In order to further understand how animals and humans acquire spatial information, MIT scientists in the third paper analyzed these knockout mice as they explored an environment freely by using a highly sophisticated electrophysiological technique which precisely monitors the electrical activity of a large number of the individual nerve cells in the CA1 region of the hippocampus. For the first time, it was demonstrated beyond doubt that synaptic plasticity in a specific region of the brain is essential for spatial memory. The new gene knockout technology will also be extremely valuable for medical researchers to study the precise functions of disease genes in neurological disease processes as well as in drug addictions. On the first two papers, the lead authors were Joe Z. Tsien, a post-doctoral associate with Dr. Tonegawa, and Thomas J. McHugh, a biology graduate student in Dr. Tonegawa's lab who has been supervised principally by Dr. Wilson for this work. The knockout mice grew into adulthood without obvious abnormalities.
Mice are natural swimmers but they prefer to be on land or a solid surface.
A test of memory used in Paper 2 is the Morris water maze, a round pool in milky water where there is a platform that is just below the surface. The platform can be easily spotted by all mice, including the new knockout mice, when there is a flag that extends above the water attached to the platform. But it's different when the flag is gone. The mice were placed in the Morris water maze three or four times a day for several days. They explored the maze and swam into the platform.