As I understand HTM theory, if an SDR input arrives and a cell within that input was predicted from the previous input it will depolarize quickly causing an inhibition of the other non-predicted cells in its column. However, there are far fewer inhibitory cells vs excitatory in the cortex.
My questions are:
Does inhibition require a similar set (number) of synapses to achieve the unique properties of excitatory input? In other words, a key premise of HTM is that different inputs can be differentiated because their overlap score is unlikely to be high provided there are enough synapses to go around. But with fewer synapses available on the inhibitory side this seems to suggest a bottleneck issue.
I’ve read that inhibitory synapses tend to target dendritic shafts rather than spine heads. Based from on-path and off-path inhibition it seems likely that inhibitory synapses provide a more general functionality then the site specificity of excitatory synapses (perhaps answering my first question), but if that’s true it still places the network prohibitively at the discretion of only a few inhibitory cells. In this scenario, how does the system retain insensitivity to background noise?
Thank you for thoughts on these questions.