Volitional control of neural activity in the oculomotor system

项目总结 感觉运动转换是由运动前大脑网络介导的，其中单个神经元代表 与感觉、认知和运动相关的信息。在上丘(SC)，有一个中枢，用于 产生视觉引导的扫视眼球运动，许多神经元在 对视觉刺激的响应以及当产生眼动命令时。这些所谓的视觉运动者 神经元投射到产生眼跳的脑干脉冲发生器。因此，这个下游元素是 面临区分传入的“视觉”和“运动”脉冲的挑战。已经有了多种机制 建议对运动生成进行说明。“固定阈值”假说假定扫视是 一旦单个神经元或整个群体的放电率超过阈值，就会产生 只有在发动机爆炸时才会发生。然而，现有数据表明，一个简单的阈值机制是 这可能是不够的，需要考虑其他框架。“最优子空间”假设使用 动力系统方法，提出当人口活动进入或转移时产生的流动 驻留在状态空间的特定区域内。这意味着SC视觉的状态空间表示 而发动机爆裂是不可联想的。“时间稳定性”假说指出，运动是产生的。 当一组神经元的突发性活动在一段时间内保持一致的时间结构时 时间到了。事实上，SC群体活动的稳定性在视觉反应期间降低(不稳定的时间 结构)，并在眼球运动过程中增加(“稳定的”时间结构)。我们寻求一个框架， 协调这些模型。我们的中心假设是，SC种群活动被解读为一种运动 当它既表现出高度的时间结构又驻留在最佳子空间内时。我们的特定 目的是使用一种闭环式脑机接口，在这种接口中，猴子被训练来控制听觉 通过有意识地调节多个SC神经元的活动模式以位于视觉或运动内的光标 子空间和时间稳定或不稳定。我们将首先测试最优子空间和时间稳定性 在2x2设计中将两者相互竞争之前，先将两个框架分开。审查在哪些试验中 观察到的眼球运动将揭示人口活动用来代表运动的模式 指挥部。我们预测，这种动物将能够调节两种视觉运动的种群活动 子空间和稳定-不稳定维度，但运动产生的可能性将最高 当种群活动既稳定又处于最优子空间时。

PROJECT SUMMARY Sensorimotor transformations are mediated by premotor brain networks where individual neurons represent sensory, cognitive, and movement-related information. In the superior colliculus (SC), a central hub for producing visually-guided saccadic eye movements, many neurons emit a burst of action potentials both in response to a visual stimulus and when generating an eye movement command. These so-called visuomotor neurons project to the brainstem burst generator that produces the saccade. Thus, this downstream element is challenged to differentiate between the incoming “visual” and “motor” bursts. Multiple mechanisms have been proposed to account for movement generation. The “fixed threshold” hypothesis posits that a saccade is produced once the firing rate of either an individual neuron or across a population crosses a threshold, which only happens during the motor burst. Existing data, however, indicate that a simple thresholding mechanism is likely not sufficient and requires consideration of other frameworks. The “optimal subspace” hypothesis uses a dynamical systems approach to propose that a movement is generated when the population activity enters or resides within a particular region of state space. This implies that the state space representations of SC visual and motor bursts are dissociable. The “temporal stability” hypothesis states that a movement is generated when bursting activity across a population of neurons preserves consistent temporal structure for a period of time. Indeed, the stability of SC population activity is reduced during a visual response (“unstable” temporal structure) and increased during an eye movement (“stable” temporal structure). We seek a framework that reconciles these models. Our central hypothesis is that SC population activity is decoded as a movement command when it both exhibits high temporal structure and resides within an optimal subspace. Our specific aim is to employ a closed-loop brain-computer interface in which monkeys are trained to control an auditory cursor by volitionally modulating the activity pattern across multiple SC neurons to lie within a visual or motor subspace and to be temporally stable or unstable. We will first test the optimal subspace and temporal stability frameworks individually before pitting the two against each other in a 2x2 design. Examining the trials in which an eye movement is observed will reveal the patterns used by population activity to represent a movement command. We predict that the animals will be able to modulate population activity along both visual-motor subspace and stable-unstable dimensions, but that the likelihood of movement generation will be the highest when the population activity is both stable and in the optimal subspace.