Epigenetic changes in brain development. Nature and nurture work together.
The old adagio nature vs nurture is shaky.
“The environment is a critical player in how your genetic endowments work” (Yehuda)
and the development of a human being is not anymore a decision between “nature vs nurture” (genes or upbringing) but an interplay between the two: development is driven by a continuous interaction between biology (= DNA code or genetic predispositions) and ecology (=social and physical environment).
Epigenetics is the science that studies the fairly stable alterations in gene expression (‘turning on’ of genes) that arise during development, differentiation and growth under the influence of the environment.
Among the several studies of epigenetics in the process of a human growth is the development of the human brain and how this is affected by external conditions.
The billions of neurons in a single brain have the same DNA sequence but their diverse functions are created by epigenetic programming during pre- and postnatal development and possibly throughout life. Epigenetic mechanisms have the care of brain development, differentiation and maturation and are at the base of complex behaviors like memory and learning.
The most studied type of “external conditions” from the environment during brain development has been the study of stressors or stimuli that entice a “fight-flight-freeze” response from the organism.
Early life stress: certain conditions of life environment in the early stages of development can cause epigenetic programming of critical genes involved in regulating the stress response.
The stress response is carried out by the hypothalamus-pituitary-adrenal axis in the brain. Consequent to a stressor, the amygdala in the center of the brain sends a message of alarm to the hypothalamus to release a neurotransmitter (corticotropin releasing hormone) to the pituitary gland which in turn sends a message (adrenal corticoptic hormone) to the adrenal glands, which then release adrenaline, noradrenalin and later cortisol. This chain of events results in an
increase of heart rate, breathing efficiency, blood pressure,
decrease in digestive and reproductive functions etc.
which is the stress response: either fight the danger or fly from it. (reference to another blog).
Some abnormal conditions of early life environment (lack of nurturing, neglect, abandonment, abuse) can provoke changes in DNA methylation, facilitating activation of critical genes involved both in regulating the stress response and in reducing expression of hormones that regulate neurodevelopment, neuroplasticity and neuronal functions.
These dysregulated responses to abandonment, abuse and neglect of a child can result in a distorted behavioral reaction and diseases in childhood and adulthood:
~ early life: anger, despair, detachment, temporary delay in intellectual development;
~ adulthood: same lack of care to the future generation (perpetuating the damage),
increased stress response activity, increased risk of depression or anxiety, risk of cognitive impairment, social and emotional difficulties, risk of psychiatric and neurodegenerative disorders and physical diseases (obesity, osteoporosis and cardiovascular problems).
The good news is that such types of epigenetics responses can be undone by changing the nurturing environment (but how late can this be done?).
Offering the child the best caring enviornment will insure a safe place for proper development and preparation for his/her offspring to be taken care in the same healthy way.
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