What are the relations between top-down and bottom-up processings and the flows of information in the brain? For example, does top-down processing start from some layers and go to lower layers? If so does the information remain in the same area of the brain or can it travel from a layer of one area down to lower layers of an others areas? Also how are feedforward (feedback) pathways related to bottom-up (top-down)?
It is generally thought that thalamic input comes in layer 4, feed back from higher areas come through layer 1 to layer 2/3 and feed forward is sent from the deeper layers.
see Canonical Microcircuits for Predictive Coding
Andre Bastos, W. Martin Usrey, Rick Adams, George Mangun, Pascal Fries, and Karl Friston
who cite Douglas, R.J., and Martin, K.A. (1991). A functional microcircuit for cat visual cortex. J. Physiol. 440, 735–769.