Lecture 25 Flashcards
What is Procedural memory?
Skills and association largely unavailable to conscious mind
What is Declarative memory?
Available to conscious mind. Can be encoded in symbols and language
How long does immediate memory last?
Few seconds
How long does short-term memory last?
Seconds or minutes
What is a type of short-term memory which has a limited capacity?
Working memory
How long does long-term memory last?
Days, months, years
How can long-term memories be triggered?
Random events
e. g. olfactory systems
- smells can trigger events that happened many years ago
What does the pre-frontal cortex store?
Working memory
Which structure is essential for converting short to long term memory and stores declarative memory?
the hippocampus
What does the amygdala do?
Multiple, processed sensory inputs (smell)
Implicit/emotional/learnt fear
What does the cerebellum do?
Procedural, sensorimotor
What do hippocampal lesions cause?
Memory loss
Not able to remember declarative memories
What are two theories in which London taxi drivers have larger hippocampuses?
Hippocampus grows with experience
People have larger hippocampus which shrinks over time when lacking stimulation
What is the structure of the hippocampus?
Three layered cortex Unusual development - layers wrap around one another - invagination occurs then fusion Contains different cells Choroid plexus is the main output - neurons project to different parts of the brain
How are long-term memories stored?
Distributed - changes all over the brain
What is the theory of Reverberating circuits?
Memory is not static and stored but some form of constant activity in neurons which can be triggered by some other events
What is the Hebbian synapse concept?
Activity modifiable plastic synapse
Memory is a change in synapse between two neurons
Synapse can become weaker or stronger depending on activity
What is Facilitation?
Synapse become stronger
What is Depression?
Synapse become weaker
What are merits of Depression?
Can lead to different acquisition or memory, so not necessarily “forgetting”
Can be presynaptic, postsynaptic, and depends on different types of memory
What processes affect memory and synaptic plasticity?
Short term:
Ca availability/vesicle depletion
Long term:
Sustained
What affects Long-term potentiation (LTP)?
LTP in hippocampal slices (and elsewhere)
CA1, CA3: connected with each other with a synapse
What is post-“tetanic” LTP?
Can record from CA1 and CA3 neurons
- stimulate electrode and record synaptic potentials
What do high frequency bursts do?
1000Hz neurons starts changing Amplitude of EPSP will increase Can last for years (or even decades!) Specific to input e.g. Different stimulatory electrodes When only CA1 is stimulated CA3 doesn't change - long term specifity
What causes paired LTP?
Simultaneous depolarization of both neurons trigger long term potentiation
- decrease in EPSP
- can last for a long time
Associativity
- link between stimuli e.g. Pavlovian dog
- mechanisms that explains associative form of memory (simultaneous depolarization)
Where does Long term depression (LTD) occur?
Cerebellum
What happens when LTD occurs?
Decrease in amplitude of EPSP
Certain stimulation on neurons decrease EPSP and amplitude
Not simultaneous
What is an animal model for memory investigations?
Aplysia californica
- different invertebrates experience variety of memories
How does Aplysia californica act as a good animal model?
Gill withdrawal reflex - animal doesn't like to be touched - withdraws gills into body Have big neurons (easy to record) Simple nervous system (Humans: billions of neurons, Aplysia: thousands of neurons)
What does Gill habituation reflex show?
Habituation
- keep touching gills then animal stops withdrawing gilk
Short-term sensitization
Long-term sensitization
What are two types of conditioning?
Classical (pavlovian) and operant (skinner)
How would short-term sensitization show in Aplysia?
Repeated gentle stimuli to siphon causes reduced gill withdrawal
Pair single tail pinch (aversive) with siphon touch
- Re-establish siphon reflex
- Short-term 60 mins
How would long-term sensitization show in Aplysia?
Repeated pairing of siphon touch and tail pinch
Non-habituating siphon/gill reflex
What is needed in LTP and LTD?
Require receptor activation (glutamate, serotonin)
- post-synaptic
- AMPA receptors
- NMDA receptors
Second messengers (cAMP, Ca)
Involve biochemical and structural pre and post synaptic changes
How are AMPA receptors involved in LTP and LTD?
Ionotropic regulated by glutamate
Open as long as glutamate is bound
Responsible for depolarization
How are NMDA receptors involved in LTP and LTD?
Ca channel
Flow of Ca is important
What is considered to be important in memory formation?
Altered synaptic responsivity
What is needed to long-term changes?
Require protein phosphorylation changes in early stages
Require protein synthesis for late stages
How does LTP occur?
Evidence suggests often a post-synaptic event
Most indicate a critical role for Ca
Involves trafficking of AMPA receptors to the post-synaptic membrane
