Horizontal connections of blob and interblob compartments in neonatal monkey visual cortex

Purpose. To determine the topology iind morphology of neuronal connections mediating spatial and motion vision in area VI of infant primate we performed behavioral and anatomic experiments on normal, neonatal macaques. Methods. Four macaque monkeys had behavioral testing of grating acuity, monocular optokinetic nystagmus, and motion VEPs starting in the first days of life. At postnatal ages ranging from P10 - P 60, injections were made of the anterograde tracer biotinyiateddextran-amine (BDA) into individual ocu ar dominance columns (ODCs) of opercular VI. Simultaneously, WGA-HRP was in ected into one eye to transneuronally label ODCs. After a survival time of three da> s, the cortex was sectioned tangemially and alternate sections were processed U reveal BDA, WGA-HRP and CytOx histochemistry. Results Even in neonatal macaque as young as P10, patchy horizontal connections showed compartmental specificity. Injections into CytOx blobs resulted in labeling restricted to othei CytOx blobs. Similarly, injections into interblobs resulted in labeling of other int'Tblobs. Adult-like patchy connections were evident both in layers 2β and 4B. The elliptical anisotropy and extent of horizontal connections was similar to that observed in normal adult macaque. Conclusions. Horizontal connections in layers of VI known to be important for spatial and motion vision appear remarkably mature even in young, infant macaque. The postnaial pruning of connections observed in non-primate species is not as apparent in monkey. Despite adult like topology and morphobgv of VI connections, functional vision is remarkably immature.