Cross section of the auditory cortex of a transgenic mouse used for in vivo imaging of dendritic spines. A single neuron is highlighted by green fluorescent protein. The dendritic processes are decorated with spines, the morphological correlate of excitatory synapses. Counter staining for synaptic marker proteins ErbB4 (cyan) and Synapsin1 (magenta). Simon Rumpel. Institute of Physiology, Universtiy Medical Center, Johannes Gutenberg University Mainz