London, Feb 13 (IANS): If she is not in the mood tonight, do not just blame her for spoiling yours. New research suggests a woman's desire to make love is linked to how her hormones affect neurons in a particular brain area.

In lab experiments, researchers discovered that hormones affect brain cells in the hypothalamus region which controls many instinctive behaviours including feeding, sleep and sexual behaviour.

"We recorded the activity of neurons in an area within the hypothalamus dedicated to socio-sexual behaviour. The activity of the neurons was observed while the females interacted with males or with other females," explained Kensaku Nomoto from the lab of Susana Lima, principal investigator at the Champalimaud Centre for the Unknown in Lisbon, Portugal.

The researchers found that the activity of these neurons changed dramatically depending on the reproductive state of the female.

When the female was not in a receptive state, the activity of the neurons was similar for social encounters with males and females.

"However, when the female was in the receptive state, the activity of the neurons was enhanced only when interacting with males", Nomoto explained.

Simply put, this area in the brain that drives a woman's desire to make love can also make a woman ignore sexual advances.

This is the first time that the activity of these neurons is recorded in naturally cycling females.

"It establishes that there is, in fact, a brain region where hormonal state and social interaction are integrated," Lima noted.

In humans, the effect of hormonal state on attraction and rejection is quite controversial.

"Studies such as this one may help shed light on the neural circuits that mediate these behaviours," Lima concluded.

The study was published in the journal Current Biology.