extensions. Finally, only synapses that had a PSD profile in the reference, but not in the look-up section, were counted. At least seven neuropil fields (each 163.65 μm2) were photographed from each animal, corresponding to a total section area of 3.437 μm2. Synapse density was calculated as the number of synapses per counting divided by the product of area of the counting frame and the height of the dissector.
