Memory part 2 Flashcards
Decay Theory
Memories are lost when not used
Interference theory
Before consolidation into long term memory, memories are weak and prone to disruption and interfering information effects
Proactive interference (‘forward in time’)
Prior information interferes with encoding a new memory
Retroactive interference (‘backward in time’)
Newly learned information interferes with a prior encoded memory
Similarity effects
The more alike something is to what is already learned, the more it will mingle and interfere with memory
The encoding specificity hypothesis
- Memory retrieval is better when there is overlap in some source with encoding
Context : Easier to remember something when we are in the same context when we retrieve it as when we encoded it
Context can refer to:
- Internal state (e.g., mood)
- External environment
- Processing
Internal context: State-dependent learning
- 2 groups were tested in a matched state (sober, then tested sober) or mismatched test
Results : - Both matched groups retrieved more information
External context
People are better at retrieving when there is match in context (place)
(e.g. learned underwater then recalled underwater)
Processing context: Transfer-appropriate processing
The overlap between processes during encoding and retrieval determines memory strength
E.g. deep encoding and evaluated at deep level
Episodic memory
- recollecting unique events : what, where, when
- Mentally reexperiencing an event
Semantic dementia
Affects temporal poles
Early in disease:
* Relatively spared at episodic memory tasks
* Impaired at word naming and picture matching tasks (semantic memory)
Semantic memory
culturally-shared knowledge and knowledge about the self that isn’t
attached to a time and place
Children with hippocampal damage cannot…
Copy images after a delay
- Due to episodic memory impairment (not semantic)
3 types of consciousness of long-term Memory
- Anoetic
- Noetic
- Autonoetic
Anoetic Consciousness
- Implicit Memory
- No awareness or personal engagement
Noetic consciousness
- Semantic Memory
- Awareness but no personal engagement
Autonoetic Consciousness
- Episodic Memory Awareness AND personal engagement
- Mental time travel
Memory retrieval: The reappearance hypothesis
An episodic memory trace is recalled the same way at each retrieval
* It is reproduced, not reconstructed
Involuntary memories
Memories that come to mind with no retrieval attempt, often emotional and repetitive
Flashbulb memories form form events that are:
- Emotionally arousing
- Surprising or shocking
- Important to the self (have consequence)
Flashbulb and everyday memories both change over time, but flashbulb memories are linked to more ______ over time
Confidence (belief, vividness)
Change in memory over time show that memories are..
Reconstructed as they are retrieved
How the hippocampus can distort memories
The hippocampus binds details. Across details, it can bind different details, changing memories.
Schemas
Organize and categorize information, provide expectations about how things should occur
Bartlett (1932) : The War of Ghosts experiments
Participants read an unfamiliar Native American folk story that did not match Western story schema
Results :
* Participants remembered a simplified version of the story and it became more conventional with repeated retrievals
* Omissions and alterations to match Western schema
Context and schemas forming false memories
Asked to study scenes associated with schema-consistent items removed
E.g. classroom without a chalkboard
Then asked if item was in the scene
Result : 50% reported seeing the lure item
Misattribution effect
Retrieving familiar information from the wrong source (place)
* A failure in source monitoring (not remembering the where or when accurately)
Misinformation effect
Leading questions can cause false memory formation : the way something is asked can alter your memory
(e.g. how fast were the cars going when they crashed into each other vs contacted each other : faster for “crashed”)
Implanting memories
Participants recalled childhood experiences recounted by their parents
* A false memory was added to the list of experiences by the experimenter : An overnight stay in a hospital
* 20% of people had a false memory of this event by the end of the third session
Memory consolidation
Stabilization : The formation of stable cortical representations of memories
Memory reconsolidation
When a trace becomes activated, a memory retrieved, it becomes de-stable
At this point, the memory can be modified : cortical connections can be strengthened or modified
You then reconsolidate that (possibly altered) memory back into a stable long term memory trace
How are memories linked to the future ?
