Neuronal density determines network connectivity and spontaneous activity in cultured hippocampus

J Neurophysiol. 2010 Aug;104(2):1052-60. doi: 10.1152/jn.00914.2009. Epub 2010 Jun 16.


The effects of neuronal density on morphological and functional attributes of the evolving networks were studied in cultured dissociated hippocampal neurons. Plating at different densities affected connectivity among the neurons, such that sparse networks exhibited stronger synaptic connections between pairs of recorded neurons. This was associated with different patterns of spontaneous network activity with enhanced burst size but reduced burst frequency in the sparse cultures. Neuronal density also affected the morphology of the dendrites and spines of these neurons, such that sparse neurons had a simpler dendritic tree and fewer dendritic spines. Additionally, analysis of neurons transfected with PSD95 revealed that in sparse cultures the synapses are formed on the dendritic shaft, whereas in dense cultures the synapses are formed primarily on spine heads. These experiments provide important clues on the role of neuronal density in population activity and should yield new insights into the rules governing neuronal network connectivity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Calcium / metabolism
  • Cell Count
  • Disks Large Homolog 4 Protein
  • Excitatory Postsynaptic Potentials / physiology
  • Glutamate Decarboxylase / metabolism
  • Hippocampus / anatomy & histology*
  • Inhibitory Postsynaptic Potentials / physiology
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Membrane Proteins / metabolism
  • Microscopy, Confocal
  • Nerve Net / cytology*
  • Nerve Net / physiology*
  • Neurons / classification
  • Neurons / physiology*
  • Organ Culture Techniques
  • Patch-Clamp Techniques / methods
  • Phosphopyruvate Hydratase / metabolism
  • Rats
  • gamma-Aminobutyric Acid / metabolism


  • Disks Large Homolog 4 Protein
  • Dlg4 protein, rat
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • gamma-Aminobutyric Acid
  • Glutamate Decarboxylase
  • Phosphopyruvate Hydratase
  • Calcium