Anticipatory Hemodynamic Signals in Primary Visual Cortex

项目总监/首席调查员(最后、第一、中间)： 项目总结 我们的长期目标是在皮质通路的早期了解视觉处理的神经机制。 为此，我们记录了猕猴的视觉皮质，使用了固有信号光学的组合 成像和电生理学，而动物则从事视觉形式处理任务。 当前项目的目标有两个。我们建议研究一种新的刺激非依赖预测 我们之前在警觉猕猴V1(初级视觉皮质)中观察到的血流动力学信号。通过这件事 过程中，我们还建议更好地理解包括功能磁共振成像在内的神经成像信号的生理基础。 这个项目源于我们最近的发现，警觉的猴子V1的血流动力学信号有两个截然不同的 组件。其中一个成分可以通过视觉输入和相关的V1神经元活动来预测。另一个 具有相当强度的组件是一种迄今未知的血流动力学信号标记任务预期。它 反映了一种动脉泵送机制，为大脑皮质带来新鲜血液，以预测视觉事件。 与光学成像同时进行的电极记录表明，这种新的血流动力学 信号不是由局部V1神经元活动驱动的，这与获得的视觉诱发反应形成了鲜明对比 来自相同的录音地点。 我们假设预期的非刺激性血流动力学信号是一种预测机制 唤醒。我们建议通过表征预期和视觉诱发的信号来检验这一假设，并且 他们的相互作用，并询问预期信号是否可以调节视觉诱发的反应和行为。 我们对新的血流动力学信号的发现也挑战了目前对神经成像信号的理解， 值得注意的是功能磁共振成像(FMRI)，这是人类神经成像最常用的工具。 通过这个项目的过程，我们将研究神经成像信号和 电生理学在警觉的猕猴的各种视觉感知任务中。这将是一个无与伦比的 有机会在尽可能接近人类的动物模型中获得对功能磁共振成像的新见解。 我们的新发现是我们实验室开发的一种新的成像技术的结果， 连续双波长本征信号光学成像，结合电极记录，处于警戒状态 举止乖巧的猕猴。对于成像，一个波长优先被含氧的血红蛋白吸收， 从而监测血液的氧合作用；另一个波长，在充氧和去氧状态下被同等吸收 血红蛋白是用来测量血容量的。同时的电极记录给出了电生理 对潜在神经元活动的测量。连续的录音使我们能够区分 持续的信号和刺激引起的反应。这项技术将构成当前项目的基础， 提供了一种独特的工具组合来回答手头的问题。 PHS 398/2590(11/07版)页面续格式页面

Program Director/Principal Investigator (Last, First, Middle): PROJECT SUMMARY Our long-term goal is to understand the neural mechanisms of visual processing early in the cortical pathway. To this end we record from rhesus macaque visual cortex using a combination of intrinsic-signal optical imaging and electrophysiology while the animals are engaged in visual form processing tasks. The goal of the current project is two-fold. We propose to study a novel stimulus-independent anticipatory haemodynamic signal that we observed earlier in alert macaque V1 (primary visual cortex). Through this process we also propose to better understand the physiological basis of neuroimaging signals including fMRI. This project derives from our recent discovery that haemodynamic signals in alert monkey V1 have two distinct components. One component is predictable by visual input and associated V1 neuronal activity. The other component - of comparable strength - is a hitherto unknown haemodynamic signal marking task anticipation. It reflects an arterial pumping mechanism bringing fresh blood to cortex in anticipation of predicted visual events. Electrode recordings conducted simultaneously with the optical imaging showed that this novel haemodynamic signal is not driven by local V1 neuronal activity, in dramatic contrast to visually evoked responses obtained from the same recording sites. We hypothesize that the anticipatory stimulus-independent haemodynamic signal is a mechanism of predictive arousal. We propose to test this hypothesis by characterizing the anticipatory and visually evoked signals, and their interaction, and asking if the anticipatory signal can modulate visually evoked responses and behavior. Our finding of the novel haemodynamic signal also challenges current understandings of neuroimaging signals, notably functional magnetic resonance imaging (fMRI), the most commonly used tool for human neuroimaging. Through the course of this project we will investigate the links between neuroimaging signals and electrophysiology in the alert macaque in a variety of visual perceptual tasks. This will be an unparalleled opportunity to gain new insights into fMRI in an animal model that is the closest possible to the human. Our novel findings were obtained as a result of a new imaging technique developed in our laboratory, continuous dual-wavelength intrinsic-signal optical imaging, combined with electrode recordings, in alert behaving macaques. For the imaging, one wavelength is absorbed preferentially in oxygenated haemoglobin, thus monitoring blood oxygenation; the other wavelength, absorbed equally in oxygenated and deoxygenated haemoglobin, measures blood volume. The simultaneous electrode recordings give an electrophysiological measure of the underlying neuronal activity. The continuous recording allows us to distinguish between ongoing signals and stimulus-evoked responses. This technique will form the basis of the current project, giving a unique combination of tools to answer the questions at hand. PHS 398/2590 (Rev. 11/07) Page Continuation Format Page