Figure 2.

Both hand and local thresholding segmentation methods yield transsynaptic assemblies connected by transmembrane structures. Local thresholding was used as an alternative segmenting method. For this method, thresholds were applied to small 3D regions of interests around electron-dense structures. To be included in renderings, an intracellular structure must contact a transmembrane and cleft structure. A, Examples of hand segmented transcleft structures (pink) from each excitatory synapse are shown with connecting presynaptic transmembrane and intracellular membrane-bound structures (light green and light blue, respectively), postsynaptic transmembrane and intracellular structures (dark green and blue, respectively). B, All structures in a hand segmented synapse are separated with the same color code as A to show the general morphology of material in each compartment. C, Examples structures from A segmented using the local thresholding method, demonstrating how the thresholding method affects morphology. D, All local threshold segmented structures of the synapse separated by compartment, demonstrating the similarity in the amount of material connected through transmembrane structures by the two segmentation methods. Scale bars: 40 nm.