Role of Mechanical Factors in the Morphology of the Primate Cerebral Cortex
Figure 5
Relationship of Axonal Trajectories to Connections
(A) Relative densities of individual projections in the different trajectory classes, straight (st), intermediate (im), and curved (cu). Horizontal lines denote median values. (Spearman's rank correlation of individual projections with trajectory class: ρ = −0.27, p < 0. 00001).
(B) Relative distribution of projection trajectories. Relative density of projections (on the x-axis) was calculated as the number of corticocortical projection neurons in each area, divided by the total number of labeled neurons found for all areas in the prefrontal cortex for one injection case. The y-axis indicates the relative frequency of all projections in the given density interval (normalized by all projections in a trajectory class). The diagram demonstrates that weak projections (<10% of relative density) tended to form mostly curved, then intermediate and straight trajectories, whereas greater densities (>10%) resulted predominantly in straight trajectories.
(C) Average cumulative density of straight, intermediate, and curved projections originating from individual prefrontal areas. The individual density values also followed the trend displayed here (rank correlation, ρ = −0.50, p < 0.0001).