Sensory regulation of immediate-early genes c-fos and zif268 in monkey visual cortex at birth and throughout the critical period.

The postnatal development of ocular dominance columns (ODCs) in monkey visual cortex provides an exquisite model for studying mechanisms of experience-guided neuronal plasticity. While the presence of columns at birth in Old World monkeys is now well established, it remains unclear whether cortical neurons at this early stage are capable of modulating gene expression in response to changing sensory conditions. Using a set of monocular deprivation and stimulation protocols, we examined activity-driven expression of the immediate-early genes (IEGs) c-fos and zif268 during the critical period of development. We observed well-delineated patterns of ODCs produced by sensory regulation of both IEGs throughout the critical period, starting as early as the first postnatal day. The expression levels are similar in layers II/II, IVC and VI throughout development, with no selective decline in the thalamorecepient layer (layer IVC) of adult monkeys. A narrow strip of non-columnar c-Fos expression was observed at the border of layers IVC and V. Our results show that neurons in monkey visual cortex are equipped at birth with the molecular machinery for coupling sensory inputs to active genomic responses and that this responsivity extends throughout the critical period. The findings are discussed within the context of a possible role for IEGs in sensory-driven cortical plasticity during development.