Link between socioeconomic status and hippocampal density

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Link between socioeconomic status and hippocampal density

#1  Postby natselrox » May 06, 2011 3:54 am

http://www.plosone.org/article/info:doi ... uroscience)

Abstract wrote:Facets of the post-natal environment including the type and complexity of environmental stimuli, the quality of parenting behaviors, and the amount and type of stress experienced by a child affects brain and behavioral functioning. Poverty is a type of pervasive experience that is likely to influence biobehavioral processes because children developing in such environments often encounter high levels of stress and reduced environmental stimulation. This study explores the association between socioeconomic status and the hippocampus, a brain region involved in learning and memory that is known to be affected by stress. We employ a voxel-based morphometry analytic framework with region of interest drawing for structural brain images acquired from participants across the socioeconomic spectrum (n = 317). Children from lower income backgrounds had lower hippocampal gray matter density, a measure of volume. This finding is discussed in terms of disparities in education and health that are observed across the socioeconomic spectrum.


Explains my piss-poor memory. :(
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Re: Link between socioeconomic status and hippocampal densit

#2  Postby Mr.Samsa » May 06, 2011 4:25 am

I wonder why they didn't discuss the effects of the mother having a poor diet during pregnancy, as that can severely affect memory and learning, and it would surely be an issue when looking at families from low socioeconomic backgrounds. For example: http://www.ncbi.nlm.nih.gov/pubmed/17688181

Whilst I don't deny that an environment without any kind of enrichment will produce learning and memory deficits, it would have been interesting to see how much is caused by what, or even whether malnutrition during pregnancy is even an issue here. Interestingly, the effects found in the article I linked to can be reversed through environmental enrichment and exercise, if given early enough...
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Re: Link between socioeconomic status and hippocampal densit

#3  Postby Tyrannical » May 06, 2011 4:50 am

Mr.Samsa wrote:I wonder why they didn't discuss the effects of the mother having a poor diet during pregnancy, as that can severely affect memory and learning, and it would surely be an issue when looking at families from low socioeconomic backgrounds. For example: http://www.ncbi.nlm.nih.gov/pubmed/17688181

Whilst I don't deny that an environment without any kind of enrichment will produce learning and memory deficits, it would have been interesting to see how much is caused by what, or even whether malnutrition during pregnancy is even an issue here. Interestingly, the effects found in the article I linked to can be reversed through environmental enrichment and exercise, if given early enough...


Nutrition certainly isn't an issue in the US unless obesity is linked to low IQ. Low IQ linked to nutrition is normally at near starvation levels I thought.
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Re: Link between socioeconomic status and hippocampal densit

#4  Postby Mr.Samsa » May 06, 2011 5:22 am

Tyrannical wrote:Nutrition certainly isn't an issue in the US unless obesity is linked to low IQ.


I don't quite follow? Poor nutrition is what causes cognitive deficiencies, not the obesity. Obesity can of course be a result, or indicator, of malnutrition though. If people were eating healthily, and eating the "correct" foods, they are (presumably) unlikely to become obese.

Tyrannical wrote:Low IQ linked to nutrition is normally at near starvation levels I thought.


Firstly, again to clarify, someone can be fat and have poor nutrition so 'starvation' levels aren't really relevant here. Secondly, I think what you're referring to is nutrition in the child's early years. However, we do know that poor nutrition can have severe, and permanent, effects on someone's IQ - obviously the worse the malnutrition the greater the deficits, but it's undeniable that deficiencies during childhood can produce differences of around 10 IQ points. Thirdly, what I'm referring to is not nutrition levels during childhood, but rather during pregnancy, which is one of the primary causes of intrauterine growth retardation. This has been demonstrated to have significant effects on learning and other cognitive functions in the individuals affected, but for a lot of humans this isn't so much of a problem because they are given an environment which can counteract these effects - but clearly people from lower socioeconomic groups don't have these same advantages, and mixed with the other disadvantages of being raised in a poor family, the effects tend to be significant and irreversible.
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Re: Link between socioeconomic status and hippocampal densit

#5  Postby natselrox » May 08, 2011 4:34 am

Mr.Samsa wrote:I wonder why they didn't discuss the effects of the mother having a poor diet during pregnancy, as that can severely affect memory and learning, and it would surely be an issue when looking at families from low socioeconomic backgrounds. For example: http://www.ncbi.nlm.nih.gov/pubmed/17688181


Indeed. Intrauterine environment plays a key role in the neurodevelopment process. In fact, the structure of the brain remains pretty plastic up to quite an advanced age (the upper limit is going up each day, as we have seen). And high stress levels are usually unfavorable for the proper development. So, I think, instead of viewing this study as an isolated one, we'd probably be better off if we take is as another evidence of the counter-productive effects of stress (from socio-economic causes) during the development of the nervous system (pre/post-natal).

Whilst I don't deny that an environment without any kind of enrichment will produce learning and memory deficits, it would have been interesting to see how much is caused by what, or even whether malnutrition during pregnancy is even an issue here. Interestingly, the effects found in the article I linked to can be reversed through environmental enrichment and exercise, if given early enough...


