• Tactics employed by neuronal networks to modulate synapse number as a function of neuronal density, depend of development maturity and aging.
• Complex degree of spatial interactions even in planar high-density cultures.
• Relationship between neuronal density and synapse number may have implications in the neurobiology of developing neuronal networks.
• Synaptogenesis occurs throughout the entire life span of an organism.
• Although the mature human cerebral cortex has one-fifth the neuronal density as found in the mouse, there is at least two times the number of synapses per neuron.
• d_N ~ H_s
• Regression analysis.
• Student’s t-tests.
• Synaptic plasticity.
• Neuronal percentage depends on DIV but not on plating density.
• Total neuronal number, interneuronal spacing, on synapse formation.
• Network connectivity, neuronal maturation, synaptic distribution electrophysiological parameters.
• Problem of culture thickness to quantify the total number of synapses.
• Necessity of 3D neuronal cultures.
• Problem of normalization.
• Neurotrophic factors.
• 3D matrices.
• 5000 synapses per neuron in low-density mature brains.