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MsC Seminar- Stability of propagation patterns over prolonged time scales in cultured neural networks

February 26 @ 10:30 - 12:30 IST

Background

An important aspect of network function concerns pathways of activity propagation – the identities, firing times, and/or firing rates of neurons downstream from points at which activity enters the network. Propagation pathways are sensitive to many dynamic variables, the most important ones being neuronal excitability, synaptic plasticity and relative strengths of excitation and inhibition. Prior studies carried out in cortical networks in primary culture suggest that these variables fluctuate considerably. As neuronal and network excitability are combinatorial and highly non-linear, the effects of such fluctuations on activity propagation pathways on long  time scales (5-6 days) are difficult to predict.

Results

Our work aims to characterize and quantify spontaneous changes in activity propagation pathways in cortical neuron networks over time scales of days. To that end we used primary cultures of rat cortical neurons plated on multi-electrode arrays (MEA). The networks (16 days in vitro) were mounted in setups that allowed for continuous recording and stimulation and stimulated electrically at low frequency (0.1Hz) from four spatially separated sources to trigger network responses. Several well-established measures as well as others we devised were used to quantify similarities between propagation pathways evoked by stimuli delivered from the same (and different) sources. Interestingly, we found that changes in network responses tended to be abrupt, effectively resulting in networks shifting among multiple discrete propagation pathways. Such shifts sometimes involved reversions to previously used pathways.

Conclusions

While biological processes underlying changes in neuronal features tend to be monotonic and continuous, changes in activity propagation pathways tend to be abrupt and discrete. Stated differently, networks ‘choose’ propagation patterns from a limited repertoire, switching to alternative ones when these become unavailable.

Details

Date:
February 26
Time:
10:30 - 12:30
Event Category: