The Fundamentals of Brain Development: Integrating Nature and Nurture, authored by Joan Stiles, is a momentous volume in a too sparse literature regarding the developmental processes that accompany brain maturation. This volume takes the reader from conception and embryo formation into childhood and adolescence. Its stated purpose, “to provide nonexperts with an overview of the fundamentals of mammalian brain development… understand the biological underpinnings of the complex changes…inform key arguments about the biological feasibility of the core assumptions that are at the heart of the psychological debate over nature versus nurture.” (p. 17), is exceeded as Stiles details the complex interplay of intrinsic and extrinsic factors that influence brain development. The author’s clear writing and logical progression from chapter to chapter serves the reader well. Eleven exceptionally well-organized chapters review essential concepts with considerable depth of coverage and pertinent examples. Each chapter concludes with a bulleted list of precise summary points. A helpful glossary of biological terms is an additional bonus feature.
Chapter 1, “The Central Questions about Psychological and Biological Development,” begins the overview of brain development with a balanced discussion of the psychological debate on the origins of knowledge, and emphasizes the importance of bridging core disciplines. Central conventions and terminology, e.g., regarding notation systems for prenatal age and nomenclature for genes and transcription products, prepares the reader for later content. Chapter 2, “The Gene: Evolution of a Concept,” begins with an insightful and focused discussion of debated perspectives about whether and how much inherited factors and experience affect biological processes of development. This “must read” section includes historical and philosophical perspectives about biological inheritance, reviews constructs of preformationism and epigenesis, and adds a measured summary of thinking about central tenets that evolved throughout the nineteenth and twentieth centuries, leading to a remarkably eloquent clarification about gene hypotheses and the structure and relatedness of DNA and RNA.
In Chapter 3, “Formation of the Neural Plate,” the developmental journey continues through the period of gastrulation, i.e., in the third gestational week when undifferentiated embryonic tissue is transformed into three distinct progenitor cell lines within the trilaminar disc. This chapter explains through text, figures and a Table, how specific cell types destined for different parts of the embryo differentiate and migrate to their respective target locations in response to molecular signaling among cells. It includes detailed discussion of organization along three spatial axes (right-left, dorsal-ventral, and anterior-posterior), neural induction, molecules and proteins whose action is to induce or suppress, and critical genes and proteins. This is accomplished maintaining an historical focus that clarifies the links between the findings of earlier and recent investigators. The chapter concludes with clinical correlation using the example of holoprosencephaly. This discussion of forebrain compromise early in gestation leads to the content of Chapter 4, “Formation of the Neural Tube.” The processes of neurulation, i.e., the period from human embryonic days 18 to 28 during which central nervous system development begins, is this chapter’s focus. Primary and secondary neurulation processes that result in brain and spinal cord formation are explained through text and figures. In Chapter 5, “Molecular Patterning of the Primary Spatial Dimensions of the Embryo,” the reader’s attention is directed to the next stage of embryo development once the neural tube has closed, when major dimensional axes are being refined. Critical proteins and genes are covered, including HOX genes, and the influences of Emx2 and Pax6 transcription factors in early organization of the mammalian central nervous system. This chapter details dorsal-ventral specification of the spinal cord and anterior brain regions, and anterior-posterior specification, especially in hindbrain and spinal cord regions. Early patterning of the cerebral cortex resulting from differential signaling of populations of neural progenitor cells of the dorsal telencephalon is described. The chapter concludes with clinically relevant discussion about the teratogenicity of retinoic acid, a regulator of HOX gene expression, first recognized in the 1950’s, and initial reports of isotretinoin exposure’s effects on the developing human fetus in 1985.
Chapter 6, “The Production of Brain Cells: Neurons and Glia,” covers the emergence of the six-layered neocortex and begins the discussion about neurogenesis and the three stages of neuronal development, and neuronal cell type. The discussion continues in Chapter 7, entitled “Neuronal Migration and Neuronal Differentiation,” about migration by somal translocation along radial glides and by tangential migration. This is followed by discussion about axonal and dendritic growth and synapse formation, and the modulatory roles of neurotransmitters in early development. Chapter 8, “Shaping the Emerging Cortical Network: The Role of Intrinsic and Extrinsic Factors” takes the reader through midgestation, defining and considering the competing protomap and protocortex hypotheses about neocortical organization. Also addressed is the regulatory functions of apoptosis or programmed cell death and synaptic exuberance and elimination.
Changes in cortical morphology during late prenatal and postnatal periods comprise the content of Chapter 9, “Late Prenatal and Postnatal Changes in Human Brain Structure.” The reader is led from gyrification through the protracted period of axonal myelination. Childhood and adolescent patterns of regional change in macroscopic cortical organization are reviewed. Clinical correlation is made using the examples of periventricular leukomalacia and oligodendrocyte maturation. That the impact of experience may be better appreciated during the postnatal period is the subject of Chapter 10, “Plasticity and the Role of Experience in Neocortical Development.” The examples of primary visual cortex development, and ocular dominance columns, prepares the reader for discussion about neocortical changes that can or cannot occur once function is defined in the embryonic period. A number of examples of the effects of early vs. late localized brain injury and unilateral vs. bilateral lesions are included, along with studies in which experimental manipulations, e.g., cortical explant studies, occur in the rearing environment. This chapter should be compulsory reading for any researcher studying plasticity or clinician concerned about whether an early documented brain insult may have resulted in lasting effects. The concluding Chapter 11, “The Importance of Brain Development for Psychology,” summarizes for psychologists the relevance of the biological perspective on the concept of innateness and development, the nature and function of critical or sensitive periods in postnatal development, and the espoused model of brain development as it relates to constancy and variability.
The Fundamentals of Brain Development: Integrating Nature and Nurture, a comprehensive overview of the dynamic processes of brain development, takes the reader seamlessly from highly complex and basic cellular and genetic considerations to neurobehavioral considerations and useful clinical correlations. It highlights the critical importance of acquiring knowledge about basic neuroscience processes of brain development, content often buried in neurobiology texts, in order to better inform our models of behavioral development. The reader of this exceptional volume will better appreciate that one gains this understanding by recognizing that both genetic information (nature) and experience (nurture) operate in dynamic interactions that are the substance of development. Stiles has written a sophisticated treatise that is mandatory reading for any graduate student, researcher, or practitioner concerned with mammalian brain development and function.
