HOW THE BRAIN PROTECTS ITSELF FROM STRESS AND RELATED DISORDERS†
The degree of control that an animal has over a stressor is a potent modulator of the stressorís impact on central nervous system (CNS) and the whole organism. It is known that uncontrollable stressors produce a number of outcomes that do not occur if stress is controllable. Trevor W. Robbins in Nature Neuroscience (Controlling stress: how the brain protects itself from depression. Nature Neurosci. 8, 261-262, 2005) presents a new study in rats indicating that descending inputs from the prefrontal cortex to the serotoninergic midbrain system signal the controllability of stress.
Recent research on controllability has focused on brainstem nuclei such as the dorsal raphe nucleus (DRN). J. Amat et al. (Medial prefrontal cortex determines how stressor controllability affects behaviour and dorsal raphe nucleus. Nature Neurosci. 8, 365-371, 2005) found that infra-limbic and pre-limbic regions of the ventral medial prefrontal cortex (mPFCv) in rats detect whether a stressor is under the organismís control. When a stressor is controllable, stress induced activation of the DRN is inhibited by the mPFCv, and the behavioural consequences of uncontrollable stress are blocked.
This suggests a new function for the mPFCv, and implies that the presence of control inhibits stress-induced neural activity in brainstem nuclei, in contrast to the prevalent view that such activity is induced by a lack of control.