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The multi-channel recording environment provides a wealth
of data on the activity of cultured neuronal networks. The 3
figures show network activity from different segments of an experiment
in which a novel synthesized compound which had been shown to
inhibit the enzymatic cleavage of acetylcholine is applied to
a culture grown from dissociated tissue dissected from embryonic
murine frontal cortex. The panels display multiple simultaneous
spike trains of 30 discriminated units, recorded on 16 channels.
The first panel shows a 20-second window of spontaneous network
activity 6 minutes before the initial application of the drug.
The majority of the units are producing single action potentials,
with an occasional burst evident on some units. Panel 2 is shows
activity 10 minutes after the concentration of the compound was
raised to 50 µM. The initial 6-8 seconds represents a period
of higher-density bursting and spiking that resolves into a somewhat
coordinated pattern of activity between the majority of units,
with very little inter-burst spiking evident, even on the units
that do not burst. The final panel is 40-seconds in length, and
shows the activity 15 minutes after the concentration reaches
100 µM. The activity is obviously much more coordinated
between units. Statistically, the mean spike rate of the 30 individual
units was increased 62% by 100 µM of the drug. However
the effect was unit-specific; for example 8a actually decreased
spike production, while other units such as 9a increased their
spike rate over 100% and transformed from a predominately spiking
neuron to a predominately bursting one. The constant challenge
in a multi-channel environment is to choose the parameters that
most accurately depict the network behavior.
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