Differential signaling via the same axon of neocortical pyramidal neurons

Markram, H. Wang, Y. Tsodyks, M. (1998) Differential signaling via the same axon of neocortical pyramidal neurons. PNAS 95: 5323-5328.

Somatosensory slice in rats, whole cell triple recordings. They model facilitation with the paramter u, which increases by U * (1-u) for each pre-spike and decays to U for its equilibrium. This gives them that facilitation, but its only truly facilitation over some regime.

L5 tufted Py to py depressed with different values. Same pyramidal neuron could show depression onto another Py and facilitation onto a bipolar cell.

Different pyramidal cells show slightly different types of facilitation onto the same interneuron:

He talks about a super-linear, linear, and sub-linear regime for the dynamics, which I think is a consequence of his model the data somewhat show that too.

So, yeah, in his model u goes through this sigmoidal shape depending on the pre-synaptic firing rate. This causes different levels of current build-up - that's his super-lin-sub (SLS). In SLS he just means the efficacy of each psp, not the total integral. His model looks quadratic over some regime, depending on all the parameters.