Imaging of the brain response to magnetoreception

50多年来的行为研究表明，许多动物能够感知比地球磁场更弱的稳定磁场，并利用这种非凡的定向、导航和归巢能力。磁感受如何在身体和神经生理学上发挥作用的有趣问题仍然是一个有争议的问题。主要的候选机制是磁性纳米颗粒以某种方式与神经系统耦合，以及涉及光诱导自旋相关自由基的场依赖性化学反应。在该项目中，将进一步开发一种新的非侵入性光学技术，即近红外扩散波光谱（DWS），并用于在受控实验室条件下监测和成像不同动物（主要是信鸽）的磁感受相关大脑活动。 DWS 可在低于微秒的时间尺度上检测到纳米级的机械运动，因此有可能补充其他技术，例如相对较慢的功能性磁共振成像，通过获取刺激后的毫秒时间，可以区分诱发神经活动和代谢变化。各种刺激，例如磁场强度、梯度和方向、强场脉冲、调制场、光强度和偏振以及气味将单独或组合使用。这应该可以对两种磁接收机制的特征进行关键测试，并量化它们的重要性和最终的相互作用。

Behavioural studies over more than 50 years have shown that many animals are able to sense steady magnetic fields even weaker than the earth field and exploit this extraordinary capacity for orientation, navigation and homing. The intriguing question how magnetoreception works, both physically and neuro-physiologically, is still a matter of debate. Major candidate mechanisms are magnetic nanoparticles somehow coupled to the nervous system and field dependent chemical reactions involving photo-induced spin-correlated free radicals. In this project a new non-invasive optical technique, Near Infrared Diffusing Wave Spectroscopy (DWS), will be further developed and used to monitor and image magnetoreception-related brain activity in different animals, primarily homing pigeons, under controlled laboratory conditions. DWS detects mechanical motions down to nm at time scales below µsec and thus has potential to complement other techniques, such as functional Magnetic Resonance Imaging which is comparably slow, by accessing msec post-stimulus times were evoked nervous activity and metabolic changes can be distinguished. Various stimuli such as magnetic field strength, gradient and direction, strong field pulses, modulated fields, light intensity and polarization, and odours will be used either separately or in combinations. This should allow critical tests of the features of both mechanisms of magnetoreception and quantify their significance and eventual interplay.