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Copyright © 2011 Pearson Education, Inc. All rights reserved. PowerPoint Presentation for Biopsychology, 8th Edition by John P.J. Pinel Prepared by Jeffrey.

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Presentation on theme: "Copyright © 2011 Pearson Education, Inc. All rights reserved. PowerPoint Presentation for Biopsychology, 8th Edition by John P.J. Pinel Prepared by Jeffrey."— Presentation transcript:

1 Copyright © 2011 Pearson Education, Inc. All rights reserved. PowerPoint Presentation for Biopsychology, 8th Edition by John P.J. Pinel Prepared by Jeffrey W. Grimm Western Washington University This multimedia product and its contents are protected under copyright law. The following are prohibited by law: any public performance or display, including transmission of any image over a network; preparation of any derivative work, including the extraction, in whole or in part, of any images; any rental, lease, or lending of the program.

2 Copyright © 2011 Pearson Education, Inc. All rights reserved. From Fertilized Egg to You Chapter 9 Development of the Nervous System

3 Copyright © 2011 Pearson Education, Inc. All rights reserved. Neurodevelopment Neural development – an ongoing process; the nervous system is plastic A complex process Experience plays a key role Dire consequences when something goes wrong

4 Copyright © 2011 Pearson Education, Inc. All rights reserved. The Case of Genie 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 rescue, her behavior never became normal Case of Genie illustrates the impact of severe deprivation on development

5 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

6 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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)

7 Copyright © 2011 Pearson Education, Inc. All rights reserved. Induction of the Neural Plate Continued 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

8 Copyright © 2011 Pearson Education, Inc. All rights reserved. FIGURE 9.1 How the neural plate develops into the neural tube during the third and fourth weeks of human embryological development. (Adapted from Cowan, 1979.)

9 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

10 Copyright © 2011 Pearson Education, Inc. All rights reserved. Migration 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

11 Copyright © 2011 Pearson Education, Inc. All rights reserved. Migration Continued Two types of neural tube migration Radial migration (moving out) – usually by moving along radial glial cells 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

12 Copyright © 2011 Pearson Education, Inc. All rights reserved. FIGURE 9.2 The two types of neural migration: radial migration and tangential migration.

13 Copyright © 2011 Pearson Education, Inc. All rights reserved. FIGURE 9.3 Two methods by which cells migrate in the develping neural tube: somal translocation and glia-mediated migration.

14 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

15 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

16 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

17 Copyright © 2011 Pearson Education, Inc. All rights reserved. FIGURE 9.5 Sperry’s classic study of eye rotation and regeneration.

18 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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 Axon Growth and Synapse Formation Continued

19 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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 Axon Growth and Synapse Formation Continued

20 Copyright © 2011 Pearson Education, Inc. All rights reserved. FIGURE 9.7 The topographic gradient hypothesis. Gradients of ephrin-A and ephrin-B on the developing retina (see McLaughlin, Hindges, & O’Leary, 2003).

21 Copyright © 2011 Pearson Education, Inc. All rights reserved. Synapse Formation Formation of new synapses Depends on the presence of glial cells – especially astrocytes High levels of cholesterol are needed – supplied by astrocytes Chemical signal exchange between pre- and postsynaptic neurons is needed A variety of signals act on developing neurons

22 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

23 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

24 Copyright © 2011 Pearson Education, Inc. All rights reserved. Synapse Rearrangement 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

25 Copyright © 2011 Pearson Education, Inc. All rights reserved. FIGURE 9.8 The effect of neuron death and synapse rearrangement on the selectivity of synaptic transmission. The synaptic contacts of each axon become focused on a smaller number of cells

26 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

27 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

28 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

29 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

30 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

31 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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.)

32 Copyright © 2011 Pearson Education, Inc. All rights reserved. Effects of Experience on Topographic Sensory Cortex Maps Cross-modal rewiring experiments demon- strate 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

33 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

34 Copyright © 2011 Pearson Education, Inc. All rights reserved. Neuroplasticity in Adults The mature 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 ependymal layer lining in ventricles and adjacent tissues enriched environments and exercise can promote neurogenesis

35 Copyright © 2011 Pearson Education, Inc. All rights reserved. FIGURE 9.11 Adult neurogenesis. (Courtesy of Carl Ernst and Brian Christie, Department of Psychology, University of British Columbia.)

36 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

37 Copyright © 2011 Pearson Education, Inc. All rights reserved. Disorders of Neurodevelopment: Autism Three core symptoms Reduced ability to interpret emotions and intentions Reduced capacity for social interaction Preoccupation with a single subject or activity

38 Copyright © 2011 Pearson Education, Inc. All rights reserved. Disorders of Neurodevelopment: Autism Continued Intensive behavioral therapy may improve function Heterogenous – level of brain damage and dysfunction varies Often considered a spectrum disorder Autism spectrum disorders Asperger’s syndrome  Mild autism spectrum disorder in which cognitive and linguistic functions are well preserved

39 Copyright © 2011 Pearson Education, Inc. All rights reserved. Incidence: 6.6 per 1,000 births (or 1 in 166) 80% males, 60% mentally retarded, 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 Disorders of Neurodevelopment: Autism Continued

40 Copyright © 2011 Pearson Education, Inc. All rights reserved. Genetic Basis of Autism Siblings of the autistic have a 5% chance of being autistic 60% concordance rate for monozygotic twins Several genes interacting with the environment

41 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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

42 Copyright © 2011 Pearson Education, Inc. All rights reserved. Disorders of Neurodevelopment: Williams Syndrome 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

43 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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 Disorders of Neurodevelopment: Williams Syndrome Continued

44 Copyright © 2011 Pearson Education, Inc. All rights reserved. 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.)


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