1. Wood1.1 Credits lightning ©istockphoto.com/Soubrette
background texture
©istockphoto.com/Hedda Gjerpen
person rock climbing
©istockphoto.com/Greg Epperson
Wood1.1

2. Topics 9.1 Phases of Neurodevelopment 9.2
Postnatal Cerebral Development in Human Infants
9.3
Effects of Experience on the Early Development, Maintenance, and Reorganization of Neural Circuits
9.4
Neuroplasticity in Adults
9.5
Disorders of Neurodevelopment: Autism and Williams Syndrome
Credits
lightning
©istockphoto.com/Soubrette
background texture
©istockphoto.com/Hedda Gjerpen
Wood1.

3. Neurodevelopment
Neural Development – an ongoing process; the nervous system is plastic
Experience plays a key role
Dire consequences when something goes wrong
Wood1.
Credit
brain
©istockphoto.com/Stephen Kirklys

4. At age 13, Genie weighed 62 pounds and could not chew solid food
Beaten, starved, restrained, kept in a dark room, denied normal human interactions
Even with special care and training after her rescue, her behavior never became normal
The Case of Genie Illustrates the impact of severe deprivation on development
Credits
paper clip
©istockphoto.com/Jon Patton
folder
©istockphoto.com/kyoshino
tabletop
©istockphoto.com/Andrew Cribb

5. Developing neurons accomplish these things in five phases
Phases of Development
Ovum + sperm = zygote
Developing neurons accomplish these things in five phases
Induction of the neural plate
Neural proliferation
Migration and aggregation
Axon growth and synapse formation
Neuron death and synapse rearrangement
Wade3.34

6. Induction of the Neural Plate
A patch of tissue on the dorsal surface of the embryo becomes the neural plate
Development induced by chemical signals from the mesoderm (the “organizer”)
Visible three weeks after conception
Three layers of embryonic cells:
Ectoderm (outermost)
Mesoderm (middle)
Endoderm (innermost)
Neural plate cells are often referred to as embryonic stem cells
Have unlimited capacity for self renewal
Can become any kind of mature cell
Totipotent – earliest cells have the ability to become any type of body cell
Multipotent – with development, neural plate cells are limited to becoming one of the range of mature nervous system cells
FIGURE 9.1: How the neural plate develops

7. Neural Proliferation
Neural plate folds to form the neural groove, which then fuses to form the neural tube
Inside will be the cerebral ventricles and neural tube
Neural tube cells proliferate in species-specific ways: three swellings at the anterior end in humans will become the forebrain, midbrain, and hindbrain
Proliferation is chemically guided by the organizer areas – the roof plate and the floor plate
Credit
person thinking
©istockphoto.com/akurtz

8. m
igration
Once cells have been created through cell division in the ventricular zone of the neural tube, they migrate
Migrating cells are immature, lacking axons and dendrites
Wade3.3

9. Migration Two types of neural tube migration Two methods of migration
Radial migration (moving out)
Tangential migration (moving up)
Two methods of migration
Somal – an extension develops that leads migration, cell body follows
Glial-mediated migration – cell moves along a radial glial network
Most cells engage in both types of migration
FIGURE 9.2: Radial Migration and Tangential Migration

10. Migration
FIGURE 9.3: Somal Translocation and Glia-Mediated Migration

11. Neural Crest
A structure dorsal to the neural tube and formed from neural tube cells
Develops into the cells of the peripheral nervous system
Cells migrate long distances
Credit
book
©istockphoto.com/Carmen Martínez Banús 11

12. Aggregation
After migration, cells align themselves with others cells and form structures
Cell-adhesion molecules (CAMs):
Aid both migration and aggregation
CAMs recognize and adhere to molecules
Gap junctions pass cytoplasm between cells
Prevalent in brain development
May play a role in aggregation and other processes
Wade4.14

13. Axon Growth and Synapse Formation
Once migration is complete and structures have formed (aggregation), axons and dendrites begin to grow
Growth cone – at the growing tip of each extension, extends and retracts filopodia as if finding its way
Chemoaffinity hypothesis – postsynaptic targets release a chemical that guides axonal growth, but this does not explain the often circuitous routes often observed
Credits
ruler
©istockphoto.com/Christopher Hudson
woman observing & taking notes
©istockphoto.com/Claudio Arnese

14. Axon Growth and Synapse Formation
Mechanisms underlying axonal growth are the same across species
A series of chemical signals exist along the way – attracting and repelling
Such guidance molecules are often released by glia
Adjacent growing axons also provide signals
FIGURE 9.5: Sperry’s classic study of eye rotation and regeneration.
Credits
ruler
©istockphoto.com/Christopher Hudson
woman observing & taking notes
©istockphoto.com/Claudio Arnese

15. Axon Growth and Synapse Formation
Pioneer growth cones – the first to travel a route, interact with guidance molecules
Fasciculation – the tendency of developing axons to grow along the paths established by preceding axons
Topographic gradient hypothesis – seeks to explain topographic maps
FIGURE 9.7: The topographic gradient hyphothesis
Credits
ruler
©istockphoto.com/Christopher Hudson
woman observing & taking notes
©istockphoto.com/Claudio Arnese

