ИСТИНА

Traditional methods of analysis of animal behaviour in the open field test (path length, velocity, rearing, grooming and freezing scores etc) are not always sufficient to reveal subtle effects of experimental factors. In the present study we applied a method of trajectory segmentation based on stops and motion acceleration/deceleration characteristics (Segment Analyzer software, Mukhina, Anokhin, 2005) to analyze the effect of caudal bilateral cytotoxic lesions of hippocampus in laboratory C57BL/6 mice and wild bank voles (Clethrionomys glareolus) on their exploratory behavior and locomotion in the open field. The method allows to separate segments of animal locomotion between stops or deceleration/acceleration episodes and to calculate segment characteristics (length, duration, maximal and mean velocity). These data together with information on quantity and percentage of segments with different characteristics (especially maximal velocity) can give detailed information on trajectory structure. We used round open field arenas of three sizes (diameter 75, 150 and 220 cm). The trajectories and behavioural scores were registered using Noldus EthoVision 3.0 video-tracking system. The standard tools of analysis included in EthoVision software revealed only one significant effect in all arenas in both species: reduction in the number of rears. Analysis of segment characteristics of trajectory revealed a reduced number of stops, an increased percentage of high-speed segments and a decreased percentage of middle-speed segments in lesioned mice compared to controls. These effects were more pronounced in larger arenas. Similar impairments of track structure were found in bank voles. Thus our analysis of rodent motion trajectory based on processing of its segment characteristics allowed to reveal subtle impairments in locomotion and exploration that would not be noticed otherwise. Such approach can be useful for studies of effects of subtle influences, when the behavioural changes are unapparent and complicated. Supported by RFBR #10-04-00891