Lecture 7- Learning And Memory Flashcards
What’s declarative memory
Facts and events
What’s nondeclarative memory
Muscle memory, classical conditioning
Cells that fire together
Wire together
Sensory inputs from stimuli processed and converge on a cell in the
Hippocampus, converge on the hippocampus
What is EPSP
Excitatory PostSynaptic Potential
What is long term potentiation (LTP)
Mechanism underlying synaptic strengthening
One high frequency electrical stimulation in the dentate gyrus causes
Long term potentiation to last hours, multiple lasts days
High frequency electrical stimulation permanently changes
The properties of the dentate gyrus
Strong stimulation of synapse results in
Long term potentiation of pathway even when frequency is lower
Properties of Long term potentiation
- Temporal, (repetitive stimulation)
- Input specific, (one synapse not adjacent)
- Associative, (spatial summation, coincidence detection)
Morris water maze with hippocampus leisons
- Spatial learning task
- Will begin to remember where escape platform is
- Rats with hippocampus leisoned doesn’t remember platform location
Morris water maze with NMDA antagonists
- Control found platform quicker each trial
- NMDA antagonist didn’t remember platform, no evidence of LTP
What receptors are essential in LTP
NMDA
Ca2+ entry through NMDA receptor leads to
Activation of CaMKII
What does CaMKII do
- Phosphorylates existing AMPA receptors increasing their effectiveness
- Stimulates the insertion of new AMPA receptors into the membrane
- Larger EPSPs, LTP
CaMKII is known as a
Molecular switch
CaMKII is autocatalytic meaning
It phosphorylates its self
When phosphorylated is constitutively activated it
No longer requires Ca2+
Post synaptic neuron can feed back to presynaptic neuron by
Retrograde neurotransmission- Nitric Oxide, NO
Ca2+ through the NMDA channel activates
Nitric Oxide synthase
NO diffuses from site of production and activated
Guanylyl cyclase in the presynaptic terminal
Guanylyl cyclase produces
The second messenger of cGMP which leads to increased glutamate release from the synaptic bouton
Activating NMDA receptors triggers the events that
Strengthen both the post synaptic and pre synaptic terminals of a synapse
Protein synthesis required for
Long lasting LTP
Protein synthesis inhibitors prevent
The consolidation of long term memories and LTP
Stages of memory formation
- Acquisition
- Consolation
- Recall
If a protein synthesis inhibitor is injected just after acquisition it inhibits
Recall
What is CREB activated by
- Phosphorylation
- Phosphorylated by kinases (eg CaMKII)
Tetanic stimulation is followed by
Development of new synaptic connections
LTP is created in
Slice preparations by High frequency stimulation
Low frequency stimulation can cause
Opposite effects of LTP, rather than increase in EPSP amplitude on further stimulation it’s a decrease
Low frequency stimulation has different or the same process as high frequency stimulation
Same just small amounts of calcium which activates phosphatase, taking off phosphate groups (opposite to kinases)
A decrease after low frequency stimulation results in a
Decrease in depression in the resting membrane state (Long term depression LTD)
What’s phosphorylation
A chemical modification to a protein, adding a chemical onto it
Hippocampal theta activity seems to play a role in
Synchronising activity in different brain regions
Hippocampal theta activity accompanies behaviours such as
Running, swimming, spatially orientated responses
Hippocampal theta rhythms involved in
Arousal, alertnes
Depolarising stimulation coincident with peak of theta wave generates
LTP
Depolarising stimulation coincident with trough of theta wave generates
LTD
Disruption in theta waves causes
Deficits in learning tasks that are similar to hippocampal lesions
A way of enhancing memory is done through
Genetically increasing NMDA receptors
How does age affect memory
- Decreased acquisition in Morris water maze
- Decreased LTP
- Decreased expression of the NMDA receptors
What effect does enrichment have on memory
- Enhanced acquisition in Morris water maze
- Potentiated LTP
Aged mice in impoverished environments show
Greater deficits than those in normal or enriched environments
Strong stimulus of one neuron with weak stimulus of another neurone results in
Both Strengthened stimulation and increase LTP
