A friend sent me this article. Kinda interesting when you think about it.

Parents' brains tuned to babies' tears
Emotions triggered by wailing tots.
22 December 2003

The brains of mums and dads are tuned in to the sound of toddlers' cries, reveals a brain-imaging study. Non-parents, on the other hand, remain largely oblivious.

Researchers at the University of Basel, Switzerland, played parents and childless adults recordings of babies' cries and laughter. They measured their brain activity using functional magnetic resonance imaging (fMRI).

Parents' brains fired up more in response to sobs than giggles, the researchers found1. The cries activated one brain region in particular, called the amygdala, which is involved in processing emotions.

"This makes biological sense," says Erich Seifritz, who led the study. Tears signify to parents that something is amiss, generating emotions such as concern or fear, which prompt parental care. In evolutionary terms, this means that a child is more likely to survive and pass on his or her genes.

Childless grown-ups, by contrast, reacted more to infant laughter than whimpers. This shows that the parental brain activity is learned, says Seifritz.

Brain cells may work differently in parents and non-parents, says Jeffrey Lorberbaum who studies mother-child interactions at the Medical University of South Carolina in Charleston. In rats, one cell type spurs parents to approach their pups; another prompts non-parents to avoid them. Humans may share a similar make-up.

Maternal instinct

Men and women also respond differently to infant sounds, according to the study. When females hear baby noises, activity drops in a brain region called the prefrontal cortex, which filters out irrelevant sounds. Males are unaffected.

Crying may open up the noise filter in the prefrontal cortex, so that a woman interprets the toddler's sounds as important. Electrical impulses are then relayed to other brain areas, triggering strong emotions, as well as caring behaviour such as feeding or cuddling.

Women respond to cries and wails whether or not they are mothers themselves, the researchers found, suggesting that their responses, unlike those of men, are innate. "This sex difference is wired rather than acquired," says Seifritz.

The study may also help researchers to understand other social attachments between people, says Lorberbaum - as well as gaining insight into medical conditions in which these bonds go awry.

In borderline personality disorder, for example, sufferers are clingy and tend to overreact emotionally. Around 2% of the population are affected to some degree.

People with borderline personality disorder may have faulty brain connections between the prefrontal cortex and the amygdala. Knowing how these areas normally react in social situations may help determine what goes wrong in those with the disorder, says Lorberbaum.

Seifritz, E. et al. Differential sex-independent amygdala response to infant crying and laughing in parents versus nonparents. Biological Psychiatry, 54, 1367 - 1375, (2003). |Article|

© Nature News Service / Macmillan Magazines Ltd 2003