Memory Disorders Flashcards
week 4
what would happen to memory if there was damage to the hippocampus?
Poor episodic memory- personal history, memory for events
what would happen to memory if there was damage to the para-hippocampal cortex?
Poor semantic memory- general knowledge and the way the world works
what would happen to memory if there was damage to both the hippocampus and the para-hippocampal cortex?
Poor episodic/semantic memory
what are the causes of amnesia?
- Damage to different structures of the brain causes different amnesiac syndromes
○ Surgery
○ Chronic alcohol abuse
○ Brain tumours
○ Encephalitis
○ Bilateral stroke
○ Dementia
○ Closed head injury
what are the 3 main types of amnesia?
- Retrograde
- Anterograde
- Global
what is retrograde amnesia?
- Poor recall for memories formed before onset of amnesia
○ Greater for episodic than semantic memories
○ Greater recall of general knowledge
○ Poor for personal memory recall - Retro= past
- Temporal gradient (time, slope)
○ Before amnesia started, the percentage of recall for old memories is poorer than the memories remembered after the amnesia.
○ Childhood memories are in tact in comparison to memories occurring near the name of amnesia.
what is a temporal gradient?
the concept within retorgrade amnesia that sates memories before the onset of amnesia are forgotten but memories after the onset of amnesia are remembered.
what are the 3 main explanations of the temporal gradient?
- consolodation theory
- semanticisation
- reduced learning opportunity
what is consolodation theory?
○ Acquisition= learning new memories
○ Acquisition and consolidation require different structures
○ Physiological process in the hippocampus leads to formation of long-lasting memories
○ Consolidated memories stored elsewhere, protecting them from effects of hippocampal damage
* Protects the older memories from being forgotten.
what is semanticisation?
○ Episodic memories become more like semantic memories over time = protected from effects of brain-damage
○ Over time memories lose personal detail.
Become protected due to becoming more like semantic memories so are stored in a different area- protects them from brain damage.
what is reduced learning opportunity?
○ Episodic memories depend on a single learning experience = reduced learning opportunity explains amnesia
§ Lived experience of an event
○ Semantic memories depend on several learning experiences
§ More robust memory trace
* All combinations contribute to the temporal gradient.
what is anterograde amnesia?
- Loss of ability to form new memories after onset of amnesia= Impaired learning after amnesia
- Results from damage to the areas of the brain that are involved in forming new memories after the onset of amnesia.
- Damage to the hippocampus the main cause in most instances
Mammillary bodies and fornix also commonly involved
what is global amnesia?
- Moderate retrograde amnesia and severe anterograde amnesia
- A mix of both retrograde and anterograde amnesia
- Results from lesions of structures in the medial temporal lobe, specifically the hippocampus
○ Hippocampus= vital for the formation of new memories.
Patient HM
who is patentint HM and what is the significance with global amnesia?
- Most studied amnesiac patient
- Suffered from severe epilepsy from age of 10 years old
- At age of 27 years, surgery to remove entire medial temporal lobe
○ Drastic surgery - Moderate retrograde and severe anterograde amnesia
Epileptic seizures were relieved- they were lessened.
what is Korsakoff’s syndrome?
- Also known as diencephalic amnesia
- Most amnesic research looked at individuals who were alcoholics.
- Vitamin B1 deficiency from chronic alcoholism
Damage to mammillary bodies in hypothalamus - Memory impairment consists of the following:
○ Poor ability to remember events before and after onset of amnesia (retrograde/ anterograde)
§ Both forms of amnesia
○ Some new learning ability (e.g. motor skills)
Slight impairment of STM (e.g. digit span)
what are the issues with the sympotomology of Korsakoff’s syndrome?
- typically has a grdual onset= events happen before or after the onset of amnesia
- brain damage widespread (hippocampus and frontal)= may lead to other functional/cognitive deficits
- precise pattern of damage varies across patients (difficult to determine the generalisability)
- brain plasticity and learing od compensatpry strategies= does ot provide a direct assessment of the impact of brain damage on LTM
what is semantic dementia?
