THIS WEEK

12 | NewScientist | 8 October 2011

YOU may not wonder why women have bumps around their nipples but it has bemused many. Now the mystery has been solved. Smelly secretions released from the nipples of women who have just given birth may help babies find and extract their mother’s milk.

During pregnancy, women often notice an increase in the number of bumps, or areolar glands, on the pigmented skin surrounding the nipple – some notice small amounts of secretions from them. It had been assumed that this fluid was to help lubricate the skin, but now it seems it may also contain odoursome molecules that help an infant to find its way to the breast.

Benoist Schaal of the National Centre for Scientific Research in Dijon, France, and his colleagues counted the number of areolar glands on the nipples of 121 new mothers in the first three days after birth, and recorded their babies’ sucking performance, body weight, and the time it took for the women to start lactating.

Women with more than nine glands per breast started lactating

sooner than those with fewer glands, and their babies gained weight faster. The effect was greater in first-time mothers, who began lactating an average of 10 hours earlier than those with fewer glands. Their infants also fed more frequently (Early Human Behaviour, DOI: 10.1016/

j.earlhumdev.2011.07.020).“The breastfeeding relationship

is less easy to establish for first-time mothers bearing low amounts of areolar glands,” says Schaal, who adds that babies of first-time mothers may be more reliant on olfactory cues as their mothers are less familiar with other signals that their infant wants to feed.

Schaal’s team also found that three-day-old infants exhibit more head and mouth movements related to feeding, such as sucking and licking, when

they smell gland secretions, compared with other odours from the human breast – including that of milk itself (PLoS One, DOI: 10.1371/journal.pone.0007579).

Olfactory cues are already known to help other mammals, such as rabbits, to find the breast.

“The finding is important, but might be only one factor among [many] enhancing breastfeeding,” says Heili Varendi of the University of Tartu in Estonia, who discovered that newborns prefer to feed from an unwashed breast than a recently cleaned one.

Schaal believes his discovery could have practical implications. If the factors responsible could be extracted, these could be used to help train the mouth muscles of babies who are temporarily unable to breastfeed due to prematurity or illness, so they do better when introduced to the breast. “It could help to prepare them for the transition from tube-feeding to direct sucking on the nipple of the mother or a bottle,” says Schaal.

The findings also add support to the existence of pheromone-like compounds in humans. A previous study found that the sexual desire of women is boosted by odours given off by breastfeeding women. “Finding olfactory ways of communication between human newborns and mothers would be a strong demonstration that olfaction is still functional in the human social context,” he adds. n

Linda Geddes

–Followed his nose–

Bumpy nipples guide babies to milk

Monkeys ‘feel’ the texture of virtual objectsMONKEY see, monkey do. Now they feel too. Rhesus macaques have learned to “feel” the texture of virtual objects without physically touching a thing. In the future, prosthetic limbs modelled on similar technology could return a sense of touch to amputees.

Using two-way communication between brain and machine, the monkeys manoeuvred a cursor with

their minds and identified objects by texture, based on electrical feedback from the computer.

Miguel Nicolelis of Duke University Medical Center in Durham, North Carolina, and his colleagues implanted electrodes into the brains of two monkeys. The electrodes recorded activity in the motor cortex and somatosensory cortex (SSC) – brain areas that orchestrate voluntary movement and sense of touch. Electrical activity from the motor cortex was sent to a computer, which translated the neural chatter into instructions that moved a cursor

on screen. The monkeys learned what patterns of thought reliably changed the cursor’s position.

The team then assigned a unique texture to each of three identical circles on the screen. When the cursor hovered over each circle, the computer zapped the monkeys’ SSCs with the same electrical impulses that occurred when they touched each texture in real life. Finally, the team

taught the monkeys to associate a particular texture with a reward.

When the circles were randomly moved on the screen, the monkeys were able to identify the circle associated with the reward with 90 per cent accuracy (Nature, DOI: 10.1038/nature10489).

“Amazing stuff – you can take information from the brain, analyse it outside, bring it back to the brain and affect computation,” says psychobiologist Matti Mintz of Tel Aviv University in Israel. “That’s the model vision of brain-computer interfaces.” Ferris Jabr n

“Prosthetic limbs modelled on similar technology could return a sense of touch to people with amputations”

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