Other Types of Amnesia

Korsakoff's Syndrome
1. Brain damage caused by prolonged thiamine deficiency
  1. Severe thiamine deficiency occurs mostly in chronic alcoholics with diet of alcohol and lack of vitamins
    1. Brain news thiamine (VB) to metabolise glucose (primary fuel)
  2. leads to loss or shrinkage of neurones throughout brain
2. Most effected area is dorsomedial thalamus - main source of input to prefrontal cortex
3. Symptoms similar to those of people with damage to prefrontal cortex
  1. apathy, confusion and memory loss
  2. Overlap those of hippo damage, with major impairment of episodic and sparing of implicit
4. Distinctive symptom is confabulation
  1. patients fill in memory gaps with guesses
    1. Mainly about episodic memory
      1. Usually more pleasant than actual truth
        may reflect patients attempt to maintain pleasant emotions
  2. produced fascinating influence on strategies for studying
    1. completing sentences forces you to be more active and call attention to items you have not yet learned
5. Patients learn much better the first way by reading list over and over
  1. when they rest themselves, they confabulate
    1. they remember their confabulation instead of correct answer
      1. Hamann & Squire (1995)
Alzheimer's Disease
1. Alzheimer's patients have better procedural than declarative memory
  1. they learn new skills but surprise themselves with good performance because they don't remember doing it before
  2. Memory and alertness vary substantially from time to time
    1. suggesting that many of their problems result from malfunctioning neurones, rather than the death of neurones rather than death of neurons
      1. Palop, Chin & Mucke (2006)
2. increased arousal improves memory.
  1. People who drink 3-5 cups coffee per day less likely than average to develop alzheimer's
3. Gradually progresses to more serious memory loss, confusion, depression,hallucinations, sleeplessness, delusions, restlessness, loss of appetite
  1. occasionally strikes younger than 40
4. people with don syndrome most invariably get alzheimer's disease if they survive to middle age
  1. Lott (1982)
  2. DS have 3 copies of chromosome 21 rather than 2
    1. this led INV to examine chromo 21
      1. they found a gene linked to many cases of early-onset Alzheimer's disease
        Goate et al (1991)
5. Research found 2 more genes links to early-onset
6. Genes were found for late onset
  1. increase risk only slightly, as opposed to early onset increase it strongly
7. Genes don't completely control Alzheimer's disease but understanding genes shed light on disease.
8. Gene controlling early-onset cause protein called amyloid-B to accumulate both inside and outside neurones
  1. tau proven in intracellular support structure of axons
    1. Davies (2000)
    2. high levels of amyloid cause more phosphate groups to attach to tau proteins
      1. altered tau can't bind to its usual targets within axons and starts spreading into cell body and dendrites
        attack from tau in dendrites adds to attack by amyloid magnifying damage
        altered tau also increased production of amyloid causing a vicious cycle.
      2. altered tu responsible for tangles, structures formed from degeneration within neurones
    3. Pattern of amyloid, tau and other chemicals varies from one Alz to another and may be useful to distinguish subtypes of patients
  2. Curcumin inhibits amyloid deposits and phosphate attachment to tau proteins
9. As amyloid damages axons and dendrites, damaged structures cluster into structures called plaques
  1. Selkoe (2000)
  2. As plaques accumulate, cerebral cortex, hippo and other areas atrophy (waste away)
10. drugs stimulating acetylcholine receptors or prolong release
  1. results increased arousal

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Other Types of Amnesia

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	Created by n.c.wetmore about 11 years ago