New York: Scientists have developed a new tool to scan the human brain for changes in synapses that are associated with common brain disorders. A synapse is a junction between two nerve cells, consisting of a minute gap across which impulses pass. The team from Yale University set out to develop a method for measuring the number of synapses, or synaptic density, in the living brain. To quantify synapses throughout the brain, they combined Positron Emission Tomography (PET) scanning technology with biochemistry. A radioactive tracer was developed that, when injected into the body, binds with a key protein that is present in all synapses across the brain. The researchers used the imaging technique in both baboons and humans and confirmed that the new method did serve as a marker for synaptic density. It also revealed synaptic loss in three patients with epilepsy compared to healthy individuals. "This is the first time we have synaptic density measurement in live human beings," said study senior author Richard Carson. "Up to now any measurement of synaptic density was post-mortem," he added in a paper published in the journal Science Translational Medicine. The technique may provide insights into the diagnosis and treatment of a broad range of disorders, including epilepsy and Alzheimer's disease.