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)?

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    $\begingroup$ nature.com/nature/journal/v503/n7474/box/nature12654_BX1.html $\endgroup$ Nov 18, 2015 at 19:03
  • $\begingroup$ @brucesmitherson, make that an answer! $\endgroup$
    – honi
    Nov 18, 2015 at 19:15
  • $\begingroup$ @bruce smitherson , thanks for the link. I am still confused by the use of the vocabulary. And that was part of my original question in fact. What do they mean by "higher order cortex"? is it the "higher order association" that we see here for example indiana.edu/~p1013447/dictionary/brocwern.htm ? $\endgroup$
    – ceillac
    Nov 18, 2015 at 19:33
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    $\begingroup$ yes, that would be an example. In general a higher area is any area that received forward input for additional processing or is upstream in this sense, as opposed to areas lower in the hierarchy that are closer to the sensory input. Thus, green arrow are forward connections, and purple ones are feedback connections (to and from higher areas relative to the one you are looking). $\endgroup$ Nov 18, 2015 at 19:46
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    $\begingroup$ yes, in addition to direct feedback connections many areas have their feedback connections pass first through the thalamus. It is not clear yet what function these loops have, but they are not thought to be just a relay. $\endgroup$ Nov 18, 2015 at 21:13

1 Answer 1


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.

  • $\begingroup$ what do you mean by higher areas? $\endgroup$
    – ceillac
    Nov 18, 2015 at 17:47
  • $\begingroup$ "top-down processing" would be equivalent to "feedback from higher areas" $\endgroup$
    – honi
    Nov 18, 2015 at 17:52
  • $\begingroup$ what are higher areas? $\endgroup$
    – ceillac
    Nov 18, 2015 at 18:53
  • $\begingroup$ what is top-down processing? $\endgroup$
    – honi
    Nov 18, 2015 at 19:14
  • $\begingroup$ Correct me if I'm wrong, but don't top-down predictions (feedback) arise from deep layers of agranular cortex, and prediction error neurons (feedforward) in the superficial layers? $\endgroup$
    – mrt
    Nov 18, 2015 at 23:34

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