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CHAPTER 13. Intelligence And Cognitive Functioning Deficiencies and Disorders of Intelligence. Developmental disabiliteis and mental retardation. The criteria for retardation =arbitrary, and based on judgments about the abilities required to get along in our complex world.

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chapter 13

CHAPTER 13

Intelligence And Cognitive Functioning

Deficiencies and Disorders of Intelligence

slide2

Developmental disabiliteis and mental retardation

  • The criteria for retardation =arbitrary, and based on judgments about the abilities required to get along in our complex world.
    • In 1978, then 1994 the American Psychiatric Association set the criteria for retardation as a combination of an IQ below 70 points and difficulty meeting routine needs like self-care.
    • Prior to that, cut off was 85
    • “cured” thousands of individuals
  • Not only is any definition arbitrary, but it is situational and cultural as well.
    • A person considered retarded in our society might fare reasonably well in a simpler environment.
    • 6-hour retarded child
slide3

Developmental disabiliteis and mental retardation

  • MANY causes of retardation
  • Retardation can be inherited or due to improper cell division
    • Fragile X
    • Tay Sachs
    • Williams Syndrome
    • Prader Willy
    • Down Syndrome
  • Retardation can be caused by diseases contracted during infancy
    • Meningitis; infection, etc.
    • prenatal exposure to viruses such as rubella (measles).
slide4

Developmental disabiliteis and mental retardation

  • Can be due to teratogen exposure
    • Maternal alcoholism is now the leading cause of mental retardation
    • Other drugs
  • Can be caused by prematurity
    • 50% of preterm infants have significant disability
    • Two most common: Cerebral palsy and mental retardation
  • What about autism?
    • Used to be generically called retardation
    • Now identify it as separate disorder
    • Many of individual who would have been diagnosed as retarded are now labeled autistic
slide5

Down syndrome

  • Down syndrome usually caused by
    • the presence of an extra 21st chromosome,
    • Mosaicism: chromosome splits into many small parts
    • Trisomy 21: chromosonal split resembles presence of 3 21st chromosomes
    • Related to maternal age, but not necessarily caused by age
  • Typically results in individuals with IQs in the 40 to 55 range.
    • Early intervention critical
    • Early that begin intervention, typically higher the IQ
  • Amyloid precursor protein gene that involved in early-onset Alzheimer’s disease is located on chromosome 21
    • was discovered because Down syndrome individuals also develop amyloid plaques.
    • 95% of people with Down syndrome have the entire extra chromosome
    • In a few cases: only an end portion is present, and attached to another chromosome.
slide6

Phenylketonuria

  • Phenylketonuria or PKU
    • due to an inherited inability to metabolize the amino acid phenylalanine.
    • excess phenylalanine interferes with myelination during development.
  • Without dietary treatment
    • the individual is severely or profoundly retarded
    • an adult IQ of around 20 points.
  • Much more rare today: Postnatal blood tests and routine hospital screenings followed by dietary changes has greatly reduced incidence in this country.
slide7

Other causes of retardation

  • Hydrocephalus
    • Water on the brain
    • occurs when cerebrospinal fluid builds up in the cerebral ventricles.
    • The increased fluid volume crowds out neural tissue, usually causing retardation.
  • Hydrocephalus can be relatively easily treated if caught early
    • installing a shunt that prevents the accumulation of the excess cerebrospinal fluid.
    • Eliminate or greatly reduce likelihood of long term brain damage
slide8

autism

  • Autism is a disorder that typically includes
    • compulsive, ritualistic behavior
    • impaired sociability
    • Language deficits
    • Often to usually: mental retardation.
  • Autism is one of 5 autism spectrum disorders
    • Autism, classic autism, high functioning autism
    • Autistic Disorder
    • Asperger Syndrome or Asperger's Disorder
    • Pervasive Developmental Disorder (PDD),
    • Autism Spectrum Disorder (ASD).
slide9

autism

  • Autism diagnosis given based on
    • Number and particular kinds of symptoms
    • Severity - mild to severe
    • Age of onset
    • Levels of functioning
    • Challenges with social interactions
  • Autism is the most common neurological disorder affecting children and one of the most common developmental disabilities
  • http://www.youtube.com/watch?v=FDMMwG7RrFQ
slide10

autism

  • Asperger’s syndrome
    • is the most similar to autism
    • most likely to share common causes.
  • People with Asperger’s syndrome are
    • socially impaired
    • display repetitive movements
    • preoccupations with narrow interests like autistic individuals,
    • But language and cognitive development and self help skills are more normal.
slide11

