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> Delay between neurons
mway
post Feb 27, 2011, 07:15 PM
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Hi.

Imagine two neurons connected to a third. If the distance between the first neuron and the target was double the distance of the second neuron to the target, what kind of temporal difference would their arrival times be if both spiked at the same time? Assume that the synaptic delay in both cases is identical.

Another way to ask the question is; as the distance between neurons gets larger, does the time between spikes leaving and arriving grow linearly (ignoring synaptic delay)? Is the time negligable when compared to the synaptic delay?

Thanks in advance.
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lucid_dream
post Feb 28, 2011, 12:58 AM
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temporal delays in action potential propagation are significant. Synaptic integration is on a timescale of 2 - 10 ms. Considering an action potential propagation speed of 1 m/s, then it takes 10 ms (i.e, synaptic integration timescale) to travel 10 mm. There is a lot of discussion about the role of synchrony in neural population coding, but little consideration of the effects of temporal delays in signal propagation and how they constrain synchronous neural population events. From a neurons perspective, it would see synchronous events asynchronously, precisely because of temporal delays in signal propagation; which brings up the question, if neurons see synchronous activity asynchronously, then under what conditions can synchronous neural activity be sustained? Definitely an interesting direction to look further into.
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mway
post Feb 28, 2011, 03:53 AM
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Thanks for the reply. So we are talking approximately 1mm per ms? Now for a follow up. What kind of distances are we talking on average between neurons? I know that is a very general question, as they can vary greatly, but lets say an L2/3 cortical interneuron as an example. What sort of ranges would an average one connect to others in the same layer?

I'm just tweaking variables in an emulator i've built. Thanks again in advance.
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lucid_dream
post Feb 28, 2011, 06:53 AM
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local connections are 10s to 100s of microns. Long-range connections are millimeters or more.
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mway
post Feb 28, 2011, 08:12 PM
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QUOTE(lucid_dream @ Mar 01, 2011, 12:53 AM) *

local connections are 10s to 100s of microns. Long-range connections are millimeters or more.

Thanks again for the replies.
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