The same hippocampal episodic processes that help us construct memories help us imagine the future and plan for our lives
The same hippocampal neural processes that help us construct the past also …
Help us imagine future scenarios
How the hippocampus may help us imagine the future
Maybe the hippocampus take details from different past experiences (even unrelated) and bring them together to form a novel mental simulation (collage of new events from little bits of past experiences)
Implicit memory: Procedural memory
Automatic behavior/actions related to motor movements and organization of sequences
e.g. playing the piano
These brain structures are responsible for procedural memory
Striatum : in basal ganglia (center), active for refining sequences and shaping habits
Prefrontal cortex - organization, to retrieve and monitor sequences
This type of memory is more immune to forgetting compared to other types
Procedural memory
Habits
Initially relies on explicit memory → with training and/or exposure, relies on implicit memory
Examples :
- Motor action sequences (like learning an instrument)
- Repetitive thoughts and emotions [Obsessive Compulsive Disorder (OCD)]
- Addictive behaviours
Habit Formation
Rats trained on a T-shaped maze with tones to signal reward (chocolate milk; sugar water) at left or right end
- Over time, the rat response to signal becomes habitual thanks to the striatum
Breaking Habits
Removing a reward, or making one reward gross (nonrewarding) did not break the habit
* To break habit, you must inhibit prefrontal cortex to reduce association between action and reward (no association made = no habit action)
Technique to break habits
In the same context/cue as the original habit, you can introduce a new behavior with a very rewarding experience (can be different from the original reward of the other habit)
Priming
Prior exposure facilitates information processing without awareness
Priming word completion
Participants are shown a list of words
* Asked to complete word fragments
* Participants are likely to use prior words to complete the fragments without knowing it
Implicit emotional responses
Adaptative conditioned emotional responses (e.g. fear of snakes)
déjà vu: The implicit memory theory
The location you’re in primes an implicit memory of a familiar location (just not actively bringing it to mind)
The ______ supports automatic reactions that help us survive by staying away from harm, and explicit emotional memory
Amygdala
Semantic memory
Acquired knowledge that includes facts about the world and the self, concepts, general ideas, meaning
How is semantic memory usually acquired ?
Often begins as episodic memory from which you remove details from episodes of learning to store general knowledge
Semantic memory organization
We store semantic concepts as an interconnected network
The semantic network allows us to access and represent concepts at different levels of _______
Specificity (general to very specific idea)
Spreading activation in the semantic network
Automatic activity spread from an activated concept to interconnected concepts (features)
- How a related concept pops up when thinking of another concept (priming)
Patient H.M.
Bilateral removal of the medial temporal lobe, including the hippocampus
Symptoms :
Selective and severe episodic memory loss : He couldn’t learn new information and recalled his past in sparse detail
Patient HM was stuck in the _____
Present
(could not remember past nor imagine future)
Anterograde amnesia
Inability to form or encode new episodic memories because memory cannot move from short term to long term store
Retrograde amnesia
- Loss of past memories from before the onset of the amnestic event
- Self identity and semantic memories are typically preserved (specific to episodic memories)
Temporally graded memory loss in retrograde amnesia
Remote or older memories are more preserved than recent memories
Why can people with retrograde amnesia recall older memories better ?
Older memories have consolidated to the prefrontal cortex and do not rely as much on the hippocampus
Korsakoff’s Syndrome
Chronic alcoholism → thiamine deficiency → damaged mammillary bodies of the hypothalamus, connected to the hippocampus
Types of memory loss in Korsakoff’s Syndrome
Anterograde and retrograde amnesia
Symptoms of Korsakoff’s Syndrome
- Personality + other behavioral changes (apathy)
- Confabulation
Confabulation
Narrative story of an event that has not been experienced without awareness and intention to deceive
- Due to deficits in monitoring, memory organization processes supported by the prefrontal cortex
Dissociative amnesia
Very rare psychiatric disorder
* Usually, a response to psychological or physical trauma
* Not from brain injury
Symptoms of dissociative amnesia
Retrograde amnesia
- Episodic memories
* Autobiographical knowledge – skills
Shifts in lifestyle
* Moving to a new place
* Assuming a new identity
Alzheimer’s disease
- Most common form of dementia
Build up of amyloid plaques and neurofibrillary tangles that cause cell death, and brain shrink
First brain regions to be affected by Alzheimer’s
Medial temporal lobe (MTL) regions (where hippocampus is)
Earliest symptom of Alzheimer’s
Deficit in episodic memory
What causes a decline in all forms of memories, changes in emotions, motor function, in Alzheimer’s ?
