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4.9: Growth Patterns of Brain Matter

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    Brain Matter

    Looking at the tissue in the brain, there are regions that predominantly contain neuron cell bodies and dendrites and regions that are largely composed of just axons. These two regions are often referred to as gray matter (the regions with many cell bodies and dendrites) or white matter (the regions with many myelinated axons). Figure \(\PageIndex{1}\) demonstrates the appearance of these regions in the brain and spinal cord. The colors ascribed to these regions are what would be seen in “fresh,” or unstained, brain tissue. Gray matter is not necessarily gray. It can be pinkish because of blood content, or even slightly tan, depending on how long the tissue has been preserved. But white matter is white because axons are insulated by a lipid-rich substance called myelin. Lipids can appear as white (“fatty”) material, much like the fat on a raw piece of chicken or beef.

    Definition: Gray matter

    Brain tissue primarily composed of cell bodies and dendrites

    Actually, gray matter may have that color ascribed to it because next to the white matter, it is just darker—hence, gray. [1]

    Gray Matter and White Matter
    Figure \(\PageIndex{1}\): Gray Matter and White Matter of an exposed brain. A brain removed during an autopsy, with a partial section removed, shows white matter surrounded by gray matter. Gray matter makes up the outer cortex of the brain. ([2])

    There is a rapid growth of total brain volume in the first three years, but the rate of growth is different for gray and white matter. Figure \(\PageIndex{2}\) depicts the pattern of average total brain volume growth across the first 547 days (approximately 18 months) of development as well as the individual growth trajectories of white and gray matter. Figure \(\PageIndex{2}\) illustrates the relatively faster growing trend of gray matter compared with white matter growth suggesting that early brain volume growth is dominated primarily by increases in gray matter. [3] Figure \(\PageIndex{3}\) and Figure \(\PageIndex{4}\) show the growth of gray and white matter for females and males separately, across the first three years and for each year after that, until eighteen years of age. These graphs further emphasize the rapid growth of brain volume, for both white and gray matter, during infancy and toddlerhood.

    This chart shows data provided in the figure caption
    Figure \(\PageIndex{2}\): Depicts the pattern of average total brain volume growth across the first 547 days (approximately 18 months) of development as well as the individual growth trajectories of white and gray matter. Postnatal age and Volume (x105 mm3 ) Total brain Volume (TBV): 1 day =1 progressively increasing to 547 days=2, Gray matter(GM): 2 days - 2 increasing to 5 at 547 days, Total White matter (WM): 1 day = 4 progressively to 10 at 547 days. ([4])
    This chart shows data provided in the figure caption
    Figure \(\PageIndex{3}\): illustrates the relatively faster growing trend of gray matter compared with white matter growth suggesting that early brain volume growth is dominated primarily by increases in gray matter. Figure \(\PageIndex{3}\) and Figure \(\PageIndex{4}\) show the growth of gray and white matter for females and males separately, across the first three years and for each year after that, until eighteen years of age. ([5])
    Growth trajectories of white matter. This chart shows data provided in the figure caption
    Figure \(\PageIndex{4}\): Growth trajectories of white matter. Figure \(\PageIndex{3}\) and Figure \(\PageIndex{4}\) show the growth of gray and white matter for females and males separately, across the first three years and for each year after that, until eighteen years of age ([6])
    Social Justice Insight: Family Income Affects the Rate of Infant & Toddler Brain Growth

    Hanson et al., (2013) analyzed repeated measures of brain development of children between five months and four years of age from economically diverse backgrounds. The data suggest that low socioeconomic status (SES) environments influence the rate of human infant brain development. As Figure# shows, infants and toddlers from lower income families began their lives with similar gray matter brain volumes but by toddlerhood, they had lower total gray matter compared with those from middle and high-income households.

    Total gray matter. Figure caption provides graph data.
    Figure \(\PageIndex{1}\): Total Gray Matter: As infants aged—and presumably had increased exposure to the effects of their environments— the differences in brain volume between children from lower SES homes and those from higher SES homes widened. Furthermore, smaller volumes in this brain tissue were related to greater behavior problems in the preschool years. Age in months is shown on the horizontal axis, spanning from 5 to 37 months. Total gray matter volume is shown on the vertical axis. The blue line, which starts as the top line above 500000, shows children from Low SES households; children from Mid SES households are shown in red, which starts as the bottom line. The green line, which starts as the middle line, shows children from High SES households (Growth trajectories of gray matter by SES group. [7])
    Questions to consider:
    • What are the different environmental factors between high versus low SES families that may be mainly driving this data?
    • Are group care facilities that primarily serve high or low SES families different? In which ways?
    • In what ways may infant and toddler care facilities be biased toward serving a particular SES population?
    • What policies and practices can we better implement in an attempt to improve the environments for infants and toddler in group care?

    Attributions

    This page titled 4.9: Growth Patterns of Brain Matter is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Todd LaMarr (ASCCC Open Educational Resources Initiative) .