Visuomotor integration and perceptual decision-making in monkey parietal cortex

描述（由申请人提供）：决策是一种重要的认知能力，通常需要在采取行动之前权衡和积累不确定的证据。我们对这一证据积累过程的神经机制的理解大部分来自于对猴子执行苛刻的感知决策任务的神经生理学研究。在一个研究得特别充分的模型中，猴子被训练来决定嘈杂的视觉刺激的运动方向，并通过眼睛运动来表明他们的决定，目标位于感知到的运动方向上。这些研究表明，顶叶皮层外侧顶叶内区（LIP）的神经元在积累噪声运动证据中起作用，用于指导动眼肌反应。然而，在这项任务中，方向决定的形成与适当的动眼肌反应的选择之间的密切关系使得LIP的确切作用难以确定。特别是，LIP是否编码了独立于运动行为的关于运动方向的决定，或者它是否反映了一个可以获取相关知觉信息的动眼运动选择过程？我们的中心假设是LIP编码动眼肌选择过程。为了验证这一假设，我们将使用一种创新的任务设计来训练猴子，在这种设计中，猴子对运动方向的决定与选择目标的颜色有关，而不是与目标的位置有关（红色代表向右运动，绿色代表向左运动）。对于给定的会话，两个目标的位置是固定的，但我们随机分配给它们两种颜色。关键的是，我们操纵了分配颜色的时间，并测量了LIP中证据积累表征的影响。当颜色分配发生在运动观看之前，方向决定可以直接用于选择适当的动眼肌反应，LIP可能会参与。当运动观看后发生颜色分配时，在决策形成时，特定的动眼肌反应是未知的，LIP可能没有参与。当运动观察过程中发生颜色分配时，LIP神经元可能能够动态地进入正在大脑其他地方进行的证据积累过程。研究结果将阐明LIP在感知决策中的作用，并提供对支配行为环境如何影响大脑中如何以及在何处产生决策等高阶能力的原理的更普遍的理解。

DESCRIPTION (provided by applicant): Decision-making is an important cognitive ability that often requires uncertain evidence to be weighed and accumulated over time before committing to a course of action. Much of our understanding of the neural mechanisms responsible for this process of evidence accumulation comes from neurophysiological studies in monkeys performing demanding perceptual decision- making tasks. In one particularly well-studied model, monkeys are trained to decide the direction of motion of a noisy visual stimulus and indicate their decision with an eye movement to a target located in the perceived direction of motion. These studies suggest that neurons in the lateral intraparietal area (LIP) of parietal cortex play a role in accumulating noisy motion evidence used to instruct the oculomotor response. However, in this task the close relationship between formation of the direction decision and selection of the appropriate oculomotor response makes it difficult to identify the exact role of LIP. In particular, does LIP encode the decision about motion direction independent of the motor act, or does it reflect an oculomotor selection process that can access relevant perceptual information? Our central hypothesis is that LIP encodes an oculomotor selection process. To test this hypothesis we will train monkeys using an innovative task design in which their decision about the direction of motion is associated with the color, instead of the location, of the choice target (red for rightward motion, green for leftward). For a given session the locations of the two targets are fixed, but we randomly assign to them the two colors. Critically, we manipulate the time when the colors are assigned and measure the effects on the representation of evidence accumulation in LIP. When the color assignment occurs before motion viewing, the direction decision can be used directly to select the appropriate oculomotor response and LIP is likely to be engaged. When the color assignment occurs after motion viewing, the specific oculomotor response is not known while the decision is formed and LIP might not be engaged. When the color assignment occurs during motion viewing, LIP neurons might be able to gain dynamic access to a process of evidence accumulation that is being carried out elsewhere in the brain. The results will clarify the role of LIP in perceptual decision-making and provide a more general understanding of the principles that govern how behavioral context can influence how and where in the brain high-order abilities like decision-making are generated. PUBLIC HEALTH RELEVANCE: The proposed work is basic research, designed to provide new insights into how a healthy nervous system evaluates evidence to form a decision. Thus, direct benefits to public health are expected to come in the longer term, as these new insights can be used to design new ways to diagnose and treat disorders that affect perception and judgment.