Category B - full version without watermark 1024x576 (check terms and conditions at www.teledesign.de) The embed version with watermark is free of charge. Acting, thinking, feeling -- a network of billions of neurons throughout the whole body controls all this information. It is transmitted in the form of electrical impulses that rush like lightning through the neural fibers. At the so called synaptic clefts the electrical impulses come to a halt. Special messenger substances now see to transmission. They cross the gap and trigger a new electrical impulse at the downstream neuron. Having fulfilled this task they are reabsorbed. In depression neural activity is reduced -- too little messenger substance is available. The equilibrium is disturbed and symptoms like depressed mood, listlessness and sleep disturbances develop.