What you need to know

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What you need to know

• What you need to know
• Two types of memory disorder (amnesia and
  Alzheimer's)
• A description of these two disorders
• Explanations of these two disorders
• Research into these explanations

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Amnesia

• Definition A partial or total loss of memory,
  either temporarily or permanently
• Retrograde amnesia the total or partial loss of
  memory for past events
• Anterograde amnesia the inability to form new
  long term memories.
• HM (info on green box pg 95)
• Clive Wearing

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Explanations of amnesia

• Explanations of amnesia - 1
• Loss of explicit memory
• Explanations of amnesia 2
• Inability to consolidate new memories

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Explanations of Amnesia - 1

• Explicit vs implicit memory
• Explicit memory information deliberately and
  consciously recalled.
• Implicit memory something known without
  conscious recollection
• Learning a list of words deliberately so that
  they can be recalled
• Being asked to recall a list of all the pubs you
  have been to

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Explanations of Amnesia - 1

• Schacter (1987)
• One possible explanation of amnesia is that it is
  caused by an impairment in explicit memory. (AO1)
• When tested, amnesiacs perform poorly on tests of
  explicit memory but their performance on implicit
  memory is almost normal.
• Warrington Weiskrantz (1968) (AO2)
• Tested HM (anterograde amnesia) using the Gollin
  test (see pg 109)
• Was able to recognise partial images, although he
  had no memory of doing the test

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Explanations of Amnesia - 1

• Stickgold (2000)
• People with normal memory can learn Tetris in a
  few hours, and describe it
• People with amnesia can improve (although slower)
  showing implicit memory, but have no explicit
  memory of having done so.

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Explanations of Amnesia - 1

• Procedural vs declarative memory (LTM)
• Procedural memory how to do something. Motor
  skills. The skill of swimming for example.
• Declarative fact based memory. Knowing the fact
  that you can swim for example.
• If amnesiacs are better at implicit rather than
  explicit memory, how do you think they would
  perform on procedural vs declarative tasks?

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Explanations of Amnesia - 1

• Milner (1962)
• Taught HM how to draw using a mirror
• After practice, HM had learned the skill
  (procedural) of drawing with a mirror, although
  he had no memory of being able to do it
  (declarative)
• Stickgold (2000)
• It could be argued that participants in
  Stickgolds study were able to develop a
  procedural memory for Tetris, but not a
  declarative memory

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Explanations of Amnesia 1

• All of the previous suggests that amnesia may be
  caused by an impairment in explicit/declarative
  memory.
• This explanation is descriptive rather than
  explanatory.
• Ryan et al (2000)
• Relational memory binding
• Amnesiacs lack the function which makes a link
  between implicit and explicit memory (Still
  descriptive?)

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Explanations of Amnesia - 2

• An alternative theory is that Amnesia is the
  result of a problem with the consolidation of
  long term memory
• Issac and Mayes (1999)
• Tested anterograde amnesiacs by learning word
  lists. Amnesiacs performed normally on cued
  recall and recognition, but poorer than controls
  on free recall of semantically similar words.
• Suggests that there is an impairment in
  consolidation of long-term memory, not with
  retrieval.

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Explanations of Amnesia - 2

• Temporal gradient
• In people with retrograde amnesia recall is
  poorer the closer the memory is to the onset of
  amnesia

Onset of amnesia
Recall of memory
Time
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Explanations of Amnesia - 2

• This temporal gradient indicates that memories
  need to be consolidated and integrated into LTM,
  otherwise they are lost.
• Therefore, amnesia is caused by a disruption of
  this consolidation.

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Explanations of Amnesia - 2

• What causes problems with consolidation?
• Problems with consolidation may be due to damage
  to the hippocampus

• HM
• His amnesia was caused by surgery that removed
  his hippocampus, amygdala and parts of the
  temporal lobes
• Clive Wearing
• Had a virus which attacked his brain, damaging
  the hippocampus amongst other parts

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Explanations of Amnesia - 2

• Gabrieli (1998)
• Although many amnesiacs have both retrograde and
  anterograde amnesia, damage to a specific part of
  the hippocampus (CA1) causes anterograde amnesia
  alone.
• Reed and Squire (1998)
• Used MRI scans on retrograde amnesiacs. All had
  damage to the hippocampus, but those with the
  worst symptoms also had damage to the temporal
  lobe.
• Think HM

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Explanations of Amnesia - 2

• Remondes Scman (2004)
• Rats with damage to the hippocampus could learn a
  new maze, but forgot it quickly.
• Suggests that hippocampus in involved in the
  consolidation of new memories.

