They have found that there are four tiny areas in brain which they call "circuit of love". These regions are ventral tegmental area (VTA), the nucleus accumbens, the ventral pallidum and raphe nucleus.
When people newly in love were put in a functional magnetic resonance imaging machine and shown pictures of their beloved, the VTA lit up. Same for people still madly in love after 20 years.
The VTA is part of a key reward system in the brain. These are cells that make dopamine and send it to different brain regions. When newly love struck couples were examined, it was found that they have high levels of the neurotransmitter dopamine.
This chemical stimulates 'desire and reward' by triggering an intense rush of pleasure. It has the same effect on the brain as taking cocaine! Thus, Love works chemically in the brain like a drug addiction.
``Romantic love is an addiction; a wonderful addiction when it is going well, a horrible one when it is going poorly,' Fisher (a researcher) said. ``People kill for love. They die for love.''
Fisher suggests "couples often show the signs of surging dopamine: increased energy, less need for sleep or food, focused attention and exquisite delight in smallest details of this novel relationship" .
So what about the broken heart? So the scientists studied the brains of the recently heartbroken and found additional activity in the nucleus accumbens, which is even more strongly associated with addiction.
``The brokenhearted show more evidence of what I'll call craving,'' said Lucy Brown, a neuroscientist also at Einstein medical college. ``Similar to craving the drug cocaine.''
This happens due to serotonin level. When serotonin is dangerously low, the mind dips into depression.
By analysing blood samples from the lovers, Dr Marazitti discovered that serotonin levels of new lovers were equivalent to the low serotonin levels of Obsessive-Compulsive Disorder patients.
Selective serotonin reuptake inhibitors (SSRIs) can jeopardize the user's relationship with a loved one.
The raphe nucleus pumps out serotonin, which gives you a sense of calm. One of love's most important chemicals that may explain why when you're falling in love, your new lover keeps popping into your thoughts.
The team's most recent brain scans were aimed at people married about 20 years who say they are still holding hands, lovey-dovey as newlyweds, a group that is a minority of married people. In these men and women, two more areas of the brain lit up, along with the VTA: the ventral pallidum and raphe nucleus.
Attachment is stage of love that keeps couples together in marriage. Scientists think there might be two major hormones involved in this feeling of attachment; oxytocin and vasopressin.
In females, the key bonding hormone is oxytocin, also produced in humans during childbirth. Oxytocin also seems to help cement the strong bond between mum and baby.
In males, it's vasopressin.When male prairie voles were given a drug that suppresses the effect of vasopressin, the bond with their partner deteriorated immediately as they lost their devotion and failed to protect their partner from new suitors.
When vasopressin receptors put into the brains of male meadow voles a promiscuous cousin of the prairie voles, "those guys who should never, ever bond with a female, bonded with a female.'' Young.