Autism: Common core of impairment

  • Whether retarded or not, autistic individuals share a common core of impairment in
    • Communication: often difficulty with communication
    • Imagination: very literal
    • Socialization: poor social skills
  • May be mute or show delayed language development
    • have trouble understanding verbal and nonverbal communication.
    • Again, very literal and concrete
  • Much of social behavior problem may be because autistic person lacks a theory of mind
    • ability to attribute mental states to oneself and to others.
    • An individual with autism cannot infer what other people are thinking.
slide12

Theory of mind

  • Two hypotheses as to how we develop a theory of mind.
    • “theory theory:” We build hypotheses over time based on our experience.
    • Simulation theory: We gain insight into people’s thoughts and intentions by mentally mimicking the behavior of others.
  • Data tends to support simulation view:
    • Existence of mirror neurons
    • Poor imitation skills in individuals with autism
    • Very different from Williams syndrome
slide13

How does poor mirror function affect intelligence?

  • Impaired mirror functions reduces the autistic person’s ability to
    • Empathize
    • learn language through imitation.
  • For example, some individuals with autism show no mirror neuron activity while
    • imitating facial expressions
    • or when observing a model’s hand movements.
  • Other studies show reduced activation in the inferior frontal cortex and motor cortex,
    • Suggests weakness in the dorsal stream connections
    • Provide important input to those areas containing mirror neurons.
slide14

Superior abilities?

  • Savant
    • person with exceptional intellectual skills
    • beyond the level of “ordinary” genius, like Leonardo da Vinci or Albert Einstein.
    • term is more frequently used to describe individuals who have one or more remarkable skills but whose overall functioning is below normal.
    • http://www.youtube.com/watch?v=lkDMaJ-wZmQ
  • Half of these individuals with islands of exceptional capabilities are autistic savants.
slide15

How can you be retarded and superior?

  • The source of the autistic savant’s enhanced ability is unknown.
  • Dehaene (1997):
    • may be due to intensely concentrated practice,
    • more typically the skill appears without either practice or instruction
    • Suggests innate ability.
  • Ramachandran and Blakeslee (1998): specialized area of the brain becomes enlarged at the expense of others.
  • Snyder and Mitchell (1999):
    • savant capabilities within us all,
    • are released when brain centers that control executive or integrative functions are compromised.
    • Brain damage studies lend support this hypothesis
slide16

Brain areas affected

in autism

  • Subtle but widespread brain anomalies have been found,
  • Especially in the
    • brain stem,
    • the cerebellum,
    • temporal lobes.
    • The location of damage is inconsistent, which may mean only that there are various pathways to autism.
  • What causes these brain defects?
    • is uncertain,
    • at least we know they occur early, during brain development
    • So: know where and when to look for the answer.
    • NOT caused by parental rejection!
slide17

Autism and environmental influence

  • Environmental influence: Teratogens?
    • received the most public attention
    • generated the greatest controversy is vaccines,
      • either the MMR vaccine (for measles, mumps, and rubella)
      • Or mercury as a vaccine preservative.
    • Research does not support this hypothesis.
  • Another possibility: Brain damage = autoimmune reaction.
    • A likely source for such an autoimmunity is viral diseases like measles.
    • Immune system attacks brain
    • Could easily be genetic/familial
slide18

What DO we know?

  • Elevated serotonin levels
    • biological or biochemical abnormality most consistently found in autistics
    • One of the genes suspected of playing a role in autism = responsible for the mechanism involved in serotonin reuptake.
  • Serotonin drugs improve functioning in autism
    • Supports 5HT model
    • Changes in serotonin activity suggests that SSRI therapeutic effect is in producing compensatory changes in receptor activity.
slide19

What DO we know?

  • Oxytocin referred to as “sociability molecule”
  • Affects social behavior and bonding in lower animals.
  • Autistic children were found to have lower levels of oxytocin than normal controls,
    • this difference pronounced in the autistic children who were described as aloof.
    • Thus, may be that low levels of oxytocin are involved
    • Interestingly, Williams syndrome kids have HIGHER levels than normal
    • http://video.nytimes.com/video/2007/07/06/magazine/1194817106646/my-life-with-williams.html
    • http://www.williams-syndrome.org/forparents/whatiswilliams.html
  • May be in the eyes:
    • Interest in eyes related to oxytocin levels
    • Individuals with autism avoid eye contact
    • Individuals with Williams syndrome seek out eye contact
slide20

Is autism “genetic’ or inherited?

  • Siblings of autistics are 40 to 60 times more likely to be diagnosed with autism than other children.
    • The number would be even higher, but parents tend to stop having children after the first autistic diagnosis.
    • Suggests strong familial, if not genetic, link
  • Autism occurs two to four times more frequently in males than in females,
    • suggests that the genes for autism might be on the X chromosome
    • Currently: at least four areas on the X chromosome that are potential sites for autism genes.