Glutamate-Bound NMDARs Arising from In Vivo-like Network Activity Extend Spatio-temporal Integration in a L5 Cortical Pyramidal Cell Model
Figure 5
Background inhibition modulates spatio-temporal integration.
(A) Probability of an NMDAR spike (P(NMDAR spike)) occurring in a terminal branch versus number of nearly synchronous stimulus evoked synapses during control (black), in presence of background activity from 1500 excitatory synapses (blue) and during mixed excitatory and inhibitory background (gGABA/gAMPA ratio of 1.5) provided by 130 pure GABAA receptor (SOM-like) synapses firing random trains at 3 Hz (2×SOM, red) or by a combination of 65 SOM-like synapses and 13 NGF-like synapses providing both GABAA and GABAB receptor-mediated inhibition, firing random trains at 14 Hz (SOM+NGF, green). (B1) Example of voltages in 6 apical branches (grey) and soma (green) during nearly synchronous stimulation of 6 branches in the presence of ballanced background input (SOM+NGF). (B2) Example of voltages in all apical branches (grey) and soma (green) during nearly synchronous stimulation of 100 spatially distributed stimulus evokes synaptic inputs in the presence of balanced background input (SOM+NGF). (C1) Probability of triggering APs (P(AP)) versus number of nearly synchronously stimulated branches (5 ms, filled circles, solid lines) or asynchronously stimulated branches during a 100 ms window (open circles, dashed lines) for conditions in (A). (C2) Increase, from the nearly synchronous condition, in the number of stimulated branches required to trigger an AP (P(AP) = 0.5) with different levels of temporal dispersion (input) for conditions in (A) excluding control. (D1) P(AP) versus number of stimulated synapses for spatially distributed input over the apical tuft for conditions in (A). Synapses activated with random trains at 200 Hz for 5 ms (solid markers) or 10 Hz for 100 ms (empty markers). (D2) Number of spatially distributed synapses required to trigger an AP (P(AP) = 0.5) for different levels of temporal dispersion (input window), for conditions in (A).