- Severe problems with semantic memory, but intact episodic memory
- Presents itself as a language deficit.
○ Severe loss of information about meanings of words and concepts
○ Difficulty naming pictures/objects, single word comprehension, categorising, and knowing uses and features of objects. - Episodic memory and most executive functions (e.g. attention) reasonably intact in the early stages of semantic dementia
○ As it progresses, the damage to the brain widens out so overtime the semantic memories get lost. - Overtime, the brain regions affected spread, leads to decline in episodic memory as well as semantic memory.
- Patients differ in terms of precise symptoms
- Always involves degeneration of the anterior temporal lobe
– Where semantic memories are stored
– Perirhinal and entorhinal cortices where semantic memories formed
what is double dissociation?
Amnesia and semantic dementia point to a double dissociation in long-term memory
○ identify that brain damage to one structure disrupts one cognitive process (‘X’) but not another (‘Y’)
○ Also, identify that brain damage to different structure disrupts cognitive process ‘Y’ but not ‘X’
○ E.g.: one brain area influences semantic memory but not episodic memory
Another brain area influences episodic memory but not semantic memory.
wat is dissociation?
○ Identification of a brain region responsible for a cognitive process
One brain region is responsible for a brain process.
what is single-dissociation?
○ Identify that brain damage to one structure disrupts one cognitive process (‘X’) but not another (‘Y’)
Only one type of memory is affected- e.g.: semantic memory affected but not episodic memory.
what tpe of amnesia was experienced by Patient HM?
Global amnesia
What type of amnesia is characterised by poor recall for memories formed before onset of amnesia?
retrograde amnesia
What type of amnesia is characterised by a loss of ability to form new memories after amnesia onset?
Anterograde amnesia
what is eyewitness testimony?
- The accuracy of an individual’s memory is sometimes of enormous importance
○ You are the sole witness to a serious crime
○ You have to identify the perpetrator in a line-up: identification process
○ Your decision will be used as evidence
Help solve a case
how reliable is eyewitness testimony according to Wells & Olson (2003)?
○ “Eyewitness misidentification is the single greatest cause of wrongful convictions nationwide, playing a role in more than 75% of convictions overturned through DNA testing.” Still, the criminal justice system profoundly relies on eyewitness identification and testimony for investigating and prosecuting crimes.
what are memory errors?
○ Forgetting= easier to remember recent events than distant ones
§ Recall increases and retention decreases and time increases.
○ Intrusions= Mistakes in which elements not part of original memory trace get mixed-up or intrude recall
§ Didn’t actually happen during the event.
○ Bias= Memory influenced by observer’s prior expectations
Due to individual bias
what is forgetting?
Easier to remember recent events than distant ones
1. Decay
○ Memory traces fade over time
○ Less information available for retrieval as time passes
○ Temporal phasing
2. Interference
○ Similar information gets in the way of to-be-remembered information
○ 2 different types:
§ Retroactive, more recent information gets in the way of trying to recall older information
§ New memories obstruct our old memories
§ Proactive, previously learned materials get in the way of trying to recall newer materials
Old memories obstruct new memories
what are intrusions?
DRM PARADIGM
* Named after Deese, Roediger and McDermott.
* Recall words semantically associated with list words (e.g., sleep), that aren’t included in list
○ Related through concept
○ Make connections between list words and this associated word, leading to memory error.
§ Like to take short cuts- leads to memory error
* Background knowledge helps to link together the list of words according to a theme, which aids recall.
When we need perform the task- doesn’t mean it is accurate.
what is the isinformation effect?
- Memories easily distorted by misleading information presented afterwards
- Source misattribution
○ A memory probe (e.g., a question) activates memory traces with overlapping information
§ Probe the memory to activate memory traces.
○ Need to decide on the source of activated information
§ What is the source of the attribution?
Misattribution occurs when memories from one source resemble those from another
- Source misattribution
what did loftus and palmer study in relation to eye witness testimony?
- Participants shown a film of a car accident
- Actually travelling 12 mph.
