Late Maturation (Age >5 Years) of Long-Range Spatial Interactions in Humans

Abstract

We have studied the development of long-range spatial interactions in children (age 5 – 14 years) with normal vision. In our field study involving 410 normal children we used a battery of contour-integration cards that were developed earlier to test amblyopic patients (Kovács, Polat, and Norcia, paper presented at ARVO 1996). Each card consisted of a closed chain of collinearly aligned Gabor patches (contour) and a background of randomly oriented and positioned Gabor patches (noise). Subjects were asked to identify the location of the contour, and also to trace the contour within each card. The value of P was varied across cards (1.1 > P > 0.65), where P is the ratio of noise spacing to contour spacing. It is assumed that long-range, orientation-specific facilitatory interactions connect collinear contour segments together for P < 1. The strength of long-range interactions is defined by the minimal value of P yielding contour segregation. Children in the 13 – 14 years age group were able to see most of the contours (P_min < 0.7), while 5 – 6-year-old children missed the contours in about half of the cards (P_min < 0.9). This result indicates a very late maturation of long-range spatial interactions. It is possible that the late formation of horizontal connections in superficial layers of the human primary visual cortex (Burkhalter et al, 1993 Journal of Neuroscience 13 1916 – 1931) is the neural basis of our developmental finding.