Visual inputs from the 2 eyes in most primates activate alternating bands of 
cortex in layer 4C of primary visual cortex, thereby forming the well-studied 
ocular dominance columns (ODCs). In addition, the enzymatic reactivity of 
cytochrome oxidase (CO) reveals "blob" structures within the supragranular 
layers of ODCs. Here, we present evidence for compartments within ODCs that have 
not been clearly defined previously. These compartments are revealed by the 
activity-dependent mRNA expression of immediate-early genes (IEGs), zif268 and 
c-fos, after brief periods of monocular inactivation (MI). After a 1-3-h period 
of MI produced by an injection of tetrodotoxin, IEGs were expressed in a patchy 
pattern that included infragranular layers, as well as supragranular layers, 
where they corresponded to the CO blobs. In addition, the expressions of IEGs in 
layer 4C were especially high in narrow zones along boundaries of ODCs, referred 
to here as the "border strips" of the ODCs. After longer periods of MI (>5 h), 
the border strips were no longer apparent. When either eyelid was sutured, 
changes in IEG expression were not evident in layer 4C; however, the patchy 
pattern of the expression in the infragranular and supragranular layers 
remained. These changes of IEG expression after MI indicate that cortical 
circuits involving the CO blobs of the supragranular layers include aligned 
groups of neurons in the infragranular layers and that the border strip neurons 
of layer 4C are highly active for a 3-h period after MI.