Quantitative Analysis of the Synaptic Organization of the Human Temporal Lobe Neocortex

Synapses are key structural elements that govern the computational properties of any given network in the brain. Although the term synapse was introduced more than 100 years ago, our knowledge about these structures was considerably improved only recently by applying modern techniques including high-end fine-scale transmission and focused ion beam electron microscopy. One of the most important parameters in synaptic neuroscience is the size and shape of the active zone (AZ, equivalent to a functional neurotransmitter release site) and the size and organization of synaptic vesicle pools. Both structural parameters critically determine synaptic efficacy and strength but also the modulation of synaptic plasticity. Meanwhile, there are numerous quantitative studies about the synaptic organization in various mammalian synapses. However, whether findings in experimental animals can be transferred to the human brain one to one is still rather unknown and is thus discussed controversially. Here, we provide a protocol suitable to describe in great detail the synaptic organization in the human brain, as exemplified by the human temporal lobe neocortex (TLN) taken from biopsy samples during epilepsy surgery.