Optogenetics Based Rat-Robot Control: Optical Stimulation Encodes "Stop" and "Escape" Commands.

Electric brain stimulation is frequently used in bio-robot control. However, one possible limitation of electric stimulation is the resultant wide range of influences that may lead to unexpected side-effects. Although there has been prior research done towards optogenetics based brain activation, there has not been much development regarding the comparisons between electric and optical methods of brain activation. In this study, we first encode "Stop" and "Escape" commands by optical stimulation in the dorsal periaqueductal grey (dPAG). The rats behavioral comparisons are then noted down under these two methods. The dPAG neural activity recorded during optical stimulation suggests rate and temporal coding mechanisms in behavioral control. The behavioral comparisons show that rats exhibit anxiety under the "Stop" command conveyed through both optical and electric methods. However, rats are able to recover more quickly from freezing only under optical "Stop" command. Under "Escape" commands, also conveyed through optical means, the rat would move with lessened urgency but the results are more stable. Moreover, c-Fos study shows the optical stimulation activates restricted range in midbrain: the optical stimulation affected only dPAG and its downstreams but electric stimulation activates both the upstream and downstream circuits, in which the glutamatergic neurons are largely occupied and play important role in "Stop" and "Escape" behavior controls. We conclude that optical stimulation is more suited for encoding "Stop" and "Escape" commands for rat-robot control.