I was watching one of Numenta’s videos and heard Jeff mention having sleepless nights over why there are multiple pathways for a single sense leading to the neocortex (one through the thalamus and one directly to the neocortex). I’d like to present a hypothesis that could explain this. First, though, I’d like to say that I just recently started teaching myself about the interregional connections of the brain and the neuronal structure of different areas of the brain so more detailed answers / feedback would be greatly appreciated.
My hypothesis is that both of these pathways are required for sensory attention to manifest. For example, we need to determine what a sound is in order to determine whether or not it requires our attentions. In order to do this, the first pathway that circumvents the thalamus is used to feed sensory input directly into the neocortex. The neocortex determines the source of the sound and potentially (this next part might be determined by converging inputs in the thalamus instead of by the neocortex) whether or not it requires our attention. Once the neocortex has identified the source of the sound, it feeds that information into the thalamus. The thalamus then uses the inhibitory pathway of the thalamic reticular nucleus to prevent that information from continuing up the cortical hierarchy (to parts of the brain of which we are more consciously aware). This allows the thalamus to modulate our attention to sensory input while still allowing the neocortex to do the heavy lifting on the parts at which it’s good.
I think this hypothesis also requires the assumption that conscious attention derives from the level at which you look in the cortical hierarchy and I’m not sure about the efficacy of that assumption.