Hippocampus and Memory Flashcards
What is the result of a hippocampal lesion?
Anterograde episodic amnesia
What are the 2 main types of long-term memory?
Declarative
Non-declarative
What are the 2 types of declarative memory?
Episodic
Semantic
What are the 4 types of non-declarative memory?
Procedural
Priming
Classical conditioning
Non-associative learning
What is the Standard Consolidation model of declarative memory?
Fast-changing connections between medial temporal lobe (MTL) and 2 cortical areas - change when remembering info
Slow-changing connections between 2 cortical areas - change when memory becomes embedded
MTL binds together cortical memory traces - by repeated reactivation - become independent of MTL
What is the evidence against the SC model of declarative memory?
Individuals with developmental hippocampal damage
Impaired episodic memory
Normal semantic knowledge
Dissociation between semantic and episodic memory
Is the hippocampus required for semantic recall?
No
Is the hippocampus required for episodic recall?
Yes
What is the evidence against a permanent role of the MTL in declarative memory?
Graded retrograde amnesia in MTL lesion patients
Gradient from loss of recent memory - preservation of remote memory
What is the Multiple Trace theory of declarative memory?
Episodic memories stored in hippocampus
Every time event remembered - make new memory trace in hippocampus - overlaps old traces
Re-encoding memory multiple times causes them to be semanticised - integrates with semantic memory stores
Episodic component of memory (spatial and temporal context) requires hippocampus
Semantic component (basic event outline) does not
Define encoding
Linking neurons into networks that can store memories
Define consolidation
Strengthening memory traces
What are Martin et al.’s (2000) 4 proposed tests for the synaptic plasticity and memory hypothesis?
Detectability - of LTP after learning
Anterograde alteration - if LTP disruption blocks learning
Retrograde alteration - if disruption of established LTP disrupts previously-acquired memories
Mimicry - artificially induce memory using LTP
What is traditionally thought to be the role of PKMzeta?
LTP maintenance
What does ZIP do?
Prevents PKMzeta auto-catalysis
What is the currant bun model of memory storage?
Memory trace involves potentiation in some CA1 cells - but not others
What are the 2 types of oscillations involved in memory in the hippocampus?
Theta
Sharp wave ripples
When do theta oscillations occur in the hippocampus and what is their role?
During active experience
Online learning - encoding
When do sharp wave ripples occur in the hippocampus and what is their role?
During offline post-learning phases
Post-experience consolidation - e.g. slow wave sleep
What is the effect of shutting down the hippocampus during sharp wave ripples in sleep?
Impairs learning - no memory consolidation
What is a possible neural mechanism for system consolidation?
Reactivation
What is likely to be the purpose of sequential place cell reactivation during slow wave sleep?
Strengthen connections between neurons that fired together
Enable episodic memory - link objects/events to places
Define pattern completion
Process where system can recover entire familiar stimulus - when presented with only part of it
Which process is performed by auto-associative networks for memory retrieval?
Pattern completion
What are the 2 components of auto-associative networks that enables them to perform pattern completion?
Dense recurrent collateral projections
Recurrent synapses strengthened by Hebbian plasticity - simultaneous pre- and post-synaptic spike
Which area of the hippocampus may be an auto-associative network?
CA3
