A mini-column recognizes little part of a pattern in space, and transitions from one pattern to another in time. It is not just two letter digraph side by side but two letter digraph one after the other. This is happening in all sensory modalities at the same time. How does this fit into the overall structure of a vast sea of mini-columns to do useful things?
The brain consume vast amounts of energy compared to the rest of the body. Evolution has built in some optimizations so that the population of cells firing is kept sparse as much as possible. In nature there is a lot of the same things going on in your environment most of the time. You need to notice changes (Surprise!) as these are most likely to be something good or bad. And mostly recognize and ignore the familiar things.
So - with this in mind what tasks are being supported by this mini-column? You have to recognize that something has been seen before and somehow group it with a decision of naughty or nice. This should trigger some action - eat it or drink it or run from it or have sex with it. Some action. You have to know when you have NOT seen this before and learn it as rapidly as possible. It would be handy if while you are learning it you learned if it was good or bad - how you felt about the encounter.
In all this our little mini-column is sampling the stream of sensations. All by itself all it can do is learn a very limited size pattern (about 500 um of cortex space) and burst if it is not able to match any of the dendrites in any of it’s cells to the time/space pattern being sensed. Also - if any of the mini-columns within its neighborhood do recognize it bursting should be suppressed.
Some parts of the column (L2/3, L4) are selective to the stream of information coming from the senses, some parts (L5, L6) are responding to the stream coming from the bodies command and control centers. I should point out that the concept of a mini-column extends from the cortex down to the layers of the thalamus. There are important command and control functions there, including gating of sensation and routing of activation.
Focusing on the part related to your question, the incoming stream part - it is like a tuning fork that resonates if the pitch it is tuned to is present. if a collection of mini-columns resonates to the stream it has seen this time/space pattern before and the axon activation signal coming out of some extent of this area/map are very sparse. This is what goes down to the thalamus and it enters tonic mode. This is picked up by the lower brain structures as “I have seen this before and recognize it locally.” This also acts to spread activation to the other maps/areas connected to this section of thalamus. Part of this activation is the thalamo-cortical resonance which binds this recognition together like a beating heart. This starts the processing in the hierarchy, which goes on the to do its own processing on these sensations. This stream of recognition is spread by axon projections from the L2/3 layer.
Also - a winning mini-column activates inhibitory inter-neurons that shuts down local mini-columns that don’t recognize the pattern in any dendrite - no bursting here! There is no need to learn this pattern because some nearby mini-column knows this.
But we are still in this little bit of one map. I have gone back to my previous post and added text that describes how maps going up the hierarchy learn progressively more complex patterns. It is still little patches of recognition - but of a larger pattern. They are also ringing like a tuning fork - trying to fit some larger patterns like words or phrases. In my mind I think it looks like the “suggest a word” function when you are typing something on a computer or smartphone. In speech production you are snapping (intents of meanings) to (word sounds) to (templates of sentences) as you go along. Each area is trying to fit its local version of a pattern into the stream in a cooperative process. In the sensing direction the stream of the world provides this guiding template to form the sensed stream. In the production direction the prior produced stream is sensed and provides part of this template.
What if NO dendrite matches the sensed time/space pattern? Then the mini-column(s) signal its surprise by bursting. This loud signal goes to the thalamus and it does NOT do tonic mode - it has a burst mode response all of its own. This acts to gate more of the confusing signal to the cortex for processing. It takes energy to learn something new. This process has been referred to as the Spotlight Of Attention.
The last little bit of function that I want to point out is memory. There is no one spot for memory - it is everywhere in little spots on dendrites in the cells in the mini-columns. Each area works to remember what it sees - what passes by it in whatever form it takes.
I have posted about all these aspects and how they fit together before.
This is a more detailed bit on memory:
This is a more detailed bit on the thalamus and how to make HTM retrieve stored memories. The memories stay distributed and local but they are retrieved as a whole:
Putting it all together:
I hope that this has answered your question.