“How fast were the cars going when they […] into each other?” - Had 5 different verbs that were shown to participants.
○ SMASHED: Estimated speed = 41mph (due to perceived higher speed, greater contact)
HIT: Estimated speed = 34mph (due to lower perceived speed) - One week later, asked (2nd condition)
“Did you see any broken glass?” - SMASHED: Yes = 34% (misattribution effect)
- HIT: Yes = 14%
○ Demonstrates that memory is fragile – can be distorted by changing just one word!
§ No broken glass shown in the video.
Misattribution effect was higher for the smashed condition rather than the hit condition.
- Actually travelling 12 mph.
what did Loftus study to show the effects of stress on eyewiotness testimony?
- Unusual= arranged for people to have a stressful experience.
○ Teach them what it would be like if they were ever captured as a prisoner of war.
○ Have to identify who it was who conducted the investigation
§ When led to believe it was someone, often got it wrong= misinformation effect
Shows wen you provide misinformation about an event, it can distort memory.
what is bias?
- Memory influenced by observer’s prior expectations
- Various different forms:
○ Confirmation bias
○ Other-race effect
○ Unconscious transference
○ Age
Weapon focus
what is confirmation bias?
- Tendency to recall information in a way that confirms pre-existing beliefs
- Helps fill in gaps and make reasonable assumptions about what has happened
- Schemas can lead us to form specific expectations
○ assume something must have happened due to our typical belief of an event.
○ Packets of knowledge stored in long-term memory
○ Cause us to reconstruct events based on…
“what must have been true”
what did Tuckey & Brewer (2003) study?
- Participants shown film of a simulated bank robbery
- Recalled information relevant to bank robbery schema
○ Robbers were male, wore disguises and demanded money
○ Generic information that is perceived to have occurred - Less likely to recall information irrelevant to schema
Colour of getaway car- didn’t know what it was due to it not being perceived relevant.
- Recalled information relevant to bank robbery schema
what is the significance of facial recognition on eyewitness testimony?
- Eyewitness identification from line-ups typically depends on face recognition
- However, often fallible- prone to error
○ Unconscious transference: misidentify a familiar (but innocent) face as being person responsible
§ Recognise the face from somewhere, incorrectly judge them to be responsible.
○ Other-race effect: recognition for same-race faces generally more accurate than other-race faces
§ Recognition for same race faces is more accurate because it is based upon a familiarity reason.
○ Own-age bias: more accurate when culprit is similar age to witness
More accurate with same age due to familiarity with those who are the same age as us- more accurate recognition.
- However, often fallible- prone to error
how does anxiety and violence influence eyewitness testimony?
- Anxiety and stress generally impair memory
○ Causes a narrowing of attention on important stimuli - tunnel vision attention.
§ Reduces ability to remember peripheral details - wider information- Weapon focus = attend to weapon, reducing memory for other information
Attend to unexpected stimuli inconsistent with schema of that situation
- Weapon focus = attend to weapon, reducing memory for other information
how do we avoid memory errors?
use the cognitive interview technique
what is the cognitive interview technique?
○ Increases information obtained and it effective.
1. Mental reinstatement of the environment- what happened on the day, draw upon the 5 senses
2. Encourage the reporting of every detail- even things that aren’t important, can trigger another memory of the event- encourage full report
3. Describe the incident in several different orders- start in the middle or work backwards, enhance the accuracy.
4. Report the incident from different viewpoints- as the witness, victim, criminal etc.
* Stages 1 & 2 are based on the encoding specificity principle- overlap or match of context in which the event was witnessed (take them back to the place?) relive it- more likely to accurately recall info.
* Stages 3 & 4 are based on different retrieval routes
* encoding specificity princliple
* different retrieval routes
how does speed indicate the reliability of eyewotness testimony?
Studies show that the longer it takes an eyewitness to decide if the perpetrator is in a line-up, the less confident they actually are about their decision
Eyewitnesses typically take several minutes to point out the perpetrator because they often feel pressured to choose the correct one