16. Synapse Formation Formation of new synapses:
Depends on the presence of glial cells
High levels of cholesterol are needed—supplied by astrocytes
Chemical signal exchange between pre- and postsynapctic neurons is needed
A variety of signals act on developing neurons
Wood1.
Credit
brain
©istockphoto.com/Stephen Kirklys

17. Neuron Death and Synapse Rearrangement
~50% more neurons than are needed are produced – death is normal
Neurons die due to failure to compete for chemicals provided by targets:
The more targets, the fewer cell deaths
Destroying some cells increases survival rate of remaining cells
Increasing number of innervating axons decreases the proportion that survives
The human brain
Credits
brain
©istockphoto.com/Stephen Kirklys
neuron
©istockphoto.com/ktsimage
Wood1. 17

18. Life-Preserving Chemicals
Neurotrophins – promote growth and survival, guide axons, stimulate synaptogenesis
Nerve growth factor (NGF)
Both passive cell death (necrosis) and active cell death (apoptosis)
Apoptosis is safer than necrosis – does not promote inflammation
Wade3.20

19. Life-Preserving Chemicals
FIGURE 9.8: The effect of neuron death and synapse rearrangement on the selectivity of synaptic transmission
Neurons that fail to establish correct connections are particularly likely to die
Space left after apoptosis is filled by sprouting axon terminals of surviving neurons
Ultimately leads to increased selectivity of transmission
Wade3.20

20. Postnatal Cerebral Development in Human Infants
Postnatal growth is a consequence of:
Synaptogenesis
Myelination – sensory areas and then motor areas. Myelination of prefrontal cortex continues into adolescence
Increased dendritic branches
Overproduction of synapses may underlie the greater plasticity of the young brain
Wade3.18

21. Development of the Prefrontal Cortex
Believed to underlie age-related changes in cognitive function
No single theory explains the function of this area
Prefrontal cortex plays a role in working memory, planning and carrying out sequences of actions, and inhibiting inappropriate responses

22. Effects of experience on development are time-dependent
Effects of Experience on the Early Development, Maintenance, and Reorganization of Neural Circuits
Permissive experiences: those that are necessary for information in genetic programs to be manifested
Instructive experiences: those that contribute to the direction of development
Effects of experience on development are time-dependent
Critical period
Sensitive period
Wade6.25

23. Early Studies of Experience and Neurodevelopment
Early visual deprivation
Fewer synapses and dendritic spines in primary visual cortex
Deficits in depth and pattern vision
Enriched environment
Thicker cortexes
Greater dendritic development
More synapses per neuron
Credit
hand holding rat
©iStockphoto.com/sidsnapper

24. Competitive Nature of Experience and Neurodevelopment
Ocular Dominance Columns example:
Monocular deprivation changes the pattern of synaptic input into layer IV of V1 (but not binocular deprivation)
Altered exposure during a sensitive period leads to reorganization
Active motor neurons take precedence over inactive ones
Wade6.32

25. Competitive Nature of Experience and Neurodevelopment
FIGURE 9.10: The effect of a few days of early monocular deprivation on the structure of axons projecting from the lateral geniculate nucleus into layer IV of the primary visual cortex. Axons carrying information from the deprived eye displayed substantially less branching. (Adapted from Antonini & Stryker, 1993.)
Wade6.32

26. Effects of Experience on Topographic Sensory Cortex Maps
Cross-modal rewiring experiments demonstrate the plasticity of sensory cortexes – with visual input, the auditory cortex can see
Change input, change cortical topography – shifted auditory map in prism-exposed owls
Early music training influences the organization of human auditory cortex – fMRI studies

27. Experience Fine-Tunes Neurodevelopment
Neural activity regulates the expression of genes that direct the synthesis of CAMs
Neural activity influences the release of neurotrophins
Some neural circuits are spontaneously active and this activity is needed for normal development
L11.25

28. Neuroplasticity in Adults
The brain changes and adapts
Neurogenesis (growth of new neurons) seen in olfactory bulbs and hippocampuses of adult mammals'—adult neural stem cells created in the epedymal layer lining in ventricles and adjacent tissues
Enriched environments and exercise can promote neurogenesis
Credits
person with thought bubble
©istockphoto.com/Digital Savant LLC
brain
©istockphoto.com/Stephen Kirklys 28

29. Effects of Experience on the Reorganization of the Adult Cortex
Tinnitus (ringing in the ears) – produces major reorganization of primary auditory cortex
Adult musicians who play instruments fingered by left hand have an enlarged representation of the hand in the right somatosensory cortex
Skill training leads to reorganization of motor cortex
Wade6.49

