List of Figures

Figures listed below without a page number appear in the color plate section.The color plate section appears between pages 136 and 137.

Figure 1.1 Drawings such as this influenced a 17th-century school of thought, the "spermists," who believed that there was a complete preformed person in each male sperm and that development merely consisted of increasing size. Figure 1.2 The epigenetic landscape of Waddington (1975). Figure 2.1 An illustration of the relative strengths and weaknesses of different functional brain imaging methods used with infants and children. Figure 2.2 An infant wearing a high-density ERP/EEG system (EGI Geodesic Sensor Net) during a study on the "mirror neuron system". The sensor net consists of damp sponge contacts that rest gently on the scalp. Figure 2.3 Infants in (a) the UK, (b) Bangladesh, and (c) The Gambia engaged in functional near-infrared spectroscopy studies. Light emitters and detectors are incorporated into the head caps. Figure 2.4 The expansion of myelinated fibers over early postnatal development as revealed by a new structural MRI technique. Figure 3.1 (a) The basic double helix structure of DNA in which two nucleotide strands coil around each other. (b) Detail showing how the two strands are linked by chemical bonds between the bases of nucleotides. Figure 3.2 An illustration of the complex causal pathway between a genetic level defect and its consequences for behavior from Fragile-X syndrome. Figure 4.1 A simplified schematic diagram which illustrates that, despite its convoluted surface appearance (top), the cerebral cortex is a thin sheet (middle) composed of six layers (bottom). The convolutions in the cortex arise from a combination of growth patterns and the restricted space inside the skull. In general, differences between mammals involve the total area of the cortical sheet, and not its layered structure. Each of the layers possesses certain neuron types and characteristic input and projection patterns. Figure 4.2 A typical cortical pyramidal cell. The apical dendrite is the long process that extends to the upper layers and may allow the cell to be influenced by other neurons. An axon projects to subcortical regions. Figure 4.3 A sequence of drawings of the embryonic and fetal development of the human brain. The drawings of brains beneath those of 25-100 days are the same images but drawn to the same scale as those in the row below. The forebrain, midbrain, and hindbrain originate as swellings at the head end of the neural tube. In primates, the convoluted cortex grows to cover the midbrain, hindbrain, and parts of the cerebellum. Prior to birth, neurons are generated in the developing brain at a rate of more than 250,000 per minute. Figure 4.4 MRI structural scans of a 4-month-old infant (top) and a 12-year-old adolescent (below). Figure 4.5 A drawing of the cellular structure of the human visual cortex based on Golgi stain preparations from Conel (1939-1967). Figure 4.6 The sequence of axon myelination by an oligodendrocyte. (a-d) show the sequence of initial contact, then engulfing and surrounding the axon, followed by spiraling around the axon to form the final myelin sheath. Figure 4.7 Resting state networks in a single representative infant. Rows A to E each show one resting state network at three axial sections. Figure 4.8 Figure illustrating the approximate timeline for some of the most important changes in human brain development, including the characteristic rise and fall of synaptic density. Figure 4.9 Graph showing the development of density of synapses in human primary visual cortex and resting glucose uptake in the occipital cortex as measured by PET. ICMRGlc is a measure of the local cerebral metabolic rates for glucose. Figure 4.10 A color-coded map of changes in cortical gray matter with development. The maps illustrate regional variations in decreases in gray matter density between the ages of 5 and 20 years. Figure 4.11 The brain maps (center panel) show prominent clusters where "superior" and "average" intelligence groups differ significantly in the trajectories of cortical development. The graphs show the developmental trajectories for these regions. The age of peak cortical thickness is arrowed for each of the three groups in each region. Figure 4.12 Cytoarchitectural map of the cerebral cortex. Some of the most important specific areas are as follows. Motor cortex: motor strip, area 4; pre-motor area, area 6; frontal eye fields, area 8. Somatosensory cortex: areas 3, 1, 2. Visual cortex: areas 17, 18, 19. Auditory cortex: areas 41 and 42. Wernicke's speech area: approximately area 22. Broca's speech area: approximately area 44 (in the left hemisphere). Figure 4.13 The radial unit model of Rakic (1987). Radial glial fibers span from the ventricular zone (VZ) to the cortical plate (CP) via a number of regions: the intermediate zone (IZ) and the subplate zone (SP). RG indicates a radial glial fiber, and MN a migrating neuron. Each MN traverses the IZ and SP zones that contain waiting terminals from the thalamic radiation (TR) and corticocortical afferents (CC). As described in the text, after entering the cortical plate, the neurons migrate past their predecessors to the marginal zone (MZ). Figure 4.14 Patterning of areal units in somatosensory cortex. The pattern of "barrels" in the somatosensory cortex of rodents is an isomorphic representation of the geometric arrangement of vibrissae found on the animal's face. Similar patterns are present in the brain stem and thalamic nuclei that relay inputs from the face to the barrel cortex. Figure 4.15 PET images illustrating developmental changes in local cerebral metabolic rates for glucose (ICMRGlc) in the normal human infant with increasing age. Level 1 is a superior section, at the level of the cingulate gyrus. Level 2 is more inferior, at the level of caudate, putamen, and thalamus. Level 3 is an inferior section of the brain, at the level of cerebellum and inferior position of the temporal lobes. Gray scale is proportional to ICMRGlc, with black being highest. Images from all subjects are not shown on the same absolute gray scale of ICMRGlc; instead, images of each subject are shown with the full gray scale to maximize gray scale display of ICMRGlc at each age. (A) In the 5-day-old, ICMRGlc is highest in sensorimotor cortex, thalamus, cerebellar vermis (arrows), and brain stem (not shown). (B, C, D) ICMRGlc gradually increases in parietal, temporal, and calcarine cortices; basal ganglia; and cerebellar cortex (arrows), particularly during the second and third months. (E) In the frontal cortex, ICMRGlc increases first in the lateral prefrontal regions by approximately 6 months. (F) By approximately 8 months, ICMRGlc also increases in the medial aspects of the frontal cortex (arrows), as well as the dorsolateral occipital cortex. (G) By 1 year, the ICMRGlc pattern resembles that of adults (H). Figure 5.1 Diagram of the developmental sequence of visual behavior (left of vertical line) and ventral- and dorsal-stream neural systems contributing to this (right of vertical line). Figure 5.2 Simplified schematic diagram illustrating how projections from the two eyes form ocular dominance columns in the visual cortex. LGN, lateral geniculate nucleus. Figure 5.3 (a) Afferents from both eyes synapse on the same cells in layer 4, thereby losing information about the eye of origin. (b) Afferents are segregated on the basis of eye origin (R and L), and consequently recipient cells in layer 4 may send their axons to cells outside of that layer so as to synapse on cells that may be disparity-selective. Figure 5.4 Diagram representing some of the main neural pathways and structures involved in visual orienting and attention. BS, brain stem; LGN, lateral geniculate nucleus; V1, V2, and V4, visual cortical areas; MT, middle temporal area; SC, superior colliculus; SN, substantia nigra; BG, basal ganglia. Figure 5.5 Brain areas involved in stimulus-driven and goa-driven attention. Figure provide by Iroise Dumontheil. Figure 5.6 The oculomotor delayed response task as designed for use with infants. Infant subjects face three computer screens on which brightly colored moving stimuli appear. At the...