Monday, November 10, 2008

Neurological correlates of Poverty

While people generally do not squirm on reading a headline claiming neural correlates of religion, god, trust, consciousness, political/ sexual orientation etc, I am sure the title neural correlates of Poverty would have lead to some uneasy shuffling around. How can poverty that is clearly a result of economic opportunities/ capabilities be reduced to brain? Are we claiming that low inherent IQ and the neural correlates thereof define and lead to poverty? Or is the claim instead that poverty leads to definite changes in the brain, which may lead to manifestation of low IQ and the sustenance of the vicious circle of poverty? The regular readers of the blog will know which side of the fence I am sitting on!

The blogosphere is normally abuzz with controversial topics like atheism, meaninglessness of evolution and race and gender differences(for eg.  in IQ) and people defend these sacred dictum doggedly, claiming that 'is' and 'ought' need not be confused, especially in a cold, logical science which deals with all facts and should not be guided by values. Yet, the same blogosphere generally silently ignores, or does not take a stand , when the 'is' and 'ought' are in sync and something morally significant is also found to be scientifically valid. Rather the apology for such facts is made very cautiously, with the spirit of not offending the people who have a different, and in my view, an inferior moral system.

I believe whenever people discuss poverty/SES, they have either of the two moral systems: first, the world is unfair and poor people are poor because of some external factors/ circumstances; addressing them may solve/ eliminate the problem of poverty;  and second: the world is fair (like an idealized free market) and if someone is poor they are due to either inherent internal flaws (bad genes) or maybe bad choices (they want to be poor/ are lazy and unindustrious etc); so the problem of poverty cannot/ should not be solved.  I subscribe to the first moral system and believe in interventions to solve the problem of poverty. I am glad to have scientific facts to my side and have been addressing these issues in a series of posts .

The latest impetus to write on the topic comes form reading Lehrer's post titled Poverty and the brain at the Frontal cortex and I am glad to have found a fellow blogger who doesn't mind speaking on such controversial topics and take a stand for 'is' that is in sync with 'ought'. It is an excellent post regarding how early interventions can help alleviate poverty and how a poor person suffers from the viscous circle of poverty by the mediating influence of brain and IQ.

Lehrer also mentions the work of Martha Farah (of Visual Agnosia fame whose earlier work was on vision) on the same and I recommend reading at least this article by Martha and colleagues, although many other invaluable gems are present on her site.

The article begins with an anecdotal reference to how Martha first became aware of the gravity of the issue, when she saw her babysitters / maids steeped in poverty and the low IQ and SES viscous circle. this resonates with me and I can easily relate to this as my child enjoys a lot of toys while our maid's children are faced with lack.

I would now quote extensively from the aforementioned article:

It seemed to me that children’s experience of the world is very different in low and middle SES environments. Most middle SES children have abundant opportunities to explore the world, literally, in terms of people met and places seen, and figuratively, in terms of the world of ideas. In contrast, low SES children generally have fewer interactions with the wider world and much of what they do experience is stressful. Basic research with animals has established the powerful effects of both environmental impoverishment and stress on the developing brain.


She then goes on to make out the case for NCC of poverty:

For the sake of exploring the cognitive neuroscience perspective on transgenerational poverty, and discovering what, if anything, it can contribute to correcting socioeconomic inequality, the first order of business is to ask whether socioeconomic status bears any straightforward relation to brain development. On the face of things it might seem unlikely that characteristics such as income, education and job status, which are typically used to estimate SES, would bear any systematic relationship to physiological processes such as those involved in brain development. It is, however, well established that SES affects physical health through a number of different causal pathways (Adler et al. 1994), many of which could play a role in brain development. It is also clear that poverty is associated with differences in brain function on the basis of the differences in standardized test performance cited earlier, as cognitive tests reflect the function of the brain. However, for a cognitive neuroscience approach to be helpful, the relations between socioeconomic status and the brain must be relatively straightforward and generalizable. The first question that my collaborators and I addressed was therefore: Can we generalize about the neurocognitive correlates of socioeconomic status? Once we have established the neurocognitive profile of childhood poverty, we can begin to test more specific hypotheses about causal mechanisms.

