Functional MRI at Columnar Resolution

柱状分辨率的功能 MRI

• 批准号: 8446987
• 负责人: MITSUHIRO FUKUDA
• 金额: $ 30.25万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-12-01 至 2016-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8446987
• 关键词: Animals; Blood; Blood Volume; Blood capillaries; Brain; Cerebrovascular Circulation; Cerebrum; Communities; Contrast Media; Cortical Column; Data; Development; Felis catus; Functional Magnetic Resonance Imaging; Funding; Goals; Grant; Human; Imaging Techniques; Injection of therapeutic agent; Investigation; Longitudinal Studies; Maps; Measurement; Measures; Medical; Methods; Modeling; Oxygen measurement, partial pressure, arterial; Patients; Physiological; Recovery; Research; Resolution; Role; Sensitivity and Specificity; Signal Transduction; Slice; Source; Specificity; Stimulus; Structure; Techniques; Time; Tissues; Veins; Visual Cortex; Weight; arteriole; base; blood oxygen level dependent; capillary; deoxyhemoglobin; design; hemodynamics; improved; magnetic field; millimeter; novel; optical imaging; orientation columns; relating to nervous system; response; tool

DESCRIPTION (provided by applicant): Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) is an essential tool for mapping human brain activity in the medical and scientific communities. Despite its indispensable role, BOLD fMRI has not been routinely used to map sub-millimeter functional structures due to draining vein contributions, a relatively broad point spread function, and low neural activity-specific signal sensitivity. Multipe approaches to overcome these problems have included the use of ultrahigh magnetic fields, improved imaging techniques, and continuous cyclic stimulation paradigm (vs. block design). During the last grant period, optical imaging of intrinsic signals (OIS) confirmed that with these improvements, high BOLD fMRI responses co- localize with active orientation columns, thus demonstrating that functional columns can be mapped with hemodynamic-based fMRI. However, even with these approaches, the physiological source of columnar- resolution BOLD fMRI signals is unclear and there is relatively poor signal contrast between active and inactive columns. High-specificity fMRI techniques must be further explored and optimized before they can be more widely applied to the study of basic mechanisms with relevance to human brain. In this competitive renewal application investigating a well-established orientation column model of the cat visual cortex at 9.4 Tesla, we aim to systematically determine the physiological source of columnar-resolution BOLD fMRI signals, and investigate whether these signals can be enhanced non-invasively. Specific Aim #1 is to determine the physiological source of columnar-resolution BOLD fMRI signals. There is an apparent discrepancy between BOLD and OIS results for neuronally-active vs. neighboring inactive columns; BOLD results suggest highest hyper-oxygenation in active columns, while OIS studies suggest highest hyper-oxygenation in inactive columns. To determine the physiological sources of columnar-resolution BOLD fMRI signals, BOLD fMRI, tissue oxygen tension, multi-unit activity, and OIS will be measured whether highest hyper-oxygenation occurs during stimulation at preferred or at non-preferred orientations. We hypothesize that change in the blood oxygenation levels are not the dominant contribution to column-specific BOLD fMRI responses. Specific Aim #2 is to enhance sub-millimeter column-specific fMRI signals by non-invasive methods. BOLD fMRI has relatively poor sub-millimeter column-specific signal, thus its sensitivity may be enhanced with cerebral blood flow (CBF)-weighted fMRI and cerebral blood volume (CBV)-weighted fMRI. Thus, we propose to compare non-invasive, sub-millimeter column-specific responses for multiple techniques including BOLD fMRI, arterial CBV-enhanced fMRI with magnetization transfer effect, and CBF-enhanced fMRI. We hypothesize that non- invasive arterial CBV-weighted and CBF-weighted fMRI techniques will show enhanced fMRI responses from sub-millimeter functional structures. The long-term goal of these investigations is to improve the capability of mapping responses from fine functional structures in both animals and humans non-invasively.

描述（由申请人提供）：血氧水平依赖（BOLD）功能磁共振成像（fMRI）是医学和科学界绘制人脑活动的重要工具。尽管其不可或缺的作用，BOLD功能磁共振成像尚未被常规用于映射亚毫米功能结构，由于引流静脉的贡献，一个相对较宽的点扩散函数，和低的神经活动特异性信号灵敏度。克服这些问题的多种方法包括使用超高磁场、改进的成像技术和连续循环刺激范式（与区块设计相比）。在最后一次授权期间，内在信号的光学成像（OIS）证实，随着这些改进，高BOLD fMRI响应与主动定向列共定位，从而证明功能列可以用基于血液动力学的fMRI映射。然而，即使使用这些方法，柱状分辨率BOLD fMRI信号的生理来源也不清楚，并且在活动和非活动柱状之间存在相对较差的信号对比度。高特异性的功能磁共振成像技术还有待进一步探索和优化，才能更广泛地应用于与人脑相关的基本机制的研究。在这个竞争性的更新应用程序调查一个完善的方向柱模型的猫视觉皮层在9.4特斯拉，我们的目标是系统地确定柱分辨率BOLD功能磁共振成像信号的生理来源，并调查这些信号是否可以增强非侵入性。具体目标#1是确定列分辨率BOLD fMRI信号的生理来源。对于神经元活性柱与相邻的非活性柱，BOLD和OIS结果之间存在明显差异; BOLD结果表明活性柱中的过度氧合最高，而OIS研究表明非活性柱中的过度氧合最高。为了确定柱分辨率BOLD fMRI信号的生理来源，将测量BOLD fMRI、组织氧张力、多单位活动和OIS，无论在优选或非优选方向的刺激期间是否发生最高的过度氧合。我们假设血氧水平的变化不是柱特异性BOLD fMRI反应的主要贡献。具体目标#2是通过非侵入性方法增强亚毫米柱特异性fMRI信号。BOLD fMRI亚毫米柱特异性信号相对较差，脑血流量（CBF）加权fMRI和脑血容量（CBV）加权fMRI可提高BOLD fMRI的敏感性。因此，我们建议比较非侵入性的，亚毫米柱特定的反应，多种技术，包括BOLD功能磁共振成像，动脉CBV增强功能磁共振成像与磁化传递效应，和CBF增强功能磁共振成像。我们假设，非侵入性动脉CBV加权和CBF加权功能磁共振成像技术将显示增强功能磁共振成像反应从亚毫米功能结构。这些研究的长期目标是提高非侵入性地从动物和人类的精细功能结构映射响应的能力。