Fast Electrical Oscillations in Somatosensory Cortex

也许最古老、最广为人知、但最不为人所知的人类大脑在疾病和健康状态下的电现象是它特有的大振幅电振荡。最近，在理解振荡和大脑功能之间的关系方面取得了重大进展。伽马绑定的皮层电振荡（约40赫兹），以及频率更高的快速和非常快的振荡（分别约300和500赫兹），似乎在感觉皮层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。在本实验系列中，我们通过结合体内三维细胞外记录和细胞内记录和标记来解决这两个问题，研究大鼠体感皮层后内桶子场（PMBSF）中负责产生和传播快速振荡的神经回路。首先，我们将把我们在听觉系统中关于丘脑调节皮层伽马振荡的结果外推到体感觉系统。在此过程中，我们将建立结构和功能的类比，这将有力地支持或反驳关于不同的丘脑系统参与皮层伽马振荡的产生或调节，以及体感觉系统的假设。在此过程中，我们将建立结构和功能的类比，这将有力地支持或反驳关于不同的丘脑系统参与皮层伽马振荡的产生或调节的假设。其次，我们将确定PMBSF中丘脑诱发的伽马振荡的神经发生器，并将其与听觉皮层细胞内记录的结果进行比较，以评估我们的假设，即皮层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，我们将测量单触颤刺激的时空响应场，以建立PMBSF中刺激诱发的γ、FO和VFO的体位组织和二维形状，并更好地预测每种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表面测量到的由多重振动刺激引起的快速振荡可能的时空相互作用模式。通过观察每一类快速振荡如何从PMBSF的多个起点传播，并在场的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态振动接触的精确时间，以及/或者当被一个共同的和更持久的刺激激活时，它们如何在多个皮质柱中同步活动。最后，我们将探索皮层内和细胞内支持PMBSF内每个振荡类的时间整合的阈下和阈上事件，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.