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Learning and Long-term Memory

開催日 2014/9/13
時間 14:00 - 15:00
会場 Poster / Exhibition(Event Hall B)

Effects of low frequency alternating magnetic field exposure on the spatial cognitive learning and memory in mice

  • P3-210
  • 松林 宏樹 / Hiroki Matsubayashi:1 今村 一之 / Kazuyuki Imamura:1 
  • 1:前橋工科大学大学院・工・システム生体 / Dept. System Life Engineering, Maebashi Institute of Technology, Maebashi, Gunma, Japan 

Spatial cognitive learning in young mice is improved by the exposure to the low frequency alternating magnetic field (LFMF, Yoshihara et al., 2013). We wanted to study whether such enhancing effects of the LFMF were also found in aged mice (> 40 weeks age). Morris Water Maze (MWM) and T-maze tasks were used following the exposure to the LFMF. Conscious mouse was set in a specially designed restrainer and exposed to the LFMF (50Hz, 10mT intensity) for 30 minutes. Control mouse was also restrained for the same period without the LFMF. In T-maze task, we found that the number of mean correct choices was elevated by 18% in exposed mice. To study the maintenance of the spatial memory, we repeated the tasks one week after the last session at which all mice exhibited over 80% of correct choices. The number of mean correct choices in the exposed mice maintained high for 1 week, while the number decreased 25% (last session vs 1week, p<0.05, in control mice). The exposure to the LFMF enhanced maintaining the spatial memory. In MWM task, we found that the escape latency of exposed mice was 9% shorter than control at the end of the trials (not significance). In order to evaluate the swimming trail precisely, we evaluate the head-tail direction of mouse toward the platform. The tip of the mouse's nose and the root of the tail were detected by semi-automatic image processing programs. We found that the mouse was in the range of 0 to 180 degrees in the first half of swimming. It became narrower in the range of 0 to 30 degrees in the last half of swimming. We also found that the ratio of angles of mouse's body axis in the limited range (0 to 15 degrees) increased from 3% (first trial) to 13% (last trial) in both groups. The ratio of the range of 0 to 15 degrees was found to be most sensitive index of MWM task. Intriguingly, the exposure to the LFMF reduced the ratio of being in the range of 0 to 15 degrees up to 54% of control in the exposed mice. The measure of mouse's body axis was useful to evaluate the effects of the LFMF in the spatial cognitive learning of mice. These results suggest that the effects of the LFMF are larger in T-maze task than MWM task.

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