The research was conducted in the Laboratory of Behaviour Physiology and Genetics of MSU Biology Faculty Higher Nervous Activity Department. Under the supervision of I.I. Poletaeva (Doctor of Science in Biology), N.V. Markina and O.V. Perepelkina have studied behaviour of two groups of mice split according to their brain weight – mice with heavy brain (HB) and light brain (LB). Their brain weight can differ up to 18-20%. And is there any difference in their behaviour and cognitive (intellectual) abilities? Recent studies have shown that HB mice are less shy, less excitable and stress-resistant. Alcohol injections in the same dose stimulated HB mice’ motion activities, whether LB mice became less movable. At the same time mice of both groups showed no will for solving complex logic tasks – extrapolating irritant’s movements – and for spatial learning in water labyrinth.
 

Irritant’s moving direction extrapolation test is following: an animal chooses the side to bypass the screen, where feed box full of food has just went in its sight. This is the test for elementary abstract behaviour. As for the test of water labyrinth (Morris labyrinth), a mouse or a rat during this test learns to find a hidden underwater platform (to rest on it) in the tank with cloudy water according extrinsic stimuli. Finding it once, it uses spatial memory, when it gets in to the tank again and search path shortens.
 

Does the brain weight influence the intellect? Humanity asks this question for many years. Brain weight seems to increase due to neuron cells, which should promote complexity of transneuronal interactions and complicate higher nervous activity as a consequence. However, the experiments showed that mice brain growth led to some other changes in their nervous system.