  The modification of mesonic observables in a hot medium is analyzed as a tool
to investigate the restoration of chiral and axial symmetries in the context of
the Polyakov-loop extended Nambu--Jona-Lasinio model. The results of the
extended model lead to the conclusion that the effects of the Polyakov loop are
fundamental for reproducing lattice findings. In particular, the partial
restoration of the chiral symmetry is faster in the PNJL model than in the NJL
one, and it is responsible for several effects: the meson-quark coupling
constants show a remarkable difference in both models, there is a faster
tendency to recover the Okubo-Zweig-Iizuka rule, and finally the topological
susceptibility nicely reproduces the lattice results around $T/T_c\approx 1.0$.
