What you need to know What you need

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. (AO 1) – When tested, amnesiacs perform poorly on tests of explicit memory but their performance on implicit memory is almost normal. • Warrington & Weiskrantz (1968) (AO 2) – 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

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

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 (CA 1) 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 40 s or 50 s. – 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 Individuals with Normal Individuals Amyloid precursor protein (APP) broken down into β-amyloid protein 40 Builds up in spaces between neurons causing plaques Plaques cause damage to cerebral cortex, hippocampus and basal forebrain Alzheimers Amyloid precursor protein (APP) broken down into β-amyloid protein 42 (referred to as β-amyloid) 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 & Le. Vine (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