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

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

Explanations of amnesia

• Explanations of amnesia - 1– Loss of explicit

memory

• Explanations of amnesia – 2– Inability to

consolidate new memories

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:

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

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.

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?

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 Stickgold’s study were able to develop a procedural memory for Tetris, but not a declarative memory

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?)

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.

Explanations of Amnesia - 2• Temporal gradient

– In people with retrograde amnesia recall is poorer the closer the memory is to the onset of amnesia

Time

Onset of amnesia

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.

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

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

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.

Evaluation of Research

• Issues with using brain damaged patients?

• Issues with using animals?

Alzheimer’s 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

Explanations of Alzheimer’s

• Explanation of Alzheimer’s 1– β-amyloids, plaques and tangles

• Explanation of Alzheimer’s 2– Genes

Explanation of Alzheimer’s - 1

Normal Individuals Individuals with Alzheimers

Amyloid precursor protein (APP)

β-amyloid protein 40

broken down into

Amyloid precursor protein (APP)

β-amyloid protein 42 (referred to as β-amyloid)

broken down into

Builds up in spaces between neurons causing plaques

Plaques cause damage to cerebral cortex, hippocampus

and basal forebrain

Interferes with neurotransmitter NDMA

Interferes with changes to neurons during learning

Explanation of Alzheimer’s - 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

Explanation of Alzheimer’s - 1• The link between the build up of

plaque and Alzheimer’s is weak and hard to explain.

• Murphy & LeVine (2010)– The presence of β-amyloid protein 42

early in the disease starts a chain of events that leads to the illness

– This has yet to be tested

Explanation of Alzheimer’s - 1

• Snyder (2005)– β-amyloid protein 42 interferes with

NDMA, a neurotransmitter which produces changes in neurons when we learn

• Cleary et al (2005)– Injecting rats with β-amyloid disrupts

memory

Explanation of Alzheimer’s - 1

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

Explanation of Alzheimer’s - 1

• Much of the research into Alzheimer’s comes from animal studies

• However, every animal investigated is different– Primates have the same β-amyloid protein as

humans, but do not develop cognitive problems in old age

– Dogs do deposit β-amyloid with age, but do not develop plaques and tangles

• Generalisability?

Explanation of Alzheimer’s - 2

• Most individuals with Downs Syndrome (DS) who reach middle age develop early onset Alzheimer’s: 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

Explanation of Alzheimer’s - 2

• Levy-Lahad eta al (1995)– Early onset Alzheimer’s gene found on

chromosome 1

• Schellenberg et al (1992)– Early onset Alzheimer’s gene found on

chromosome 14

• Ertekin-Taner et al (2000)– Gene for later onset Alzheimer’s found on

chromosome 10

Explanation of Alzheimer’s - 2

• What do the genes do?– These genes play a role in

producing more β-amyloid, explaining why these individuals are more prone to Alzheimer’s

• However: St George-Hislop (2000)– Half of all Alzheimer’s patients

have no known relative with the disorder

– Suggests the genetic influence is small.

Explanation of Alzheimer’s - 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 Alzheimer’s related genes, but a much lower incidence of the illness

• Other factors such as diet play a part

Evaluation of Research

• Issues with using animal studies• Nature vs nurture