Project Summary / Abstract A fundamental goal in neuroscience is understanding how neural network function arises from circuit structure. However, the immense complexity of most brain networks has been a significant barrier to progress. We do not have a comprehensive wiring diagram for any mammalian local circuit, much less a whole brain. We do not yet have a comprehensive list of cell types and how they are defined for even the simplest mammalian neuronal circuit. Moreover, synapse resolution connectomics has focused almost entirely on chemical synapses and ignored electrical synapses formed by gap junctions, which are thought to be crucial for network synchrony and oscillations. Recent advances in automated sample collection and imaging for transmission electron microscopy (TEM) and molecular genetic tools have allowed us to begin detailed mapping of neural network anatomy. Development of intermediate voltage TEMs has demonstrated the ability to volumetrically image through thick (~1 μm) sections with high resolution tomography. Here, we propose combining automated sample collection and imaging using GridTape, with electron microscopic tomography (EMT) and conical beam procession “VortexBeam” imaging. This new combination of approaches will increase both the resolution and throughput of connectomics, while decreasing the number of sections that need to be collected and acquired. The cerebellum is an ideal system to validate our novel platform as part of a systematic effort to reverse engineer a functional neural circuit that is involved in motor control and social behavior. Its basic structure is well ordered, relatively simple and sufficiently described to have inspired computational models that capture aspects of cerebellar function. However, even the most advanced models are limited by an incomplete characterization of the cell types and connectivity within the cerebellum. Here, we propose to validate our next-generation EMT platforms and characterize long-range, local, and gap junctional connectivity in the cerebellum. We will combine tools recently developed in our labs to a circuit that offers the advantages of relative simplicity and a strong starting foundation. These studies will allow us to understand principles of cerebellar circuit organization and may help us determine the role of specific circuit elements in neurodegenerative disorders.

Project Narrative The goal of this proposal is to understand the organizational principles and connectivity of cell types in the cerebellum. We will develop, automate, and scale electron tomography to extract the structure and connectivity of cerebellar cell types. Understanding rules underlying cell type-specific neuronal connectivity may help to reveal how the brain is altered in neurodegenerative disorders, specific cell types that are affected, and guide effective treatment strategies.