Flashcards
Lecture 9 - The Remembering Brain 2
Cards in this deck (47)
- 1How is episodic memory defined?Many criteria on which episodic memory differs from other kinds of memory, but which of those are most important varies among researchers.
Some emphasize 1st person subjective sense of 'mental time travel' that accompanies the retrieval of episodic memory.
Others emphasize ability to link disparate pieces of an experience together to create coherent memory.
Many emphasize episodic memory's importance for situating a past experience within a particular time and place, and the ability to recollect those contextual details. - 2Why does the way episodic memory is defined matter?The way episodic memory is conceptualized influences the way it is studied.
- 3Why is it difficult to study retrograde amnesia in patients with brain damage?Because these studies rely on retrospective tests.
- it is difficult to compare performance across time points.
- the extent of the damage varies from one case to another.
- real life memories are complex - how do you score a change in vividness of the memory? - 4What can researchers use to study the relationship between hippocampal damage and retrograde amnesia?Animal models enable researchers to study the relationships between hippocampal damage and retrograde amnesia.
Can create brain damage in animals. - 5How can researchers test this on animals?Researchers must use tasks that require animals to represent complex relations among stimuli e.g. integrate contextual, spatial or temporal information.
- 6What is one way we can study contextual memory in animals?Contextual conditioning:
Many learning and memory processes involved in acquiring and expressing info about contexts.
Exposing animals to novel contexts results in a memory of that context.
If that context is subsequently paired with an aversive stimulus it will yield an association between the context and shock - a context memory that can be tested. - 7What did Maren, Phan and Liberzon (2013) show in their contextual conditioning study?Placed rat in new context (blue box) - context encoding.
Context conditioning :
Unsignalled - rat given electric shock whilst in blue box. Then when placed in blue box in future, exhibits fear. But no fear when in purple box. Context memory
Signalled - rat hears bell and receives shock whilst in blue box. Then when placed in blue box in future, exhibits fear (context memory). When placed in purple box and hears bell, exhibits fear (item memory).
Can separate context and item memory - 8What is the difference between cue and context processing?The brain has separate, parallel systems for processing cues (e.g. snake) and contexts (e.g. woodland).
- 9What task can be used to test episodic like memory in animals?The-what-where-which task
- 10What is the what-where-which task?Animal placed in blue box.
Then in stripy box - objects switched.
Then in blue - two identical objects presented. Never seen ball on left before in that context, but have seen blue on right in that context.
Left ball should be treated as novel.
Find:
Animals show interest in left ball, suggesting they have retrieved previous situation.
Delay manipulated to see how long episodic memory lasts. - 11What is the what-where-which task seen as?A gold standard for studying episodic memory in animals which emphasizes the ability to situate a stimulus in a context.
- 12What are the neural mechanisms of episodic like memory in animals?Lesions within the hippocampal system impair rat performance on WWW task but not on tasks which taxed sub components of this ability (what-where and what-which)
- 13What could this single dissociation be due to?Due to differences in difficulty.
3 components harder than 2 components. - 14What evidence is there for a double dissociation?Other rats with lesions outside the hippocampal system were impaired at what-which but not impaired at WWW.
- 15What is the role of the hippocampus?Binding items and their context together
Info from different cortical modules bound to form a single episode. - 16What did Horner et al show about the role of the hippocampus in binding?People shown object-person-location combinations e.g. hammer, Obama, kitchen.
Pairs of words were reinforced e.g. Obama-hammer
2 conditions:
Coherent episode condition (closed loop)
Less coherent episode condition (open loop)
Then tested - 'Obama' choose correct location. How confident?
Coherent episode condition - encourages encoding of single episode.
If ppt encode the target items as events in an episode, likelihood of retrieving one item will be statistically related to the likelihood of retrieving another item from the same episode.
Dependency was found to be sig higher in closed loop conditions.
- 17What neural predictions did Horner et al make?If hippocampus that binds together the elements of an event then:
1. During encoding, the signal associated with successful encoding in the hippocampus will be stronger when items are bound into a single, coherent episode.
