Long term memory part 2 Flashcards
Implicit Memory: Priming
Change in stimulus processing due to prior exposure to same or
related stimulus without conscious awareness
Perceptual
Priming: Warrington and Weiskrantz (1968)
Korsakoff’s syndrome patients
- Amnesia due to severe alcoholism
- Task:
- Show fragmented pictures (Gollin
figures) - Identify object in as few frames as
possible
Participants improved day to day, despite
not…
remembering the previous day’s
training
* Fewer frames needed to identify object
Semantic priming
A process where exposure to one word (prime) speeds up the response to a related word.
Lexical decision: word or non-word?
Determine whether a string of letters is a valid word or a non-word.
Example: Deciding if “apple” is a word or “plapple” is not.
Significance: Measures the speed and accuracy of word recognition, providing insight into lexical processing in the brain.
Semantic priming( Will Ps)
Will Ps be faster at identifying a
word if primed with a related word vs an unrelated word?…
YES!
* Prime words activate other related words in your mind
Neural basis of Priming
Perceptual priming:
* Sensory cortices (e.g. occipital lobe for vision)
- Conceptual/semantic priming:
- Unimodal & multimodal association cortices (e.g. anterior temporal, inferior parietal, prefrontal cortex)
Explicit Memory: Semantic Memory
Memory for facts, concepts, and general knowledge, independent of personal experience.
Sensory/Functional Theory:
Proposes that we store concepts based on their sensory properties (e.g., visual or auditory) or their functional use (e.g., how something is used)
Domain-Specific Theory:
Proposes that the brain has specialized systems for processing different types of knowledge, such as concepts related to living things, tools, or social information.
How Are Meanings Organized in the Brain?
Meaning is partly categorical (tools vs.
animals)
- Meaning also depends on shared sensory
and functional features (action-related vs.
perceptual)
How are new
semantic
memories
formed?
We often start with episodic memories and over
time (after many activations and retrievals), they
convert into semantic memories
Encoding of episodic memory.
Sensory input is processed with attention, deep processing, and emotional context, primarily by the hippocampus, and then consolidated into long-term memory.
Retrieval of episodic memory
Episodic memory is retrieved by reactivating the hippocampus and associated cortical areas, based on cues like context, emotions, and sensory details.
Parahippocampal cortex
encoding
spatial layout and visuospatial memory
Perirhinal cortex
object recognition/
familiarity
* Binds features of objects
Entorhinal cortex
integrative function
for input/ output to hippocampus.
Hippocampus
formation and
consolidation of memory + spatial navigation
Fornix
pathway from hippocampus to other cortical/ subcortical structures
Medial temporal lobes & H.M
Bilateral resection of
hippocampus, entorhinal
cortex and parahippocampal cortex
Amnesia
Severe anterograde amnesia
* Unable to form new LTMs after surgery
- Temporally-graded retrograde
amnesia - Unable to recall existing LTMs from
just before the surgery
Cognitive map theory
The medial temporal lobes, especially the hippocampus, help create mental maps of spatial environments.
Place Cells
Neurons in the hippocampus that become active when an individual is in a specific location in their environment.
Relational memory theory
The medial temporal lobes, particularly the hippocampus, are crucial for forming and retrieving memories that involve relationships between different pieces of information (e.g., people, places, events).
Hebbian Learning
“Neurons that fire together wire together”
When presynaptic action potential leads to postsynaptic action potential, connection is strengthened
Hebbian learning & LTP
Long-term potentiation
* Increase in synaptic strength
- Exhibits necessary properties for Hebbian learning
- Found in hippocampus (and other brain regions)
Early LTP
Increased presynaptic release of
neurotransmitter
- Increased number of
postsynaptic receptors
Late LTP
Increased number of dendritic spines and synapses.
Long-term depression (LTD)
When presynaptic action potential doesn’t lead to a postsynaptic action potential, the connection between neurons is weakened.
Mechanism: This leads to a reduction in neurotransmitter release, number of receptors, and synapses, weakening the synaptic connection.
Episodic
retrieval = reconstruction
Retrieval is a “best guess” based on:
Memory trace
Genes
Past experience
Internal state
Environmental context
Lab activity: False
Memory
Explore how false memories can be created in a controlled environment.
Method:
Participants are exposed to misleading information or suggestions.
Memory retrieval tasks are used to see if false memories emerge.
Consolidation
new memories rely on cortical representations and hippocampal links. Over time, retrieval and sleep replay reduce hippocampal dependence. Old memories depend on cortical representations and links.
Complementary learning systems hypothesis. ( why have two memory systems)
Hippocampus: Rapid learning, distinct event memories, key for episodic memory.
Cortex: Slow learning, generalization across events, key for semantic memory.
Is the distinction “new” versus “old” or “episodic” versus “semantic”?
New semantic information often begins as episodic memory (“I just learned that…”).
Over time, old autobiographical memories can become more semantic (“Have you heard the one about…”).
Is consolidation a “permanent” process?
Old idea:
Once a memory is formed it is more or less permanent
- New idea:
Reconsolidation: When a memory is retrieved, it is reformed, and is once
again subject to interference
Reconsolidation
Conclusions
* Recall/reactivation leads to reconsolidation
* If memory re-formation is blocked during reconsolidation, then the
memory is forgotten!
- Since this study, reconsolidation has been demonstrated in many
LTM systems across many organisms, including humans
Long-Term Memory (LTM) Types & Systems( declarative)
Explicit (Declarative): Conscious recall
Episodic: Personal experiences
Semantic: General knowledge
Long-Term Memory (LTM) Types & Systems( Non declarative)
Implicit (Nondeclarative): Unconscious skills & habits
Procedural: Motor skills
Priming & Conditioning: Learned associations