Yep. It'd be better if we could trace the exact mechanism and hence, the extent of the damage. If I'm allowed to throw a guess, I'd say that the effects are manifold, including reversible (inhibition of growth factors etc.) and irreversible (epigenetic, malformation of synapses, improper activities of the growth cones etc.) components.
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Re: Link between socioeconomic status and hippocampal densit

#6  Postby Mr.Samsa » May 08, 2011 4:38 am

:nod: Yeah, the study was interesting and it looked to be well-conducted, I was just interested in seeing how the authors would relate their work to similar research and how they would place it within that greater framework. Unfortunately they didn't seem to touch upon much at all.
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Re: Link between socioeconomic status and hippocampal densit

#7  Postby natselrox » May 08, 2011 4:44 am

Maybe the urge to make a social point overshadowed the scientific rigour. :dunno:
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Re: Link between socioeconomic status and hippocampal densit

#8  Postby Mr.Samsa » May 08, 2011 4:57 am

natselrox wrote:Maybe the urge to make a social point overshadowed the scientific rigour. :dunno:


Yeah, I think it's more about the intentions behind the research and their perspective on the issue rather than something as necessarily political as making a 'social point' - for example, when I study behavior I rarely touch upon genetics and evolution, not because those areas aren't relevant but simply because they aren't relevant to what I'm trying to study. So I don't think there's necessarily any problem with the scientific rigour, meaning that although a discussion on those points would have been nice, and a comment on how future research could aim to separate the effect they found from IUGR and epigenetic effects etc, I don't think it affects the 'rigourousness' of their work. Just would have been interesting if they were able to expand on those points. And maybe they did, but the editor removed it for space or because it wasn't relevant to a particular topic that the issue was dedicated to.
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Re: Link between socioeconomic status and hippocampal densit

#9  Postby natselrox » May 08, 2011 5:04 am

Mr.Samsa wrote:
natselrox wrote:Maybe the urge to make a social point overshadowed the scientific rigour. :dunno:


Yeah, I think it's more about the intentions behind the research and their perspective on the issue rather than something as necessarily political as making a 'social point' - for example, when I study behavior I rarely touch upon genetics and evolution, not because those areas aren't relevant but simply because they aren't relevant to what I'm trying to study. So I don't think there's necessarily any problem with the scientific rigour, meaning that although a discussion on those points would have been nice, and a comment on how future research could aim to separate the effect they found from IUGR and epigenetic effects etc, I don't think it affects the 'rigourousness' of their work. Just would have been interesting if they were able to expand on those points. And maybe they did, but the editor removed it for space or because it wasn't relevant to a particular topic that the issue was dedicated to.


I get your point but there were some obvious things that were missing in the article.

I just mailed one of the authors asking him about how they linked the effects to the post-natal environment (and not the pre-natal/hereditary causes). Hope he replies. :roll:
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Re: Link between socioeconomic status and hippocampal densit

#10  Postby Mr.Samsa » May 08, 2011 5:06 am

natselrox wrote:I get your point but there were some obvious things that were missing in the article.

I just mailed one of the authors asking him about how they linked the effects to the post-natal environment (and not the pre-natal/hereditary causes). Hope he replies. :roll:


Ah yeah, that's true. Make sure you post his reply here, if he does. :cheers:
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Re: Link between socioeconomic status and hippocampal densit

#11  Postby jlhanson5 » May 10, 2011 11:45 pm

Hi folks-

I'm actually one of the authors of this paper. I emailed natselrox about this, but figured I would also posted on here. Regarding this specific work, we could not rule out all pre-natal effects & influences. We were limited since we did not personally collect the data (it was part of a project from the US' National Institute of Health; additional info here: https://nihpd.crbs.ucsd.edu/nihpd/info/index.html). The investigators who collected the data had a number of rigorous exclusion criteria (e.g., Low current height or weight, Intra-uterine exposures to substances known or highly suspected to alter brain structure or function, gestational age at birth of 37 weeks - 42 weeks; multiple birth; delivery by high forceps or vacuum extraction; maternal metabolic conditions (e.g., phenylketonuria, diabetes); low-birth weight pre-eclampsia; serious obstetric complication; general anesthesia during pregnancy/delivery; C- section for maternal or infant distress). These criteria were aimed at minimizing some of the confounds previous question suggested (but we must be honest & say we can not 100% rule out pre-natal factors). Some of my future work is aimed at assaying factors related to your questions (e.g., by doing longitudinal analyses of this sample to see if associations strengthen; or local data collection where we can collect more information about the household & early development).

In addition, the statistical models we used (regression) point to a linear relationship between household income and hippocampal volume (e.g., increasingly larger volume with higher household incomes). If we had done a group comparison (via a group t-test) where our measure of income wasn't continuous (and just compared a more affluent group to a less affluent group), nutritional deprivation would be a factor of greater concern (since it may be more common in less affluent households). Use of linear regression basically point to something more like "a dose effect" where a t-test would just look if one group was higher or lower. [Pardon the stats discussion, I wasn't sure of people's background].

I also ran post-hoc analyses (not in the paper, but related to the question) where even if you exclude the kids from the less affluent households (living in poverty where nutritional issues may be common) the relationship between household income and hippocampal volume is still significant. Folks can feel free to ask additional questions also.

Related to ideas of the paper and making a social point, my research centers on the neurobiological effects of/associations with early stress. I tend to share the views of someone like Gary Evans, a professor at Cornell, who talks about poverty as chronic stress & cumulative risk.
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