3D ultrastructural study of synapses using FIB/SEM in the human Entorhinal Cortex

We used Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM) to perform a three-dimensional analysis of the synapses in the neuropil in different layers of the medial Entorhinal Cortex (EC) from human brain autopsies. Specifically, we studied synaptic structural parameters of synapses, which were fully reconstructed in 3D. We analyzed the synaptic density, 3D spatial distribution, and type (excitatory and inhibitory), as well as the shape and size of each synaptic junction. Moreover, the postsynaptic targets of synapses could be clearly determined. The present work constitutes a detailed description of the synaptic organization of the human EC, which is a necessary step to better understand the functional organization of this region in both health and disease.