DISSECTION OF FREE EXPLORATORY ACTIVITY I NTO SUB-UNITS OF BEHAVIOR IN MICE

When a mouse is placed in a novel environment, it exhibits a wide vari ety of rapidly executed acts in a non stereotyped manner. After having joined the mouse's home box to an observation device, we filmed and c oded this activity In order to determine any degree of organisation of mouse activity, we used a technique usually found in textual data ana lysis, using a descending hierarchical classification analysis after d ivision of the major textual body of items expressed by the mouse into sub-units of varying size. We were thus able to demonstrate two disti nct groups of activities which concern either information obtaining ac tivities through contact with the different elements of the apparatus (floor, walls, food) or activities of posturing and displacement (stre tched postures, air sniffing postures) related to frequent coming & go ing between the home box and the apparatus. The clear separation betwe en these two groups suggest two different psychological states during exploration. This type of analysis also clearly points out the possibl e impact of the choices made by observers concerning the definition of the items used to describe behavior.