Monday, February 21, 2011
Achieving sexual climax requires a complex conspiracy of sensory and psychological signals—and the eventual silencing of critical brain areas. Sexual desire and orgasm are subject to various influences on the brain and nervous system, which controls the sex glands and genitals. The ingredients of desire may differ for men and women, but researchers have revealed some surprising similarities. For example, visual stimuli spur sexual stirrings in women, as they do in men.
Studies in neuroscience have involved chemicals that are present in the brain and might be involved when people experience love. These chemicals include: nerve growth factor, testosterone, estrogen, dopamine, norepinephrine, serotonine, oxytocin and vasopressin. Adequate brain levels of testosterone seem important for both human male and female sexual behavior. Dopamine, norepinephrine, and serotonin are more commonly found during the attraction phase of a relationship.Oxytocin and vasopressin seemed to be more closely linked to long term bonding and relationships characterized by strong attachments.
A scan developed by American scientists could sneak a peek inside the brain of a woman while she is enjoying orgasm. Researchers from the Rutgers University were able to discover that that sexual arousal tends to numb the female nervous system to such an extent that she does not feel as much pain-only pleasure.
The researchers asked eight women to stimulate themselves while lying under a blanket inside a Magnetic Resonance Imaging (MRI) scanner, a tunnel-like machine often used to detect brain tumours. Most women took less than five minutes to reach an orgasm although some took as long as 20. During that time, the MRI scanner took images of their brain every two seconds to show which parts became active during the orgasm. The scientists found that two minutes before the orgasm, the brain’s reward centres become active, the areas usually activated when eating food and drink.
Clitoral stimulation by itself led to activation in areas of the brain involved in receiving and perceiving sensory signals from that part of the body and in describing a body sensation—for instance, labeling it “sexual.” But when a woman reached orgasm, something unexpected happened: much of her brain went silent. Some of the most muted neurons sat in the left lateral orbitofrontal cortex, which may govern self-control over basic desires such as sex. Decreased activity there, the researchers suggest, might correspond to a release of tension and inhibition. The scientists also saw a dip in excitation in the dorsomedial prefrontal cortex, which has an apparent role in moral reasoning and social judgment—a change that may be tied to a suspension of judgment and reflection. Brain activity fell in the amygdala, too, suggesting a depression of vigilance similar to that seen in men, who generally showed far less deactivation in their brain during orgasm than their female counterparts did. “Fear and anxiety need to be avoided at all costs if a woman wishes to have an orgasm.
“At the moment of orgasm, women do not have any emotional feelings.”
Source : Scientific American Mind