  We study the four-point dynamic susceptibility $\chi_4(t)$ obtained from
Brownian dynamics computer simulations of the Kob-Andersen Lennard-Jones
mixture. We compare the results of the simulations with qualitative predictions
of the mode-coupling theory. In addition, we test an estimate of the four-point
susceptibility recently proposed by Berthier \textit{et al.} [Science,
\textbf{310}, 1797 (2005)].
