Comparison of the relative origin of projection neurons in superficial cortical layers II-III in ipsilateral and contralateral areas. Relative laminar origin of: (A)ipsilateral; (B)contralateral projections. The x-axis shows the proportion of projection neurons found in the upper cortical layers II-III, plotted into intervals of 10% (e.g., in the interval '.8,.9', 80%–90% of projection neurons were located in layers II-III, and the remaining 10%–20% were found in the deep layers, V-VI). Projections originating predominantly from layers V-VI are shown on the left, and projections originating in layers II-III are shown on the right. Projection neurons found in approximately equal proportions in superficial and deep layers are shown in the center. Ipsilateral projections (A)showed a broad Gaussian distribution of laminar origin patterns. By contrast, the distribution of contralateral projection origins (B)was more restricted and skewed towards the superficial layers.