Calcium reveals connections between neurons

A team led by MIT neuroscientists has developed a way to monitor how brain cells coordinate with each other to control specific behaviours, such as initiating movement or detecting an odour.

The researchers' new imaging technique, based on the detection of calcium ions in neurons, could help them map the brain circuits that perform such functions. It could also provide new insights into the origins of autism, obsessive-compulsive disorder and other psychiatric diseases, says Guoping Feng, senior author of a paper appearing in the Oct. 18 issue of the journal Neuron.

''To understand psychiatric disorders we need to study animal models, and to find out what's happening in the brain when the animal is behaving abnormally,'' says Feng, the James W and Patricia Poitras Professor of Neuroscience and a member of the McGovern Institute for Brain Research at MIT. ''This is a very powerful tool that will really help us understand animal models of these diseases and study how the brain functions normally and in a diseased state.''

Lead author of the Neuron paper is McGovern Institute postdoc Qian Chen.

Performing any kind of brain function requires many neurons in different parts of the brain to communicate with each other. They achieve this communication by sending electrical signals, triggering an influx of calcium ions into active cells. Using dyes that bind to calcium, researchers have imaged neural activity in neurons. However, the brain contains thousands of cell types, each with distinct functions, and the dye is taken up nonselectively by all cells, making it impossible to pinpoint calcium in specific cell types with this approach.

To overcome this, the MIT-led team created a calcium-imaging system that can be targeted to specific cell types, using a type of green fluorescent protein (GFP). Junichi Nakai of Saitama University in Japan first developed a GFP that is activated when it binds to calcium, and one of the Neuron paper authors, Loren Looger of the Howard Hughes Medical Institute, modified the protein so its signal is strong enough to use in living animals.