Factor analysis to understand the inner structure of mouse agonistic behavior

O.Vekovischeva¹, T. Aitta-aho¹, E.V. Verbitskaya² and E.R. Korpi¹

¹Institute of Biomedicine/Pharmacology, University of Helsinki, Helsinki, Finland
²Laboratory of Biomedical Statistics, Pavlov State Medical University, St-.Petersburg, Russia

Male aggression appears a main behavioral pattern of mouse behavior and widely involved in pharmacological testing as a model for human psychiatric disorders. However, a complete interpretation of all behavior data that might suffer from subjectivity remains problematic. We wanted here to test a usefulness of Factor analysis that allows to group behavioral elements based on their space vectors and indicates causal relationship between them, for comparison of social behavior of Turku Aggressive (TA) with acute form of aggression towards an intruder and Turku Non-aggressive (TNA) mice displaying feebly marked agonistic behavior.

The pair encounters between TA or TNA males and group-housed unfamiliar Swiss albino males on neutral territory were video-recorded and analyzed subsequently using computerassisted data acquisition software (Ethograph 2.06, Ritec, St. Petersburg, Russia). Total and mean durations of the elements as well total and relative frequencies were monitored. To compare behavioral structures of TA and TNA males Factor analysis was used with Equamax rotation method (SPSS 12.0.1). This is a combination of the Varimax method, which simplifies the factors, and the Quartimax method, which simplifies the variables.

Two main Factors were identified in behavior of TA mice based on very emotional aggression (biting, rush and tremor) and avoidance any near contacts with the partner (kicking, evasion, freezing). The behavior of TNA mice contained also an aggressive patter (biting) that was related most likely with provocation from the partner. It was accompanied by prior exploration of the partner and demonstration of the aggressive intentions (tail rattling, threats). Moreover, the elements which were highly associated with the same Factor as ambivalent demonstration was, might be interpreted similarly.

Factor analysis confirmed statistically that TA and TNA mice demonstrated opposite coping strategies despite of presence of an aggressive pattern in both of them. The behavioral structure of expressed aggressions was different suggesting distinct regulative mechanisms.

Paper presented at Measuring Behavior 2005 , 5^th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands.

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