The role of many-electron correlations in photoabsorption processes has been investigated. The results of numerical calculations of photoionization cross sections of sodium atom are presented. The many-body effects such as interchannel correlations resulting in autoionization resonance peaks, as well as effects of atomic core polarization were taken into account in the calculations in terms of RPAE. Polarization corrections were accounted for using both static and dynamic polarization potentials. The influence of correlations on the position and the form of resonance peaks was studied. The obtained results demonstrate necessity of taking into account polarization effects, especially for clarification of autoionization resonance peaks position and the cross-section magnitudes in the low energy range. The best agreement with experimental data was reached with the model of dynamic polarization potential based on Dyson equation.