  Complementary $^{77}$Se nuclear magnetic resonance (NMR) and electrical
transport have been used to correlate the spin density dynamics with the
subphases of the field-induced spin density wave (FISDW) ground state in \tmt.
We find that the peaks in the spin-lattice relaxation rate 1/T$_1$ appear
within the metal-FISDW phase boundary and/or at first-order subphase
transitions. In the quantum limit above 25 T, the NMR data gives an insight
into the FISDW electronic structure.
