Introduction to Neuropsychology

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Introduction to Neuropsychology

• Dr. Ingrid C. Friesen
• icf_at_direct.ca (881-1145)

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Origin and Development of the Brain
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The Brain is 3-D Any point can be localized on 3
axes or planes
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Coronal
Sagittal
Horizontal
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• Terminology
• Posterior/anterior
• Ventral/dorsal
• Ipslateral/contralateral
• Medial/Lateral
• Superior/Inferior

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Origin of the Brain

• Nervous system (NS) developed in 4 general steps
  over time

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(1) Spinal Cord

• (1) NS was first a simple tube (spinal cord)
• Receiving information from the dorsal portion
• Sending motor fibers to body parts from ventral
  portion

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(1) Spinal Cord
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(2) Primitive Brain or Brainstem

• One end of cord became specialized to respond to
  sensory features and tell the rest of the body
  what to do
• Further specialization at this front end with
  development of enlargements
• Cells surrounding each enlargement multiplied to
  form centers specialized for receiving and
  responding to special features in world

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• Prosencephalon (frontbrain) - olfaction, taste
• Mesencephalon (midbrain) - vision, audition
• Rhombencephalon (hindbrain) - equilibrium,
  perception of where organism is in environment
• Dorsal portion - sensory
• Ventral portion - motor
• Same format in brain of mammals

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(2) Brainstem
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(3) Mammalian Brain

• Brain next developed primarily in its first and
  third segments
• Prosencephalon 2 major divisions
• (1) Telencephalon (endbrain) - cerebral
  hemispheres - became highest level of control
• (2) Diencephalon (between brain)

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• Rhombencephalon also divided
• (1) Metencephalon (across brain) growth of
  Cerebellum (coordinating movement)
• (2)Myelencephalon - spinal brain

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(3) Mammalian Brain
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(4) Human Brain

• Evolved from mammalian brain with no change in
  basic design
• But cerebellum and cerebral hemispheres are much
  larger in humans

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(4) Human Brain
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Ventricular System

• Primitive spinal cord had form of a tube
• Filled with CSF
• Cavity larger in some parts - ventricles
• Lateral ventricles (1 2) - cerebral hemispheres
• 3rd ventricle - diencephalon
• 4th ventricle - metencephalon myelencephalon

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Forebrain

• Most highly developed
• Contains nuclei surrounded by nerve fibers
  sheathed in myelin (white matter) and covered by
  cerebral cortex (grey matter)

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• Very little of brain primary sensory or motor
  cortex
• Most is association cortex

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Cerebral Cortex

• Convoluted surface consisting of multiple layers
  of intercorrelated neurons
• New, well-developed in mammals
• Contains about 9 billion of 12 billion neurons in
  the CNS
• Responsible for highest functions

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Midbrain Structures
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Slide 21
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Early Brain DevelopmentIn Humans

• All behavioural development has to do with the
  brain (i.e., brainbehavour)
• Brain development is dependent upon both genetics
  and experience
• (i.e., nature vs. nurture)
• The brain has a great deal of plasticity and can
  recover over time.

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• Growth of the brain occurs from the inside out
  and the bottom up
• You are born with 100 billion brain cells
• There are 15,000 synaptic connections for each
  cell
• At birth brain is 400 g and in adulthood it is
  1500 g

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3 Stages of Neuronal Development

• 1. Proliferation
• Prenatal period (up to 7 mos postconception)
• Production of neurons

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• Migration
• neurons move to permanent place to form major
  parts of the brain (most by 5 months)
• Disruption in migration may result in
  developmental disorders

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• 3. Differentiation
• Once in place, neurons grow more and longer
  dendrites, axons extend farther and farther from
  cell body
• Creation of synapses

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Composition of the Brain

• The brain is comprised of four areas
• stem
• diencephalon
• limbic system
• cortex

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Slide 21
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Dentritic Arborization

• Begins prenatally but continues postnatally
• Significant changes between 5 and 21 weeks
  postnatally
• Completion in visual areas 6 months of age but
  development in prefrontal areas through
  adolescence

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Synaptogenesis

• process of synapse formation
• Continues throughout development
• Pruning and selective cell death occurs at
  different rates in different parts of the brain
• Experience is vital!

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• Experience-expectant processes neurons/synapses
  form when an organism has species-typical
  experiences (pre-wired)
• Experience-dependent processes neuronal
  connections are made to reflect the unique
  experiences of individuals

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Metabolism

• Increases dramatically after first year of life
  and peaks between 4 and 5 years (150 of adult
  rate)
• At 9 years of age, adult levels are reached
• Hypermetabolism may assist in rapid learning and
  allow for greater plasticity at younger ages

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Myelination

• Myelin is a fatty sheath that surrounds an axon
• Purpose to allow faster transmission, lowers the
  threshold of sensitivity to stimulation
• Occurs first for sensory structures and last for
  prefrontal areas
• Affected by experience

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Human Brain at Birth
14 Years Old
6 Years Old
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2 Months
5 Days
28 Years
1 Year
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Early Experiences are Important

• By age 3, 80 of synaptic connections are already
  made
• By the second decade of life growth levels off
  and pruning begins
• Increased experiences define the wiring of an
  infants brain

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• During the first 10 years of life the brain is
  twice as active as that of an adults
• 60 of nutrition is used by the brain during the
  first year of life. This decreases to 30 by age
  3
• Genetic and environmental factors have a dynamic
  and qualitative interplay
• Nature vs. nuture is a complex equation

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• There is little scientific evidence that special
  stimulation activities above and beyond normal
  growth-promoting experiences lead to advanced
  brain development in early childhood
• Poor nutrition, specific infections,
  environmental neurotoxins, drug exposures, and
  chronic stress can harm the developing brain
• Significant parent mental health problems,
  substance abuse,and family violence impose heavy
  developmental burdens on young children