\approx 0.85\times10^{-2}~{\rm eV} \;\; ;  \end{aligned}$$ and $$\begin{aligned}
m_{\nu_{4}} \approx 96.8~{\rm GeV}  \;\; , \end{aligned}$$ which satisfies the current 95% CL heavy neutrino mass limit, $m_{\nu_{4}} > 90.3$ GeV for Dirac coupling and $m_{\nu_{4}} > 80.5$ GeV for Majorana coupling [@PDG]. Here the splitting of the fourth generation neutrino from the three active neutrinos is caused by the hierarchical spectrum $M_{1}, M_{2}$ of right-handed Majorana fields, so it can be argued that the masses of $N^{(1)}_{R}$ and $N_{R5}$ have different origins, as shown in Eqs. (\[A5Yukawa\]) and (\[MR\]). We note that $m_{\nu_{2}}$ is too small to accommodate the oscillation data. However, the three perturbations $\delta_{1,2,3}$ are different non-zero quantities, and in general they can be varied at the same time independently. We find that the inclusion of a VEV for $H_{3}$ and the relaxation of the condition $v_{\phi_1} = v_{\phi_{2}} = v_{\phi_{3}}$ will alter the tribimaximal mixings and can lead to masses in the range $10^{-1}-10^{-3}$ eV for the three light neutrinos for certain choices of parameters. [^4] Therefore, we anticipate that higher order corrections will provide enough degrees of freedom to fit the experimental data and a degenerate mass spectrum of neutrino masses is preferred in the present model.

