Optogenetic Mimicry of the Transient Activation of Dopamine Neurons by Natural Reward Is Sufficient for Operant Reinforcement
A, Positions of viral injections in a coronal section of ventral midbrain (−3.28 mm from bregma). All injections were found to be within 0.06 mm rostral or caudal of this section. Each dot represents the injection site for an individual mouse (red circles for ChR2-H mice, black circles for ChR2-L mice, and blue triangles for AAV- mice). Vertical scale bar at right: 0.5 mm. B, Top, ChR2-tdTomato (red) colocalized with TH immunostaining (green) as shown in the overlay at right (yellow). Bottom, ChR2-tdTomato expression was not observed in another mouse. The center of these images corresponds to the ‘X’ marks in ‘A.’ Inset scale bars: 0.15 mm. C, Number of TH+ and ChR2+ neurons in each mouse. Based upon these results, mice were categorized as “ChR2-H” (red) or “ChR2-L” (black).