8 The Remembering Brain Flashcards
long term memory consists of
declarative and non delcarative
what is declarative memory
explicit memory
what is non declarative
implicit memory
short term memory
sensory memory
working memory
what does declarative memory consist of
events - episodic memory
facts - semantic memory
what is episodic memory
specific personal experiences from a particular time and place
what is semantic memory
world, object, language knowlege, conceptual priming
what does non-declarative memory consist of
procedural memory
preceptual representation system
classical conditioning
nonassociative learning
what is procedural memory
skills - motor and cognitive
what is procedural memory
skills - motor and cognitive
what is perceptual representation system
perceptual priming
what is classical conditioning
conditioned responses between two stimuli
what is nonassociative learning
habituation
sensitization
the structure-function relationship
• But function and structure do not match
exactly • A structure can participate in multiple
functions • A function may rely on multiple structures
multiple memory systems for episodic and semantic memories
medial temporal lobe
middle diencephalon
neocortex
memory system for procedural memory
basal ganglia and skeletal muscle
memory system for perceptual representation system
perceptual and association neocortex
memory system for classical conditioning
cerebellum
memory system for nonassociative learning
reflex pathways
definitions of episodic memory
Episodic memory is the system responsible for encoding storing and retrieving memories for personal events and episodes
Definitions depending on criteria emphasised in definitions
episodic memory and mental time travel
Mental time travel: Tulving’s definition emphasised the first-person ”mental time travel” – emphasis on re-experience
episodic memory and links
Links: Ability to create links between unrelated bits of information, making a
coherent episode – emphasis on relational memory
episodic memory and time and place
Time and Place: placing a past experience within a particular time and place- emphasis
on context
what is retrival success dependent on in time and space episodic memory
Retrieval success is dependent on the ability to recollect these contextual details including the spatial-temporal context in which something took place
what is episodic memory
Episodic memory is the result of associative learning
• The what, where, when and who of an episode (its context) are associated and bound together
• They can then be retrieved (and reexperienced) as a single episode
• Autobiographical memory: Personal memory
• Events from personal past (like EM)
• Semantic personal past (facts about oneself e.g., address)
the MTL
The MTL is not a single structure its a group of structures deep inside the temporal lobe
what does the hippocampus consist of
Hippocampus
3 cortical regions of the medial temporal lobe
Sometimes referred to as the parahippocampal gyrus
what is in the hippocampus
entorhinal cortex
rhinal sulcus
perirhinal cortex
parahippocampal cortex
parrahipocampal gyrus
rhinal sulcus
perirhinal cortex
parahippocampal cortex
the hippocampus
resembles a seahorse
hippocampus includes 3 main areas
dentate gyrus
cornu ammonis subfields CA1,2,3,4
subiculum
cornu ammonis subfields (CA)
Subregions depending on the type of brain cells you can see in these regions
CA- Cornu ammonis - rams horn - resembles horn like shape
CA3 and CA1 - the largest - studied more extensively
CA2 CA4 - smaller not been studied very systematically
information flow description
Hippocampus belongs to the medial temporal lobe system
Information flows from the cortical regions of the MTL via the entorhinal cortex into the various sub field of the hippocampus
Information is also going away from the entorhinal cortex and then the rest of the cortical regions of the MTL creating therefore a loop of information processing
information flow -
entorhinal cortex perforant pathway dentate gyrus hippo ca3 hippo ca1 hippo subiculum
information flow within the MTL
- Hierarchical organisation of the MTL: information is initially collected through the perirhinal and parahippocampal cortices.
