New replicable anxiety-related measures of wall vs. center behavior of mice in the open field

1 Department of Zoology, George S. Wise Faculty of Life Sciences, and 2 Department of Statistics and Operations Research, The Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel 69978; and 3 Maryland Psychiatric Research Center, Department of Psychiatry, School of Medicine, University of Maryland, Baltimore, Maryland 21228 Submitted 10 February 2004 ; accepted in final form 15 February 2004 Anxiety is a widely studied psychiatric disorder and is thought to be a complex and multidimensional phenomenon. Sensitive behavioral discrimination of animal models of anxiety is crucial for the elucidation of the behavioral components of anxiety and the physiological processes that mediate them. Commonly used behavior paradigms of anxiety usually include only a few automatically collected measures; these do not exhaust the behavioral richness exhibited by animals, thus perhaps missing important differences between preparations. The aim of the present study was to expand the repertoire of automatically collected measures in a classical test of anxiety: behavior in relation to the wall in the open field. We present an algorithm, based on the Software for the Exploration of Exploration strategy, which automatically partitions the mouse path into intrinsically defined patterns of movement near the wall and in the center. These patterns are used to design new end points, which provide an articulated description of various aspects of behavior near the wall and in the center. Sixteen new end points were designed with data from C57BL/6J and DBA/2J mice tested in three laboratories. The strain differences in all end points were evaluated on another data set to assess their validity and were found to remain stable. Ten of the sixteen end points were found to discriminate between the two strains in a replicable manner. The entire set of end points can be used on various genetic and pharmacological models of anxiety with good prospects of providing fine discrimination in a replicable manner. behavioral phenotyping; thigmotaxis; ethological measures; Mouse Phenome Project; C57BL/6J; DBA/2J Address for reprint requests and other correspondence: D. Lipkind, Dept. of Zoology, George S. Wise Faculty of life Sciences, Tel Aviv Univ., Tel Aviv, Israel 69978 (E-mail: lipkind{at}post.tau.ac.il ).