Emerging Activity Patterns and Synaptogenesis in Dissociated Hippocampal Cultures

Area of Science:

• Neuroscience
• Developmental Biology
• Computational Biology

Background:

• Hippocampal neuron cultures show predictable network activity development within three weeks.
• Understanding neural circuit organization requires characterizing network structure and synaptogenesis.
• Existing automated synapse quantification methods have limitations, including arbitrary thresholding and lack of random-chance correction.

Approach:

• Developed and validated a novel, automated synapse quantification algorithm with minimal operator intervention.
• Applied the algorithm to confocal microscopy images of dissociated hippocampal neurons at various developmental stages (5, 8, 14, 20 days in vitro).
• Quantified excitatory and inhibitory synaptogenesis during the critical period of network activity pattern emergence.

Key Points:

• Synaptic density increases with neuronal maturation, correlating with rising network spiking activity.
• A decrease in excitatory synaptic density was observed in the third week of maturation.
• This reduction in excitatory synapses suggests synaptic pruning, coinciding with the onset of regular network bursting activity.

Conclusions:

• The developed algorithm offers a robust method for synapse quantification in neuronal cultures.
• Synaptic pruning of excitatory connections occurs during the third week of hippocampal network maturation.
• This pruning event is temporally linked to the emergence of synchronized bursting activity in the developing neural network.