I’m always puzzled by the absolute need of a lot of peoble to explain the brain in terms of logic gates.
What is so hard about Hebbian learning?
Thats all a synapse can do.
XOR is: x y || z
1 1 || 0
0 1 || 1
1 0 || 1
0 0 || 0
All agree that a single synapse on a dentrite does nothing.
So you would have lets say at least 10 synapses on a dentritic segment.
XOR on that means that any permutation of 5 zeros and 5 ones will give a 1, the rest a zero.
Who actually believes that synapses work that precise???
We know they don’t! So it does not help very much to think of it in terms of logic gates.
Because 4 ones and 6 zeros is not almost 1, its zero! But i’m pretty sure in the brain its sometimes one.
Also the distal dentritic segments are not an AND gate!
It’s a treshold.
Because with an AND all the synapses on a segment need to be active,
with a treshold one or two can be missing.
And so on …
We know that those Calcium spikes are a bit stronger and longer than NMDA spikes.
So how about that: they do the same biasing as the NMDA spike to enable the temporal memory,
just that this signal comes from above
so a higher region has “understood” something and now it “tries” to put the lower hypercolumn in agreement if at all possible
enabled by the fact that they can potenialy overwrite an NMDA spike
Just a hypothesis, but certainly more plausible than an XOR.