The third is to minimize the energy consumption of the neural system, that is to use as little current input I as possible:13\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${f}_{s}=\sum _{k}{I}^{2}$$\end{document}fs=∑kI2This objective is biologically valid since the individuals use less energy for neural control gains advantages during the process of evolution.