Comparison of border distance and structural type (Δ) as determinants of the pattern of contralateral projections. (A)Frequency of contralateral projections depending on border distance, defined as the number of borders between the contralateral area of projection origin and the area homotopic to the injection site. (B)The relationship of the density of contralateral projections to border distance (Spearman's ρ = -0.87; p (two-tailed) < 0.0002). (C)Frequency of contralateral projections as a function of the absolute structural type difference of the linked areas, delta (|Δ|). (D)The relationship of the density of contralateral projections to the type similarity between the contralateral area of origin and the ipsilateral target area, |Δ| (Spearman's ρ = -0.96; p (two-tailed) < 0.0005). Note that in panels A and C data were pooled over adjacent intervals to avoid artificial variance from sparsely filled categories. In these cases, a distance or Δ of '2', for instance, included data for distance or Δ for 2 proper as well as for 2.5.