I will now digress a little from the main topic and introduce the five neurocognitive systems that Martha and colleagues have identified and how they tested some children from low and middle SES for finding their capabilities in these systems.

The children were tested on a battery of tasks adapted from the cognitive neuroscience literature, designed to assess the functioning of five key neurocognitive systems. These systems are described briefly here.
The Prefrontal/Executive system enables flexible responding in situations where the appropriate response may not be the most routine or attractive one, or where it requires maintenance or updating of information concerning recent events. It is dependent on prefrontal cortex, a late-maturing brain region that is disproportionately developed in humans.
The Left perisylvian/Language system is a complex, distributed system encompassing semantic, syntactic and phonological aspects of language and dependent predominantly on the temporal and frontal areas of the left hemisphere that surround the Sylvian fissure.
The Medial temporal/Memory system is responsible for one-trial learning, the ability to retain a representation of a stimulus after a single exposure to it (which contrasts with the ability to gradually strengthen a representation through conditioning-like mechanisms), and is dependent on the hippocampus and related structures of the medial temporal lobe.
The Parietal/Spatial cognition system underlies our ability to mentally represent and manipulate the spatial relations among objects, and is primarily dependent upon posterior parietal cortex.
The Occipitotemporal/Visual cognition system is responsible for pattern recognition and visual mental imagery, translating image format visual representations into more abstract representations of object shape and identity, and reciprocally translating visual memory knowledge into image format representations (mental images).

Not surprisingly, in view of the literature on SES and standardized cognitive tests, the middle SES children performed better than the low SES children on the battery of tasks as a whole. For some systems, most notably the Left perisylvian/Language system and the Prefrontal/Executive system, the disparity between low and middle SES kindergarteners was both large and statistically significant.

Thus, they found, in a small group of children , that Language and Executive systems' performance differed in low and middle SES children and they were able to replicate this finding with a larger group of children too. This time they broke executive function further into components and found a finer granularity of how SES affects the brain:

As before, the language system showed a highly significant relationship to SES, as did executive functions including Lateral prefrontal/Working memory and Anterior cingulate/Cognitive control components and the Parietal/Spatial cognition system. With a more demanding delay between exposure and test in the memory tasks, we also found a difference in the Medial temporal/Memory system. Performance on the Parietal/spatial system tests also differed as a function of SES.


They also did some studies with older children and to summarize the results of all these studies in their own words:

In sum, although the outcome of each study was different, there were also commonalities among them despite different tasks and different children tested at different ages. The most robust neurocognitive correlates of SES appear to involve the Left perisylvian/Language system, the Medial temporal/Memory system (insofar as SES effects were found in both studies that tested memory with an adequate delay) and the Prefrontal/Executive system, in particular its Lateral prefrontal/Working memory and Anterior cingulate/Cognitive control components. Children growing up in low SES environments perform less well on tests that tax the functioning of these specific systems.

Next they look at the causal versus correlational nature of findings and if causal, then the directions of causality. It is this paragraph , that amazed me, for they seem to be apologetic for the fact that their findings are also ethically good ones.

Do these associations reflect the effects of SES on brain development, or the opposite direction of causality? Perhaps families with higher innate language, executive and memory abilities tend to acquire and maintain a higher SES. Such a mechanism seems likely, a priori, as it would be surprising if genetic influences on cognitive ability did not, in the aggregate, contribute to individual and family SES. However, it seems also seems likely that causality operates in the opposite direction as well, with SES influencing cognitive ability through childhood environment. Note that the direction of causality is an empirical issue, not an ethical one. The issue of whether and to what extent SES differences cause neurocognitive differences or visa versa should not be confused with the issue of whether we have an obligation to help children of any background become educated, productive citizens.

