Synaptic plasticity

Short-term plasticity

Consecutive presynaptic spikes affecting subsequent EPSPs (facilitation or depression). The effect is heavily dependent on specific synapses, Ca2+ concentration etc. Thought to be caused by leftover Ca2+. Known to regulate balance between different microcircuit pathways by shifting balance between them via STP.

Long-term plasticity

"Enduring changes in the strength of interneuronal connections likely underlie most forms of experience-dependent learning .."

Ramon y Cajal

Mechanistic process of LTP and LTD is currently still unknown. Research is ongoing though:

• Likely has to do with NMDA-Rs, blocking them seems to block LTP.
• NMDA-Rs are also permeable to Ca2+ in addition to K+. The resulting free Ca2+ could be promoting LTP.
• LTD also seems to be NMDA-R dependent, maybe due to Ca2+?
  • This observation motivated the BCM model.
• Other factors that have been found to be important for gating plasticity: (dis-)inhibition, CaMKII, neuromodulators.
• The precise mechanism of plasticity is also very cell-type-dependent.