Figure 1From: A sub-Riemannian model of the visual cortex with frequency and phaseAn integral curve along the vector field \(X_{1}+X_{2}\). It represents an orientation fiber once ω and ϕ are fixed. The tangent planes spanned by \(X_{1}\), \(X_{2}\) (left) and \(X_{3}\), \(X_{4}\) (right) are shown at six points on the curveBack to article page