Fast Electrical Oscillations in Somatosensory Cortex

也许人类大脑中最古老、最广为人知、最不为人所知的电现象，无论是疾病还是健康，都是其特有的大幅度电振荡。最近，在了解振荡和大脑功能之间的关系方面取得了重大进展。伽马束中的皮层振荡(约40赫兹)，以及更高频率的快和非常快的振荡(FO和VFO；分别约300和500赫兹)，似乎在感觉皮质的时间编码中发挥作用。然而，它们的功能意义和潜在的细胞机制仍然是一个猜测和争议的问题。在目前的实验系列中，我们通过将在体三维细胞外记录与细胞内记录和标记相结合来解决这两个问题，以研究负责产生和传播大鼠躯体感觉皮质后内侧桶状亚区(PMBSF)快速振荡的神经电路。首先，我们将把我们在听觉系统中关于丘脑调节皮质伽马振荡的结果外推到躯体感觉系统。在这样做的过程中，我们将建立结构和功能的类比，这些类比应该有力地支持或驳斥关于不同的丘脑系统参与皮质伽马振荡的产生或调制的假说，以及躯体感觉系统。在这样做的过程中，我们将建立结构和功能类比，这些类比应该有力地支持或驳斥关于不同丘脑系统参与皮质伽马振荡产生或调制的假说。其次，我们将确定PMBSF中丘脑诱发伽马振荡的神经生成器，并将这些结果与听觉皮质细胞内记录的结果进行比较，以评估我们的假设，即皮质伽马振荡的产生可能基于两种感觉模式中的常见细胞类型，而不依赖于专门的神经起搏器。第三，我们将测量单个触觉刺激的时空响应场，以建立刺激在PMBSF中诱发的伽马、FO和VFO的体位组织和二维形状，并更好地预测每个振荡类别如何促进相邻皮质柱之间的时间相互作用。第四，我们将评估在PMBSF表面测量到的由多振动刺激引起的快速振荡的可能的时空相互作用模式。通过观察每类快速振荡如何从PMBSF中的多个起始点传播，并在场子区域内以相位敏感的方式相互作用，我们希望更好地理解这些振荡如何编码与物体的连续瞬时振动接触的精确时间，和/或当它们被常见且更长时间的刺激激活时，它们如何同步多个大脑皮层柱中的活动。最后，我们将探索皮层内和细胞内水平的阈值下和阈值上的事件，这些事件支持PMBSF内每一振荡类别的时间整合，并从组织学上标记和识别负责这种空间整合的神经元及其过程。

Perhaps the oldest, most widely recognized, and least understood electrical phenomena of the human brain in sickness and in health are its characteristic large amplitude electrical oscillations. Recently, there has been a major advance towards understanding the relationship between oscillations and brain function. Electrocortical oscillations in the gamma bind (approximately 4o Hz), and much higher frequency fast and very fast oscillations (FO and VFO; approximately 300 and 500 Hz, respectively), appear to play a role in temporal coding in sensory cortex. Yet, their functional significance and underlying cellular mechanisms are still a matter of speculation and controversy. In the present experimental series, we address both of these issues by combining in vivo three dimensional extracellular recording with intracellular recording and labeling to study the neural circuitry responsible for generating and propagating fast oscillations in the posteromedial barrel subfield (PMBSF) of rat somatosensory cortex. First, we will extrapolate our results in the auditory system concerning thalamic modulation of cortical gamma oscillations, to the somatosensory system. In so doing, we will establish structural and functional analogies that should strongly support or refute hypotheses about the participation of distinct thalamic systems in the generation or modulation of cortical gamma oscillations, to the somatosensory system. In so doing, we will establish structural and functional analogies that should strongly support or refute hypotheses about the participation of distinct thalamic systems in the generation or modulation of cortical gamma oscillations. Second, we will determine the neural generators of thalamically evoked gamma oscillations in the PMBSF and compare these to our results from intracellular recordings in auditory cortex to evaluate our hypotheses that the generation of cortical gamma oscillations may be based on common cell types in both sensory modalities and not rely on specialized neural pacemakers. Third, we will measure the spatiotemporal response field of single vibrissa stimulation to establish the somatotopic organization and two dimensional shape of stimulus evoked gamma, FO and VFO in the PMBSF and to better anticipate how each oscillatory class could contribute to temporal interactions between adjacent cortical columns. Fourth, we will evaluate possible spatiotemporal interaction patterns of fast oscillations measured at the surface of the PMBSF, evoked by multi-vibrissal stimulation. By looking at how each class of fast oscillations may propagate from multiple start points in the PMBSF and interact in phase sensitive ways within sub-regions of the field, we expect to better understand how these oscillations may encoded the precise timing of sequential transient vibrissal contact with objects and/or how they may synchronize activity in multiple cortical columns when activated by a common and more prolonged stimulus. Finally, we will explore both sub- and suprathreshold events at the intracortical and intracellular level that support temporal integration of each oscillatory class within the PMBSF and histologically label and identify neurons and their processes responsible for this spatio integration.