Non-selective | Growth rule | Affinity groups | Totally selective | |
---|---|---|---|---|

Number of spiny cells contacted by one axon | 40 | 10 | 10 | 1 |

Average number of synapses per axon per contacted cell | 1 | 4 | 4 | 40 |

Percent of total number of spiny neurons in the volume of one dendritic field contacted by one axon | 1.4% | 0.35% | 0.35% | 0.035% |

Average number of axons shared by two spiny neurons | 75.3 | 4.7 | 1300 | 0.0 |

Percent of total population of cortical axons shared by a randomly selected pair of spiny neurons | 1.4% | 0.09% | 0.34% | 0.0% |

Average number of cortical cells innervating each spiny cell | 5360 | 1340 | 1340 | 134 |

Average number of spiny cells within the volume of one dendritic field shared by a randomly selected pair of cortical neurons | 0.55 | 0.035 | 0.97 | 0.00035 |

Chances that two randomly selected cortical axons arborizing in the same volume converge onto a given spiny neuron | 0.02% | 3.4% | 0.35% | 0.035% |

All calculations are for contacts within the volume of one spiny neuron, as in Table 2. Nonselective, Axons contact any spiny neurons in the volume with constant probability. Growth rule, Axons contact any spiny neuron but make multiple synapses per contacted neuron (calculations are for four synapses per neuron). Affinity groups, Axons and spiny neurons are divided into subsets and only make synapses within their groups. Group sizes were adjusted to average four synapses per contacted neuron (284 groups) for comparison with the Growth rule.