The ground state of the single layer half-doped manganite Pr0.5Ca1.5MnO4 has the canonical CE antiferromagnetic charge- and orbitally-ordered (CO-OO) structure characteristic of so many half-doped manganites. We have just measured the full spin wave dispersion in the ground state, and now propose to measure (1) above the 3D ordering temperature T_N = 130K but below the charge-and orbital ordering temperature T_CO=320K, and (2) above T_CO. The spins form one-dimensional magnetic chains which are relatively weakly coupled. The goal is determine how the loss of long-range magnetic order and then also orbital order alters the 1D spin dynamics; one feature we propose to look for is possible dimerisation of Mn spins along the chain.