Mechanisms underlying reshuffling of visual responses by optogenetic stimulation in mice and monkeys.

The ability to optogenetically perturb neural circuits opens an unprecedented window into mechanisms governing circuit function. We analyzed and theoretically modeled neuronal responses to visual and optogenetic inputs in mouse and monkey V1. In both species, optogenetic stimulation of excitatory neurons strongly modulated the activity of single neurons yet had weak or no effects on the distribution of firing rates across the population. Thus, the optogenetic inputs reshuffled firing rates across the network. Key statistics of mouse and monkey responses lay on a continuum, with mice/monkeys occupying the low-/high-rate regions, respectively. We show that neuronal reshuffling emerges generically in randomly connected excitatory/inhibitory networks, provided the coupling strength (combination of recurrent coupling and external input) is sufficient that powerful inhibitory feedback cancels the mean optogenetic input. A more realistic model, distinguishing tuned visual vs. untuned optogenetic input in a structured network, reduces the coupling strength needed to explain reshuffling. [Display omitted] • In mouse and monkey V1, optogenetic stimulation of E cells reshuffles firing rates • Response statistics form a continuum, mice/monkeys lying in the low-/high-rate regions • Model networks produce reshuffling if coupling is strong and optogenetic input weak • Structured connectivity lessens required coupling strength and optogenetic weakness Sanzeni et al. find that in both mouse and monkey V1, optogenetic stimulation of excitatory cells strongly changes individual neuronal firing rates but not their distribution: "rate reshuffling." Network models reproduce reshuffling given sufficiently strong interactions between neurons. The results demonstrate the importance of recurrent interactions in shaping network response. [ABSTRACT FROM AUTHOR]