30. Disorders of Neurodevelopment: Autism
Three core symptoms:
Reduced ability to interpret emotions
Reduced capacity for social interaction
Preoccupation with a single subject or activity
Intensive behavioral therapy may improve function
Heterogenous – level of brain damage and dysfunction varies
Often considered a spectrum disorder
Often considered a spectrum disorder
Autism spectrum disorders
Asperger’s syndrome
Mild autism spectrum disorder in which cognitive and linguistic functions are well preserved
Wood1.
Credit
brain
©istockphoto.com/Stephen Kirklys

31. Disorders of Neurodevelopment: Autism
Incidence: 6.6 per 1,000 births (or 1 in 166)
80% males, 60% have mental retardation, 35% epileptic, 25% have little or no language ability
Most have some abilities preserved – rote memory, jigsaw puzzles, musical ability, artistic ability
Autistic Savants – intellectually handicapped individuals who display specific cognitive or artistic abilities
~1/10 autistic individuals display savant abilities
Perhaps a consequence of compensatory functional improvement in one area following damage to another
Wood1.
Credit
brain
©istockphoto.com/Stephen Kirklys

32. Genetic Basis of Autism
Siblings of children with autism have a 5% chance of having autism
60% concordance rate for monozygotic twins
Several genes interacting with the environment
Source: Bouchard & McGue, 1981
Wade3.37

33. Neural Mechanisms of Autism
Understanding of brain structures involved in autism is still limited, so far implicated:
Cerebellum
Amygdala
Frontal cortex
Two lines of research on cortical involvement in autism:
Abnormal response to faces in autistic patients
Spend less time than non-autistic subjects looking at faces, especially eyes
Low fMRI activity in fusiform face area
Possibly deficient in mirror neuron function
Wood1.
Credit
brain
©istockphoto.com/Stephen Kirklys

34. Disorders of Neurodevelopment: Williams Syndrome
Incidence: 1 in every 7,500 births
Mental retardation and an uneven pattern of abilities and disabilities
Sociable, empathetic, and talkative– exhibit language skills, music skills, and an enhanced ability to recognize faces
Profound impairments in spatial cognition
Usually have heart disorders associated with a mutation in a gene on chromosome 7 – the gene (and others) is absent in 95% of those with Williams
Wood1.
Credit
brain
©istockphoto.com/Stephen Kirklys

35. Disorders of Neurodevelopment: Williams Syndrome
Evidence for a role of chromosome 7 (as in autism)
General thinning of cortex at juncture of occipital and parietal lobes, and at the orbitofrontal cortex
“Elfin” appearance – short, small upturned noses, oval ears, broad mouths
FIGURE 9.13 Two areas of reduced cortical volume and one area of increased cortical volume observed in people with Williams syndrome. (See Meyer-Lindenberg et al., 2006; Toga & Thompson, 2005.)
Wood1.
Credit
brain
©istockphoto.com/Stephen Kirklys

36. Watch: The Central Nervous System
Watch: Brain Building
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37. Acknowledgments Slide Image Description Image Source template
lightning
©istockphoto.com/Soubrette
background texture
©istockphoto.com/Hedda Gjerpen
Chapter 09 image
Grandmother and grandchild smelling flowers
©iStockphoto.com/hanhanpeggy
3, 16, 21 28, 30, 33
brain
©istockphoto.com/Stephen Kirklys 4
paper clip
©istockphoto.com/Jon Patton
folder
©istockphoto.com/kyoshino
tabletop
©istockphoto.com/Andrew Cribb 5
human egg
©istockphoto.com/ChristianAnthony
human sperm
©istockphoto.com/Alexander Kozachok 6
Figure 9.1
Pinel 8e, p. 221 7
person thinking
©istockphoto.com/akurtz 9
Figure 9.2
Pinel 8e, p. 222 10
Figure 9.3
Pinel 8e, p. 223 11
book
©istockphoto.com/Carmen Martínez Banús 12
two puzzle pieces
©istockphoto.com/Henrik Jonsson 13
woman observing & taking notes
©istockphoto.com/Claudio Arnese 14
Figure 9.5
Pinel 8e, p.224 15
Figure 9.7
Pinel 8e, p. 227 17
neuron
©istockphoto.com/ktsimage 18
toddler listening to adult speak
©istockphoto.com/Jani Bryson Studios, Inc.

38. Acknowledgments 19 Figure 9.8 Pinel 8e, p. 228 20 two babies
©istockphoto.com/schwester 22
head - woman
©istockphoto.com/Angel Herrero de Frutos 23
hand holding rat
©iStockphoto.com/sidsnapper 24
binoculars
©iStockphoto.com/Alex Staroseltsev 25
Figure 9.10
Pinel 8e, p. 231 26
wires
©istockphoto.com/Take A Pix Media 27
swinging
©istockphoto.com/HooRoo Graphics 28
person with thought bubble
©istockphoto.com/Digital Savant LLC 29
piano and violin
©iStockphoto.com/Yenwen Lu 32
twins
©istockphoto.com/Thomas Gordon 35
Figure 9.13
Pinel 8e, p. 237 36
laptop
©istockphoto.com/CostinT
table and wall
©istockphoto.com/David Clark