This is a very good overview of what voltage sensitive dyes are and what they can measure. Just world of caution could be stated somewhat stronger: the adverse photodynamic and/or pharmacological effects vary greatly with the specific preparation (can be minor but also can kill cells relatively quickly) and thus should be assessed individually for every experimental design.
I suggest adding a paragraph describing application of voltage-sensitive dye imaging to examine "spatiotemporal patterns of population activity". Neocortical and hippocampal neuronal networks contain extensive interconnections, and activity in these networks is neither completely synchronized nor completely uncorrelated. Instead, activity in one local area may spread into other regions through distributed excitatory connections leading to "propagating waves". The patterns of these waves determine when and where neurons are depolarized in the network, and have been observed in visual, auditory, somatosensory, olfactory and motor systems.
One of the authors of this article, Dr. Lawrence B. Cohen, was among the first to describe wave patterns in cortex (e.g., Prechtl et al., 1997). A number of recent articles may also be listed as references.