Glutamate-Bound NMDARs Arising from In Vivo-like Network Activity Extend Spatio-temporal Integration in a L5 Cortical Pyramidal Cell Model
Figure 1
Background excitatory input lowers NMDAR spike threshold and increases gain of the input-output relationship of apical dendrites.
(A) Morphology of L5 pyramidal neuron model [29] with apical tuft highlighted in blue. (B) The 28 terminal branches (red) on the dendritic tuft. (C) Membrane potential in an apical branch for different numbers of near-synchronous stimulated (5 ms window) quantal AMPAR/NMDAR synaptic inputs. Dashed line shows NMDAR spike threshold criterion (−30 mV). (D) Probability of NMDAR spike (P(NMDAR spike)) versus number of stimulated synapses randomly distributed along the branch. Red lines show fits for each of the 28 branches. Black line denotes average across all branches. (E) Membrane potential from a single branch during different levels of background excitatory input (exc, 900, 1200 and 1500 synapses firing at 0.85 Hz) distributed on the apical tuft (blue region in A). (F) Mean and standard deviation of branch voltage for different levels of background activity. (G) EPSP during control (black) and NMDAR spike during background excitatory input (blue) on the apical tuft. (H) Mean branch I-O relationship for 5 ms window (computed from ∼50 trials across randomly selected branches) during different levels of background input (as indicated). (I) Same as H but comparing results for a 5 ms stimulation window (filled circles, solid lines) and 15 ms window (open circles, dashed lines) for 1500 background inputs.