long-term memory Flashcards
steps from DNA to protein (3)
- transcription: DNA transcribed to mRNA in nucleus
- translation: mRNA transported from nucleus to cytoplasm (or distal sites); translated in cytoplasm by ribosomes
- PTMs: changes (phosphorylation) to protein
difference bw STM and LTM in terms of transcription/translation
LTM require transcription/translation, STM don’t
inducing STF and LTF with shocks/5HT
STF: one shock/one application of 5HT to isolated sensory-motor neurons -> lasts about 30 min
LTF: 5 spaced shocks/applications of 5HT -> lasts at least 24h; multiple training days leads to LTF lasting 1 week
molecular mechanisms of memories that last different times (2)
STM -> phosphorylation
LTM -> phosphorylation, translation & transcription, new synapses
arguments against ‘transcription required for memory’ (2)
- transcription only occurs in nucleus; memories stored in synapses
- transcription may be necessary, but not instructive (no transcription -> less proteins needed for memory; but proteins maybe not necessary during learning)
how do TFs regulate gene expression (2)
- recruiting enzymes that make RNA from DNA (RNA polymerase)
- recruiting enzymes that open up DNA for transcription by modifying histones
TF required for LTF
CREB
effect of blocking CREB
blocked LTF without blocking STF
what activates CREB
5HT
how did they find CREB (3)
- cAMP was increased by 5HT so looked for cAMP-dep TF
- found small sequence necessary and sufficient for mRNA to be transcribed when cAMP levels high (CRE)
- found TF that bound to CRE -> CREB
which factors regulate CREB activity (2)
- CREB activator
- CREB repressor
what proteins does CREB recruit and when does it recruit them
proteins that recruit RNA polymerase; when it is phosphorylated
activation of … and removal of … required for transcription
CREB kinases; CREB repressor
complexes formed by CREB (2)
- dimerizes with itself
- dimer with repressor
how does training that induces learning affect CREB complex
reduces level of CREB repressor
effect of reducing/removing CREB repressor
easier to activate CREB, but still requires some stimulation; LTM formed more easily
how do multiple training periods lead to LTF
multiple training periods required to activate transcription, leading to LTF
how convert stimuli that normally gives STF, to one that gives LTF
activating CREB
effects of (a) 5HT x 1 (b) 5HT x 5 (c) 5HT x 1 + anti-CREB repressor
(a) STM
(b) STM + LTM
(c) STM + LTM
effect of overexpressing CREB inhibitor
blocks long term odor avoidance memory in drosophila
effect of removing CREB
prevents LTM
effect of overexpressing CREB on stimulus
converts stimulus that usually doesn’t induce LTM to one that does
variation of neurons that encode memory in different species
aplysia -> in every animal, same neuron (invariant)
more complex nervous system -> neurons not invariant
how test if neurons that activate transcription during learning also reactivated during recall
- put marker turned on by gene expression at time of learning -> can recognize neurons later
- when animals remember (recall), do same neurons specifically turn on gene expression again