  Recent efforts in neuroscience research seek to obtain detailed anatomical
neuronal wiring maps as well as information on how neurons in these networks
engage in dynamic activities. Although the entire connectivity map of the
nervous system of C. elegans has been known for more than 25 years, this
knowledge has not been sufficient to predict all functional connections
underlying behavior. To approach this goal, we developed a two-photon technique
for brain-wide calcium imaging in C. elegans using wide-field temporal focusing
(WF-TEFO). Pivotal to our results was the use of a nuclear-localized,
genetically encoded calcium indicator (NLS-GCaMP5K) that permits unambiguous
discrimination of individual neurons within the densely-packed head ganglia of
C. elegans. We demonstrate near-simultaneous recording of activity of up to 70%
of all head neurons. In combination with a lab-on-a-chip device for stimulus
delivery, this method provides an enabling platform for establishing functional
maps of neuronal networks.