2. During retrieval, when ppts see a single item, the hippocampus will 'reinstate' all elements of the episode (the context).
-Retrieval of any one element from an event should coincide with activation of neurons corresponding to all events elements. - 18What is the subsequent memory paradigm?Prevalent paradigm in study of memory
Helps us to understand how encoding processes drive subsequent memory for encoded items. - 19What are a couple of unrelated studies to explain the subsequent memory paradigm?Paller and Wagner:
People encoded words, then given memory test. Some items were forgotten, some were remembered.
Researchers take these items and go back to time of recording e.g. EEG or fMRI and look at neural signal collected for that item.
Signal for remembered and the signal for forgotten are compared.
Found:
left medial temporal lobe and left inferior PFC - higher signal for remembered items over forgotten.
Lower left VLPFC and hippocampus activation predicts later forgetting.
VLPFC may play a role in situating an item in context.
Kensinger and Corkin 2004:
Remember-know paradigm
Remember - recollection
Know - familiarization
Items were arousal related; valence only (sad but less arousing); neutral.
Found:
Stronger signals in hippocampus for remembered words than forgotten words for all 3 conditions.
Amygdala - more sensitive to successful encoding of highly arousing words.
L inferior PFC - more sensitive to successful encoding of valence only and neutral words.
See double dissociation. - 20What does the subsequent memory paradigm show in Horner et al's study?Items from each episode were encoded 3 times and each of the 3 encoding trials was analysed separately.
Hippocampal activation predicted successful retrieval of all pairs of the event.
In the 3rd encoding trials, this was stronger in the closed loop > open-loop condition.
This is consistent with the idea that the hippocampus binds multiple items into a single coherent episode. - 21Which brain regions activated when ppts retrieved the 3 items of each episode?The different types of elements comprising each event produced region specific activity.
Location - parahippocampal gyrus.
People - medial frontal cortex
Object/animal - lateral parietal cortex - 22How did the activity in these specific regions differ for closed loop and open loop conditions?Researchers examined the signal in location region when ppts retrieved people or objects.
Found:
Activation in this region was stronger in closed loop > open loop condition.
Same for all 3 regions.
Called neocortical non-target reinstatement - 23How did the relation of neocortical non-target reinstatement and activity in hippocampus differ in closed loop compared to the open loop condition?Neocortical non-target reinstatement was related to activity in the hippocampus more so in closed loop > open loop condition.
Evidence that the hippocampus is associated with a reactivation of item memory traces if they were encoded in the same episode. - 24What is long term memory consolidation?'to make firm'
Progressive post-acquisition stabilization of LTM = the process by which moment-to-moment changes in brain activity are translated into permanent structural changes. - 25Why do memories need to be consolidated?More susceptible to interference before consolidation.
- 26What finding supports this claim?The finding described in Jost's law
- 27What is Jost's law?If 2 memories are of the same strength but different ages, the older will decay more slowly than the younger.
- 28What is a hypothetical example of Jost's law?List 1 learnt to an initial level of 10 items recalled.
After 20 units of time, during which some of List 1 items were forgotten, List 2 was learnt to a level of 8 items recalled.
The younger traces are lost at a relatively fast rate. - 29What are the 2 types of consolidation?Consolidation involves reorganization at both synaptic and system levels.
Synaptic consolidation - stabilization of changes in synaptic connectivity in localized circuits.
- growth of new synaptic connections
- restructuring of existing ones
- can be indexed with long-term potentiation.
Systems consolidation:
- time dependent shift in the circuits that support memory recall
-time limited role of hippocampus. - 30According to Dudai 2004, what are the time expectancy of these two types of consolidation?Synaptic - minutes to hours
Systems - days to months - 31What is the core mechanism in consolidation models?Memory reactivation:
Reactivation of the hippocampal memory trace is thought to lead to the reinstatement of experience-dependent patterns of neural activity in the cortex.
Such reactivation results in stabilization and refinement of cortical traces.
Eventually leading to storage and recall becoming completely dependent on cortex, and independent of the hippocampus. - 32What is the neural structure involved in system consolidation?Many believe the hippocampus (and related regions link together different kinds of info in many regions on brain.
