short-term memory Flashcards
what is a memory
change in behavior of the organism = memory of the experience that caused the change
what kind of change must happen so an experience has an impact on future behavior
physical change; molecular or biochemical change in function of the neuron
how can computers make memories (3)
- charging a capacitor
- making a very small magnetic field (hard drive)
- quantum electrical tunneling (USB keys)
biological ways of storing memories (6)
- changes in phosphorylation state
- insertion or removal of membrane proteins
- persistent activation of protein kinases
- production of new proteins
- morphological changes at pre-existing synapses
- new synapses
reductionist approach to discover how biological organisms replicate (4)
- define question: how do biological organisms replicate?
- find simple system that still gives insight into question: 1 bacteriophage infects a bacteria; 20 minutes later, 100 bacteriophages come out
- use system to reduce question as much as possible: what molecules do bacteriophages replicate in the bacteria?
- answer question: DNA
reductionist approach to discover how DNA replicates (4)
- question: what about DNA allows it to replicate?
- simple system: x-ray crystallography of DNA
- reduce question: can’t reduce it further
- answer: double helix
reductionist approach to how memories are made (4)
- question: how are memories made?
- simple system: aplysia have large invariant neurons and they make memories
- reduce question: which neurons store the memory and how do those neurons change after memories are made?
- answer: sensory neurons; change in protein phosphorylation
habituation vs sensitization in aplysia
habituation: decrease in defensive reflex due to repetitive non-noxious stimulation
sensitization: increase in defensive reflex due to noxious stimulus
what kind of stimulus creates habituation and sensitization
conditioned stimulus triggers habituation; unconditioned (shock) stimulus triggers sensitization
what are non-associative memories
learning that doesn’t require association bw conditioned and unconditioned stimuli
change in aplysia behavior when sensitized and habituated
sensitizes: noxious stimulus to head/tail causes increase in time and extent of gill withdrawal to touch to siphon
habituated: repetitive touches to siphon causes decreased gill withdrawal (without shock)
how do you measure synaptic strength
- place electrode in post-synaptic cell
- fire AP in pre-synaptic cell
- measure voltage change (post-synaptic potential) -> measures synaptic strength
EPSP while stimulating siphon of aplysia every 10 min
with every touch (10 min interval), the EPSP decreases -> habituation
EPSP after habituation and coupled with shock
increased EPSP -> sensitization (novel stimulus)
effect of habituation on sensory and motor neuron of aplysia
didn’t decrease the ability of the sensory neuron to fire APs; decreased size of EPSP in motor neuron
effect of sensitization on sensory and motor neuron of aplysia
increased EPSP in motor neuron after single AP in sensory neuron
what mimics shocking the tail/stimulating the nerve of aplysia
application of 5HT
action of 5HT on synaptic strength
sufficient to increase synaptic strength bw sensory and motor neurons
effect of removing 5HT-containing neurons on synaptic strength
reduced sensitization
action of 5HT during sensitization (2)
- 5HT-containing neurons fire during sensitization
- 5HT released during sensitization
circuit underlying sensitization in aplysia (5)
- shock to tail -> activates sensory neuron
- sensory neuron activates 5HT neuron
- release of 5HT on sensory neuron in siphon + motor neuron
- siphon sensory neuron synapses motor neuron
- motor neuron causes gill withdrawal
behavioral habituation and cellular depression
behavioral habituation -> repeated touches leads to decreased withdrawal;
repeated touches = repeated firing of sensory neuron -> leads to less release and decrease of EPSP to motor neuron -> decreased withdrawal
behavioral sensitization and cellular facilitation
behavioral sensitization -> shocking tail/head leads to increase of withdrawal; shocking nerve/adding 5HT -> more release and increase of EPSP to motor neuron -> increased withdrawal
how can synaptic strength be increased (3)
- releasing more transmitter/AP
- increase effect of releasing same amount of transmitter by having bigger post-synaptic response (increase chance of NT release)
- more synapses