A time-structured analysis of hypothalamically induced increases in self-grooming and activity in the rat.

Stressors and different manipulations of the paraventricular nucleus of the hypothalamus (PVH) increase self-grooming in the rat. To assess the effect of these PVH manipulations on the timing of grooming in relation to other ongoing behavior, the authors describe these behavioral responses by a time-structured model. The authors show the following: (a) Behavior in each treatment group can be described by a semi-Markov model.

Time structure of self-grooming in the rat: self-facilitation and effects of hypothalamic stimulation and neuropeptides.

Specific brain manipulations, such as stimulation of the paraventricular nucleus of the hypothalamus (PVH) or injections of neuropeptides, increase self-grooming in the rat. Such manipulations also affect the different movements that constitute grooming. Using models to assess the time structure of these movements, the authors demonstrate that the rules that control the time structure within grooming are different from the ones that control its initiation.

When did it really start or stop: the impact of censored observations on the analysis of duration.

Behaviour is often described in terms of bout lengths. Because of censoring, some of these bout lengths may only be observed partially. For instance, when observation is finished after a fixed period the end moment of the last bout remains unknown.

Detection of time-inhomogeneity in behavioural processes: tests for multiple abrupt changes in boutlengths.

Behavioural records often contain inhomogeinities. The number of such changes is usually not known beforehand. In this paper a description is given of parametric as well as non-parametric methods to determine the number of abrupt changes in which have been published in several papers in the biological and statistical literature have been gathered and completed here.

Detection of low dose effects of psychopharmaca: Application of a semi-Marcov model to rhesus monkey behaviour.

Behavioural testing of psycho-active drugs at lower doses is needed for medical applications and for the study of pharmacological brain mechanisms. Sensitive methods to detect effects on the time structure of behaviour are lacking. We propose a procedure based on a description within the framework of continuous time Marcov chain models.