Synaptic Plasticity

what is Hebbian theory?

When A & B fire APs at the same time, the connection between them becomes stronger (Neurons that fire together, wire together)

What is synaptic plasticity?

A change in the strength of synaptic communication between two neurons.

what are the 4 general properties of Long-Term Potentiation (LTP)?

1) Input specificity 2) Associativity 3) Cooperativity 4) Persistence

what is input specificity?

changes in synaptic strength occurs specifically between presynaptic neuron A and postsynaptic neuron B that are simultaneously active together

what is associativity?

a weak stimulus in one pathway isn't enough to elicit LTP, however if paired with activity from a strong pathway= you get LTP in both pathways

what is cooperatively?

several input pathways active at the same time, results in strengthening in both (regardless of individual strength as long as reaches threshold for LTP)

what is persistence?

change in synaptic strength will last across time

in the context of LTP, why are NMDA receptors important?

NMDA receptors act as coincidence detectors: able to detect both pre (glutamate) and post (depolarisation) synaptic activity simultaneously

how do NMDA receptor activation lead to LTP?

following the Mg2+ blockage removed at depolarisation, the travelling of Ca2+ into the postsynaptic cell drives LTP

What does Ca2+ do to drive LTP?

activating downstream effectors like protein kinase C, Calpain, ect

what are the 3 potential mechanisms by which LTP is expressed?

1) change in presynaptic release properties 2) change in AMPAR properties 3) change in AMPAR number

how is Long Term Depression (LTD) usually achieved?

low frequency stimulation

What receptors activation are some forms of LTD dependent on?

NMDA activation

what are the 2 alternative mechanisms that induce LTD, by low frequency stimulation?

NMDA receptors activate, then: 1) activation of metabotropic glutamate receptors 2) activation of muscarinic ACh receptors

what induces LTD following NMDA receptor activation, with high frequency stimulation?

Ca2+ influx, activating intracellular cascades