It's well known that women can become aroused just by their nipples alone. But till now, scientists failed to explain the reason behind it.
Now, psychologists at Rutgers University in the U.S. found that when women's nipples are stimulated the sensation travels to the same part of the brain as when their genitals are aroused.
Brain scans of women who made themselves aroused showed that the nipples hit the same spot as the vagina and clitoris.
The research confirms for the first time what many women have experienced themselves - that their nipples can be an erogenous zone too.
The researchers asked 11 non-pregnant women between 23 and 56 to stimulate themselves while they lay inside a brain scanner. The resulting images show the areas of the brain which were affected were like a 'cluster of grapes' in the medial paracentral lobule, which is in the middle and at the top of the brain.
In men, the same area also lights up when they are stimulated.
"My speculation is that this could be the basis for many women saying that nipple stimulation is erotogenic, because it stimulates the same area as the genitals," the Daily Mail quoted lead researcher Barry Komisaruk as telling LiveScience.
He added that four nerves bring signals from a woman's genitals up to her brain.
The clitoris relies on the pudendal nerve, the vagina uses the pelvic nerve and the hypogastric nerve connects with the cervix and uterus.
In addition the cervix uses the vagus nerve, which bypasses the spinal cord, and explains how people who have been paralysed can still orgasm.
Komisaruk said that although it is unlikely, another explanation for why the nipples hit the same part of the brain as other erogenous zones could be to do with breast feeding.
Stimulating the nipples releases the hormone oxytocin which is normally secreted during labour and causes the uterus to contract, thus causing sensations in the brain.