\begin{table}
\begin{center}
\caption{Types of Aggregation}
\label{table:my_label1}
\begin{tabular}{|c |c| c| c|}
\multicolumn{4}{c}{}{$\overbrace{\rule{12.5em}{0pt}}^{Spatial Aggregation}$}\\
\hline
Meters & $time_1$ & $time_2$ & $time_3$ \\ [0.5ex]
\hline
$SM_{1}$ & $R_{1,1}$ & $R_{1,2}$ & $R_{1,3}$\\
\hline
$SM_2$ & $R_{2,1}$ & $R_{2,2}$ & $R_{2,3}$\\
\hline
$SM_3$ & $R_{3,1}$ & $R_{3,2}$ & $R_{3,3}$\\
\hline
\end{tabular}
\end{center}
\end{table}
I want to name the 2nd, 3rd and 4th column using \overbrace. How can I do that?

