I am attempting to determine which current inputs (in uA) are subthreshold for inducing a burst of activity. This is because I am attempting to model DBS form epilepsy in vitro, which clinically should be below after discharge threshold.
I have shown that a biphasic +/- 5 and 10 uA are subthreshold when using a 100 ms train at 100 Hz (10 ms IPI) with 100 us phase duration (200 us total pulse).
I am recalling first year electrophysiology. Is it possible that, even with a longer spike train (say even 1 second) EPSPs will no longer accumulate linearly and they will reach a plateau below AP threshold? (Similar to a limit in calculus.)
Perhaps AP threshold can be reached by shortening the pulse interval (higher frequencies), or increasing the pulse width.
Is this correct?
Thanks
You should be able to trade off all the parameters: current, pulse duration, train duration, and pulse frequency to evoke a fixed amount of potential in your neuron. This will tell you how these parameters co-vary to trigger an action potential and whether the signals combine (or negate) over time, which should be related to the membrane time constant. Depending on the spatial relationship of your delivery electrode and the intracellular situation of your neuron, space constant may also come into play whereby different membrane locations have different excitabilities.
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