amnesia ppt Amnesia What is it

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					        Amnesia - What is it?
A selective disruption of the processes
 underlying long-term memory
Short-term and sensory memory are
 typically functional
Other cognitive functions are not impaired
  Intelligence, attention...
        Amnesia - What is it?
A selective disruption of the processes
 underlying long-term memory
Short-term and sensory memory are
 typically functional
Other cognitive functions are not impaired
  Intelligence, attention...
         Recency vs Primacy
• Amnesia patients exhibit recency effect but
  not primacy effect
        Long-term                                 Short-term
        memory                                    memory



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        Amnesia - What is it?
A selective disruption of the processes
 underlying long-term memory
Short-term and sensory memory are
 typically functional
Other cognitive functions are not impaired
  Intelligence, attention...
    Retrograde & Anterograde
• Retrograde amnesia - Loss of information
  that was learned before the onset of amnesia

• Anterograde amnesia - inability to learn
  new information after the onset of amnesia

• Both can occur in the same patient and
  commonly do
    Retrograde & Anterograde
• Retrograde amnesia - Loss of information
  that was learned before the onset of amnesia

• Anterograde amnesia - inability to learn
  new information after the onset of amnesia

• Both can occur in the same patient and
  commonly do
Causes of Amnesia
•   Concussion
•   Migraines
•   Hypoglycemia
•   Epilepsy
•   Electroconvulsive shock therapy
•   Specific brain lesions (i.e. surgical removal)
•   Ischemic events
•   Drugs (esp. anesthetics)
•   Infection
•   Psychological
•   Nutritional deficiency
Types of memory
                       Proposed types of memory
Fact memory                        Skill memory
Declarative                        Non-declarative (Procedural)
Memory                             Habit
Explicit                           Implicit
Knowing that                       Knowing How
Cognitive mediation                Semantic
Conscious recollection             Skills
Elaboration                        Integration
Memory with record                 Memory without record
Autobiographical                   Perceptual
representational                   Dispositional
Vertical association               Horizontal association
Locale                             Taxon
Episodic                           Semantic
Working                            Reference
  Brain regions associated with
         human amnesia
• Diencephalic amnesia - damage to the
  medial thalamus and mamillary nuclei

• Medial temporal lobe amnesia - damage to
  the hippocampal formation, uncus,
  amygdala, and surrounding cortical areas
  Brain regions associated with
         human amnesia
• Diencephalic amnesia - damage to the
  medial thalamus and mamillary nuclei

• Medial temporal lobe amnesia - damage to
  the hippocampal formation, uncus,
  amygdala, and surrounding cortical areas
        Diencephalic Amnesia
• Damage to the medial
  thalamus and/or
  mamillary bodies
  – stroke
• Korsakoff’s syndrome
  – Caused by thiamine
    deficiency as a result
    of chronic alcoholism
            Korsakoff’s symptoms
• Anterograde amnesia
• Retrograde amnesia
    – Covers most of the adult life
• Lack of insight
    – Typically unaware of memory
      problems
                                                    QuickTime™ and a
• Confabulation                          TIFF ( Uncompressed) decompr essor
                                            ar e needed to see this pictur e.
    – Patient makes up stories to fill
      in the past
 Medial Temporal lobe amnesia
• Hippocampus is most important site of
  damage
                  Case H.M.
• Epileptic patient

• Had medial temporal lobes removed to stop
  seizures

• Seizures were reduced but H.M. became severely
  amnesiac.
               Case H.M.
• His intelligence is above normal
  – IQ = 112
• Performs normally on all tests of short-term
  memory
• Selective long-term memory impairment
            Case H.M.
Control brain                                 H.M.




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                 Case H.M.
• Memory impairment for recent events
  – spans the 3 years prior to his surgery
• Capable of recalling childhood memories
• Anterograde amnesia was initially thought
  to be global (all types of memory)
• later discovered that certain types of
  learning are intact    QuickTime™ and a
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                 Case H.M.
• Grave memory impairment for recent events
  – spans the 3 years prior to his surgery
• Capable of recalling childhood memories
• Anterograde amnesia was initially thought
  to be global (all types of memory)
• later discovered that certain types of
  learning are intact
               Case H.M.
• Priming still works

• H.M. can still form procedural memories
                 Case H.M.
• The Gollin incomplete picture test
  – subjects asked to identify the object
  – pictures are shown in sequence from least to
    most clear
  – shown the same images at a later date
  – both amnesiacs and control subjects identify the
    object at an earlier stage

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                               Case H.M.
• Mirror drawing task.
  – Trace figure while looking in a mirror
  – Control subjects get better at this with repetitive
    training.


           QuickTime™ and a
       TIFF (LZ W) decompressor
    are needed to see this picture.
                   Case H.M.
• Mirror drawing task
  – H.M. improved with




                            number of errors per attempt
    repeated training.                                     40
                                                                Day 1   Day 2    Day3
  – Procedural memory is                                   30
    intact
                                                           20
  – He cannot recall ever
                                                           10
    having performed this
    task before                                            0
                                                                   Attempts each day
              Case H.M.
– Doesn’t remember the death of his father
– Can’t remember or describe his job
– Doesn’t remember his examiners
               Case H.M.
• According to our memory dichotomies,
  what type of memory is the medial temporal
  lobe (especially the hippocampus)
  responsible for?
Types of memory
                                       Case H.M.
• H.M.s Retrograde amnesia is temporally graded
   – remote memory is spared but recent memory is lost
• Not all amnesia patients show this pattern
   – V.C., N.A. have extensive retrograde amnesia (flat
     gradient)
                                                Memory recall ability
                  recall performance




                                                                                 H.M.
                                                                                 Control
                                                                                 N.A.




                                       Recent                           Remote
                                                 Age of memory
       Lessons from amnesia
• Existence of Multiple memory systems

• Localization of cognitive functions
                    S.
• “Photographic” extreme memory ability (a
  mnemonist)
• Able to recall complex test stimuli
                             S.
• “Photographic” extreme memory ability (a
  mnemonist)
• Able to recall complex test stimuli
• S. used two “strategies” or abilities typical of
  mnemonists:
   – rich synesthesia-like quality to his perception of stimuli
     - leads to stronger associative links
   – vivid and elaborate mental imagery of things he should
     remember
                          S.
• “ Even numbers remind me of images.
  Take the number 1. This is a proud, well-
  built man; 2 is a high-spirited woman; 3 a
  gloomy person (shy, I don’t Know); 6 a
  man with a swollen foot...”


      Luria, A.R. The mind of a mnemonist. 1968

      Luria, A.R. The man with a shattered world. 1972

				
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