Skip to main content
. Author manuscript; available in PMC: 2010 Aug 16.
Published in final edited form as: Neuron. 2009 Jul 30;63(2):171–177. doi: 10.1016/j.neuron.2009.06.023

Figure 3. Functional consequences of synapse distribution.

Figure 3

(A) The reconstructed CA1 pyramidal neuron morphology used for the models and the apical oblique dendrites used for the simulations (region between dashed lines enlarged).

(B) Sample voltage traces from a simulation in which fifteen synapses were randomly selected and activated on branch 4 in the two-stage integration model (188 μm from the soma). Voltage is indicated at the branch end (black trace), center of the branch (red trace), branch origin (green trace), and soma (blue trace). Synapses were distributed along each branch shown in (A) with decreasing density and strength from branch origin to branch end as observed experimentally (two-stage integration model) and the reverse (global integration model).

(C) For each branch, synapses were randomly activated until a dendritic spike occurred (200 trials/branch). Probability distribution (bin size = 0.2) showing the location along the dendritic branch of the input triggering the spike (the last synapse selected) for the two models (black and blue lines). The dashed line indicates the uniform distribution expected if the final input contributes equally to the spike at all locations.

(D) Somatic depolarization averaged over 500 trials resulting from activation of 5, 10, 15, and 20 synapses in the two models: global integration (black bars) and two-stage integration (blue bars). The white numbers indicate the percentage of trials that resulted in a dendritic spike.

(E) Top: The percentage of trials resulting in a dendritic spike for the global (black bars) and two-stage (blue bars) integration models when ten synapses are activated on each branch (500 trials per branch). Bottom: The average somatic depolarization resulting from these simulations shown separately for trials in which a dendritic spike was triggered (dark bars) and trials that did not produce a dendritic spike (light bars).

(F) Schematic of the proposed synapse distribution for the CA1 apical dendritic tree based upon previous (Nicholson et al., 2006, Magee and Cook, 2000) and current results.