Spin force dependence of the parton distributions: the ratio F2n(x,Q2)/F2p(x,Q2)

Light-front Hamiltonian dynamics is used to relate low-energy constituent quark models to deep inelastic unpolarized structure functions of the nucleon. The approach incorporates the correct Pauli principle prescription consistently and it allows a transparent investigation of the effects due to the spin-dependent SU(6)-breaking terms in the quark model Hamiltonian. Both the Goldstone-boson-exchange interaction and hyperfine-potential models are discussed in a unified scheme and a detailed comparison between the two (apparently) different potential prescriptions is presented.