learning and memory Flashcards
define learning.
response of the brain to environmental events and involves adaptive changes in synaptic connectivity which will alter behaviour.
describe Hebbs hypothesis for how the brain processes and stores information.
‘when an axon of cell A is near enough to excite cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A’s efficiency, as one of the cells firing B is increased.
wha part of the Brian is associated with memory?
hippocampus.
give an example of Hebbs hypothesis.
if association between sight of adult A and their smell of perfume is repeatedly made, synapses of A and B onto hippocampul neurone will be strengthened, so that individual inputs are strong to fire the hippocampul neurone, and just the smell of perfume or picture of adult A is sufficient to recall a memory.
define long-term potentiation.
mechanism underlying synaptic strengthening.
one high frequency electrical stimulation means what for the LTP?
LTP lasts hours
multiple high frequency stimulation means what for the LTP?
LTP lasts days/months
state LTP properties.
temporal - summation of inputs reaches a stimulus threshold that leads to induction of LTP.
associative - simultaneous stimulation of a strong and weak pathway induces LTP at both pathways (spatial summation)
input specific - LTP at one synapse is not propagated to adjacent synapses.
what is happening at the synapse?
- glutamate release onto inactive cell (RMP)
- AMPA receptor activated to create EPSP.
- NMDA receptor blocked by Mg2+ ion.
- depolarisation for AMPA activation not sufficient to Mg2+.
what happens at the synapse when glutamate is released onto active cell?
- AMPA receptor activated
- Mg2+ block on NMDA receptor relived
- Na+ through AMPA and NMDA channels
- Ca+ through NMDA channel
Ca2+ entry through NMDA receptor leads to…
- activation of calcium calmodulin-dependent protein kinase 11.
1. phosphorylates existing AMPA receptors increasing their effectiveness
2. stimulates the insertion of new AMPA receptors into the membrane
Ca2+ entry through NMDA leads to activation of CaMK11, describe this process.
- CaMKII has autocatalytic activity
- when phosphorylated is constitutively activate (no longer requires Ca2+)
- maintains phosphorylation, insertion of AMPA receptors, after the depolarising stimulus has receded
- molecular switch which maintains increased excitability of neurone for minutes to hours.
describe presynaptic events in LTP.
- postsynaptic neurone can feedback to presynaptic neurone by retrograde NT - nitric oxide (NO).
1. Ca2+ through NMDA channel activates NO synthase
2. NO diffuses from site of production and activates guanylyl cyclase in pre-synaptic terminal
3. guanylyl cyclase produces the second messenger cGMP
4. single transduction cascade leads to increased glutamate release from synaptic bouton.
describe the late phase LTP.
- protein synthesis required for long-lasting LTP
- protein synthesis inhibitors prevents consolidation of LT memories and LTP.
- protein synthesis inhibitor injected just post-acquisition inhibit recall
state stages of memory formation.
- acquisition
- consolidation
- recall
