  Both isoscalar and isovector spin-dipole excitations of $^4$He are studied
using realistic nuclear forces in the complex scaling method. The ground state
of $^4$He and discretized continuum states with $J^{\pi}=0^-, 1^-, 2^-$ for A=4
nuclei are described in explicitly correlated Gaussians reinforced with global
vectors for angular motion. Two- and three-body decay channels are specifically
treated to take into account final state interactions. The observed resonance
energies and widths of the negative-parity levels are all in fair agreement
with those calculated from both the spin-dipole and electric-dipole strength
functions as well as the energy eigenvalues of the complex scaled Hamiltonian.
Spin-dipole sum rules, both non energy-weighted and energy-weighted, are
discussed in relation to tensor correlations in the ground state of $^4$He.
