Abstract: In the present investigation, the spontaneous activity, the behavior of learning and memory of 20-dayold mice were studied by using open field and Y-maze after hyperbaric oxygen treatment. Theneuronal density, cell nuclear area and the ratio of nuclear and plasma of memory-related brain areas(cerebral cortex, hippocampus) of these mice were measured by using computer image analysis system.The results ale as follows: (1) Compared with the control group, 0.1 MPa hyperbaric oxygen canremarkably ameliorate the learning and memory retention of young mice. (2) The neuronal density, cellnuclear area and the ratio of nuclear and plasma of the mice were significantly increased after 0.1 MPahyperbaric oxygen treatment. Compared with the control group, 0.25 MPa hyperbaric oxygen canremarkably decreace ace the spontaneous activity of young mice. These results indicated that 0.1 MPahyperbaric oxygen treatment not only could enhance brain development but also improve the function oflearning-memory of young mice.

Key words: hyperbaric oxygen, learning and memory behavior, cerebral cortex, hippocampus, morphometry