Typical combination opto- chemogenetic paper--this time odorant system

I'm frequently asked

"Which is better, opto- or chemogenetics?"

To which I'm tempted to reply:  "Which is better, red or green?"

Clearly, depends on the experiment and it is likely that there is a perfect (or nearly so) way to do it.  Sometimes this will be with light, other times with chemicals--sometimes neither.

At any rate, here's a nice example of combining them to deconstruct interneuron activity and odorant in Nature Neurosciences

"Neuronal pattern separation is thought to enable the brain to disambiguate sensory stimuli with overlapping features, thereby extracting valuable information. In the olfactory system, it remains unknown whether pattern separation acts as a driving force for sensory discrimination and the learning thereof. We found that overlapping odor-evoked input patterns to the mouse olfactory bulb (OB) were dynamically reformatted in the network on the timescale of a single breath, giving rise to separated patterns of activity in an ensemble of output neurons, mitral/tufted (M/T) cells. Notably, the extent of pattern separation in M/T assemblies predicted behavioral discrimination performance during the learning phase. Furthermore, exciting or inhibiting GABAergic OB interneurons, using optogenetics or pharmacogenetics, altered pattern separation and thereby odor discrimination learning in a bidirectional way. In conclusion, we propose that the OB network can act as a pattern separator facilitating olfactory stimulus distinction, a process that is sculpted by synaptic inhibition."

I also note that opto and chemogenetics now appear to be so ubiquitous in the neuroscience literature that the original references to the technologies are no longer cited.