The shape’s outline is first extracted using the edge_extraction circuit. In the curve detection circuit, this outline is then decomposed into four parts: the left and right upper arcs, and the left and right bottom arcs. Because all arcs are processed in the same way, we’ll illustrate the method using the left bottom arc. For the left bottom arc, the steep_left_bottom mapping links each source neuron to a set of destination neurons positioned along the left bottom arc.

For additional processing (if needed for your application), the upper and bottom arc signals on each side are merged into left_arc and right_arc. Finally, each side’s arc signals, together with curve_input, converge onto the left_curve and right_curve cortical areas, again relying on thresholded summation so that only sufficiently strong combined activation triggers firing in the destination neurons.