Working Memory (Short-term Memory)
- holds a small amount of information for a short period of time
- 3-5 chunks
- predictive of intellectual ability
Types of Long Term Memory
declarative and non-declarative
Declarative Memory
- memory of facts and events
- memories that can be consciously recalled
- 2 types ( episodic and semantic)
Episodic Memory
memory of events
Semantic Memory
memory of facts
Non-declarative (procedural) Memory
- memory of skills and how to do things
- memories are acquired through repetition
“H.M” - Henry Molaison
-suffered from seizures ; had hippocampi taken out ; effected memory
- suffered from anterograde and retrograde amnesia
- no declarative memory but non-declarative remained
Anterograde Amnesia
inability to form new memories
Retrograde Amnesia
inability to recall old memories
Hippocampus
- located in the medial temporal lobes (MTL)
- Multiple areas
Areas CA1
- responsible for primary output from HC to other parts of brain
- damage results in moderate anterograde and minimal retrograde amnesia
Rest of HC proper damaged…
results in severe anterograde amnesia
If whole HC formation is damaged …
retrograde is severe
HC Formation
hippocampus proper,
- new memories
denate gyrus, subiculum, entorhinal cortex
- old memories
Consolidation
-brain forms permanent physical representation of memory
- occurs during long-term potentiation
-occurs a few hours after learning and during sleep
- hippocampus participates in consolidation
- requires glutamate
Retrieval
-accessing stored memories
- requires glutamate
- prefrontal area - direct search for retrieval
Place Cells
- increase firing when individual is in a specific location in an environment
- form a spatial map
Hebb Rule
- “Cells that fire together wire together”
- if an axon of a presynaptic neuron is active while the postsynaptic neuron is firing, the synapse will be strengthened
Long- Term Potentiation
- synapse becomes stronger over time
- forming and recalling memories
Long-Term Depression
- decrease in the strength of the synapse
- forgetting, deleting, making space for new info
Associative LTP
if a weak synapse and a strong synapse on the same postsynaptic neuron are active simultaneously, the weak synapse will be potentiated
Process of LTP
- glutamate is released ; attaches to the receptor : sodium (Na+) depolarizes
- small amount -> triggers AMPA receptors (short-acting)
- large amount -> triggers NMDA receptors (long-lasting)
Structural Changes in LTP
- increased number, enlargement, and growth of dendritic spines
- transport of additional AMPA receptors into the spines
Reconsolidation
- during memory retrieval
- opportunity to refine , correct errors
- opportunity to create false memories
