Hi. Although I conduct optogenetic experiments in my study, I am not familiar with activating a particular region of a neuron such as dendrites in vivo. Could you explain how you can achieve this?

Many studies have already shown that stimulating axons expressing rhodopsin is susficient to altered the circuit-mediated behavior. I can't recall any study doing dendritic activation. My guess is that if dendritic stimulation is strong enough to activate somatic firing, you should observe behavioral consequence if these neurons are critical.