Children that at early ages have similar or even greater gray matter than their wealthier peers, get stuck in a weaker development as they grow just for being poor. That is what a new study has found:
Jamie L. Hanson et al., Family Poverty Affects the Rate of Human Infant Brain Growth. PLoS ONE 2013. Open access → LINK [doi:10.1371/journal.pone.0080954]
Living in poverty places children at very high risk for problems across a variety of domains, including schooling, behavioral regulation, and health. Aspects of cognitive functioning, such as information processing, may underlie these kinds of problems. How might poverty affect the brain functions underlying these cognitive processes? Here, we address this question by observing and analyzing repeated measures of brain development of young children between five months and four years of age from economically diverse backgrounds (n = 77). In doing so, we have the opportunity to observe changes in brain growth as children begin to experience the effects of poverty. These children underwent MRI scanning, with subjects completing between 1 and 7 scans longitudinally. Two hundred and three MRI scans were divided into different tissue types using a novel image processing algorithm specifically designed to analyze brain data from young infants. Total gray, white, and cerebral (summation of total gray and white matter) volumes were examined along with volumes of the frontal, parietal, temporal, and occipital lobes. Infants from low-income families had lower volumes of gray matter, tissue critical for processing of information and execution of actions. These differences were found for both the frontal and parietal lobes. No differences were detected in white matter, temporal lobe volumes, or occipital lobe volumes. In addition, differences in brain growth were found to vary with socioeconomic status (SES), with children from lower-income households having slower trajectories of growth during infancy and early childhood. Volumetric differences were associated with the emergence of disruptive behavioral problems.
|Figure 2. This figure shows total gray matter volume for group by age.|
The data is clear (for details of the localized frontal and parietal evolution see figs. 3 and 4). The question is: why does this happen? The paper attempts also to discuss that:
These results extend a consistent literature in rodents, non-human primates, and humans suggesting that early environments marked by stress or deprivation negatively influence brain development –. This emerging body of research has found differences in brain structure in portions of the frontal lobe, which fits well with the analysis presented here . These findings suggest that aspects of low SES environments have important functional implications for children's health and adaptation , perhaps by influencing key features of central nervous system development. In regards to neurobiological mechanisms, the differences in volume we find are likely due to neuronal remodeling, rather than birth of new neurons (or neurogenesis) , , .
Candidate factors might include the effects of household resources, environmental stimulation, crowding, exposure to pathogens and noise, parental stress, and nutrition. It is also possible that pre-natal experiences affect brain development and reflect other disadvantages and risks related to poverty. Because humans are able to adapt to a range of environmental conditions, we must understand more about the level at which impoverished environments become toxic for children.
And quite suggestively in the introduction they mention as well that:
The specific causes can be many but I'd dare say that "caging", i.e. the limitation of stimuli for living in smaller, impoverished, artificial habitats (including of course whatever limitations that the adults around them may have, such as low culture or emotional instability) is likely to be a key negative environmental factor for brain development.
On the other hand I can imagine that certain enrichment (cultural, health even technological, why not?) that has happened to our species in general in the last centuries, may be behind the so-called Flynn effect, which is that the measured IQ has been growing everywhere quite steadily.
But in any case it is quite worrying that these social differences have such a big effect on the children and emphasizes the need to overcome them and to provide the best possible environment for the development of the future generations.