  We report on inelastic neutron scattering measurements that find
incommensurate itinerant like magnetic excitations in the normal state of
superconducting FeTe$_{0.6}$Se$_{0.4}$ (\Tc=14K) at wave-vector
$\mathbf{Q}_{inc}=(1/2\pm\epsilon,1/2\mp\epsilon)$ with $\epsilon$=0.09(1). In
the superconducting state only the lower energy part of the spectrum shows
significant changes by the formation of a gap and a magnetic resonance that
follows the dispersion of the normal state excitations. We use a four band
model to describe the Fermi surface topology of iron-based superconductors with
the extended $s(\pm)$ symmetry and find that it qualitatively captures the
salient features of these data.
