Since brain development in the early years is a factor in the gradi-
ents in the health status of populations, studies by a number of inves-
tigators have now shown that other functions of the brain in the
early years of development, such as language, literacy, cognition, and
behavior, are also gradients when plotted against the socioeconomic
position of individuals in society (Keating and Hertzman 1999).
The evidence reinforces the idea that the development of the brain in
the early years is a key factor affecting risks for physical and mental
health problems and learning in adult life.Experience-based Brain and Biological Development during
Early Childhood
The new knowledge from research in the neurosciences and biologi-
cal sciences is providing evidence of howthe social environment
“gets under the skin” to affect the gradients in health, learning, and
behavior. Experience-based brain development in utero and during
the early years of life can setbrain and biological pathways that affect
an individual’s health, behavior, and learning for a lifetime.
The brain is composed of billions of neurons, all of which have the
same genetic coding. There has to be, during the early stage of devel-
opment, biological processes that differentiate the function of neu-
rons that respond to the sensing pathways. As the brain develops dur-
ing the early years, specific genes are activated in different parts of
the brain to establish neurons that can respond to the signals coming
from outside the body by the sensing pathways (such as vision, hear-
ing, smell, touch).
The stimuli (experience) from the sensing pathways to which the
sensing neurons are exposed during critical, sensitive early periods of
development (including in utero) setmost of the brain’s capability
to interpret the signals and pathways in the brain which govern or
control language, intellectual, emotional, psychological, and physical
responses.
Genes can be activated and deactivated by processes (methylation
and acetylation) that affect the function of the normal gene or the his-
48 J. Fraser Mustard