Abstract
For many years, scientists have searched for structural variations between men’s and women’s brains to explain psychological studies showing that, overall, the sexes think and act differently. In general, while men on average have larger brains and some brain regions are structured or shaped differently, the effect of these differences is not well understood in terms of behavior or brain function. An additional problem is that there is a virtual lack of knowledge at the level of the synaptic organization of the human brain because the ultrastructural preservation of post-mortem human brain tissue is usually rather poor and it is generally unsuitable for detailed quantitative analysis. However, the examination of specimens removed during the course of neurosurgery in patients with tumors or intractable epilepsy represents an excellent opportunity to study human brain ultrastructure, partly because the resected tissue can be immediately immersed in the fixative so that post-mortem factors are mainly eliminated. Undoubtedly, this is why the quality of the electron microscope images of this human biopsy material is comparable to that obtained in experimental animals. Here, we will deal mainly with the finding from our laboratory—using fresh brain tissue removed during brain surgery of epileptic patients—that there are significant differences between men and women in terms of synaptic density in all cortical layers of the temporal neocortex. These differences may represent a microanatomical substrate contributing to the functional gender differences in brain activity.
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Acknowledgements
We would like to thank Dr. G. Sola (“Hospital de la Princesa,” Madrid, Spain) for supplying human tissue. This work was supported by grants from the following entities: Ministerio de Ciencia e Innovación (grants SAF2009-09394 and the Cajal Blue Brain Project, Spanish partner of the Blue Brain Project initiative from EPFL), Centre for Networked Biomedical Research into Neurodegenerative Diseases (CIBERNED, CB06/05/0066) and Fundación CIEN.
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DeFelipe, J., Alonso-Nanclares, L. (2013). The Synapse: Differences Between Men and Women. In: Pfaff, D., Christen, Y. (eds) Multiple Origins of Sex Differences in Brain. Research and Perspectives in Endocrine Interactions. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-33721-5_4
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