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Evaluation of Research

• Issues with using brain damaged patients?
• Issues with using animals?

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Alzheimers Disease

• A progressive form of dementia that usually
  starts in the 40s or 50s.
• Impaired memory
• Impaired thought and speech
• Finally complete helplessness

Auguste Deter, the first person to be diagnosed
by Alois Alzheimer in 1901
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Explanations of Alzheimers

• Explanation of Alzheimers 1
• ß-amyloids, plaques and tangles
• Explanation of Alzheimers 2
• Genes

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Explanation of Alzheimers - 1

• Normal Individuals

• Individuals with Alzheimers

Amyloid precursor protein (APP)
Amyloid precursor protein (APP)
broken down into
broken down into
ß-amyloid protein 40
ß-amyloid protein 42 (referred to as ß-amyloid)
Builds up in spaces between neurons causing
plaques
Interferes with neurotransmitter NDMA
Plaques cause damage to cerebral cortex,
hippocampus and basal forebrain
Interferes with changes to neurons during learning
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Explanation of Alzheimers - 1

• Plaques cause problems in communications between
  neurons
• Selkoe (2000)
• Plaques start to form before symptoms of
  Alzheimer's. Progressive damage causes cerebral
  cortex to shrink
• The hippocampus is also affected
• Berntson et al (2002)
• Alzheimer's effects memory is because of damage
  to the basal forebrain which is involved with
  alertness and attention

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Explanation of Alzheimers - 1

• The link between the build up of plaque and
  Alzheimers is weak and hard to explain.
• Murphy LeVine (2010)
• The presence of ß-amyloid protein 42 early in the
  disease starts a chain of events that leads to
  the illness
• This has yet to be tested

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Explanation of Alzheimers - 1

• Snyder (2005)
• ß-amyloid protein 42 interferes with NDMA, a
  neurotransmitter which produces changes in
  neurons when we learn
• Cleary et al (2005)
• Injecting rats with ß-amyloid disrupts memory

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Explanation of Alzheimers - 1

• Tangles
• Structure of the cell body disintegrates
• Build up of tau protein
• Distinct form in Alzheimer's

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Explanation of Alzheimers - 1

• Much of the research into Alzheimers comes from
  animal studies
• However, every animal investigated is different
• Primates have the same ß-amyloid protein as
  humans, but do not develop cognitive problems in
  old age
• Dogs do deposit ß-amyloid with age, but do not
  develop plaques and tangles
• Generalisability?

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Explanation of Alzheimers - 2

• Most individuals with Downs Syndrome (DS) who
  reach middle age develop early onset Alzheimers
  Lott (1982)
• As DS is caused by having an extra copy of gene
  21, this led researchers to look for and find
  genes associated with Alzheimer's on gene 21

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Explanation of Alzheimers - 2

• Levy-Lahad eta al (1995)
• Early onset Alzheimers gene found on chromosome
  1
• Schellenberg et al (1992)
• Early onset Alzheimers gene found on chromosome
  14
• Ertekin-Taner et al (2000)
• Gene for later onset Alzheimers found on
  chromosome 10

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Explanation of Alzheimers - 2

• What do the genes do?
• These genes play a role in producing more
  ß-amyloid, explaining why these individuals are
  more prone to Alzheimers
• However St George-Hislop (2000)
• Half of all Alzheimers patients have no known
  relative with the disorder
• Suggests the genetic influence is small.

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Explanation of Alzheimers - 2

• It seems unlikely that genes are the only
  influence on the development of Alzheimer

• Hendrie (2001)
• The Yoruba people of Nigeria have the same
  frequency of Alzheimers related genes, but a
  much lower incidence of the illness
• Other factors such as diet play a part

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Evaluation of Research

• Issues with using animal studies
• Nature vs nurture