Then, quite important from this blog's point of view, they review the literature that supports SES to IQ direction of causality.

Cross-fostering studies of within- and between -SES adoption suggest that roughly half the IQ disparity in children is experiential (Capron & Duyme, 1989; Schiff & Lewontin, 1986). If anything, these studies are likely to err in the direction of underestimating the influence of environment because the effects of prenatal and early postnatal environment are included in the estimates of genetic influences in adoption studies. A recent twin study by Turkheimer and colleagues (2003) showed that, within low SES families, IQ variation is far less genetic than environmental in origin. Additional evidence comes from studies of when, in a child’s life, poverty was experienced. Within a given family that experiences a period of poverty, the effects are greater on siblings who were young during that period (Duncan et al. 1994), an effect that cannot be explained by genetics. In sum, multiple sources of evidence indicate that SES does indeed have an effect on cognitive development, although its role in the specific types of neurocognitive system development investigated here is not yet known.


Next they tried to tease out what specific SES related factors can affect the different neurocognitive systems. They list both physical and psychological factors that have been hypothesized and researched on in relation to SES and IQ.
Potential causes, physical and psychological
What aspects of the environment might be responsible for the differences in neurocognitive development between low and middle SES children? A large set of possibilities exist, some affecting brain development by their direct effects on the body and some by less direct psychological mechanisms. Three somatic factors have been identified as significant risk factors for low cognitive achievement by the Center for Children and Poverty (1997): inadequate nutrition, substance abuse (particularly prenatal exposure), and lead exposure.
As with potential physical causes, the set of potential psychological causes for the SES gap in cognitive achievement is large, and the causes are likely to exert their effects synergistically. Here we will review research on differences in cognitive stimulation and stress.

They then discuss the psychological factors, which they then investigated, in more detail.

One difference between low and middle SES families that seems predictable, even in the absence of any other information, is that low SES children are likely to receive less cognitive stimulation than middle SES children. Their economic status alone predicts that they will have fewer toys and books and less exposure to zoos, museums and other cultural institutions because of the expense of such items and activities. This is indeed the case (Bradley et al. 2001a) and has been identified as a mediator between SES and measures of cognitive achievement (Bradley and Corwyn 1999; Brooks-Gunn and Duncan 1997; McLoyd 1998). Such a mediating role is consistent with the results of neuroscience research with animals. Starting many decades ago (e.g., Volkmar & Greenough, 1972) researchers began to observe the powerful effects of environmental stimulation on brain development. Animals reared in barren laboratory cages showed less well developed brains by a number of different anatomical and physiological measures, compared with those reared in more complex environments with opportunities to climb, burrow and socialize (see van Praag et al 2000 for a review).
The lives of low SES individuals tend to be more stressful for a variety of reasons, some of which are obvious: concern about providing for basic family needs, dangerous neighborhoods, and little control over one’s work life. Again, research bears out this intuition: Turner and Avison (2003) confirmed that lower SES is associated with more stressful life events by a number of different measures. The same appears to be true for children as well as adults, and is apparent in salivary levels of the stress hormone cortisol (Lupien et al. 2001).
Why is stress an important consideration for neurocognitive development? Psychological stress causes the secretion of cortisol and other stress hormones, which affect the brain in numerous ways (McEwen 2000). The immature brain is particularly sensitive to these effects. In basic research studies of rat brain development, rat pups are subjected to the severe stress of prolonged separation from the mother and stress hormone levels predictably climb. The later anatomy and function of the brain is altered by this early neuroendocrine phenomenon. The brain area most affected is the medial temporal area needed for memory, although prefrontal systems involved in the regulation of the stress response are also impacted (Meaney et al. 1996).

They then go on to discuss how this information can be used to formulate mechanisms that mediate the effect of low SES on diffrent neurocognitive systems.