Progressive cell death that will eventually spread to all the brain
Alzheimer’s trajectory
- Episodic memory is affected
- The disease spreads to temporal and parietal regions : reading problems, problems recognizing objects, having conversations
- Behavior, personality changes, impulsivity, motor issues
Dementia
Range of neurological conditions that affect the brain and that get worse over time.
Semantic dementia
Form of frontal temporal dementia
- Frontal and temporal regions are initially affected in the brain, causing problems with language and emotion.
Lewy body dementia
- Chemicals in the brain are affected
- movement, sleep and cognitive problem, hallucinations
Vascular dementia
- disrupted blood flow in your brain.
- associated with strokes and so forth
- general cognitive deficits and delusions.
Aging and brain volume loss
Volume loss ~ 5% per decade after 40 years of age
- PFC and Hippocampus are primarily affected
_____ memory (and working memory) is impaired with aging
Episodic
Older adults have deficits in general executive cognitive processes from … atrophy
Frontal lobe
Impacts of frontal lobe atrophy in adults
- Slower at processing information
- Can’t inhibit irrelevant information : difficulty focusing attention which impacts episodic memory
Older adults have problems creating _____ between items in their mind
Links
(fine retrieving single items)
Familiarity recognition memory
Recognizing single items
* Non-hippocampal memory
* Spared in aging because does not depend on hippocampus
* I know I know you from somewhere…
Recollection recognition memory
Recognizing a face AND a context where you encountered it
* Hippocampal memory
* Impaired in aging
* I know you from the dog park and we met yesterday morning
Results of name, face and name-face recognition test on 20 vs 72 years old
- older adults do have overall worse recognition memory compared to younger adults, but older adults were most impaired on the associative task : remembering the name face pairs
- Shows older adults have deficits in their associative memory (not due to general deficits like attention decline)
What were the results of this adaptive cognitive aging study ?
- Young adults (YA)
* High memory performing old adults (Old-high)
* Low memory performing old adults (Old-low)
Looked at their frontal lobes during memory test
Memory test in the scanner showed that YA and Old-low memory recruited the right PFC (important for memory retrieval)
* Old-high recruited the bilateral PFC
* Evidence of neural compensation that can lead to better memory with age
The reminiscence bump
Old adults tend to remember more events from teenage years than any other life period (e.g. music)
Why is there a reminiscence bump ?
Adaptive function of memory
* focus on novel events and experiences critical for self identity
Summary of age-related memory deficits
- Problems forming associations in episodic memory
-Recollection memory : remembering item and context of learning, such as the name of a person or where they met a person, which depends on hippocampus
Note : familiarity is spared - Remembering a single item, such as a face; because does not depend as much on hippocampus
Cases of extreme memory : taxi drivers
Taxi drivers in London have to memorize 25,000 streets within a 10-km radius
- Taxi drivers performed better on spatial memory tests than bus drivers
* Taxi drivers have greater posterior hippocampus grey matter volumes
The volume of the posterior hippocampus in London taxi drivers is related to …
Years of experience as a taxi driver
The posterior hippocampus of London taxi drivers grows with experience because…
More spatial memories are being developed
Highly Superior Autobiographical Memory
- Recalling very detailed daily memories, as if it just occurred
(do not use mnemonics and do not have photographic memory)
Downsides of Highly Superior Autobiographical Memory
Cannot forget painful memories
* Heartbreak; accidents; Deaths of loved ones
- Consistency recalling memories (not forgetting details) relates to OCD symptoms
- Forgetting can be adaptive
Goldilocks principle for memory
Memory works well with
* not too little
* not too much
