Figure 12.

Electron microscopy and number of synapses per neuron. Left, Electron micrographs illustrating the neuropil of layer IIIa in the human temporal cortex, and of layer III of the mouse barrel cortex. Note the higher density of synapses (some of them indicated by arrows) in the mouse cortex. Scale bar = 0.5 μm. Right, Number of synapses per neuron in the human, rat, and mouse. The values obtained in layers II, IIIa, and IIIb of human, and layers Va and Vb of rat were recalculated according to the relative thickness of these layers to estimate the representative values of layers II–III and V, respectively. From DeFelipe et al. (2002).