The latest phase of our research is an attempt to make use of the description of the SES disparities in neurocognitive development in testing hypotheses about the causal pathways. Drawing on our previous research that identified three neurocognitive systems as having the most robust differences as a function of SES (Perisylvian/Language, Medial temporal/Memory, and Prefrontal/Executive), we are now testing hypotheses concerning the determinants of individual differences in the development of these systems in children of low SES. Specifically, we are investigating the role of childhood cognitive stimulation and social/emotional nurturance (Farah et al. 2005; Childhood experience and neurocognitive development: Dissociation of cognitive and emotional influences).

They then describe an observational study of interaction between children and parents and how they assess the cognitive simulation an social/emotional nurturance using HOME assessment battery. What they found follows:

Children’s performance on the tests of Left perisylvian/Language was predicted by average cognitive stimulation. This was the sole factor identified as predicting language ability by forward stepwise regression, and one of three factors identified by backwards stepwise regression, along with the child’s gender and the mother’s IQ. In contrast, performance on tests of Medial temporal/Memory ability was predicted by average social/emotional nurturance. This was the sole factor identified as predicting memory ability by forward stepwise regression and one of three factors identified by backwards stepwise regression, along with the child’s age and cognitive stimulation. The relation between memory and early emotional experience is consistent with the animal research cited earlier, showing a deleterious effect of stress hormones on hippocampal development. Our analyses did not reveal any systematic relation of the predictor variables considered here to Lateral prefrontal/Working memory or Anterior cingulate/Cognitive control function. In conclusion, different aspects of early experience affect different systems of the developing brain. Cognitive stimulation influences the development of language, whereas social/emotional nurturance affects the development of memory but not language.

Here is what they conclude:

What are the implications for society of a more mechanistic understanding of the effects of childhood poverty on brain development? To different degrees, and in different ways, we regard children as the responsibility of both parents and society. Parents’ responsibility begins before birth and encompasses virtually every aspect of the child’s life. Society’s responsibility is more circumscribed. In the United States, for example, society’s contribution to the cognitive development of children begins at age 5 or 6, depending on whether public kindergarten is offered. The physical health and safety of all infants and children is a social imperative, however, well before school age. Laws requiring lead abatement in homes occupied by children exemplify our societal commitment to protect them from the neurological damage caused by this neurotoxin. Research on the effects of early life stress and limited cognitive stimulation has begun to show that these concomitants of poverty have negative effects on neurological development too, by mechanisms no less concrete and real. Thus, neuroscience may recast the disadvantages of childhood poverty as a bioethical issue rather than merely one of economic opportunity.

In my view the societal implications are far reaching, if low SES leads to lowered cognitive functioning, it becomes our duty to provide more cognitive stimulation and ensure that all children get sufficient social/ emotional nurturance so that their IQ can flower to its full potential.

I would have liked to end on this note, but cant help pointing that the five neurocognitive systems Martha has identified, to me seems to follow in stages, with the later systems maturing later :

1) Occipital/ visual : describe/ perceive the world/ self
2) Parietal/ spatial:explain the world/self (may be involved in consciousness)
3) Temporal/ Memory: predict the world/self
4) Frontal/ executive: control the world/ self
5) Sylvian/ Language: improve the world/ self


We all know that language abilities develop the oldest and vision is more or less developed at birth; also the fact that SES should affect the latter stages of neurocognitive systems also gels in. the fact that cognitive stimulation affects language and emotional/social nurturance affects memory to me also fits in.

Anyway whatever the implication sof this research for stage theories, they have far reaching and imprortanat implications for social policy and education.
ResearchBlogging.org
Farah, M.J.,Noble, K.G. and Hurt, H. (2005). Poverty, privilege and brain development: Emprical findings and ethical implications. In J. Illes (Ed.) Neuroethics in the 21st Century. New York: Oxford University Press.

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1 comment:

alcohol treatment said...

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