Using voltage-sensitive dye recording to image the functional development of neuronal circuits in vertebrate embryos

Recent developments in the design of voltage-sensitive dyes and of recording apparatuses for detecting voltage-dependent changes in the optical properties of such dyes have established voltage-sensitive dye recording as an important technique for assessing the functional development of neuronal circuits in the brain and spinal cord. Here we discuss general technical issues regarding the recording of voltage-sensitive dye signals and describe studies that have utilized this approach to follow the development of sensory and sensorimotor circuits in the embryonic brain stem. Functional imaging through voltage-sensitive dye recording permits a noninvasive analysis of synaptic development and function at submillisecond temporal resolution in widely distributed circuits. These advantages are particularly valuable in assessing sensorimotor circuit development at early stages when neurons are small and synapses are fragile.