Mothers get high on baby smiles

Mothers get high on baby smiles

Seeing her baby smile lights up the reward centres in the mother's brain in a way similar to that observed in experiments on drug addiction, said US and UK researchers who hope the findings give further insight into the development of the mother-baby bond, and how it can sometimes go wrong.

The study is the work of researchers at Baylor College of Medicine (BCM), Houston, Texas, the Texas Children's Hospital, and University College London, and is published online in the 1st July issue of the journal Pediatrics.

Dr Lane Strathearn, assistant professor of pediatrics at BCM and and a research associate at the college's Human Neuroimaging Laboratory, said in a statement:

"The relationship between mothers and infants is critical for child development."

"For whatever reason, in some cases, that relationship doesn't develop normally. Neglect and abuse can result, with devastating effects on a child's development," he added.

For the study, Strathearn and colleagues observed the brains of 28 first-time mothers of babies aged 5 to 10 months with a functional magnetic resonance imaging (fMRI) scanner while they looked at photos of facial expressions of their own and other babies. Some of the photos showed the babies happy and smiling, and others showed the babies looking sad or with neutral facial expressions.

Specifically, the researchers measured the fMRI response to each of 6 photo-observing events: (1) own baby happy face; (2) own baby neutral face; (3) own baby sad face; (4) unknown baby happy face; (5) unknown baby neutral face; and (6) unknown baby sad face. The mothers looked at each photo randomly for 2 seconds, and there was a variable 2 to 6 second pause between each photo.

The fMRI scanner measured blood flow in the brain, giving rise to the expression that the brain "lights up" in areas of increased blood flow, which shows where the brain is more active at that time.

The results showed that:

  • When the mothers looked at their own baby's face, certain dopamine-related reward centres in their brains "lit up".
  • The brain areas that appeared to be most affected were the ventral tegmental area and the substantia nigra regions (part of the midbrain reward system); the striatum (involved in reward, cognition, and motor functions); two frontal lobe regions and a primary motor area.
  • The two frontal lobe regions that lit up were: (1) the medial prefrontal, anterior cingulate, and insula cortex (involved with emotion processing), and (2) the dorsolateral prefrontal cortex (involved in cognition).
  • The nigrostriatal brain regions interconnected by dopaminergic neurons, including the substantia nigra and dorsal putamen, lit up when the mothers saw happy, but not neutral or sad photos of their own babies.
  • On the whole, the mothers reacted more strongly to their own babies' faces than to the unknown babies' faces, with the strongest reactions being to happy faces, then neutral, then sad.
The researchers concluded that when first-time mothers see their own baby's facial expression it activates an extensive network of brain connections that integrate emotional and cognitive signals and direct them to motor and behavioural outputs.

"Dopaminergic reward-related brain regions are activated specifically in response to happy, but not sad, infant faces," wrote the researchers, who suggested that:

"Understanding how a mother responds uniquely to her own infant, when smiling or crying, may be the first step in understanding the neural basis of mother-infant attachment."

Dopamine is a neurotransmitter involved in many brain functions, including motivation, emotion processing, thinking, sleep, mood, attention, learning and motor control.

The researchers said they were surprised that the mothers did not react as strongly to their babies' sad faces as they did to their smiling faces. They expected to see an equally strong, but perhaps different reaction when mothers saw their babies' crying faces.

Strathearn said that the brain areas that lit up for the mothers, are the same as the ones that light up in experiments on drug addiction.

"It may be that seeing your own baby's smiling face is like a 'natural high', the strongest activation was with smiling faces," said Strathearn.

"What's in a Smile? Maternal Brain Responses to Infant Facial Cues."

Lane Strathearn, Jian Li, Peter Fonagy, and P. Read Montague

Pediatrics Vol. 122 No. 1 July 2008, pp. 40-51


Click here for Abstract.

Source: Journal abstract, Baylor College of Medicine, wikipedia.

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