Initially - hippocampus plays active role in binding the activity of disparate cortical modules.
Over time - hippocampus plays less of a role - 33How did evidence for a contextual conditioning study support the time limited role of the hippocampus?Kim & Fanselow 1992 - contextual conditioning
Tone and shock in a certain context: rats freeze
Test - rats put back in context (no tone/shock)
Found:
Hippocampus lesion 1 day after learning - reduced learning
Hippocampus lesion at 7 days - less impaired
Hippocampus lesion at 28 days - normal freezing shown
But hippocampus lesion does not impair freezing to tone. - 34What disorder provides evidence for consolidation?Amnesia
To explain retrograde memory loss, we assume old memories are not fully consolidated at the time of injury. - 35What is retrograde amnesia? What is anterograde amnesia?Retrograde - inability to retrieve old memories before incident.
Anterograde - inability to form new memories. - 36What is the temporal gradient of retrograde amnesia?Before the incident:
Most previously memories worse recalled than memories from longer ago. - 37What are the 5 explanations for temporal gradients in amnesia?1. Temporal gradient can arise due to stimuli not being carefully matched across decades - stimuli for more remote decades are easier.
2. Apparent loss of retrograde knowledge is anterograde amnesia in disguise. Alcoholics who go on to develop Korsakoff's syndrome may not have fully encoded the memories in the first instance. Can't account for all cases but may for some.
3. Older memories became more semantic-like and less episodic with passing of time due to more rehearsal. Become more like stories than memories.
4. Each time an old event is remembered, this creates a new memory for that event. The older the event, the greater the number of traces and the more resilient to brain damage it will be .
5. The hippocampus has a time limited role and the more consolidated the memory is, the less dependent on the hippocampus it is. - 38Who was patient PZ?Butters (1984):
Uni professor who had Korsakoff syndrome at age 65.
Had written papers and book chapters before this. Completed an autobiography 2 years prior to onset of amnesia.
Unable to learn new paired associates.
Remembered some famous people from 30-40s but not later. - 39What is an issue of testing PZ with famous people?Performance may have been due to difficulty - stimuli for earlier decades easier.
- 40How was this issue overcome?Replicated experiment with famous scientists.
- 41What were the results of PZ's famous scientists test?Control - eminent scientist from PZ specialization, also 65.
PZ demonstrated loss of knowledge of professional colleagues.
After 1965 - many more of PZ's answers receive 0 score (incorrect) compared to control.
Before 1965 - memory better for this than info learned about 1965. But still didn't always get fully correct answers. - 42What did the results from PZ's test of events taken from his autobiography show?Patient PZ demonstrated severe retrograde amnesia which was temporally graded:
-remembered earlier events in autobiography better than events just before his amnesia onset. - 43What do these results suggest about the cause of retrograde amnesia?Retrograde amnesia cannot be due to poor encoding e.g. as a result of alcoholism - because he wrote about it in his autobiography.
or poor stimulus selection (due to importance of stimuli) - 44What is semantic dementia due to?Damage to anterior temporal lobes (cortex)
- 45What is Alzheimer's disease due to?Damage to hippocampus and related structures.
- 46What did Nestor et al (2002) find temporal gradients in amnesia and semantic dementia?Controls remembered childhood, early adulthood and recent events to similar extent.
SD patients - remembered recent events but not old events because memories not yet dependent on cortex, yet to be transferred out of hippocampus. Consistent with Squire's time limited role of hippocampus hypothesis. - 47What questions remain in consolidation research?Synaptic consolidation is thought to depend on synthesis of new proteins in neurons.
Classic findings show impaired memory after injection of protein synthesis inhibitors.
Cycloheximide - protein synthesis inhibitor
Gisquet-Vessier's findings pose a challenge to understanding of synaptic consolidation. Found memories can be maintained without protein synthesis.
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- Semester 2 (Cognitive Neuroscience) Flashcards on Lecture 9 - The Remembering Brain 2, created by Jess Grange on 03/05/2019.
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