p362fig10.11 Feedback between layer 2/3 to the layer 6-to-4-to-2/3 feedback loop chooses the strongest grouping in cases where there is more than one.  If only one grouping exists, then the circuit can function very quickly in a feedforward manner.  When multiple groupings exist, the cortex "runs as fast as it can" to select the one with the most evidence to support it using the self-normalizing inhibition in the layer 6-to-4 off-surround.<BR>||  How is the final grouping selected? Folded feedback LGN-> 6-> 4-> 2/3.  1. Layer 2/3 groupings feed back into 6-to-4 on-center off-surround: a) direct layer 2/3 -to-6 path; b) can also go via layer 5 (Blasdel etal 1985; Kisvarday etal 1989).  2. Strongest grouping enhanced by its on-center.  3. Inputs to weaker groupings suppressed by off-surround.  4. Interlaminar feedback creates functional columns.  Activities of conflicting groupings are reduced by self-normalizing inhibition, slowing processing; intracortical feedback selects and contrast-enhances the winning grouping, speeding processing.