  The proper definition and evaluation of the configuration space path integral
for the motion of a particle in curved space is a notoriously tricky problem.
We discuss a consistent definition which makes use of an expansion in Fourier
sine series of the particle paths. Salient features of the regularization are
the Lee-Yang ghosts fields and a specific effective potential to be added to
the classical action. The Lee-Yang ghost fields are introduced to exponentiate
the non-trivial path integral measure and make the perturbative loop expansion
finite order by order, whereas the effective potential is necessary to maintain
the general coordinate invariance of the model. We also discuss a three loop
computation which tests the mode regularization scheme and reproduces
consistently De Witt's perturbative solution of the heat kernel.
