Dynamical Systems in Neuroscience:

Dynamical Systems in Neuroscience: Dynamical Systems in Neuroscience:

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12.07.2015 Views

76 One-Dimensional Systems100806040200100806040200100806040200bistabilityF(V)rest thresholdbifurcationF(V)tangent pointmonostabilityF(V)-50 0 50membrane potential, V (mV)I=0I=16I=60membrane potential, V (mV) membrane potential, V (mV) membrane potential, V (mV)40200-20-40-6040200-20-40-6040200-20-40V(t)excited statethresholdrestV(t)excited stateV(t)excited state-600 1 2 3 4 5time (ms)Figure 3.25: Bifurcation in the I Na,p -model (3.5): The rest state and the thresholdstate coalesce and disappear when the parameter I increases.

One-Dimensional Systems 77F(V)I=18I=17I=16I=15I=14I=13I=12I=11no equilibriabifurcationtwo equilibriatangentpointVstable equilibriaunstable equilibriaFigure 3.26: Saddle-node bifurcation: As the graph of the function F (V ) is lifted up,the stable and unstable equilibria approach each other, coalesce at the tangent point,and then disappear.saddle-nodenot saddle-nodeFVnon-hyperbolichyperbolichyperbolicnon-degenerate degenerate degeneratetransversalnot transversalnot transversalFigure 3.27: Geometrical illustration of the three conditions defining saddle-node bifurcations.Arrows denote the direction of displacement of the function F (V, I) as thebifurcation parameter I changes.

76 One-Dimensional <strong>Systems</strong>100806040200100806040200100806040200bistabilityF(V)rest thresholdbifurcationF(V)tangent po<strong>in</strong>tmonostabilityF(V)-50 0 50membrane potential, V (mV)I=0I=16I=60membrane potential, V (mV) membrane potential, V (mV) membrane potential, V (mV)40200-20-40-6040200-20-40-6040200-20-40V(t)excited statethresholdrestV(t)excited stateV(t)excited state-600 1 2 3 4 5time (ms)Figure 3.25: Bifurcation <strong>in</strong> the I Na,p -model (3.5): The rest state and the thresholdstate coalesce and disappear when the parameter I <strong>in</strong>creases.

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