- Then passes to the entorhinal cortex, and ultimately reaches the hippocampus
- The cortical regions, however, do not merely funnel information to the hippocampus
- A large network of connections both within and among the subregions of the MTL cortical regions perform extensive information processing
extended MTL system
thalamus
prefrontal cortex
memory systems and amnesia
- We have learned a great deal about memory organisation by studying amnesia
- Amnesia can arise from neurosurgery (e.g. patient HM), strokes, head injury, certain viruses or as a symptom of long-term alcoholism (Korsakoff’s syndrome)
- Difficulties in acquiring new memories (anterograde amnesia) and remembering events from before their brain injury (retrograde amnesia)
retrograde amnesia
memory impairment for information acquired prior to the cause of amnesia
inability to retrieve memories from the past from the period before the damage
anterograde amnesia
deficit in learning new information after the onset of amnesia
Inability to form new memories after the damage has occurred
Normally older memories before the damage may still be accessible
More common
can retrograde and antergrade amnesia coincide
Both types may coincide - especially if damage in the brain is more diffused and spread out - global amnesia -
Affects access to both remote memories from the past and impairs commitment of new memories in the LTM storage
HM
lobectomy
• Included removal of the hippocampus and amygdala
o History:
• Suffered from severe, intractable epilepsy
• Foci in both medial temporal lobes
• Treated with bilateral medial temporal
what happened to HM
o The Good:
• Reduced convulsions (severity and frequency)
• Improved IQ (from 104 to 118)
o The Bad:
• Minor retrograde amnesia (for events within the 2 years preceding the surgery)
o And the Ugly:
• Profound anterograde amnesia: could not form long-term memories for events after surgery
medial temporal lobectomy
removed portions of medial temporal lobes - important role in memory
HMs anterograde amnesia
- Preserved memory of the past, and had good short-term/working memory
- Could not form new long-term memories
- Global amnesia: affecting all sensory modalities
- Problems were limited to declarative/explicit memory
If HM engaged his working memory by repeating a number he was able to retain it in memory for about 15 minutes but this was only possible if working memory was continuously active through verbal representation
He could not form new LTM - beyond the capacity of STM if he didn’t engage his working memory then information would vanish
digit span +1 test
Normal subjects à up to 18 digits • After 25 trials of this task, H.M. still could not
successfully repeat more than 7 digits
• H.M.’s main deficit: related to the transfr of information from a functioning STM to a stable LTM
HM implicit memory - mirror drawing task
- Retention of certain types of tasks by improved performance
- Explicit (declarative) vs Implicit (non-declarative) memory
Trace a star remaining within the borders
Only able to see drawing in reflection in mirror
Practicing - HM performance improved
Substantial increase in performance
Approached task as it was the first time
No conscious memory of performing the task
Improved performance demonstrated that he could retain certain types of tasks in his LTM - implicit aspects of LTM
what are the two types of amnesia
anterograde and retrograde
damage to the MTL produces
Damage in the MTL produces anterograde amnesia and variable levels of retrograde
amnesia
- STM/working memory normally intact
- Implicit memory intact – explicit impaired
• MTL critical for making new memories and retrieving old (but see consolidation
section below)
what does the subsequent memory paradigm aim to do
Aims to evaluate encoding-phase activity leading to successful (versus unsuccessful memory)
subsequent memory paradigm
Experimental paradigm
Evaluate how activity at encoding leads to successful or unsuccessful memory formation
Can Brain activity at the tine of encoding predict later memory outcomes
Recording neural responses whilst pps encoding a series of words
Seen each words or not
Test memory of words
Remember or forgotten
Compare brain response for later remembered and later forgotten
wagner et al 1998 - remembered vs forgotten stimuli
Activity in the left ventrolateral PFC (a) and the left MTL (b) was predictive of later remembered versus forgotten stimuli.
Should be activation within the MTL
Discriminates between later remembered vs later forgotten
This activity would indicate the successful registering of information into memory
Ability to recognise stimuli as previously encountered ones is supported by MTL at the time of registering these memories
what is familiarity
Familiarity: sense of memory that a stimulus has been encountered before
Presentation of stimulus in brain matches visual stimulus in front of us
No recall of information is taking place
Just recognising something that has been encountered before
what is recollection
Recollection: memory for the context or other associative information about a previous encounter with a stimulus
Old - recollecting additional details about context or details related to item
Remember specific event
Recall info about previous encounter
cued recall
hippocampus as binder of relational memories
- According to the model proposed by Eichenbaum et al. (2007):
- The perirhinal cortex processes item representations (important for familiarity)
- the parahippocampal cortex is assumed to process “context” (including scene perception)
- The hippocampus binds items in context (important for recollection
what does the perirhinal cortex process
The perirhinal cortex processes item representations (important for familiarity)
familiarity
visual features
what does the parahippocampal cortex process
• the parahippocampal cortex is assumed to process “context” (including scene perception)
scene perception
