This project proposal concerns the use of the dog as a natural animal model for research on the effects of a treatment used in human psychiatry that modulates the brain function in regions that are deficient in human depression and anxiety disorders. The problem with these diseases is that treatment outcome with classical modalities is suboptimal. Alternative treatments involve noninvasive stimulation of brain regions implicated in depression and anxiety. Focal repetitive transcranial magnetic stimulation (rTMS) can influence brain cell functioning with minimal side effects and is approved for use in depression. Major knowledge gaps remain regarding its working mechanism. Limitations of research in humans emphasize the need for an adequate natural animal model to further unravel its action mechanisms. The advantage of using the dog as a natural animal model is multifold. The dog develops natural behavioral disorders that resemble human disease with similar brain dysfunction, they have a larger brain that allow focal activation of specific brain regions as opposed to rats and mice, different potential targets can be investigated in the individual dog and the dog itself, as a patient, may benefit. In this proposal we will extend current research in normal dogs and anxiety disordered dogs, focussing on the effect on brain metabolism and the serotonergic system with imaging and biological markers. Both show deficits that are associated with mood and behavioural disorders.