Department of Biology, Augsburg College, Minneapolis, Minnesota 55454, USA.
J Neurosci. 2010 Sep 1;30(35):11640-53. doi: 10.1523/JNEUROSCI.0954-10.2010.
We characterized the temporal dynamics of population activity in parietal cortex of monkeys as they solved a spatial cognitive problem posed by an object construction task. We applied pattern classification techniques to characterize patterns of activity coding object-centered side, a task-defined variable specifying whether an object component was located on the left or right side of a reference object, regardless of its retinocentric position. During a period in which the value of object-centered side, as defined by task events, remained constant, parietal cortex represented this variable using a dynamic neural code by activating neurons with the same spatial preference in rapid succession so that the pattern of active neurons changed dramatically while the spatial information they collectively encoded remained stable. Furthermore, if the neurons shared the same spatial preference, then their pretrial activity (measured before objects were shown) was correlated to a degree that scaled as a positive linear function of how close together in time the neurons would be activated later in the trial. Finally, we found that while parietal cortex represented task-critical spatial information using a dynamic neural code, it simultaneously represented task-irrelevant spatial information using a stationary neural code. These data demonstrate that dynamic spatial representations exist in parietal cortex, provide novel insight into the synaptic mechanisms that generate them, and suggest they may preferentially encode task-critical spatial information.
我们描述了猴子顶叶皮层群体活动的时间动态，因为它们解决了一个由物体构建任务提出的空间认知问题。我们应用模式分类技术来描述活动模式，该模式编码以物体为中心的侧，这是一个任务定义的变量，表示物体的一个组成部分是否位于参考物体的左侧或右侧，而不管其视网膜中心位置如何。在物体以任务事件定义的侧值保持不变的一段时间内，顶叶皮层通过快速连续激活具有相同空间偏好的神经元来使用动态神经码表示这个变量，使得活动神经元的模式发生了显著变化，而它们共同编码的空间信息保持稳定。此外，如果神经元具有相同的空间偏好，那么它们的预试活动（在呈现物体之前测量）的相关性程度可以作为正线性函数来衡量，该函数与神经元在试验后期激活的时间间隔有关。最后，我们发现，虽然顶叶皮层使用动态神经码表示任务关键的空间信息，但它同时使用静态神经码表示与任务无关的空间信息。这些数据表明，动态空间表示存在于顶叶皮层中，为产生它们的突触机制提供了新的见解，并表明它们可能优先编码任务关键的空间信息。
