  The amplitude equation of Gierer-Mainhardt model has been actually derived
near the boundary abuot which Turing and Hopf modes exist. In a parameter
region where Hopf-Turing mixed mode solution is stable, a chaotic state that
generally results from interaction between mixed modes, is observed. This
chaotic region follows a strong selection of a spatially periodic order
followed by a local, resonant, very large frequency temporal oscillation. A
spatio-temporal forcing, responsible for what obseved, has been identified.
