Not really Roy, inhibition is not "sent" like a signal along axon. It's more like a chemical reaction, that happens (strictly) locally (synaptic receptors are temporaraly blocked by a chepical, eg GABA). When a certain (membrane) potential reaches a level, the neuron reduces/stops its activity -- imagine a leaky bucket that refuses to work when full, until the water drops.. This blocking mechanism is in place to avoid strong "waves" of signal occuring in the network.
On Wed, Sep 18, 2013 at 4:27 AM, Roy Gu <[email protected]> wrote: > Hi Fergal, > > Thanks. I would like to ask whether permanence be negative biologically? > We know the cell can be fired at a 'fire rate' and send the signal to > its connected cells. Can the cell sent another type of signal to its > connected cells and the signal can be treated as a 'inhibition' and > mathematically a negative weighted permanence? > > Regards, > Roy > > ---- > Hi Roy, > > In the CLA, "inhibition" is done at the column level, either globally or > locally. The Spatial Pooler picks the 2% of columns with the highest > activation potential from either the whole region (global) or sub-regions > (local) and activates them. This mimics inhibition in the neocortex, in > which high-potential (or most active) cells suppress the potential or > activity of cells in neighbouring columns. > > The overall effect is very similar, in that sparseness is imposed and the > "best" columns are activated. If we can achieve very similar outcomes, then > efficiency considerations justify the deviation from the actual process in > the neocortex. > > A recent thread on this list discussed an alternate inhibition strategy for > the CLA. This proposal involves the idea of high-potential columns imposing > a "negative potential" effect on its neighbours. Initial tests suggest that > this method is significantly faster than the current local "inhibition" > algorithm, and it is also a closer analogue to the neocortex. > > Regards, > > Fergal Byrne > > _______________________________________________ > nupic mailing list > [email protected] > http://lists.numenta.org/mailman/listinfo/nupic_lists.numenta.org > > -- Marek Otahal :o)
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