The most compelling personal memoirs -- Tobias Wolff's This Boy's Life, Mary Karr's The Liars' Club, and others -- are not happy stories. They are recollections of childhood adversity, and rarely are they triumphant survivors' tales. The most honest of these remembrances are accounts of the lingering scars and damage done.
And damage is done. Scientists have thoroughly documented the pernicious effects of traumatic childhood events, right down to the cellular level. The young brain is highly vulnerable to all sorts of stress, and study after study has shown that childhood troubles can skew the development of key neural networks involved in emotional stability.
But most of these studies have focused on extreme childhood trauma -- physical and psychological abuse, even institutionalization -- and the neurological consequences for older children and adults. What about very young kids, who might be experiencing less extreme forms of adversity, including parental discord? Household turmoil and angry conflict may be less alarming than the extremes of maltreatment, but they are presumably more common experiences. Is there a threshold for what's damaging to the developing infant's mind and brain?
A new study suggests that even moderate levels of household conflict can alter basic brain function in infants, leaving them hypersensitive to negative emotions. Even more startling, it appears that even the deep privacy of sleep cannot protect our youngest children from battling mothers and fathers.
University of Oregon psychological scientist Alice Graham and her colleagues decided to look inside the sleeping brains of 6- to 12-month-old children, to see how they process angry arguments in the home. To simulate this common kind of domestic conflict in the lab, she recruited infants for an fMRI study, conducted at their normal bedtime. The infants' families represented a range of parental conflict, from serious discord to relative harmony, but there was no documented child abuse in any of the homes.
Once the babies were sleeping, a male adult spoke nonsense sentences in a variety of tones, from irate to happy and neutral. Graham recorded activity is brain regions known for processing stress and emotion. She wanted to see if chronic family conflict made infants more likely to have abnormal brain responses to angry speech.
They did. As described in a forthcoming issue of the journal Psychological Science, infants from discordant families showed more neural activity in response to anger than to emotionally neutral speech in the brain's rostral anterior cingulated cortex, caudate, thalamus, and hypothalamus. These regions are all associated in one way or another with the processing and regulation of stress and emotion, but notably, the scientists did not target these regions for study. Instead, they scanned the whole brains of the sleeping infants, and these scans revealed abnormal activity in these clusters of neurons.
Incidentally, this fMRI study also turned up novel evidence about how the infant brain processes emotion in general, regardless of their family situation. It appears that babies as young as 6 months old differentiate happy and angry speech, even while they appear to be sound asleep. They may appear oblivious to the nighttime world of adults, but in fact they are exquisitely tuned in. Babies are completely dependent on caregivers, and this vulnerability renders them vigilant to even the most subtle disruptions of household harmony and safety.