Originality: The first attempt to elucidate the influence of attention modulation on neural tuning function by using the method of information theory. Rigor: The Fisher information was applied to quantify the dependence of neural population decoding accuracy on the parameters of the tuning function. The theoretical results well agreed with the experimental data, and had new predictions for future experiments. Significance: This work showed how the information theory method can be applied successfully to study the attention function in neural systems. Impact: This work has contributed to the recent trend of using the information theory method to study high-level brain functions. Web Knowledge=6, Google Scholar=10.