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. This study also showed that grooming is self-facilitating and that different brain manipulations in the same hypothalamic area induce structurally different kinds of grooming. The authors suggest that this part of the hypothalamus is not only involved in setting priorities to grooming, relative to other behaviors, but is also involved in the timing of different grooming components. These findings suggest that different neural mechanisms may be involved in the initiation and internal time structure of grooming.