A Tool for Synapse-level Circuit Analysis of Human Cerebral Cortex Specimens.

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Project Summary/Abstract The goal of this work is to facilitate synaptic level analysis of neurons and their interconnecting microcircuits in neurosurgical cerebral cortex biopsies from human patients. These full-thickness human cerebral cortex biopsies will be provided by neurosurgical colleagues from patients undergoing resective surgery or surgical implantation of leads for deep brain stimulation (DBS). Once we have demonstrated that the techniques and tools are sufficiently reliable, we will analyze neural circuits in samples from medical centers that study psychiatric and neurological disorders. In the initial phase we will: 1) optimize the removal of undamaged brain biopsies during neurosurgical procedures and transfer new techniques for immersion fixation and osmium staining to large (>5 cubic millimeter) fresh brain biopsies from human patients.; 2) we will optimize, with hardware and software changes, the speed and reliability of multibeam scanning electron microscopy image acquisition to automatically acquire synapse-level neural circuitry at petabyte scale in brain volumes that connect tens of thousands of neurons via hundreds of millions of synapses; 3) we will transfer methods to co-register molecular labels (for cell -types) with serial electron microscopy of the same human samples using very small novel immuno-probes that do not require permeabilization and hence, do not negatively impact the quality of the brain’s ultrastructure in order to identify ultrastructural correlates for each cell type; and 4) we will work with computer scientists at Argonne National Laboratory to develop a robust computational connectomics pipeline for stitching, alignment, segmentation, and storage of human brain circuits. This public platform will augment the efforts of a team at Google that is already begun working on our human samples. In the second phase, we will run many human biopsies through the image acquisition and analysis connectomic pipelines. We will use new software to compare circuit variability within and between individuals. We contend that detailed neural circuit analysis in human brain tissue that bridges scales from nanometers to millimeters is a prerequisite for understanding how the normal brain functions and discovering the pathological underpinnings of cognitive and developmental disorders. Our goal is that the methods we develop will be disseminated, becoming part of the toolbox for both neuropathology and fundamental human neuroscience.