Scientists have developed a new approach to scan the brain for changes linked to common disorders, an advance that may provide insights into the diagnosis and treatment of diseases such as epilepsy and Alzheimer’s. Certain changes in synapses – the junctions between nerve cells in the brain – have been linked with brain disorders. However, researchers have only been able to evaluate synaptic changes during autopsies. For their study, the research team set out to develop a method for measuring the number of synapses, or synaptic density, in the living brain. Richard Carson, a professor at Yale University and colleagues combined positron emission tomography (PET) scanning technology with biochemistry. They developed a radioactive tracer that, when injected into the body, binds with a key protein that is present in all synapses across the brain. They observed the tracer through PET imaging and then applied mathematical tools to quantify synaptic density. The researchers used the imaging technique in both baboons and humans. They confirmed that the new method served as a marker for synaptic density. It also showed 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. Up to now any measurement of synaptic density was postmortem,” said Carson. The finding has several potential applications. With this noninvasive method, researchers may be able to follow the progression of many brain disorders, including epilepsy and Alzheimer’s disease, by measuring changes in synaptic density over time. Another application may be in assessing how pharmaceuticals slow the loss of neurons. “This opens the door to follow the natural evolution of synaptic density with normal ageing and follow how drugs can alter synapses or synapse formation,” Carson said. Researchers plan future studies involving PET imaging of synapses to research epilepsy and other brain disorders, including Alzheimer’s disease, schizophrenia, depression and Parkinson’s disease. The study was published in the journal, Science Translational Medicine.