using $dumpvar on 2d register error

My design has a 4kb memory unit and I need to capture its switching activity.

If I use:
$dumpvars(1, testbench.decoder0);

in my testbench, I should get all activity from all nets/registers in my design. However, I don't get any switching activity from my memory unit which is a 2D register array.

If I try to use below to manually reference:
$dumpvars(0, testbench.decoder0.virtual_mem0.mem[1023]);
$dumpvars(0, testbench.decoder0.virtual_mem0.mem[1022]);
$dumpvars(0, testbench.decoder0.virtual_mem0.mem[1021]);
$dumpvars(0, testbench.decoder0.virtual_mem0.mem[1020]);
$dumpvars(0, testbench.decoder0.virtual_mem0.mem[1019]);
....
ModelSim says invalid argument 2.. it doesn't like "[ ]".

How can I capture my memory activity using VCD in ModelSim?

Thanks.

Just found out that from ncvlog user guide: For Verilog, you cannot probe arrays of variable data types to a VCD database. This includes Verilog memories, which are one-dimensional arrays of type reg.

Great!

Any other way?