Figure 5. Induction of transient heterosynaptic plasticity.

(A) Illustration of transient heterosynaptic plasticity. After 2 min, the number of slots in synapses 1 and 3 is increased instantaneously. The system quickly reaches a new (transient) equilibrium, where the non-stimulated synapses 2 and 4 are slightly weakened. At the same time, the number of receptors in the pool is reduced. Parameters were: $\beta =1/43{\text{s}}^{-1}$, $\delta =1/14{\text{min}}^{-1}$. The filling fraction was set to $F=0.5$ and the relative pool size was set to $\varphi =2.67$. The production rate $\gamma$ and attachment rate $\alpha$ were calculated according to Equation 12 and Equation 13, respectively. (B) Time course of relative changes in synaptic efficacies due to homosynaptic and heterosynaptic plasticity for the experiment from A. (C) Approximate maximum relative change of synaptic efficacy due to heterosynaptic plasticity as a function of the number of receptor slots after homosynaptic plasticity induction for different filling fractions. (D) Same as C but for a smaller relative pool size of $\varphi =1.0$. See text for details.