  Using the constrained curve fitting method and overlap fermions with the
lowest pion mass at $180 {\rm MeV}$, we observe that the masses of the first
positive and negative parity excited states of the nucleon tend to cross over
as the quark masses are taken to the chiral limit. Both results at the physical
pion mass agree with the experimental values of the Roper resonance
($N^{1/2+}(1440)$) and $S_{11}$ ($N^{1/2-}(1535)$). This is seen for the first
time in a lattice QCD calculation. These results are obtained on a quenched
Iwasaki $16^3 \times 28$ lattice with $a = 0.2 {\rm fm}$. We also extract the
ghost $\eta' N$ states (a quenched artifact) which are shown to decouple from
the nucleon interpolation field above $m_{\pi} \sim 300 {\rm MeV}$. From the
quark mass dependence of these states in the chiral region, we conclude that
spontaneously broken chiral symmetry dictates the dynamics of light quarks in
the nucleon.
