Figure 1.

Optogenetic MLI activation evokes eye movement. A, Mice expressing ChR2 in MLIs were bilaterally implanted with optical fibers targeting both flocculi. B, Vector plot of the average direction and amplitude of left eye movements evoked by photostimulation of MLIs in the left (ipsiversive) or right (contraversive) flocculus at different laser powers (λ473 nm, 240 ms; n = 3 mice). C, Decomposed horizontal eye movements from a quiescent mouse in response to unilateral floccular photostimulation of ChR2-expressing MLIs (10 mW). D, For photometry, bulk GCaMP6f fluorescence was collected through an implanted optical fiber targeting the left flocculus as the VOR was passively elicited by sinusoidal vestibular stimulation (1 Hz) in darkness. GCaMP6f-expressing MLIs transduced using a Cre-dependent AAV are shown in the image with the approximate location of the optical fiber also indicated. E, Top, Trial-averaged VOR-evoked eye movements (black; head position in gray) in a GCaMP6f-expressing mouse. Bottom, Calcium activity measurements from MLIs (green) with interleaved isosbestic measurements (purple) during the same recording. F, The timing of peak calcium activity in the MLI population response relative to the phase of the vestibular stimulus for each mouse (each point represents an individual mouse; n = 6 mice total). The position along the radius corresponds to the peak amplitude of the calcium response.