Functional development of the corticocortical pathway for motion analysis in the macaque monkey: a 14C-2-deoxyglucose...

The corticocortical pathway for motion analysis transmits visual information from striate cortex (V1) via V2, V3d, superior temporal sulcal areas MT, MST, and FST to motion-sensitive areas in the floor and upper bank of the anterior part of the superior temporal sulcus (AST). We studied the functional development of this pathway by applying the 14C-2-deoxyglucose method to rhesus monkeys (Macaca mulatta) ranging in age from 2 d to 3-4 years. A comparison of local cerebral glucose utilization (LCGU) in an intact and a visually deafferented hemisphere in each animal across the age range revealed that this pathway, immature at birth, reaches adult-like levels at 3 months of age. This developmental time course is reflected both in absolute LCGU and in the interhemispheric LCGU differences in all the areas of the pathway. At all ages, the interhemispheric difference in LCGU is largest in V1 and gradually declines along the pathway until a minimum is reached in AST. This decline likely reflects an increasing proportion of nonvisual inputs to the higher-order areas of the pathway. Measurements like those above taken in areas of inferior parietal cortex indicate that they mature at the same rate as those in the motion analysis pathway. However, comparison with findings on the functional development of the temporal areas of the occipitotemporal pathway for object vision (Bachevalier et al., 1991) suggests that areas along the motion analysis pathway and those in parietal cortex mature about 1 month earlier.