Scientists at the Max Planck Institute for Neurobiology in Martinsried have found a completely new, faster technique nerve cells use to evaluate the quality of the cells they contact in a very time- and energy-saving way.

Instead of synapses (which require up to two days to become fully functional), neurons use calcium for thinking.

When a lengthening extension encounters a neighboring cell, a release of calcium is triggered at its base. This calcium signal then acts like a stop sign: the extension immediately ceases to grow. At the same time, this signal already contains all the important information about the quality of the new contact: the contact only remains intact if the calcium signal is significantly higher than the surrounding calcium level of the cell. Otherwise, the extension withdraws and the nerve cell searches for a suitable partner cell at another point.