How the Emotional Motor System Controls the Pelvic Organs.

Introduction: The brain has two goals: survival of the individual and survival of the species. It ensures that the body resides in safe circumstances and can obtain sufficient drink and food. It also has to produce and protect offspring. Its most important tool is its motor system, which consists of the voluntary and emotional motor systems.

Aim: To explain how the brain uses its emotional motor system to control the pelvic organs.

Methods: Anatomic and physiologic data in cats and humans are used to find out how this motor system works and what parts of the brain and brainstem are involved.

Main Outcome Measures: Main outcome is that the brain control of the pelvic organs is a specific descending system.

Results: The pelvic organs are innervated by the sacral parasympathetic motoneurons, which are controlled by a specific group of neurons in the pontine brainstem, the pelvic organ stimulating center (POSC). Through long descending pathways, this POSC generates micturition, defecation, and sexual activities by stimulating different groups of sacral parasympathetic motoneurons. In turn the POSC is driven by the periaqueductal gray (PAG), which receives, through the sacral cord, precise information regarding the situation in all pelvic organs. In addition, the PAG receives instructions from higher brain levels such as the amygdala, bed nucleus of the stria terminalis, and various regions of the hypothalamus. Notably, in humans, the most important brain region having access to the PAG is the medial orbitofrontal cortex, which is deactivated in women with hypoactive sexual desire disorder.

Conclusion: In women with hypoactive sexual desire disorder, deactivation of their medial orbitofrontal cortex produces a decrease in PAG-POSC activation, causing absence of vaginal vasocongestion and lubrication and decreased sexual behavior in general. It often leads to major problems in their personal circumstances. The question is whether new drugs can cure this.