The Role of Thalamus in Cortical Function and Tactile Perception

项目摘要 在大多数哺乳动物中，背侧丘脑被认为是感觉信号传播的中继站 从外周到皮层。事实上，一级核(FO)从外周接受它们的输入(例如，视网膜输入到 外侧膝状核或LGN)，并将它们的主要输出发送到皮质。然而，按数量计算，大多数 灵长类动物的丘脑由高阶(HO)核组成，定义为接受来自 大脑皮层。尽管它们在丘脑中占主导地位，但HO核的功能尚未得到最终阐明。 一种假说是，鉴于HO核团的模式，它在大脑皮层区域之间的通讯中起着关键作用 与大脑皮层的互连。这些跨丘脑皮质环路通常与直接 相同的两个皮质区域之间的皮质连接。所载信号的性质和功能 由HO形成的原子核在很大程度上仍不清楚。拟议在猕猴身上进行的实验的目标是 确定它是否以及如何影响初级和高级皮质区域的神经元反应，并建立其 在触摸中介的行为中扮演的角色。为此，我们将研究Sho神经元的反应特性 动物执行两种任务中的一种--一种严重依赖于高级皮层处理的辨别任务 而另一项检测任务则没有。然后，我们将评估使Sho原子核沉默的后果 对不同皮质区域神经元的反应和动物行为的影响。 智力上的优点。新大脑皮层的扩张是人类进化的标志，赋予我们 语言，精细的运动控制，以及增强的认知能力。随着大脑皮层的相对扩张， 丘脑初级感觉核的大小保持相对稳定，而高级丘脑(HO)的大小保持相对稳定 原子核已经扩张。我们假设，这种相对扩张与 大脑皮质，因为这些核团的功能是在不同的皮质区域之间进行沟通。这个 这个跨丘脑回路的作用在很大程度上仍不清楚，我们将开始填补这一空白。 更广泛的影响。除了对基础科学的贡献外，这一结果还将具有重要的临床意义 这意味着什么。事实上，许多认知缺陷都与HO丘脑中继器有关。例如, 精神分裂症的一个值得注意的基于MRI和身体解剖的丘脑病理：HO核 (例如，背内侧核和枕核)萎缩，神经元丢失，但FO核看起来正常。 因此，精神分裂症可能会扰乱跨丘脑回路，以及其他影响和认知缺陷 精神分裂症可能至少部分与跨丘脑系统的病理有关。总的来说，这一点 FO和HO丘脑中继器的新假说可能被证明是一个有用的假说框架，可以作为对照 考虑不同临床条件下的丘脑缺陷。

Project Summary In most mammals, the dorsal thalamus is considered to be a relay station for sensory signals propagating from periphery to cortex. Indeed, first order (FO) nuclei receive their input from the periphery (e.g. retinal input to the lateral geniculate nucleus or LGN) and send their principal output to cortex. By volume, however, the majority of the thalamus in primates consists of higher-order (HO) nuclei, defined as receiving their principal input from cortex. Despite their dominance in the thalamus, the function of HO nuclei has yet to be conclusively elucidated. One hypothesis is that HO nuclei play a key role in the communication between cortical fields given their patterns of interconnectivity with cortex. These transthalamic corticocortical circuits are commonly paralleled by direct corticocortical connections between the same two cortical areas. The nature and function of the signals carried by HO nuclei remain largely unknown. The goal of the proposed experiments in macaque monkeys is to determine if and how it shapes neuronal responses in primary and higher order cortical areas, and establish its role in touch-mediated behaviors. To this end, we will study the response properties of sHO neurons while animals perform one of two tasks – a discrimination task that relies heavily on higher order cortical processing and a detection task that does not. Then, we will assess the consequences of silencing the sHO nucleus both on the responses of neurons in different cortical fields and on the animal’s behavior. INTELLECTUAL MERIT. The expansion of the neocortex is the hallmark of human evolution, endowing us with language, fine motor control, and increased cognitive capacity. With the relative expansion of the neocortex, primary sensory nuclei of the thalamus have remained relatively stable in size while higher order (HO) thalamic nuclei have expanded. We hypothesize that this relative expansion is closely associated with the expansion of cortex because the function of these nuclei is to mediate communication between different cortical fields. The role of this transthalamic circuit remains largely unknown, a gap we will begin to fill. BROADER IMPACT. In addition to their contribution to basic science, the results will also have important clinical implications. Indeed, many cognitive defects have been associated with HO thalamic relays. For instance, schizophrenia presents a noteworthy thalamic pathology based on MRI and postmortem anatomy: HO nuclei (e.g., the mediodorsal nucleus and Pulvinar) are shrunken with neuronal loss but FO nuclei appear normal. Schizophrenia may thus disrupt transthalamic circuits, among other effects and the cognitive defects in schizophrenia may be at least partly related to pathology in the transthalamic system. Generally speaking, this new hypothesis of FO and HO thalamic relays may prove a useful hypothetical framework against which to consider thalamic deficits in various clinical conditions.