助于解释在较低场强和空间分辨率下获得的测量结果。

Understanding how memories are maintained and stored in the human brain remains a key challenge for both basic and clinical neuroscience. The involvement of the hippocampus in episodic memory is well accepted. Damage to the hippocampus results in broad memory impairment that includes all modalities and extends across multiple domains. In humans, the hippocampus is subdivided along the anteroposterior axis into subregions: the hippocampal head, body, and tail. Apart from large-scale anatomical subregions, the hippocampus is a heterogeneous structure that can be further delineated into several histologically-defined subfields, including the cornu ammonis, dentate gyrus, and subiculum. It has been suggested that each hippocampal subregion and subfield could be associated with a distinct memory function. However, most structural and functional Magnetic Resonance Imaging (MRI) studies have examined the hippocampus as a single structure or hippocampal subfields within a single subregion. Therefore, it is necessary to understand how memories are organized across the entire hippocampus, both in order to predict how disease processes or medical interventions will affect the many functions of memory, and to reduce the risk or memory loss. Although conventional fMRI acquisition sequences do not have sufficient spatial resolution to identify individual hippocampal subregions and subfields, recent human high-field fMRI studies provided sufficient spatial resolution (2mm or less) to localize hippocampal activations more precisely. Our NSERC proposal will extend our previous research on hippocampus by applying a new high resolution high field fMRI technique in order to determine how memory systems in the human hippocampus are organized and interact. We will test if there is a distinction between divisions in the hippocampus in how each contributes to normal memory performance. This knowledge is essential both in order to predict how disease processes or medical interventions will affect memory functions, and to reduce the risk of memory loss. In the short term, we aim to uncover the specialized roles supported by different divisions within the hippocampus, as well as their unique interconnections with other medial temporal lobe structures. In the long term a better understanding of how memories are organized in the hippocampus is essential to improve both the prevention and the treatment of memory deficits across a wide range of diseases. fMRI scans will be performed on a 4.7 Tesla scanner at the Peter S. Allen MR Research centre, the 100% research facility within the Department of Biomedical Engineering. The proposed study will have significant implications for neurobiological studies of memory and hippocampus and will aid in the interpretation of measurements obtained at lower field strength and spatial resolution.