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， 从外周到皮层实际上，第一级（FO）核从外周接收它们的输入（例如，视网膜输入到视网膜神经元）。 外侧膝状体核或LGN）并将其主要输出发送到皮层。然而，从数量上看， 灵长类动物的丘脑由高级核团（HO）组成，其主要输入来自 皮层尽管它们在丘脑中占主导地位，HO核的功能尚未得到最终阐明。 一种假设是，HO核团在皮质场之间的通信中发挥关键作用， 与大脑皮层的相互联系这些经丘脑的皮质回路通常由直接的 两个皮质区之间的皮质联系。信号的性质和功能 HO核仍然在很大程度上未知。在猕猴中进行拟议实验的目的是 确定它是否以及如何在初级和高级皮层区域形成神经元反应，并建立其 在触觉介导的行为中的作用。为此，我们将研究sHO神经元的响应特性， 动物执行两种任务之一--一种主要依赖于高级皮层处理的辨别任务 而检测任务则不需要。然后，我们将评估沉默sHO核的后果， 对不同皮层区域神经元的反应和动物的行为的影响。 智力优势。新皮层的扩张是人类进化的标志，赋予我们 语言、精细运动控制和认知能力增加。随着新皮层的相对扩张， 丘脑的初级感觉核在大小上保持相对稳定，而高级（HO）丘脑的初级感觉核在大小上保持相对稳定。 原子核膨胀了。我们假设，这种相对膨胀是密切相关的膨胀 因为这些核团的功能是调解不同皮层区域之间的通信。的 这种经丘脑回路的作用在很大程度上仍然未知，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，这些结果还将具有重要的临床意义。 影响事实上，许多认知缺陷与HO丘脑中继有关。比如说， 精神分裂症提出了一个值得注意的丘脑病理基于MRI和死后解剖：HO核 (e.g.,背内侧核和枕）萎缩，神经元丢失，但FO核表现正常。 因此，精神分裂症可能会破坏跨丘脑回路，以及其他影响和认知缺陷， 精神分裂症可能至少部分与经丘脑系统的病理有关。一般来说，这 FO和HO丘脑中继的新假设可能证明是一个有用的假设框架， 在各种临床条件下考虑丘脑缺陷。

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.