Figure 4

Curve of the real parts of \(\pmb{z_{2}(t)}\) in (a), \(\pmb{z_{1}(t)}\) in (b), \(\pmb{z_{3}(t)}\) in (c) and \(\pmb{z_{4}(t)}\) in (d), and (e), (f) are phase portraits of the real and imaginary parts of \(\pmb{z_{1}(t)}\) , \(\pmb{z_{2}(t)}\) , \(\pmb{z_{3}(t)}\) and \(\pmb{z_{4}(t)}\) of fractional-order CVHNN with hub structure ( 50 ) with \(\pmb{\alpha=0.9}\) , \(\pmb{\gamma= 0.45 > \gamma_{0} = 0.32}\) and \(\pmb{\gamma= 0.31 < \gamma_{0} = 0.32}\) , respectively.