5.1: Introduction
- Page ID
- 198000
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Supporting Brain Development in Group Care
If you were to enroll in a college class about infant and toddler development, would you expect to see a section on brain development? The importance of brain development in a child’s early years has been emphasized in the past few decades more than ever before; however, does brain development belong in a class on infants and toddlers, or should it only be included in classes that focus on older children? Most people will probably say “yes, the topic of brain development belongs in infant and toddler college classes”, but how would you explain your reasoning--why do you think brain development is so important during the first three years of life?
If your answer focused on the rapid growth of the brain during the first three years, you are not alone in your thinking. This is how many people answer the question, and rightfully so. For example, take a look at Figure \(\PageIndex{1}\): that displays the growth trajectory of gray matter and white matter in females (red) and males (blue). Brain tissue can be divided into either white matter or gray matter. White matter regions are composed of axons. It appears white due to the myelin sheath on the axons (see Figure \(\PageIndex{1}\). Gray matter regions are composed of cell bodies and dendrites[1] [2] (see Figure \(\PageIndex{1}\)[3] [4] . Gray matter is the location of most synapses–the connection sites where neurons communicate. As both charts show, but especially the chart for gray matter, brain growth in the first three years is rapid. [1]
The outer brain is composed of the cerebrum, cerebellum, and brainstem (see Figure \(\PageIndex{1}\). The cerebrum is the most prominent region of the brain and is organized into folds called gyri and grooves called sulci. The rapid growth in gray and white matter is paralleled by the rapid growth seen in total cerebrum volume (see Figure \(\PageIndex{1}\). [4]
Another way to examine the early rapid brain growth of white and gray matter and cerebrum volume is with Figure \(\PageIndex{1}\) (Bethlehem et al., 2022). Now, this figure has a lot going on, so let’s just focus on some important features. Similar to the previous figures, Figure \(\PageIndex{1}\) also charts the growth of white and gray matter across the lifespan; however, this figure adds when rate of growth (velocity) and size both peak. Rate of growth peaks are marked by circle icons and size peaks are marked by triangle icons.[1] [2] The rate of growth for gray matter volume peaks in infancy, at around five months of age. The rate of growth for white matter volume peaks in toddlerhood, at around 2.4 years of age. Total cerebrum volume rate of growth peaks at approximately 7 months of age. All of this evidence makes it clear that in the first three years of life, the brain is rapidly growing, at rates unlike any other developmental period. A question to ponder is how much of this rapid growth is biologically driven, compared to experience-driven and can experiences, like differences in the quality of caregiving, play a role in this brain growth?
The rapid brain growth during the first three years makes infancy and toddlerhood a sensitive period in human brain development (Gilmore, Knickmeyer, & Gao, 2018; Johnson & de Haan, 2015) because the brain development that happens during the first three years serves as the basis for future brain function and related behavioral outcomes (Bornstein, 2014; Kolb & Gibb, 2011; Tau & Peterson, 2010). Furthermore, the infant and toddler brain is highly plastic and changes in response to environmental inputs (Dawson et al., 2012; Hodel, 2018; Merz, Wiltshire, & Noble, 2019; Rebello et al., 2018; Tierney & Nelson, 2009). Although many brain development processes are guided largely by biological factors (Rakic, 1988), caregiving experiences can also shape brain development through experience-expectant and experience-dependent plasticity (Greenough, Black, & Wallace, 1987). [8] [9]
References
- [1] Bethlehem et al., (2022). Brain charts for the human lifespan. Nature, 604(7906), 525-533. CC by 4.0 Brain charts for the human lifespan. Nature, 604(7906), 525-533. CC by 4.0)
- [2] Foundations of Neuroscience by Casey Henley is licensed under CC BY-NC-SA 4.0
- [3] Image by Todd LaMarr is licensed under CC BY-NC-SA
- [4] Foundations of Neuroscience by Casey Henley is licensed under CC BY-NC-SA 4.0
- [5] Image from Foundations of Neuroscience by Casey Henley is licensed under CC BY-NC-SA 4.0
- [6] Bethlehem et al., (2022). Brain charts for the human lifespan. Nature, 604(7906), 525-533. CC by 4.0
- [6] Bethlehem et al., (2022). Brain charts for the human lifespan. Nature, 604(7906), 525-533. CC by 4.0
- [7] Bethlehem et al., (2022). Brain charts for the human lifespan. Nature, 604(7906), 525-533. CC by 4.0
- [1] Chajes et al., (2022). Examining the role of socioeconomic status and maternal sensitivity in predicting functional brain network connectivity in 5-month-old infants. Frontiers in Neuroscience, 16. CC by 4.0
- [2] Leblanc et al., (2017). Attachment security in infancy: A preliminary study of prospective links to brain morphometry in late childhood. Frontiers in Psychology, 8, 2141. CC by 4.0