Ensemble Dynamics of Cortical Feedback to the Thalamus

描述（由申请人提供）：视觉处理中最引人注目和未解决的问题之一是视觉系统中许多部位发生的大量皮层反馈的作用。这种反馈的激活被认为是注意力等过程的基础。它也可以作为绑定问题的部分解决方案，该问题已经被提出依赖于神经元集合中的相关放电。最早的皮层反馈根本不发生在皮层，而是发生在丘脑。与大脑皮层中的反馈系统类似，皮质丘脑反馈的特征在于将来自皮层第6层的处理数据广泛地重输入到感觉丘脑核团（例如外侧膝状体核（LGN））中的较低处理水平。我们建议描述皮质丘脑神经元和它们的靶丘脑中继之间的通信规则（例如，什么比例的细胞参与，什么样的活动模式促进这种沟通？在丘脑内产生的活动模式如何可以地形学地表达（例如，反馈是否在某些地形区域促进某些类型的活动，而在其他区域则没有？以及这些模式中的差异如何在允许某些类型的信息访问皮层中起关键作用（例如，丘脑神经元有两种放电机制：爆发和紧张，这些对丘脑皮质（TC）突触会有不同的影响吗？）信息在已知的生理类型的神经元中是否受到选择性的影响？(e.g.,开/关、X/Y类和/或眼睛特定信息？）为了回答这些问题，多电极阵列将被用来记录丘脑合奏和他们正在进行的对话与皮层第6层。我们将测试以下假设：（H1）LGN的第6层反馈将在LGN细胞群之间产生相关性，这些LGN细胞群依赖于具有尖峰第6层神经元的视觉定位寄存器;（H2）LGN细胞将在某些放电条件和活动模式下优先激活第6层神经元;以及（H3）脑干激活将响应于层6反馈而增加跨LGN神经元的相关放电。皮质丘脑相互作用的目的是一个持久的谜，但它的解决将产生反馈在神经系统中的决定性作用的基本细节。除了正常的皮质丘脑处理的细节，我们提出的研究将提供一个基础，了解异常丘脑网络状态的中枢神经系统疾病，如癫痫，慢性疼痛和帕金森氏病。相关性：来自外周感觉系统的信息在丘脑和皮层的上升阶段进行处理。大脑皮层会将大量的投射信息传回大脑的较低处理层次，但人们对这种反馈的功能知之甚少。该项目提出了详细的检查皮层如何可能指示丘脑允许某些类型的信息进行更高的处理阶段的基础上特定的时间刺激或空间中的对象的安排。通过同时记录这两个区域的大量脑细胞，我们将发现这些区域用来交流的规则。这些在一些大脑疾病中受到干扰，因此我们将了解有关通信基本规则的信息对于理解这些异常的大脑状况至关重要。

DESCRIPTION (provided by applicant): One of the most compelling and unresolved issues of visual processing is the role of the massive cortical feedback that occurs in a number of sites in the visual system. Activation of this feedback is thought to underlie processes such as attention. It may also serve as a partial solution to the binding problem, which has been proposed to rely on correlated firing in ensembles of neurons. The earliest cortical feedback does not occur in cortex at all, but in the thalamus. Similar to feedback systems in the cerebral cortex, corticothalamic feedback is characterized by extensive reentry of processed data from Layer 6 of cortex to lower processing levels in sensory thalamic nuclei such as the lateral geniculate nucleus (LGN). We propose to characterize the rules of communication between corticothalamic neurons and their target thalamic relays (e.g., what proportion of cells engage, and what patterns of activity promote this communication?); how might the resulting activity patterns within the thalamus be expressed topographically (e.g., does feedback promote certain types of activity in certain topographic regions and not others?); and how are the differences in these patterns critical in allowing certain kinds of information access to cortex (e.g., thalamic neurons have two firing regimes: burst and tonic, will these have differing impact at thalamocortical (TC) synapses?). Is information selectively affected in well-known physiological types of neurons? (e.g., ON/OFF, X/Y-like, and/or eye specific information?) To answer these questions, multielectrode arrays will be used to record thalamic ensembles and their ongoing dialog with Layer 6 of cortex. We will test the following hypotheses: (H1) that Layer 6 feedback to the LGN will produce correlations among ensembles of LGN cells that depend upon visuotopic register with spiking Layer 6 neurons; (H2) that LGN cells will preferentially activate Layer 6 neurons under certain firing conditions and activity patterns; and (H3) that brainstem activation will increase correlated firing across LGN neurons in response to Layer 6 feedback. The purpose of corticothalamic interactions is an enduring mystery, but one whose resolution will yield fundamental details of the defining role of feedback in neural systems. In addition to the details of normal corticothalamic processing, our proposed studies will provide a foundation for understanding abnormal thalamic network states in CNS disorders such as epilepsy, chronic pain and Parkinson's disease. Relevance: Information from peripheral sensory systems is processed at ascending stages of the thalamus and cortex. The cortex sends a massive projection back to lower processing levels of the brain, but the function of this feedback is poorly understood. This project proposes the detailed examination of how the cortex may instruct the thalamus to allow certain types of information to proceed to higher processing stages based on specific timing of stimulation or arrangement of objects in space. By recording from large numbers of brain cells in both regions simultaneously, we will discover rules that the regions use to communicate. These are perturbed in a number of brain disorders, thus the information we will learn about the basic rules of communication is vital for the understanding of these abnormal brain conditions.