Neutrons show a connection between lithium concentration and depression

Making the gray cells happy

The scientists investigated the brain of a suicidal patient and compared it with two control persons. The investigation focused on the ratio of the lithium concentration in white brain matter to the concentration in the gray matter of the brain.

In order to determine where how much lithium is present in the brain, the researchers analyzed 150 samples from various brain regions – for example those regions which are presumably responsible for processing feelings. At the FRM II Prompt Gamma-Ray Activation Analysis (PGAA) instrument the researchers irradiated thin brain sections with neutrons.

"One lithium isotope is especially good at capturing neutrons; it then decays into a helium atom and a tritium atom," explains Dr. Roman Gernhäuser of the Central Technology Laboratory of the TUM Department of Physics. The two decay products are captured by detectors in front of and behind the sample and thus provide information on where exactly the lithium is located in the brain section.

Since the lithium concentration in the brain is usually very low, it is also very difficult to ascertain. "Until now it wasn't possible to detect such small traces of lithium in the brain in a spatially resolved manner," says Dr. Jutta Schöpfer of the LMU Munich Institute for Forensic Medicine. "One special aspect of the investigation using neutrons is that our samples are not destroyed. That means we can repeatedly examine them several times over a longer period of time," Gernhäuser points out.

"We saw that there was significantly more lithium present in the white matter of the healthy person than in the gray matter. By contrast, the suicidal patient had a balanced distribution, without a measurable systematic difference," summarizes Dr. Roman Gernhäuser. 

"Our results are fairly groundbreaking, because we were able for the first time to ascertain the distribution of lithium under physiological conditions," Schöpfer is glad to report. "Since we were able to ascertain trace quantities of the element in the brain without first administering medication and because the distribution is so clearly different, we assume that lithium indeed has an important function in the body."

"Of course the fact that we were only able to investigate brain sections from three persons marks only a beginning," Gernhäuser admits. "However, in each case we were able to investigate many different brain regions which confirmed the systematic behavior." 

"We would be able to find out much more with more patients, whose life stories would also be better known," says Gernhäuser, adding that it might then also be possible to answer the question as to whether the deviating lithium distribution in depressive persons is a cause or a result of the illness.