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. 2005 Oct 5;25(40):9080–9095. doi: 10.1523/JNEUROSCI.2220-05.2005

Figure 4.

Figure 4.

Dendritic activity of MSP model during synaptic input. A, Membrane potential of the soma and dendrites during state transitions. Each colored line represents voltages along a distinct path from one distal dendritic tip through the soma to a different distal dendritic tip. The soma is at x = 0. The time points indicated for each snapshot correspond to the voltage trace in C and are represented by the dots at those time points. Note that the dendrites act independently of each other except during state transitions or action potentials. State transitions occur after the depolarization of at least ∼25% of the dendrites, with the dendrites leading the soma into the up state. Action potentials are initiated at the soma and voltage propagates to the distal tips of the dendrites. B, Correlations of membrane potential with all other compartments of the cell during a 2 s simulation. The soma is well correlated with the proximal and secondary dendrites (top). The proximal node of the tertiary dendrites correlates well with other proximal segments and correlates somewhat with the distal portion of its own dendrite (middle). The distal node of the tertiary dendrite correlates well with itself only, with a slight increase in correlation with the distal dendrite attached to the same secondary branch relative to other distal dendrites (bottom). C, Top, The membrane potential of the soma and one tertiary dendrite recorded during the times indicated (APs chopped at -10 mV). Voltage was recorded at the soma (black) and at the proximal (red) and distal (blue) ends of the same tertiary dendritic compartment (indicated by arrows, inset). Bottom, The intracellular calcium concentration at the dendritic locations indicated in the inset. Action potentials initiated in the soma are able to invade even the distal ends of the dendrites and may result in calcium influx, particularly if synaptic activity has already depolarized the dendritic compartment. Note that the distal calcium response is nonlinear, because a relatively small increase in depolarization (∼4 mV in the second spike) can lead to a threefold difference in resulting calcium concentration.