Tuesday, May 5, 2009

Poverty and the Brain

• The greater proportion of life that a child has spent in poverty, the greater the neurological effects (See chart).

Measuring Stress

• Turner and Avison measured social stress in all socioeconomic brackets using five categories: recent life events, chronic stress, lifetime major and potentially traumatic events, discrimination stress, and symptoms of depression. They found that, “With the exception of recent life events, those in the lowest third of the socioeconomic status distribution reported higher stress levels in every category and, for essentially every category, the socioeconomic status-stress relationship is monotonic: The lower the socioeconomic status the higher the stress” (Turner and Avison, 2003).

Biological measures of stress

• Allostatic load: “a biological marker of cumulative wear and tear on the body that is caused by the mobilization of physiological systems in response to chronic environmental demands” (Evans et. al. April 2009).
• Relevant Hormones: Catecholamines such as norepinephrine, dopamine and epinephrine (adrenaline), and Glucocorticoids (mainly Cortisol)
o Control physiological responses to stress in the sympathetic nervous system like blood pressure and heart rate
o Fight-or-flight reactions
o Energy regulation: They replace energy reserves after high-stress events (restore homeostasis after high stress).
o Regulate cardiovascular system, metabolism, blood sugar, immunological responses, homeostatic functions
o Cortisol and epinephrine work together to create memories of stressful events (flashbulb memories).
• These neuroendocrine responses are important for adaptation to stressful situations, managing acute threats and maintaining homeostasis (internal stability) and allostasis.
• When these stress responses are engaged on a regular basis, they result in an allostatic load that causes the body and brain to deteriorate
• Chronic exposure to high levels of cortisol can inhibit development of the hippocampus and even stop the process of neurogenesis

Physical Factors
• Inadequate nutrition (including iron-deficiency anemia which inflicts 25% of low SES children in America)
• Substance abuse in pre- and post-natal development
• Trauma and abuse
• Exposure to environmental neurotoxins, including lead. For every 10 micrograms per deciliter increase of lead in the blood there is an estimated 2.6 decrease in IQ (Schwartz, 1994).

Psychological Factors


• Many low-SES families live in neighborhoods with high crime rates
• Job instability/issues
• The difficulties of providing for basic needs cause stress and tension within families and deeply affect children.
• Maternal depression (social interaction)
• Quality of daily care
• Less exposure to cognitive stimulation (books, toys, museums, zoos, etc.)
• Average total hours of one-on-one picture book reading for children entering Kindergarten: Low-SES children 25 hours, Middle-SES children 1000-1700 (Adams 1990).

What systems are affected by stress?

• The left Perisylvian/language system is responsible for many aspects of cognition and communication, including semantic, syntactic and phonological aspects of language, and is concentrated in the temporal and frontal areas of the left hemisphere of the brain.
• The Medial/Temporal Memory system makes it possible to retain a memory or representation after a single exposure to a stimulus (as opposed to representations that are strengthened gradually through repeated exposures). This ability relies on the hippocampus and parts of the medial temporal lobe.
• The Prefrontal/Executive system is dependent on the pre-frontal cortex and “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” (Farah et. al. 2005).

Specific Correlations: Home Observation and Measurement of Environment (HOME) Tests, Children at ages 4 and then 8.

o Performance on Left Perisylvian/Language abilities was correlated with average cognitive stimulation (variety of toys, availability of books, language stimulation, parental speech designed to engage child, academic stimulation, behavior modeling, etc.)
o Performance on Medial temporal/Memory ability was predicted by social/emotional nurturance (warmth, affection and engagement, acceptance, emotional and verbal responsivity, encouragement of maturity, emotional climate, paternal involvement).

Conclusions:

Contributes to the discourse about childhood poverty, framing the issue as one of bioethics rather than economic opportunity

Solutions and policy implications

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