Abstract
The hippocampal CA1 field integrates a wide variety of subcortical and cortical inputs, but its synaptic organization in humans is still unknown due to the difficulties involved studying the human brain via electron microscope techniques. However, we have shown that the 3D reconstruction method using Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM) can be applied to study in detail the synaptic organization of the human brain obtained from autopsies, yielding excellent results. Using this technology, 24,752 synapses were fully reconstructed in CA1, revealing that most of them were excitatory, targeting dendritic spines and displaying a macular shape, regardless of the layer examined. However, remarkable differences were observed between layers. These data constitute the first extensive description of the synaptic organization of the neuropil of the human CA1 region.
Highlights
The hippocampus plays a crucial role in spatial orientation, learning and memory, and many pathological conditions are closely associated with synaptic alterations in the hippocampus (Amaral and Lavenex, 2007)
We have shown that the 3D reconstruction method using Focused Ion Beam/ Scanning Electron Microscopy (FIB/SEM) can be applied to study in detail the synaptic organization of the human brain obtained from autopsies, yielding excellent results (Domınguez-Alvaro et al, 2018; Domınguez-Alvaro et al, 2019)
Light microscopy: volume fraction occupied by cortical elements
Summary
The hippocampus plays a crucial role in spatial orientation, learning and memory, and many pathological conditions (e.g., epilepsy and Alzheimer’s disease) are closely associated with synaptic alterations in the hippocampus (Amaral and Lavenex, 2007). Healthy human brain tissue that can be studied using electron microscopy is sometimes donated after death Using these donations could improve the understanding of the synapses in normal brains and possible changes associated with disease. We have shown that the 3D reconstruction method using Focused Ion Beam/ Scanning Electron Microscopy (FIB/SEM) can be applied to study in detail the synaptic organization of the human brain obtained from autopsies, yielding excellent results (Domınguez-Alvaro et al, 2018; Domınguez-Alvaro et al, 2019) For these reasons, we used FIB/SEM technology to perform a 3D analysis of the synaptic organization in the neuropil in all layers of the CA1 region from five human brain autopsies with a short postmortem delay. The data reported in the present work constitutes the first extensive description of the synaptic organization in the human hippocampal CA1 field, which is a necessary step for better understanding its functional organization in health and disease
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