multiple minor behaviors. State frequency and mean duration are indicated in site each circle. The area of each circle is proportional to state frequency. Arrows indicate absolute transition probabilities between states (transitions/minute). Found at: doi:10.1371/journal.pone.0014753.s020 (1.11 MB TIF) Acknowledgments We would like to thank Giovanni Frazzetto and Corinna Becker for help with maternal behavior observation, Francesca D’Amato and Laurent References 1. Weaver IC, Szyf M, Meaney MJ (2002) From maternal care to gene expression: DNA methylation and the maternal programming of stress responses. Endocr Res 28: 699. 2. Zhang TY, Parent C, Weaver I, Meaney MJ (2004) Maternal programming of individual differences in defensive responses in the rat. Ann N Y Acad Sci 1032: 85–103. 3. Chevalet P, Le Pape G (1989) Maternal behaviour in mice: Like mother like daughter? Behavioural processes 20: 93–99. 4. Zaharia MD, Kulczycki J, Shanks N, Meaney MJ, Anisman H (1996) The effects of early postnatal stimulation on Morris water-maze acquisition in adult mice: genetic and maternal factors. Psychopharmacology 128: 227–39. 5. Anisman H, Zaharia MD, Meaney MJ, Merali Z (1998) : Do early-life events permanently alter behavioral and hormonal responses to stressors? Int J Dev Neurosci 16: 149–64. 6. Calatayud F, Belzung C (2001) Emotional reactivity in mice, a case of nongenetic heredity? Physiol Behav 74: 355–62. 7. Caldji C, Diorio J, Meaney MJ (2003) Variations in maternal care alter GABA(A) receptor subunit expression in brain regions associated with fear. Neuropsychopharmacology 28: 1950–9. 8. Priebe K, Romeo RD, Francis DD, Sisti HM, Mueller A, et al. (2005) Maternal influences on adult stress and anxiety-like behavior in C57BL/6J and BALB/cJ mice: a cross-fostering study. Dev Psychobiol 47: 398–407. 9. Prakash P, Merali Z, Kolajova M, Tannenbaum BM, Anisman H (2006) Maternal factors and monoamine changes in stress-resilient and susceptible mice: cross-fostering effects. Brain Res 1111: 122–33. 10. Carola V, Frazzetto G, Gross C (2006) Identifying interactions between genes and early environment in the mouse. Genes Brain Behav 5: 189–99. 11. Shoji H, Kato K (2006) Maternal behavior of primiparous females in inbred strains of mice: a detailed descriptive analysis. Physiol Behav 89: 320–8. 12. Crawley JN, Belknap JK, Collins A, Crabbe JC, Frankel W, et al. (1997) Behavioural phenotypes of inbred mouse strains: implications and recommen- dations for molecular studies. Psychopharmacoloy 132: 107–24. 13. Carola V, D’Olimpio F, Brunamonti E, Mangia F, Renzi P (2002) Evaluation of the Elevated plus-maze and Open-field tests for the assessment of anxiety-related behaviour in inbred mice. Behav Brain Res 134: 49–57. HMM of Maternal Behavior Bre´he´lin for essential suggestions and criticism, and Simone Santanelli and Francesca Zonfrillo for mouse husbandry. Author Contributions Conceived and designed the experiments: VC CG. Performed the experiments: VC. Analyzed the data: VC OM. Wrote the paper: VC OM CG. Implemented and tested hidden Markov models for behavioral data: OM. 14. Roy V, Merali Z, Poulter MO, Anisman H (2007) Anxiety responses, plasma corticosterone and central monoamine variations elicited by stressors in reactive and nonreactive mice and their reciprocal F1 hybrids. Behav Brain Res 185: 49–58. 15. Calatayud F, Coubard S, Belzung C (2004) Emotional reactivity in mice may not be inherited but influenced by parents. Physiol Behav 80: 465–74. 16. Carola V, Frazzetto G, Pascucci T, Audero E, Puglisi-Allegra S, et al. (2008) Identifying molecular substrates in a mouse model of the serotonin transporter6 environment risk factor for anxiety and depression. Biol Psychiatry 63: 840–6. 17. Rabiner L (1989) A tutorial on hidden Markov models and selected applications in speech recognition. Proceedings of the IEEE 77: 257–285. 18. Krogh A, Brown M, Mian IS, Sjo¨lander K, Haussler D (1994) Hidden Markov models in computational biology. Applications to protein modeling. J Mol Biol 235: 1501–31. 19. Eddy SR (2004) What is a hidden Markov model? Nat Biotechnol 22: 1315–6. 20. Mirabeau O, Perlas E, Severini C, Audero E, Gascuel O, et al. (2007) Identification of novel peptide hormones in the human proteome by hidden Markov model screening. Genome Res 17: 320–7. 21. Sargin ME, Yemez Y, Erzin E, Tekalp AM (2008) Analysis of head gesture and prosody patterns for prosody-driven head-gesture animation. IEEE Trans Pattern Anal Mach Intell 30: 1330–45. 22. Maubourguet N, Lesne A, Changeux JP, Maskos U, Faure P (2008) Behavioral sequence analysis reveals a novel role for beta2* nicotinic receptors in exploration. PLoS Comput Biol 4: e1000229. doi: 23. Vetrov D, Kropotov D, Konushin A, Lomakina-Rumyantseva E Automatic segmentation of mouse behavior using hidden Markov model Proceedings of the 6th International Conference on Methods and Techniques in Behavioral Research, Maastricht, The Netherlands, 26–29August 2008. 241 p. 24. Hastie T, Tibshirani R, et al. (2009) The elements of statistical learning: data mining, inference, and prediction. New York: Springer. 25. Benjamini Y, Yekutieli D (2001) The control of the false discovery rate in multiple testing under dependency. the annals of statistics 29: 1165–1188. 26. Shoji H, Kato K (2006) Maternal behavior of primiparous females in inbred strains of mice: a detailed descriptive analysis. Physiol Behav 89: 320–8. PLoS ONE | www.plosone.org 10 March 2011 | Volume 6 | Issue 3 | e14753