Wednesday, June 5, 2013

PTV and Frontal

So we are starting to build this picture about what the PTV (Parietal-Temproal-Visual) cortex is doing and fitting it in with the rest of the brain. What it seems is that PTV is encoding/representing/building the current and recent state of the world. When you open your eyes and see the world around you, recognize the objects, hear the sounds, the 3D structure, etc. all of this information is being represented in PTV. . There is a tremendous amount of information continually being encoded by this circuit, and this information is the immediate state of the mind you are experiencing.

Now, this is too much information to make sense of all at once. And this is where frontal cortex comes into play. Frontal cortex essentially feedsback to all of PTV (via layer 1). Frontal cortex enhances the activity in subsets of PTV and can route subsets of PTV into working or long-term memory. To encode a long term memory, only the parts of PTV that are strongly modulated by top-down attentional feedback make it. Essentially attentional feedback activates the neurons and gets them to burst. This doesnt really change the information anywhere in PTV, but enhances is it. The burst is a signal that carries the same info about the sensory environment but tells other structures to operate differently. So to work something into say hippocampal memory (I guess this is more like medium-term), frontal cortex burst synchronizes every region of the brain it wants to remember. The entire hierarchy can be encoded in the local cortical circuits, and the hippocampus plays the role as the pointer and relates the cortical information being saved with a time-place pointer in the hippocampus. When the memory is recalled, the hippocampus can be reactivated which then reactivates the cortical areas.

PTV is creating a hierarchical model of the world from all of the information from the senses. This model is actually non-temporal (ugh, confusing in this case im referring to temporal as in time) -- it has temporal structure, but it is time-invariant. Your phone stays your phone, etc. Frontal cortex is more in charge of time. Frontal cortex is building a hierarchy to predict the future at different temporal scales. Frontal cortex is pulling information about the current state of the world from temporal cortex and routing it through working and long-term memory. Frontal routes PTV into working memory, and can reactivate hippocampal memory to route into working memory to make better predictions about the future.