[Neuroscience] What is the meaning of the variables and parameters of the systems from neurophysiology?

[Dingqi.dl from gmail.com]

    I am very interesting in solving the equations which is from
neurophysiology and posted by Sjirk Boon to sci.math.symbolic. I
really want to know what is the meaning that the variables phi1,
phi2,
C1, C2, C3, C4 and the parameters Lxxx, Lyyy, Lxxy, xyy  express.

    The following is the system:


equ1 := Lxxx-3*Lyyx = C1*Cos(3*phi1)+C2*cos(3*phi2);
equ2 := Lxxx+Lyyx = C1*cos(phi1)+C2*cos(phi2);
equ3 := 3*Lxxy-Lyyy = C1*sin(3*phi1)+C2*sin(3*phi2);
equ4 := Lxxy+Lyyy = C1*sin(phi1)+C2*sin(phi2);


substituting s1 = sin(phi1), s2 = sin(phi2), g1 = cos(phi1) and g2 =
cos(phi2). The equations change
into 6 equations with 6 unknowns:


equ1 := s1**2+g1**2 = 1;
equ2 := s2**2+g2**2 = 1;
equ3 := Lxxx = C1*g1**3+C2*g2**3;
equ4 := Lyyy = C1*s1**3+C2*s2**3;
equ5 := Lxxy = C1*g1**2*s1+C2*g2**2*s2;
equ6 := Lxyy = C1*g1*s1**2+C2*g2*s2**2;