[ExI] ANN question
col.hales at gmail.com
Thu Mar 16 03:42:04 UTC 2017
'Dendritic action potentials' just joined 'somatic action potentials'. The
game just changed.
Moore, J.J., Ravassard, P.M., Ho, D., Acharya, L., Kees, A.L., Vuong, C.,
and Mehta, M.R. (2017). Dynamics of cortical dendritic membrane potential
and spikes in freely behaving rats. Science.
Earlier Arxiv version http://biorxiv.org/content/early/2016/12/28/096941
"Why our brains may be 100 times more powerful than believed"
Check out the video of the DAP waveform in the supplementary material.
Neocortical sub- and suprathreshold dendritic membrane potential (DMP)
breaking out into localised firing within the dendrite structure. Dendrite
firing has been observed for a long time, but this is the first time anyone
has seriously accessed its origins and correlated it with behaviour.
Collectively the DMP are very strong (as represented by voltage measured in
tissue: Higher than somatic action potentials!) and much faster. This is
because neural tissue is 90% dendritic and there are collosal numbers of
post-synaptic densities (synapses).
Talking about action potentials just got orders of magnitude more involved.
On Thu, Mar 16, 2017 at 7:40 AM, William Flynn Wallace <foozler83 at gmail.com>
> addition - see at bottom
> On Wed, Mar 15, 2017 at 3:09 PM, William Flynn Wallace <
> foozler83 at gmail.com> wrote:
>> On Wed, Mar 15, 2017 at 2:26 PM, Adrian Tymes <atymes at gmail.com> wrote:
>>> On Mar 15, 2017 11:00 AM, "William Flynn Wallace" <foozler83 at gmail.com>
>>> On Wed, Mar 15, 2017 at 12:29 AM, Adrian Tymes <atymes at gmail.com> wrote:
>>>> At any given instant, a neuron may either be firing or have a time
>>>> until next firing - but a firing is a (mostly) discrete event, with
>>>> one firing distinct from the next.
>>>> If it was not distinct - if it was "always firing" - then there would
>>>> be no such thing as "speed" of firing. Rather than toggle on then off
>>>> at various rates, it would simply be always on.
>>> There is a great deal of controversy about rate of firing, from about 1
>>> every 6 seconds to 200 per second, up to a couple of thousand at the
>>> fastest (for cortical neurons). By always firing I meant only that it
>>> never rested more than a few seconds at the very most. Yes, discrete -
>>> absolute refractory period.
>>> Right. And during that refractory period, the output is 0, regardless
>>> of how long it will be or has been to the next/previous firing.
>>> So, again, that gives three states - not changing speed, slowing,
>>> No, two states: firing, or between firings.
>>> You are declaring the acceleration to be a state, when the state is more
>>> like the current position, and the simplification is that most ANNs don't
>>> even consider velocity let alone acceleration.
>> OK, I think we are in agreement: you and the ANN at looking at the
>> state of the neuron at a fixed point in time, and I am looking at it over a
>> period of time. Maybe we need to look at both to understand the neuron
> addition - come to think of it, whether the neuron is firing or not at a
> specific point in time, is a function of where on its body you measure the
> chemical exchange; we know that the spike travels the length of the cell
> body, a traveling wave, such that at the receiving end - the dendrite - you
> can measure the influx of ions into the body, whereas at its opposite end
> nothing is happening yet. Maybe this makes no difference. What do I know?
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